i need some ideas/ any tips at all on how to protect my feedline and equipment from lightning strikes...any info would be appreciated also tips on grounding my station...
thanks in advance
adam
Lightning protection
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RESCUEMAN433
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lightning protection and antennas
Your going to hear people say there is nothing that can protect you from a direct strike. That is just plain BULL. If that was the case there wouldn't be any TV, AM, FM or cellular sites that can afford to stay on the air. The fact is, there are towers that take direct hits almost every day and come away from it with everything working.
I have seen a 600 foot tower take a hit. It will steam in the rain after due to the steel being heated up a little. Went into the radio building and everything was playing fine except the ham repeater. Been after them for over a couple of years to connect to the building ground system. They just plain refused.
Bottom line, there is plenty you can do. It just matters on how much your willing to pay to protect your self. There is no one thing, device or wire that will protect you. It all is a system.
To start with, the tower needs to have a good ground system. That doesn't mean just a single ground rod at the base. That means a minimum of # 2 AWG solid, tinned copper wire ring around the tower base with at least 8 foot ground rods spaced every 16 feet along the ring. No less than 3 ground rods. It would be good if you ran radial ground wires away from the tower in at least 2 directions. Again space the ground rods 6 feet apart. All ground connections will be made with the exothermic bond to the ground rods, the intersecting ground wires and the tower. Do not make the weld to a hollow tower leg.
The radio building will have a ground ring around it. Again space the ground rods every 16 feet. The tower and building ground ring will be connected to each other in at least 2 different places. Keep all bends to no less than 8 inches. Keep the ground wires away from the foundations by at least 30 inches. Bury the wire at least 30 inches down.
The coax cables need to be grounded at the transition when they leave the tower. These cable grounds get tied to a common ground bar that ties to the tower ground ring with a # 2 AWG solid copper wire. Use the propper cable grounding kits. Use double hole lugs for all connections. Use only stainless steel hardware to make any mechanical connections. Put a little anti oxide compound under the mechanical connections.
There wil be another ground bar just as the coax cables enter the building. This ground bar gets connected to the building ground ring. Again use cable ground kits.
Inside the building should be another set of ground bars. One just under the cable entry point and another about 6 inches off the floor. The one near the floor is called the master ground bar. Everything in the building gets tied to theis ground bar. The electrical power cabinet, the telephone surge protection, the power surge protection, all the radio cabinets, all the cable trays, all the metal conduit in the building and even the ground bar under the cable entrance. If you use surge protection on the coax cables (recommend that you do) these get tied to the ground bar.
Kind of alot being said in just a short few words. It works well. Been doing this for about 20 years now in the telecommunications field. If done right, very little damage takes place with a direct strike. Most of the damage seems to be from the telephone circuits.
Jim
I have seen a 600 foot tower take a hit. It will steam in the rain after due to the steel being heated up a little. Went into the radio building and everything was playing fine except the ham repeater. Been after them for over a couple of years to connect to the building ground system. They just plain refused.
Bottom line, there is plenty you can do. It just matters on how much your willing to pay to protect your self. There is no one thing, device or wire that will protect you. It all is a system.
To start with, the tower needs to have a good ground system. That doesn't mean just a single ground rod at the base. That means a minimum of # 2 AWG solid, tinned copper wire ring around the tower base with at least 8 foot ground rods spaced every 16 feet along the ring. No less than 3 ground rods. It would be good if you ran radial ground wires away from the tower in at least 2 directions. Again space the ground rods 6 feet apart. All ground connections will be made with the exothermic bond to the ground rods, the intersecting ground wires and the tower. Do not make the weld to a hollow tower leg.
The radio building will have a ground ring around it. Again space the ground rods every 16 feet. The tower and building ground ring will be connected to each other in at least 2 different places. Keep all bends to no less than 8 inches. Keep the ground wires away from the foundations by at least 30 inches. Bury the wire at least 30 inches down.
The coax cables need to be grounded at the transition when they leave the tower. These cable grounds get tied to a common ground bar that ties to the tower ground ring with a # 2 AWG solid copper wire. Use the propper cable grounding kits. Use double hole lugs for all connections. Use only stainless steel hardware to make any mechanical connections. Put a little anti oxide compound under the mechanical connections.
There wil be another ground bar just as the coax cables enter the building. This ground bar gets connected to the building ground ring. Again use cable ground kits.
Inside the building should be another set of ground bars. One just under the cable entry point and another about 6 inches off the floor. The one near the floor is called the master ground bar. Everything in the building gets tied to theis ground bar. The electrical power cabinet, the telephone surge protection, the power surge protection, all the radio cabinets, all the cable trays, all the metal conduit in the building and even the ground bar under the cable entrance. If you use surge protection on the coax cables (recommend that you do) these get tied to the ground bar.
Kind of alot being said in just a short few words. It works well. Been doing this for about 20 years now in the telecommunications field. If done right, very little damage takes place with a direct strike. Most of the damage seems to be from the telephone circuits.
Jim
Also...lot of "damage control" takes place right at the antenna.
Use a cheapo antenna and nothing below will save the system. Many ham antennae are not of a DC-grounded design and a direct hit has no shunt to ground anywhere above the tower. Not only do you send 100% of the strike down the feedline, but it's almost a given that the antenna is scrap too.
Use a cheapo antenna and nothing below will save the system. Many ham antennae are not of a DC-grounded design and a direct hit has no shunt to ground anywhere above the tower. Not only do you send 100% of the strike down the feedline, but it's almost a given that the antenna is scrap too.
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Tom in D.C.
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Lightning protection...
Three possible GOOD sources of reliable information:
1. National Electric Code
2. ARRL
3. NFPA
1. National Electric Code
2. ARRL
3. NFPA
Tom in D.C.
In 1920, the U.S. Post Office Department ruled
that children may not be sent by parcel post.
In 1920, the U.S. Post Office Department ruled
that children may not be sent by parcel post.
The reason for the "no protection" against direct strikes is...
risk vs. reward
when protecting a commercial setup, which generates revenue...no expense is too great to protect the investment
when protecting a $500 -$1000 amateur setup which does not generate revenue ... is anybody willing to spend either time or money for protection
yes, anything can be protected, but the real question is how much are you willing to spend...for most, a polyphaser inline protector is about as much as they are willing to spend, and yes a single inline device will not protect you from a direct strike
...Z
risk vs. reward
when protecting a commercial setup, which generates revenue...no expense is too great to protect the investment
when protecting a $500 -$1000 amateur setup which does not generate revenue ... is anybody willing to spend either time or money for protection
yes, anything can be protected, but the real question is how much are you willing to spend...for most, a polyphaser inline protector is about as much as they are willing to spend, and yes a single inline device will not protect you from a direct strike
...Z
And that's all great if you are dealing with a tower. If he's talking about something roof mounted, I don't think there is going to be all that elaborate stuff. If you just have an inexpensive antenna on a mast on the roof with some LMR-400 or 1/2", your best protection from a direct strike on the antenna is probably a smoke detector and fire extinguisher.
"I'll eat you like a plate of bacon and eggs in the morning. "
- Some loser on rr.com
eBay at it's finest:
Me: "What exactly is a 900Mhz UHF CB?"
Them: "A very nice CB at 900Mhz speed!"
- Some loser on rr.com
eBay at it's finest:
Me: "What exactly is a 900Mhz UHF CB?"
Them: "A very nice CB at 900Mhz speed!"
Which is why amateur radio operators have problems getting into "commercial" sites. They may not care, but the people running equipment around them, that can be damaged by their lack of concern, do.Znarx wrote:The reason for the "no protection" against direct strikes is...
risk vs. reward
when protecting a commercial setup, which generates revenue...no expense is too great to protect the investment
when protecting a $500 -$1000 amateur setup which does not generate revenue ... is anybody willing to spend either time or money for protection
Jeff
Emoticons are the wheel chair ramps for the emotionally handicapped.
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N4DES
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Re: Lightning protection...
Motorola R56 is also an excellent document as well and it clearly defines the details from antenna/transmission line grounding all the way to correctly route transmission lines in the shelter. We built 813A using R56 as a guidebook and adding a few modifications of our own like increasing ground rod length from 10 feet to 20 and using 2AWG stranded instead of #2 solid.Tom in D.C. wrote:Three possible GOOD sources of reliable information:
1. National Electric Code
2. ARRL
3. NFPA
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spareparts
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Re: Lightning protection...
Mark,KS4VT wrote:Motorola R56 is also an excellent document as well and it clearly defines the details from antenna/transmission line grounding all the way to correctly route transmission lines in the shelter.
Amen to that! I'm building a shelter from scratch & had purchased a copy of R56 from Motorola mid-build. Had a bit of "smack hand on forehead" and went back to change several grounding related items.
BTW, The folks at Erico-Cadweld must really like me right about now, considering I the supplies I have purchased!
Martin
Re: Lightning protection...
[quote="spareparts"][quote="KS4VT"][b]Motorola R56[/b] is also an excellent document as well and it clearly defines the details from antenna/transmission line grounding all the way to correctly route transmission lines in the shelter.[/quote]
Bear in mind that the so called Motorola "R56" standard covers more than just grounding. It also is a living document. it undergoes changes on a regular basis.
One of the major differences in the R56 and what most of the telecommunication companies use is the size of the grounding wire. Motorola must have stock in one of the copper companies for wire. The R56 standard like to use # 2/0 wire for most of the outside grounding wire. The other companies use # 2.
I will say there is a slight difference in the inductance between the two of them. However, I have not seen anyone be able to prove one size is better than the other.
Then there is the cost. The larger # 2/0 wire is more expensive due to using more copper. It also requires special exothermic molds. You can also get it confused with the 2/0 lightning cable which is 2 /0 in size. However the lightning cable is slightly smaller than the normal # 2/0 AWG. This also causes the use of a special exothermic mold.
Jim
Bear in mind that the so called Motorola "R56" standard covers more than just grounding. It also is a living document. it undergoes changes on a regular basis.
One of the major differences in the R56 and what most of the telecommunication companies use is the size of the grounding wire. Motorola must have stock in one of the copper companies for wire. The R56 standard like to use # 2/0 wire for most of the outside grounding wire. The other companies use # 2.
I will say there is a slight difference in the inductance between the two of them. However, I have not seen anyone be able to prove one size is better than the other.
Then there is the cost. The larger # 2/0 wire is more expensive due to using more copper. It also requires special exothermic molds. You can also get it confused with the 2/0 lightning cable which is 2 /0 in size. However the lightning cable is slightly smaller than the normal # 2/0 AWG. This also causes the use of a special exothermic mold.
Jim
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kf4sqb
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Jim202, didn't you forget something? What about the grounds at the guy anchor-points? My 100' tower here at home has a ground rod at each guy anchor point, connected to all four guys at each anchor. I am also thinking very seriously about bonding at least the top set of guys to the tower.
Also, you need to have the neutral bus in your electrical panel tied back to your "master ground" for the tower. I've seen a few instances of damaged equipment from the power lines taking a hit, and the lightning "leaving" via the coax. Makes a real mess, too. It also needs to be bonded to the structural members of the building if it is steel construction.
I think we can pretty safely sum up most of what everyone has said here in four sentences:
1. Ground it.
2. When you think you have sufficent grounding, ground it some more.
3. After you've grounded it some more, add a few more grounds for good measure.
4. Finally, tie all individual grounding systems together (tower system to shack system, shack power system to shack system, shack power system to tower system, etc.) through several different paths.
There is no such thing as excessive grounding on a tower!
BTW, while it may sound like I'm trying to be a smart-a$$, I'm not. I am completely serious!
Also, you need to have the neutral bus in your electrical panel tied back to your "master ground" for the tower. I've seen a few instances of damaged equipment from the power lines taking a hit, and the lightning "leaving" via the coax. Makes a real mess, too. It also needs to be bonded to the structural members of the building if it is steel construction.
I think we can pretty safely sum up most of what everyone has said here in four sentences:
1. Ground it.
2. When you think you have sufficent grounding, ground it some more.
3. After you've grounded it some more, add a few more grounds for good measure.
4. Finally, tie all individual grounding systems together (tower system to shack system, shack power system to shack system, shack power system to tower system, etc.) through several different paths.
There is no such thing as excessive grounding on a tower!
BTW, while it may sound like I'm trying to be a smart-a$$, I'm not. I am completely serious!
brett "dot" kitchens "at" marel "dot" com
Look for the new "Jedi" series portables!
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Look for the new "Jedi" series portables!
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Be careful about grounding the neutral bus. It is my understanding that this connection can only be made in one place, usually in the first panel after the meter where the main disconnect is. Neutrals and grounds must be kept separate on any sub-panels.
The electrical inspector in my area wanted me to add two more 8ft ground rods outside the house when I added a generator transfer switch and replaced the service panel. He didn't want to trust just the cold water pipe ground. Of course he didn't specify the size of the wire going to these two ground rods (I probably should have used #2), but he was satisfied when he saw them buried in the ground. Whether or not this is an actual requirement or personal preference, one will never know.
Bob M.
The electrical inspector in my area wanted me to add two more 8ft ground rods outside the house when I added a generator transfer switch and replaced the service panel. He didn't want to trust just the cold water pipe ground. Of course he didn't specify the size of the wire going to these two ground rods (I probably should have used #2), but he was satisfied when he saw them buried in the ground. Whether or not this is an actual requirement or personal preference, one will never know.
Bob M.
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kf4sqb
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Can't say that I blame him for not trusting only the "water pipe" ground. It is actually listed in National Electrical Code (NEC) that while the water pipe system can be used as a grounding electrode, it must be supplemented by a "made electrode", such as a ground rod. I don't believe it requires two rods, but it may for certain applications. There are also some subjects which are left up to the judgement of "the authority having jurisdiction", the inspector in your case. I would have to look back in my code book to be sure about transfer switches. Of course, local code may supercede national, but only if it is more restrictive. They can't go below national standards, but they can certainly go above.
As for "neutrals and grounds must be kept separate on any sub-panels", not true. The neutral bus may be grounded in sub-panels. If you like, I'll try to find the related article in NEC over the next few days, and quote it for you. After all, what is a neutral, but a ground? Most homes, newer ones, anyway, will have a long screw that goes through the neutral bus, and threads into the housing of the panel inside the house. Some even have a built-in strap connecting the neutral bus with the ground bus. And yes, as a matter of fact, I am an electrician. I've been doing electrical work since I was old enough to turn a screwdriver. I've worked on everything from residential to heavy industrial.
As for "neutrals and grounds must be kept separate on any sub-panels", not true. The neutral bus may be grounded in sub-panels. If you like, I'll try to find the related article in NEC over the next few days, and quote it for you. After all, what is a neutral, but a ground? Most homes, newer ones, anyway, will have a long screw that goes through the neutral bus, and threads into the housing of the panel inside the house. Some even have a built-in strap connecting the neutral bus with the ground bus. And yes, as a matter of fact, I am an electrician. I've been doing electrical work since I was old enough to turn a screwdriver. I've worked on everything from residential to heavy industrial.
brett "dot" kitchens "at" marel "dot" com
Look for the new "Jedi" series portables!
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-.- .. ....- -.-. -.-- . .. ... -- -.-- -... .-. --- - .... . .-. .-.-.-
Look for the new "Jedi" series portables!
Bat-Phone= BAT-CAVE (2283)
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I'm not saying that you can't connect the neutral bus to ground. I believe this is only permitted in a very few places, and that's why they give you the ability to do it or not. If the panel is to be used as a sub-panel (away from the main panel where the neutral IS bonded to ground), then the neutral and ground busses need to be kept separate, and you would not use that screw. I think it has something to do with safety and what we'd call in the electronics business "ground loops".
I recently electrified a shed outside with a Square-D 60A panel. It had a neutral bus and they provided a green screw to run through it into the cabinet to provide grounding if allowed by code. In my case, it was to be used as a sub-panel on a 30A 240V circuit, so I had to go out and buy a ground bus which mounted inside the cabinet to provide the safety/earth ground. Four wires run from this panel all the way back to the main distribution panel where neutral and ground ARE one and the same.
I'm NOT an electrician, but have asked several about this connection. Some agree, some never encountered it. I'm sure there are exceptions to every rule.
Bob M.
I recently electrified a shed outside with a Square-D 60A panel. It had a neutral bus and they provided a green screw to run through it into the cabinet to provide grounding if allowed by code. In my case, it was to be used as a sub-panel on a 30A 240V circuit, so I had to go out and buy a ground bus which mounted inside the cabinet to provide the safety/earth ground. Four wires run from this panel all the way back to the main distribution panel where neutral and ground ARE one and the same.
I'm NOT an electrician, but have asked several about this connection. Some agree, some never encountered it. I'm sure there are exceptions to every rule.
Bob M.
[quote="kf4sqb"]As for "neutrals and grounds must be kept separate on any sub-panels", not true. The neutral bus may be grounded in sub-panels. [/quote]
Lets be careful here. Per the NEC, the only place you should have the electrical neutral bond is at the meter or the first disconnect within 3 feet or so of the meter.
There are exceptions to this if you have sub panels in different buildings. If you have multiple power sources this gets complicated.
However, a emergency power generator is not a separate power source and as such, the neutral should not be grounded in the generator or transfer switch. You will find a number of electricians that will argue this point.
Bottom line is only one place do you ground or bond the neutral. That is at the source. In most cases, this will be the electrical meter.
Again I have run into some electrical inspectors that have a poor understanding of the NEC and require you to bond the neutral to ground in the distribution breaker panel.
The reason for the single point bonding goes into the life safety issue and faults in the power system. There is not enough space here to go into all the details.
There is also a special section in the NEC that allows bonding of the electrical ground to the telecommunications earth ground ring. Again there are some electrical inspectors that won't allow this common bonding. Get your inspection done and signed off. Then go back and bond the 2 systems together so you don't sustain damage.
On one of my last posts, I did not mention to ground the guy wires and guy anchors. This must be done with bronze connectors on the galvanized guy wires. Never let copper wires, even tinned touch the galvanization on tower steel or guy wires. It will leach the zinc and cause rusting over time.
Jim
Lets be careful here. Per the NEC, the only place you should have the electrical neutral bond is at the meter or the first disconnect within 3 feet or so of the meter.
There are exceptions to this if you have sub panels in different buildings. If you have multiple power sources this gets complicated.
However, a emergency power generator is not a separate power source and as such, the neutral should not be grounded in the generator or transfer switch. You will find a number of electricians that will argue this point.
Bottom line is only one place do you ground or bond the neutral. That is at the source. In most cases, this will be the electrical meter.
Again I have run into some electrical inspectors that have a poor understanding of the NEC and require you to bond the neutral to ground in the distribution breaker panel.
The reason for the single point bonding goes into the life safety issue and faults in the power system. There is not enough space here to go into all the details.
There is also a special section in the NEC that allows bonding of the electrical ground to the telecommunications earth ground ring. Again there are some electrical inspectors that won't allow this common bonding. Get your inspection done and signed off. Then go back and bond the 2 systems together so you don't sustain damage.
On one of my last posts, I did not mention to ground the guy wires and guy anchors. This must be done with bronze connectors on the galvanized guy wires. Never let copper wires, even tinned touch the galvanization on tower steel or guy wires. It will leach the zinc and cause rusting over time.
Jim
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kf4sqb
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All quotes are from the 1996 edition of the NFPA published National Electrical Code.
First off, the definition of a service:
Also, the definition of a grounding conductor:
If you try to look this up for yourself, be fore-warned! The code book is about 1 1/2" thick, and over 1000 pages. Normally, if you go to school to be an electrician, there will usually be a class dedicated to nothing but how to find what you need to know in the NEC book. It's layout is that complicated.
First off, the definition of a service:
Next, the definition of a grounded conductor:NEC article 100 wrote:Service: The conductors and equipment for delivering energy from the electricity supply system to the wiring system of the premises served.
A neutral falls under this definition.NEC article 100 wrote: Grounded Conductor: A system or circuit conductor that is intentionally grounded.
Also, the definition of a grounding conductor:
With all of that out of the way,NEC article 100 wrote: Grounding Conductor: A conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes.
To provide a little clarification, the panel in your house is considered a service, not a sub-panel. A sub-panel does not usually have a main disconnecting means in it, but relies on the breaker in the panel it is fed from as a means of disconnect. The panel in a residence normally has a main breaker in it, making it a service panel. According to the above-quoted articles, the grounded circuit conductor, or neutral, shall be connected to the grounding electrode conductor, meaning the wire going out the ground rod. There are of course exceptions to this rule, but this will apply in most "normal" cases.NEC article 250-23, Grounding Service-Supplied Alternating-Current Systems wrote: (a) System Grounding Connections. A premises wiring system that is supplied by an ac service that is grounded shall have at each service a grounding electrode conductor connected to a grounding electrode that shall be connected to the grounded service conductor at any accessible point from the load end of the service drop or service lateral to and including the teminal or bus to which the grounded service conductor is connedted at the service disconnecting means.
(b) Grounded Conductor Brought to Service Equipment. Where an ac system operating at less than 1000 volts is grounded at any point, the grounded conductor shall be run to each service disconnecting means and shall be bonded to each disconnecting means enclosure.
If you try to look this up for yourself, be fore-warned! The code book is about 1 1/2" thick, and over 1000 pages. Normally, if you go to school to be an electrician, there will usually be a class dedicated to nothing but how to find what you need to know in the NEC book. It's layout is that complicated.
brett "dot" kitchens "at" marel "dot" com
Look for the new "Jedi" series portables!
Bat-Phone= BAT-CAVE (2283)
-.- .. ....- -.-. -.-- . .. ... -- -.-- -... .-. --- - .... . .-. .-.-.-
Look for the new "Jedi" series portables!
Bat-Phone= BAT-CAVE (2283)
-.- .. ....- -.-. -.-- . .. ... -- -.-- -... .-. --- - .... . .-. .-.-.-
The above seems to say (to the untrained ear) that the grounded or grounding conductor gets bonded or connected to just about everything. It doesn't mention the neutral conductor. I realize that at some point this becomes a grounded conductor and eventually connects to earth ground.
What it doesn't address is maintaining a separate neutral and grounding conductor, and where you're allowed to consider these one and the same. The point I was trying to make is that they are made one and the same only at one point, the meter or the first disconnect point within 3 ft of that. In some other panels (call them sub-panels), these still need to be kept separate.
Generator transfer switches do their own thing, but in my case it does not switch the neutral. My generator also has separate neutral and ground connections which are NOT tied together at the generator, but are all going to the transfer switch. Eventually the ground connection meets the system ground in the main disconnect panel which is on my side of the meter.
Sometimes I wonder about the electrical inspector's knowledge of the actual code vs what he/she thinks it should be, especially when a non-electrician (i.e. knowledgeable homeowner) is doing part of the job. I had much of my installation done by a licensed electrician, but the inspector just had to find fault with something, so he got me for (a) no electrical tape covering the exposed split-bolt-spliced earth ground, and (b) no marking on the generator disconnect switch outside the house.
Bob M.
What it doesn't address is maintaining a separate neutral and grounding conductor, and where you're allowed to consider these one and the same. The point I was trying to make is that they are made one and the same only at one point, the meter or the first disconnect point within 3 ft of that. In some other panels (call them sub-panels), these still need to be kept separate.
Generator transfer switches do their own thing, but in my case it does not switch the neutral. My generator also has separate neutral and ground connections which are NOT tied together at the generator, but are all going to the transfer switch. Eventually the ground connection meets the system ground in the main disconnect panel which is on my side of the meter.
Sometimes I wonder about the electrical inspector's knowledge of the actual code vs what he/she thinks it should be, especially when a non-electrician (i.e. knowledgeable homeowner) is doing part of the job. I had much of my installation done by a licensed electrician, but the inspector just had to find fault with something, so he got me for (a) no electrical tape covering the exposed split-bolt-spliced earth ground, and (b) no marking on the generator disconnect switch outside the house.
Bob M.
[quote="kcbooboo"]Sometimes I wonder about the electrical inspector's knowledge of the actual code vs what he/she thinks it should be, especially when a non-electrician (i.e. knowledgeable homeowner) is doing part of the job. I had much of my installation done by a licensed electrician, but the inspector just had to find fault with something, so he got me for (a) no electrical tape covering the exposed split-bolt-spliced earth ground, and (b) no marking on the generator disconnect switch outside the house.
Bob M.[/quote]
You should ask the electrical inspector to show you in writing where it says the split bolt connection on the earth ground connection is required to be covered by electrical tape. I don't think he will be able to show it to you.
You have to be somewhat careful as to which version of the NEC you are using. There may be a more recent one out, but if it hasn't been adopted by the local jurisdiction, they are probably going by an older one. You need to ask first of the electrical inspection department manager just which version of the code they are following.
Those of you that still think this grounding of the NEUTRAL bus or wire can be done anyplace along the electrical power distribution need to sit down and do some serious book reading for about a day. Go start by reading all the info in section 250 of the NEC and then migrate to what ever the other sections there it may send you to. Much of it depends on the type of installation. Also bear in mind that it changes.
Talk with the local electrical inspector. If there seems to be any confusion, ask the inspector to provide you with the source of his position. Do it gently as the inspector can make your life, work site, job, house the worst thing next to hell if he so desires.
Jim
Bob M.[/quote]
You should ask the electrical inspector to show you in writing where it says the split bolt connection on the earth ground connection is required to be covered by electrical tape. I don't think he will be able to show it to you.
You have to be somewhat careful as to which version of the NEC you are using. There may be a more recent one out, but if it hasn't been adopted by the local jurisdiction, they are probably going by an older one. You need to ask first of the electrical inspection department manager just which version of the code they are following.
Those of you that still think this grounding of the NEUTRAL bus or wire can be done anyplace along the electrical power distribution need to sit down and do some serious book reading for about a day. Go start by reading all the info in section 250 of the NEC and then migrate to what ever the other sections there it may send you to. Much of it depends on the type of installation. Also bear in mind that it changes.
Talk with the local electrical inspector. If there seems to be any confusion, ask the inspector to provide you with the source of his position. Do it gently as the inspector can make your life, work site, job, house the worst thing next to hell if he so desires.
Jim
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kf4sqb
- Posts: 1493
- Joined: Mon May 19, 2003 9:11 pm
- What radios do you own?: I can't enter that much....
Split-bolt spliced ground wire? Your inspector definately doesn't know what he is doing. Code specificaly forbids splicing a grounding electrode conductor by any means but a "non-reversable compression type" connection. A split-bolt is "reversable", in that it can be removed. The connections in a bus are, however, considered an acceptable means of splicing. There may be exceptions to this, but I'll have to go look for them.
Bob, read the definitions in my earlier post. The neutral falls under the catagory of a grounded conductor, especially when refered to as a "grounded service conductor", as the quoted article does. The grounding conductor is the "ground wire", and attaches to the grounding electrode, or ground rod.kcbooboo wrote:The above seems to say (to the untrained ear) that the grounded or grounding conductor gets bonded or connected to just about everything. It doesn't mention the neutral conductor. I realize that at some point this becomes a grounded conductor and eventually connects to earth ground.
brett "dot" kitchens "at" marel "dot" com
Look for the new "Jedi" series portables!
Bat-Phone= BAT-CAVE (2283)
-.- .. ....- -.-. -.-- . .. ... -- -.-- -... .-. --- - .... . .-. .-.-.-
Look for the new "Jedi" series portables!
Bat-Phone= BAT-CAVE (2283)
-.- .. ....- -.-. -.-- . .. ... -- -.-- -... .-. --- - .... . .-. .-.-.-
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RFNebraska
- Posts: 16
- Joined: Tue Feb 15, 2005 5:10 pm
Grounding of a Telecom Shelter
Over the last month, I've just gone through all these variations with a fine tooth comb to confirm what we already know. Think of two competing telecom providers sharing the same tower, and utility transformer. Each has their own electrical service and meter. Now they want to build and share ONE generator, instead of each building their own genny right next to each other.
1. The assumption some people make that the neutral is considered a grounding conductor is WRONG. The neutral conductor provides a RETURN path for currents that don't balance over the other HOT legs or phases. The SAFETY ground must NEVER deliberately carry return currents. If the neutral and ground wires are bonded in more than one place, they will SHARE the return current which is forbidden. The reason only one bond is allowed: Think TOUCH POTENTIAL and you will never go wrong. A wire with current running through a wire will have a voltage drop and this is why multiple bonds with the neutral are not allowed. You can have multiple ground connections to the safety ground, but not the neutral (on the same side of a xfmr anyway). Some exceptions apply, but they will all be considered wrt touch potential.
2. For a normal site, one electrical service and one generator, the alternator will have its neutral and ground ISOLATED. The generator FRAME will be bonded to any nearby metal building or fence within 7 ft or so (touch potential: Anything an adult can touch with hands outstreched must be bonded together). The ATS will have a SOLID neutral. Only the HOT poles get switched. The only neutral to ground bond is in the mains disconnect or meter.
3. It is forbidden to use the lightning protection system as the electrical ground. You must provide a separate electrcial ground which could be your 2 ground rods. However, again for touch potential reasons, you can BOND the electrical ground to the lightning protection grounding system... such as your buried perimeter ground. Best place to do this is underground with inspection portals. You can do it above ground too, but be reasonable how you do this. All conductors should not reverse their direction and go upward, no 90 degree bends, etc... Of course, all telecom sites will have this bond in place, else equipment damage will result. Having the two rods there seems silly, but they want those so there is no chance of loosing a ground reference if a contractor is ripping up and replacing, or rewiring the lightning ground system. Same idea as a non-reversible crimp connection in the electrical ground wire.
4. Don't even think about providing a bond to the utility transformer which is fed from a >1000V primary. It is tempting since Utility will drive their rod into sand and have an effective resistance of 800 ohms or more. It is their problem if they have to replace their transformer because your site ground is better then theirs, and their xfmr was acting as middle-man. Other than the service interruption you will suffer when the xfmr explodes.
5. Two shelters with separate electrical services want to use the same generator? One electrical service and a check meter would be easier. Otherwise the solution is to convert the generator to a BONDED neutral and ground. The customary 2 rods have to be added at the genny to provide a seperate electrical ground. Then bond the safety ground and generator enclosure to both shelter lightning ground systems, the nearby fence, etc. Each shelter must install an ATS with SWITCHED neutral. It is a bit more expensive (extra pole on the contactor) and special order so give yourself a few extra weeks for delivery. If you were to use a SOLID neutral, you would have created ground loops between the neutrals (two shelter service bonds) and thus would share current with the safety ground. Switched neutral is required.
Hope this example helps clarifies the issues.
RF Dude
1. The assumption some people make that the neutral is considered a grounding conductor is WRONG. The neutral conductor provides a RETURN path for currents that don't balance over the other HOT legs or phases. The SAFETY ground must NEVER deliberately carry return currents. If the neutral and ground wires are bonded in more than one place, they will SHARE the return current which is forbidden. The reason only one bond is allowed: Think TOUCH POTENTIAL and you will never go wrong. A wire with current running through a wire will have a voltage drop and this is why multiple bonds with the neutral are not allowed. You can have multiple ground connections to the safety ground, but not the neutral (on the same side of a xfmr anyway). Some exceptions apply, but they will all be considered wrt touch potential.
2. For a normal site, one electrical service and one generator, the alternator will have its neutral and ground ISOLATED. The generator FRAME will be bonded to any nearby metal building or fence within 7 ft or so (touch potential: Anything an adult can touch with hands outstreched must be bonded together). The ATS will have a SOLID neutral. Only the HOT poles get switched. The only neutral to ground bond is in the mains disconnect or meter.
3. It is forbidden to use the lightning protection system as the electrical ground. You must provide a separate electrcial ground which could be your 2 ground rods. However, again for touch potential reasons, you can BOND the electrical ground to the lightning protection grounding system... such as your buried perimeter ground. Best place to do this is underground with inspection portals. You can do it above ground too, but be reasonable how you do this. All conductors should not reverse their direction and go upward, no 90 degree bends, etc... Of course, all telecom sites will have this bond in place, else equipment damage will result. Having the two rods there seems silly, but they want those so there is no chance of loosing a ground reference if a contractor is ripping up and replacing, or rewiring the lightning ground system. Same idea as a non-reversible crimp connection in the electrical ground wire.
4. Don't even think about providing a bond to the utility transformer which is fed from a >1000V primary. It is tempting since Utility will drive their rod into sand and have an effective resistance of 800 ohms or more. It is their problem if they have to replace their transformer because your site ground is better then theirs, and their xfmr was acting as middle-man. Other than the service interruption you will suffer when the xfmr explodes.
5. Two shelters with separate electrical services want to use the same generator? One electrical service and a check meter would be easier. Otherwise the solution is to convert the generator to a BONDED neutral and ground. The customary 2 rods have to be added at the genny to provide a seperate electrical ground. Then bond the safety ground and generator enclosure to both shelter lightning ground systems, the nearby fence, etc. Each shelter must install an ATS with SWITCHED neutral. It is a bit more expensive (extra pole on the contactor) and special order so give yourself a few extra weeks for delivery. If you were to use a SOLID neutral, you would have created ground loops between the neutrals (two shelter service bonds) and thus would share current with the safety ground. Switched neutral is required.
Hope this example helps clarifies the issues.
RF Dude
Common generator for multiple users
RFDUDE is right on with the installation of a transfer switch for each user. Each separate transfer switch will need to have the switched neutral. This is not that uncommon to order.
Big problem here is where do you connect the control for the generator. It is possible to have an issue with one user blowing the main line fuse or circuit breaker in a storm due to better surge protection than the rest. If this happens, the power will be lost for them. Unless the generator control is on that service feed, the generator might not start.
Thinking along these lines, it may be better to have a control relay from each of the users. Each transfer switch will have a control panel. Anyone of them could cause this control relay to pull in. Just tie all the control relay contacts together in a parallel fashion. The contacts would be the start closure to start the generator. Use the DC from the generator battery as the coil voltage source. Use the generator start contacts in each ATS to pull the relay.
This way any one of the ATS panels could start the generator. Would take a little cooperation amoung the users and just a little talent to wire it up. Bottom line is it would work and ensure the generator was always available to anyone.
You would just have to work out who controlled the weekly exercise. The rest would have to bypass the auto test in their pannels. Problem with this is then you wouldn't get each of the ATS units to exercise into the load position on a regular basis.
Jim
Big problem here is where do you connect the control for the generator. It is possible to have an issue with one user blowing the main line fuse or circuit breaker in a storm due to better surge protection than the rest. If this happens, the power will be lost for them. Unless the generator control is on that service feed, the generator might not start.
Thinking along these lines, it may be better to have a control relay from each of the users. Each transfer switch will have a control panel. Anyone of them could cause this control relay to pull in. Just tie all the control relay contacts together in a parallel fashion. The contacts would be the start closure to start the generator. Use the DC from the generator battery as the coil voltage source. Use the generator start contacts in each ATS to pull the relay.
This way any one of the ATS panels could start the generator. Would take a little cooperation amoung the users and just a little talent to wire it up. Bottom line is it would work and ensure the generator was always available to anyone.
You would just have to work out who controlled the weekly exercise. The rest would have to bypass the auto test in their pannels. Problem with this is then you wouldn't get each of the ATS units to exercise into the load position on a regular basis.
Jim
Responsibility of Generator Ownership
Jim is correct in his assumptions. That is basically what is being done. For CAPEX and accounting reasons, no company likes to own part of an asset. So usually there is some "one-for-one" going on in the background with sharing multiple sites. The generator owner will wire all the alarms and monitoring, maintenance responsibility, refueling, power the parasitic loads and control generator exercise.
So for generator sharing, the "tenant" user will connect to the gen start circuit only (in parallel with the owner). No alarm or control, and their ATS has to have its exercise function disabled. We haven't gone to the additional coordination to have both users switch to generator for exercise under load purposes. For now, only the owner exercises under load.
Unfortunately, when a switched neutral ATS is requested from a vendor, only the more expensive transfer switches offer this option. The cheaper "light-commercial" / economy / mass produced versions (<=200A) don't seem to offer this feature.
Once you have a few of these on both sides of ownership, the site specific expenses tend to wash.
A point about the surge protection. I've been installing it adjoining the mains disconnect, not after the ATS. The assumption is that in most cases, the tower gets hit and the surge protection is offering a preferred path OUT of the site on the AC mains. In this way, any issues there, or mains fuse blowing, will not disrupt operation of the genny. And since the genny is tied to the extensive site ground system, in theory, it will float with the tower and shelter in the event of a strike, thus minimizing disruptive differential voltages. Some install the surge protection between the ATS and load panel, but I'm not convinced this is wise. Open to discussion.
RF Dude.
So for generator sharing, the "tenant" user will connect to the gen start circuit only (in parallel with the owner). No alarm or control, and their ATS has to have its exercise function disabled. We haven't gone to the additional coordination to have both users switch to generator for exercise under load purposes. For now, only the owner exercises under load.
Unfortunately, when a switched neutral ATS is requested from a vendor, only the more expensive transfer switches offer this option. The cheaper "light-commercial" / economy / mass produced versions (<=200A) don't seem to offer this feature.
Once you have a few of these on both sides of ownership, the site specific expenses tend to wash.
A point about the surge protection. I've been installing it adjoining the mains disconnect, not after the ATS. The assumption is that in most cases, the tower gets hit and the surge protection is offering a preferred path OUT of the site on the AC mains. In this way, any issues there, or mains fuse blowing, will not disrupt operation of the genny. And since the genny is tied to the extensive site ground system, in theory, it will float with the tower and shelter in the event of a strike, thus minimizing disruptive differential voltages. Some install the surge protection between the ATS and load panel, but I'm not convinced this is wise. Open to discussion.
RF Dude.
Re: Responsibility of Generator Ownership
You might want to check into the Asco model 300 transfer switches. They can be obtained with the switched neutral. They also take up much less space than most of the units that most of the generator companies are pushing.
Have installed a good number of them with no problems. Just don't get into a rush when trying to play with them. The timing circuits need to run their normal delays. Trying to rush the sequence will just get you hung up mid way. When this happens, it looks like the generator will not shut off. Just let the time delays run their course.
Jim
Have installed a good number of them with no problems. Just don't get into a rush when trying to play with them. The timing circuits need to run their normal delays. Trying to rush the sequence will just get you hung up mid way. When this happens, it looks like the generator will not shut off. Just let the time delays run their course.
Jim
Generator ATS
Thanks. I'll have a close look at them.
Been buying Zenith Controls (GE) which are very small at only 18"W x 24"H x 10" for the standard 200A.
Also KOHLER KDT which is marginally bigger, but has a better price point. Kohler also has neat engine controls that will now talk to the Monitor 3 software for integrated communication (MODBUS).
Both of these have a transfer switch similar to the ASCO (solenoid, not walking beam). Although, a walking beam would be easier for the cell site application. No need for a 50 ms transfer time.
Regards,
RF Dude.
Been buying Zenith Controls (GE) which are very small at only 18"W x 24"H x 10" for the standard 200A.
Also KOHLER KDT which is marginally bigger, but has a better price point. Kohler also has neat engine controls that will now talk to the Monitor 3 software for integrated communication (MODBUS).
Both of these have a transfer switch similar to the ASCO (solenoid, not walking beam). Although, a walking beam would be easier for the cell site application. No need for a 50 ms transfer time.
Regards,
RF Dude.