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#171244 - 11/22/07 10:45 PM ham radio grounding issue
watersparkfalls Offline
Member

Registered: 03/08/05
Posts: 210
Loc: Washington...Not DC
I have a cutomer building a new house, which he will have a ham radio. something about interference all outlets(not lighting) need to be on same circuit. he said he brought a 30 amp into his existing set up(at old house/future old house)and tapped 120 volt outlets off that, and drove ground rod down. I suggested putting a sub-panel and feeding ham radio 30 amp/240 volt outlet and 120 volt outlets from here.
he wants to drive a ground rod for radio, but i think that would be a violation since it wouldn't be tied with service ground rods. wouldn't the ground be well established with the four wire i feed sub with? that it would mitagate need for additional ground? and if additional ground rod neccessary then it would have to tie with the two at service which really would be redundant...of course the other suggestion could be to run 4 wire and a single gounding from service rods to sub panel. dont know much about ham radios and this interference he's worried about.

any help, comments appreciated.
thanks,
H2O


Edited by watersparkfalls (11/22/07 10:46 PM)

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#171247 - 11/23/07 07:02 AM Re: ham radio grounding issue [Re: watersparkfalls]
Tom Offline
Member

Registered: 01/01/01
Posts: 1069
Loc: Shinnston, WV USA
You can drive the ground rod your customer wants and connect it to the equipment grounding conductor at the proposed sub-panel or the transmitter. This rod does not need to be bonded to the other electrodes that may be present. See 250.54

Just remember that the earth cannot be used as the return path for ground faults, the sub-panel must have an equipment ground.
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#171248 - 11/23/07 07:16 AM Re: ham radio grounding issue [Re: Tom]
WESTUPLACE Offline
Member

Registered: 03/29/04
Posts: 252
Loc: Kingwood, TX USA
Big mistake not to bond the grounds together. All grounds need to be at the same potential. If lightning comes into the power line, and the radio ground system has a lower impedance than the power ground, the surge will seek the better ground THRU the radio. All grounds at the same potential, any voltage rise will be equal in the grounding system with no current flow, no damaged equipment. This is a code requirement. I install communications equipment, cell sites, radio towers,etc. We bond ALL grounds together. When bonding several ground rods together, do not use a complete loop, as this will create inductance, limiting current flow. (I teach a grounding course to Ham groups and others)Robert


Edited by WESTUPLACE (11/23/07 07:18 AM)

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#171253 - 11/23/07 08:26 AM Re: ham radio grounding issue [Re: WESTUPLACE]
sparkyinak Offline
Member

Registered: 07/08/07
Posts: 1286
Loc: Alaska
If the electrical system is wired properly then additional ground rods are not needed. If the customer still wants additional ground rods and want to pay for them, put them in but they HAVE to be bonded together. As for the interference issue, I presuming (never assume) that what he is talking about is when dealing with ampliphiers, you want them on the same phase. you could get poor performance since the electical "push" through the equipment is 180 dergees out of since. I do not think this is an issue with todays electronics.
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#171265 - 11/23/07 11:36 AM Re: ham radio grounding issue [Re: sparkyinak]
Alan Nadon Offline
Member

Registered: 03/10/05
Posts: 398
Loc: Elkhart, IN. USA
Fourth wire from service to sub panel will establish the bond for a supplementary ground rod. Recommend a #8 Cu even if the circuit is 30 amp wired with # 10 Cu.
See 250.54
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#171280 - 11/23/07 06:21 PM Re: ham radio grounding issue [Re: Alan Nadon]
Tom Offline
Member

Registered: 01/01/01
Posts: 1069
Loc: Shinnston, WV USA
After reading WESTUPLACE's post, I think you should explore this interference/grounding issue with your customer some more and perhaps post them again so WESTUPLACE can give us some additional guidance. I have the feeling that your customer may not be explaining his concerns properly. Though I am not a HAM operator, I'd like to find out what your customers problems might be and what the solution really is.

Supplementary grounding electrodes do not have to be bonded to other electrodes on the premises. The requirements of 250.50, 250.53(C) and 250.56 do not apply to supplementary electrodes.
_________________________
Few things are harder to put up with than the annoyance of a good example.

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#171282 - 11/23/07 07:06 PM Re: ham radio grounding issue [Re: Tom]
sparkyinak Offline
Member

Registered: 07/08/07
Posts: 1286
Loc: Alaska
 Originally Posted By: Tom


Supplementary grounding electrodes do not have to be bonded to other electrodes on the premises. The requirements of 250.50, 250.53(C) and 250.56 do not apply to supplementary electrodes.


You have my undivided attention. Please reference where it is kosher NOT to bond all the grounding electrodes together inthe NEC that applies to the ham radio issue.
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#171289 - 11/24/07 07:14 AM Re: ham radio grounding issue [Re: sparkyinak]
Tom Offline
Member

Registered: 01/01/01
Posts: 1069
Loc: Shinnston, WV USA
 Originally Posted By: sparkyinak



You have my undivided attention. Please reference where it is kosher NOT to bond all the grounding electrodes together inthe NEC that applies to the ham radio issue.


I don't see anything in Article 810 that would require a supplementary grounding electrode that is connected to a sub-panel or equipment ground of the radio equipment to be bonded to all other electrodes. If the ground rod was connected to the antenna mast or an antenna discharge unit, then there is definitely a requirement to do so.

Of course, I could be wildly mistaken, wouldn't be the first time.
_________________________
Few things are harder to put up with than the annoyance of a good example.

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#171292 - 11/24/07 09:19 AM Re: ham radio grounding issue [Re: Tom]
Alan Nadon Offline
Member

Registered: 03/10/05
Posts: 398
Loc: Elkhart, IN. USA
When the supplementary ground rod is bonded to the ground in the sub panel it is also becoming bonded to the service, and all the grounding electrodes that the service is bonded to.
The hazard arises when the supplementary ground rod is not bonded to the system ground but, is isolated. That is when the Earth becomes the only link between the two rod systems, and it is prohibited.
_________________________
Alan--
If it was easy, anyone could do it.

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#171303 - 11/24/07 03:48 PM Re: ham radio grounding issue [Re: Alan Nadon]
n1ist Offline
Member

Registered: 02/13/02
Posts: 176
Loc: Malden MA
The supplementary ground must be tied into the system ground. This ground is an RF ground; the conductors between the radio or tuner form part of the antenna's tuned circuit and must be short to be effective. The service ground is usually too far away to be useful at RF.

In reality, he probably wants to set up a ground window or ground plate to form a single-point ground where all of the cables enter the shack. This plate would have all of the lightning arrestors on it and should be bonded to the RF ground as well as the power ground. Ideally, all cables entering the shack should go thru arrestors on this plate.

They may want to look at the tech notes at http://www.polyphaser.com for more info on grounding and lightning protection.

Placing a subpanel in the shack is a very good idea; I would use a main breaker to give a single point to shutdown everything in the room (except the lights) in an emergency.

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