Pipe Bonding in Wet Location

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windandsun

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SE Michigan
We have a customer that requires RMC wherever raceway is used on the rooftop. We will be installing several islands of photovoltaic panels on the roof, which must be grounded, as well as the raceway, (per 690.43). The wiring beneath the modules will be exposed USE-2 (as permitted in 690.31 (B)), but the wiring will be in RMC where run between islands of modules. I had planned on using bonding bushings to comply with 690.43, where the RMC runs between islands of modules, but I can't find any that are listed for use in wet locations. Does anyone know of any type of mechanical grounding or bonding clamps that can connect bare solid 8 AWG to RMC (conduit sizes are from 1/2" to 1 1/4")?
Thanks, Wes
 
I am not aware of a "wet location" lock nut per se. I looked for one, but couldn't find it. But if its zinc plated, it should be fine, however I cannot confirm that.

If you really want to make it pretty, a myers bonding hub? Just my 2 cents.
 
windandsun said:
We have a customer that requires RMC wherever raceway is used on the rooftop. We will be installing several islands of photovoltaic panels on the roof, which must be grounded, as well as the raceway, (per 690.43). The wiring beneath the modules will be exposed USE-2 (as permitted in 690.31 (B)), but the wiring will be in RMC where run between islands of modules. I had planned on using bonding bushings to comply with 690.43, where the RMC runs between islands of modules, but I can't find any that are listed for use in wet locations. Does anyone know of any type of mechanical grounding or bonding clamps that can connect bare solid 8 AWG to RMC (conduit sizes are from 1/2" to 1 1/4")?
Thanks, Wes
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Unless I'm missing something, I think I would mount a steel box to the frame of each island, (1) locknut and (1) sealing locknut andlbond the first box. No bonding bushing
 
Pipe clamp preferable to Steel Box

Pipe clamp preferable to Steel Box

Thanks to both responders. In a rooftop installation, with open wiring permitted at the array, installing boxes and running RMC to them is not required by code, and would add a lot of time and cost. The lengths of RMC will serve as open-ended protective sleeves to provide protection for the wiring from physical damage where running between islands. Seems like there has to be a wet location pipe clamp available somewhere, but it's eluding me.
Thanks,
Wes
 
windandsun said:
Thanks to both responders. In a rooftop installation, with open wiring permitted at the array, installing boxes and running RMC to them is not required by code, and would add a lot of time and cost. The lengths of RMC will serve as open-ended protective sleeves to provide protection for the wiring from physical damage where running between islands. Seems like there has to be a wet location pipe clamp available somewhere, but it's eluding me.
Thanks,
Wes
Click to expand...

OK , I see. They definitely make them , I have one on my truck. It cost 51 bucks for 2" and will allow up to 1/0 bond. T&B
 
Correct me if I'm wrong. Technically those clamps are for copper water pipes not RMC.

Not that it wouldn't work, the DB clamp would adequately bond it, just thinking about it's intended purpose/listing.
 
nhfire77 said:
Correct me if I'm wrong. Technically those clamps are for copper water pipes not RMC.

Not that it wouldn't work, the DB clamp would adequately bond it, just thinking about it's intended purpose/listing.
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They make ground clamps that are suitable for a ground rod so why wouldn't that work for RMC?
 
nhfire77 said:
Correct me if I'm wrong. Technically those clamps are for copper water pipes not RMC.

Not that it wouldn't work, the DB clamp would adequately bond it, just thinking about it's intended purpose/listing.
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You are probably right, but since the local inspectors here want any mast that starts out in pvc, and goes up thru the roof in grc, bonded by using only a water pipe grounding clamp, so thats how I fly. My real pref was using a penn lug on the mast clamp that the poco secures to, but whatevers.... Get done and get paid.:):cool:
 
Cow said:
I thought those brass water pipe clamps were for any kind of water pipe, whether it's copper or steel?
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Actually if it is for copper tubing, it must be marked as such...

Ground clamps intended for use with ground rods and/or pipe electrodes in accordance with the NEC are marked with the size of electrode and electrode grounding conductor with which the clamp is intended to be used. Clamps suitable for use on copper water tubing are marked "Copper Water Tubing," or the equivalent, preceded or followed by the size of tubing. Ground rods, pipe electrodes and water tubing trade sizes are stated in fractions, such as 1/2, 5/8, etc.
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Excerpt from this UL web page.​


Additionally, using a clamp that is not the same metal as the RMC is likely a violation of...
344.14 Dissimilar Metals. Where practicable, dissimilar
metals in contact anywhere in the system shall be avoided
to eliminate the possibility of galvanic action. Aluminum
fittings and enclosures shall be permitted to be used with
steel RMC, and steel fittings and enclosures shall be permitted
to be used with aluminum RMC where not subject to
severe corrosive influences.
Click to expand...
 
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