Missing bonding on off grid PV system?

[Vikki P]

I'm going through my newly built off-grid home in preparation for rough electrical inspection Monday. My electrical contractor is on vacation for the next few weeks so I agreed to be present for the inspection.

I believe the PV system is okay - the panel mounts are bonded to the main #4 ground cable, which is connected to a ufer. The PV inverter is split phase 240 with neutral and ground separated, the bond is made at the main electrical panel.

All plumbing, including the supply line from the well, is PEX except the first 18" of the water heater connections and some copper stubouts. Fuel gas is LP and piping is black pipe.

Neither the on-demand LP hot water heater nor the LP furnace have a bond between the gas pipe and the #4 ground.

Should there be bonds between the black pipe and the #4? Between the short lengths of copper at the hot water heater? I tried to call the contractor but I'm getting his work voicemail.

In Michigan, if it makes a difference.

 

[jaggedben]

The code requires bonding the gas, but if the equipment grounds for the furnace and water heater circuits bond the frames of those appliances then that is likely sufficient. Personally I wouldn't worry about such short lengths of water pipe, which again may be bonded by the circuit equipment ground for the water heater. If you want to go the extra mile it is code compliant to bond the pipes to the grounding electrode conductor (the #4 ufer ground).

Ideally the 'main' #4 ground to the ufer goes to the main panel. This is more important than the PV panel frames being directly connected to it. (The PV panels should still definitely be bonded to the ground bar in the inverter.) Just saying because you didn't mention.

 

[ggunn]

Do off grid PV systems get inspected? Who is the AHJ?

 

[Vikki P]

The code requires bonding the gas, but if the equipment grounds for the furnace and water heater circuits bond the frames of those appliances then that is likely sufficient. Personally I wouldn't worry about such short lengths of water pipe, which again may be bonded by the circuit equipment ground for the water heater. If you want to go the extra mile it is code compliant to bond the pipes to the grounding electrode conductor (the #4 ufer ground).

Ideally the 'main' #4 ground to the ufer goes to the main panel. This is more important than the PV panel frames being directly connected to it. (The PV panels should still definitely be bonded to the ground bar in the inverter.) Just saying because you didn't mention.

@jaggedben Thanks for the thoughtful response. The AC panel is grounded with a continuous #4 to the ufer, and the PV array also connects to a ground lug in the main panel, which is bonded to PV (service) neutral at the AC panel.

The furnace is permanently connected to power, so should be fine, but the hot water heater is a cord-connected appliance and should then be bonded, correct?

I believe the well pump and pressure tank are taken care of by the EGC that ties the deep well pump EGC to the pressure switch ground screw and EGC of the supply circuit.

After a quick trip to the hardware store, I picked up and installed a pipe bonding clamp and split bolt with a foot of #4 left over from the install and installed on the gas supply to the hot water heater.

Do off grid PV systems get inspected? Who is the AHJ?

NEC covers PV systems on- or off-grid and Michigan code incorporates NEC, so our five-county building authority is our AHJ.

 

[wwhitney]

the hot water heater is a cord-connected appliance and should then be bonded, correct?

NEC 250.104(A) calls for a "metal water piping system" to be bonded. A common interpretation where the only metal water piping is the required stubs at the water heater, and everything else is plastic, is that there is no metal water piping "system," so no bonding is required.

On the other hand, bonding the water heater won't cause any harm, and a zealous AHJ might consider it a "system."

Cheers, Wayne