More grounding questions.

verdigo

Why is it not recommended to use solid bare copper wire? And if not solid is it ok to use insulated.... say 4 AWG?

Thanks

Dennis

BB.

Re: More grounding questions.

Basically, heavy solid copper wire is very difficult to bend and pull through conduit.

In the NEC, there is something about the largest diameter non-stranded cable you can use (something like 8 or 6 awg?).

Thick wire also does not tolerate bending well and will work harden and fail if bent very much.

Very fine wire (like welding cable) is actually quite difficult to terminate correctly and is not usually recommended for standard wiring (battery banks is one place where people will use fine stranded cable).

-Bill

Cariboocoot

Re: More grounding questions.

Also: one strand breaks in multistrand you still have ground. If there's only one strand and it breaks, you don't.

Insulation is more or less a waste of money on wire that normally carries zero current.

verdigo

Re: More grounding questions.

Okay. Thanks. Its just that the electrical supply stores are closed today and Lowes only sells solid wire. The weather folks are talking about severe thunderstorms tomorrow, and I was wanting to get some grounding completed. Guess I can just pull a couple of breakers though as I only have the DC side connected.

Thanks

Dennis

BB.

Re: More grounding questions.

What AWG wire are you trying to get? As long as you are not doing long pulls with lots of bends, you should not have any problems. I would not use solid cable, for example, from the battery bank to the inverter--Usually you are bending the cable more--and eventually--it will work harden and break.

-Bill

verdigo

Re: More grounding questions.

Its just from the e panel to the grounding rod, and the array to the grounding rod. This http://lib.store.yahoo.net/lib/wind-sun/E-Panel-wiring.pdf is the schematic that I am using. I bought and used some solid #4 bare copper for the array to ground rod. I have some 2 AWG insulated stranded wire that I bought and found too large for its intended use that I think will work for the E Panel to ground rod. Do I need to ground the battery negative to the ground rod as well? I didn't see one in Midnite's schematic.

Cariboocoot

Re: More grounding questions.

You don't see the negative battery post grounded on schematics anymore due to the implementation of the DC ground fault circuit interruption rules. Neither positive nor negative is connected directly to ground when using DC GFCI. Whether or not you use it is a matter of if it needs to meet code.

Some of us don't think the new rules are as much of an improvement as claimed.

verdigo

Re: More grounding questions.

Cariboocoot wrote: »

You don't see the negative battery post grounded on schematics anymore due to the implementation of the DC ground fault circuit interruption rules. Neither positive nor negative is connected directly to ground when using DC GFCI. Whether or not you use it is a matter of if it needs to meet code.

Some of us don't think the new rules are as much of an improvement as claimed.

So in addition to the ground fault breaker you would also earth ground the battery negative?

zoneblue

Re: More grounding questions.

No, one or other.

verdigo

Re: More grounding questions.

zoneblue wrote: »

No, one or other.

I don't think it would cause a problem, (earth grounding the battery negative) as the ground fault breaker only interrupts the positive PV input to the charge controller.

BB.

Re: More grounding questions.

verdigo wrote: »

I don't think it would cause a problem, (earth grounding the battery negative) as the ground fault breaker only interrupts the positive PV input to the charge controller.

Not really... The DC GFI setup uses an ~1 amp breaker (or fuse with some controllers) between safety ground and DC Return (typically the negative bus on the battery bank). This breaker (or fuse) is intended to be a current flow detector using "off the self" UL Listed components.

If there is a short from Hot to earth (or you can trip with a short from return to earth) causes current to flow therough the 1 amp breaker. The 1 amp breaker trips, and it is ganged with a ~60-80+ amp breaker which trips the breaker in the positive lead from the solar array (or charge controller to battery bank). In some installations, they may use two breakers to open both positive and negative array lines.

In general, there are huge problems with the 1 amp fuse between safety and earth ground. In any other UL/NRTL/NEC installation, it is not legal (or safe) to put a fuse between safety and earth ground. For some unknown reason, solar power systems wave this fundamental safety requirement.

Personally, I believe this is terribly unsafe and does not improve the other all safety of the solar array/power system--And it raises a whole bunch of system level design/ safety issues. But, it is in the UL/Code documentation and is (sort of) a requirement.

-Bill

verdigo

Re: More grounding questions.

I am in an area where solar is pretty uncommon. When speaking to the utility over the phone I got the impression that it wouldn't be a big deal to get it grid connected and inspected. I currently have not installed the ground fault breaker. I didn't know it was required. I ordered one last night because I don't want any hassles when I finally get it inspected. I will have the neg battery cable earth grounded inside the e panel in addition to the GFCI breaker.

Cariboocoot

Re: More grounding questions.

verdigo wrote: »

I will have the neg battery cable earth grounded inside the e panel in addition to the GFCI breaker.

No. It won't work that way. It can't. The GFCI has to check for current between ground and negative, which indicates the positive has come in contact with ground connection somewhere. If you ground the negative any current flow between it and ground is unmeasurable. The GFCI should interrupt both power sides (with a small resistor contacting between (-) and GRND) to be effective.
MidNite's has one pole: http://www.solar-electric.com/mndc-gfp.html
The second 'mini breaker' is what trips on account of negative to ground current and is ganged to the main breaker.
Outback's has two poles: http://www.solar-electric.com/obdc-gfp2.html
Read the manual on that one: http://lib.store.yahoo.net/lib/wind-sun/Outback-GFDI.pdf
Pay particular attention to the wiring diagram on page 8.

Either use the DC GFCI or ground the negative. Not both.

Like Bill, I do not believe this 'protection' is particularly advantageous but is potentially problematic.

verdigo

Re: More grounding questions.

Got it. I ordered Midnite's 80 amp version last nite.

Thanks

Dennis