should panels be grounded?

lazy_q

I am in the process of putting a system together and had a couple of questions about wiring practice.

I am wiring 2 Kyocera 130 watt panels in parallel with 10 gauge wire to a junction box on the roof of a fifth wheel. From the J-box to the controller I plan to use #4 gauge to a tri-star 60 amp charge controller. The charger is oversized for future expansion. The first question is whether or not the panels should be grounded.

If the recommendation is to ground the panel can you describe a preferred means of doing this. I read something that suggested the aluminum panel frame is not reliable long term because the screw would work its way loose. Is it reasonable to attach a ground wire to the mounting bracket. I was going to use stranded wire, but have some solid 10-2 with a ground. Is it a bad idea to use the solid wire?

Thanks for your advice.
ron q

niel

Re: should panels be grounded?

it should be fine to ground them from their designated spots on the frame with a gbl4-dbt on each pv seen here,
http://store.solar-electric.com/gbdbtsopagrl.html
if the pvs are to stay stationary then solid wire will do fine, but if angled or moved then stranded may be the better route.

lazy_q

Re: should panels be grounded?

Niel, thanks for the URL. The panels are stationery, and from your response I gather that it is necessary to ground the panels.

BB.

Re: should panels be grounded?

To be clear, there are two grounding questions:

1) The Aluminum Frame. Generally grounded to protect against Lightning and shorts if the glass gets broken (becomes a short between + side of PV array and chassis ground). For a metal RV--Lightning grounding is probably not an issue. For DC grounding, probably not a huge issue if the aluminum frame uses aluminum or stainless fastening hardware. Conceivably, the "system" is a bit safer because of frame grounding with copper bonding wire. However, I would be more concerned about getting a good mechanical mount where the hardware does not vibrate loose. And personally, I would not have a heart attack about panel grounding. If you are concerned about grounding--make sure that the grounding wire goes back to the steel frame of the RV and/or to the battery ground point.

Which brings up:

2) Grounding the negative side of the terminal... Generally, do not ground the negative side to frame ground. For many Solar Charge controllers, everything will work fine... But there are a few popular ones out there where grounding the PV Negative Lead can confuse the controller (it measures MPPT current in the negative PV lead). So, the one point the DC system should be grounded is at the Negative Battery Bus point (if you have a shunt to measure current, typically it is installed between the battery and the frame ground/negative bus point).

-Bill

lazy_q

Re: should panels be grounded?

Bill,

I would prefer not to ground the panels, but using the 10-2 with a ground in the wrapper encourages the grounding.
Great point about the chassis ground, . I was running the pv neg. directly to the charge controller. The charge controller neg. line goes directly back to the battery, so I don't think that I will have a problem.

regards,
ron q