RVIA HV DC Solar Recommended Practice

[gklott]

Several owners on this forum and FaceBook mention going with larger solar arrays - meaning 3 or more panels. Should you decide to interconnect any solar panel combination resulting in a DC voltage >= 60 V, I’ve attached the RV Industry Association’s (RVIA) recommended practice for RV mounted high voltage solar arrays.

This recommended practice is in addition to the RVIA Low Voltage standard, the NFPA 1192 Standard for RVs, and the National Electric Code §690 and §551. I previously posted about solar ground fault detection when you mount more than 3 PV panels on your trailer.

As stated in the document, this attached RVIA recommendation is available free at the RVIA store under standards.

73/gus

[Perry Butler]

Originally Posted by gklott

when you mount more than 3 PV panels on your trailer.

I believe that should read "more than 3 PV panels in one circuit on your trailer."

Used to have a Minnesota low-voltage electrical license (now called Power Limited), but used for ethernet, cable TV, and PA systems (rarely) so that just makes me dangerous and 12v camper wiring/solar was new to me. When I talked to our state board two years ago they said I can have three circuits on my camper. Never asked about more than three, and GFPD was not mentioned.

My intention for our new camper is to have two or three 24v panels on one circuit (controller) wired in parallel and perhaps one 12v or 24v panel on another circuit. The third circuit is our portable. I do ground my controllers and use in-line fuses.

When I get home I'll contact them about wiring practice for GFPD. Perhaps my pacemaker should not have a good jolt!

I do know that I've never read about GFPD on Will's DYI Solar Power forum, but perhaps I just plain missed it. However, have also seen many bad schematics there too.

Enjoy,

Perry

[gklott]

Originally Posted by Perry Butler

I believe that should read "more than 3 PV panels in one circuit on your trailer."

Recommend reading the NEC §690.41(B) reference provided in the linked post.

73/gus

[Centex]

Suggest that for the purposes of this High Voltage DC Solar Recommended Practice document folks not get distracted by the count (number) of panels in any given PV Array.

The Scope statement makes it clear that this Recommended Practice document applies to any and only PV systems having 60-150VDC on any circuit in the system (150VDC being the recommended absolute maximum for such systems in RVs).

VDC, not the number of panels, defines the applicability of this Recommended Practice; I don't find any mention of any criteria relating to the number of panels in a system in this Recommended Practice document (please correct me if I missed that).

Note that there are any number of possible and practical PV configurations employing 3 or more panels which do not fall within the scope of this Recommended Practice document (e.g. configurations such as mine with 4x '200W nominal rated' panels in all-parallel or combined series-parallel arrays having a maximum open-circuit voltage of less than 60VDC at any and every point in the system).
___________________

For systems within the Scope of this Recommended Practice I find section 4.4. Photovoltaic Array Emergency Disconnect particularly interesting / onerous:

• Interesting in that the recommended disconnect act on the positive conductor (rather than both positive and negative conductors as I believe I've seen suggested by others)
• Onerous in the recommendation that this disconnect be located on the roof of the RV before any circuit enters the RV (apparently without regard to applicable cable ampacity or other protective devices between the PV source and entry to the RV) while also being "readily accessible", thus effectively requiring an invariably rather expensive and often bulky remote-controlled disconnect rated for both the voltage and current involved. Weather-protection for that type of disconnect mounted on the roof could be a sporting challenge in itself.

[gklott]

Originally Posted by Centex

Suggest that for the purposes of this High Voltage DC Solar Recommended Practice document folks not get distracted by the count (number) of panels in any given PV Array.

The Scope statement makes it clear that this Recommended Practice document applies to any and only PV systems having 60-150VDC on any circuit in the system (150VDC being the recommended absolute maximum for such systems in RVs).

VDC, not the number of panels, defines the applicability of this Recommended Practice; I don't find any mention of any criteria relating to the number of panels in a system in this Recommended Practice document (please correct me if I missed that).

Note that there are any number of possible and practical PV configurations employing 3 or more panels which do not fall within the scope of this Recommended Practice document (e.g. configurations such as mine with 4x '200W nominal rated' panels in all-parallel or combined series-parallel arrays having a maximum open-circuit voltage of less than 60VDC at any and every point in the system).

You are correct on the voltage on any panel string being the determining factor when using this recommendation. The “3 or more panels” has caused confusion. My intent was that you would need to go beyond the two ETI installed panels to possibly reach this voltage.

Yes, if you string together any number of panels where the string voltage >= 60V, you should consider implementing this recommended practice. There are many combinations where the a string voltage will be < 60 VDC.

However, if you do install 3 or more panels, installation should follow NEC §690.41.(B), as quoted in the linked post.

Thanks for your input. Hope that clarifies the issue.

73/gus

[gklott]

Originally Posted by Centex

For systems within the Scope of this Recommended Practice I find section 4.4. Photovoltaic Array Emergency Disconnect particularly interesting / onerous:

• Interesting in that the recommended disconnect act on the positive conductor (rather than both positive and negative conductors as I believe I've seen suggested by others)
• Onerous in the recommendation that this disconnect be located on the roof of the RV before any circuit enters the RV (apparently without regard to applicable cable ampacity or other protective devices between the PV source and entry to the RV) while also being "readily accessible", thus effectively requiring an invariably rather expensive and often bulky remote-controlled disconnect rated for both the voltage and current involved. Weather-protection for that type of disconnect mounted on the roof could be a sporting challenge in itself.

This parallels the NEC quick disconnect requirement on buildings to protect first responders from life-threatening voltages. Hope there will soon be some listed disconnects for RV use. The marketplace quickly responded with products for building use.

Suspect this will apply to few Escape owners.

73/gus