Bolted Pressure Switches - Suitability for Reverse Feed

[RealGood_JDub]

I am wondering if anyone has had issues interconnecting on the load-side of bolted pressure switches (particulary the Eaton Pringle variety). Typically, the switches have a "Load" marking which (I would assume) is to make certain that the switch is wired such that the fuses don't remain live. The "Load" marking, therefore, is not an indication of the pressure switches suitability for reverse feed.

Intuitively, the fuses shouldn't care which way the power is flowing (GFP issues??). It's often difficult/impossible to pry the "suitable for reverse feed" go-ahead from the manufacturers. My only thought is that the inspector could kick it back thinking the fuses would remain live from the PV, which is not possible for my grid-tied inverters.

I've spoken to Square D about their devices, the tech's only concern was that the older switches have the potential to stick (which isn't really an issue with reverse feed, but with the switch itself).

Relevant Note:
These systems will be installed in NY state.

P.S. Is anyone aware of a centralized place for documentation regarding the "suitability for reverse feed" of breakers/switches. We have "gosolarcalifornia" for module information, but it seems like this place should exist for SFRF info as well.

Thanks for all your help in advance.

 

[BillK-AZ]

If these are in a SES that has ground fault protection, you have a problem. Four years ago I surveyed many potential schools for a local utility that was donating some PV systems.

One school has GE service equipment with a Pringle fused switch and GFP. GE advised: " If the existing switchboard is a fused switch type switchboard, please consult with GE C&I or an authorized distributor to find out if breaker-mounting hardware is available for the existing switchboard.". So basically, they said NO.

An engineer I talked to at Pringle said that he saw no practical problem with backfeeding, but that the switches have not been listed for backfeed because there is no requirement (or special method) for this testing in the UL-489 standard. These Pringle switches are usually used with a Electromagnetic Industries BGFL 159-1200 Ground Fault Relay. Made by another company. A discussion with Electromagnetic indicated that the BGFL would not be affected by any backfeed on the switch and that any listing for suitability would have to be the responsibility of the company that integrated the BGFL with a Pringle or other switch in a service entrance.

Years earlier I researched a factory with an older GE 1200A 480-volt service entrance with a GE fused switch with GFP. GE stated that this switch could not be backfed because the GFP circuit depended on the load side voltage reducing to zero quickly when the GFP was tripped because the coil that tripped the switch was powered from the load side and if a PV system (or other backfeed) kept the load side voltage on even for a few cycles, the coil would be burnt.

The Electromagnetic BGFL stores energy in a capacitor to trip the switch and can not overload a trip coil.

Hope this helps your understanding.

 

[RealGood_JDub]

Many Thanks, phenomenal response time.
It seems your experiences are very similar to mine...most manufacturers (or at least their app. engineers) are very reluctant to make any statements about SFRF. Most of my conversations involve them repeating, "Any modifications will void the UL listing" like some sort of robot. I can see where they're coming from I guess. I can also see the potential issues with harming the GFP as a primary bone of contention. It was great to get your insight, you sound like you've had your hands on this stuff, whereas I'm more of a pencil pusher.

UPDATE: Yesterday afternoon I reached out directly to Eaton. I was amazed at how quickly they responded to my request. They provided me with a "Solar Applications Letter" stating that they (Eaton) self-certify the Pringle Switches suitability for reverse feed. This included all the additional options, GFP, phase loss, etc.

It seems Eaton has made this 'leap of faith', hopefully more manufacturers will be providing SFRF documentation like this soon!