ECN Forum Forums General Topics of the Trade General Discussion Area APC wall mount Transfer Switch

This Transfer switch has been on the market for a few years and it is listed as a part available from Honda. I can't find another electrician in my area who has used it. Everyone uses the Gen Tran type for portables. First time I've seen one of these APC units... also claims that it is UL 1008 approved?

If this is like all the other small transfer panels, those onboard fuses are bypassed in utility mode and only in the circuit when the switch is in the generator position where the APC’s on board processor and current sensors would likely have control of everything. Likewise when in the generator position the utility side OCP in the normal circuit panel is bypassed, so I don’t think coordination should be an issue. Since you have to set the circuit Amps for each circuit at setup for anything over 15A, I’m guessing the APC’s big brain is monitoring circuit Amps as well as everything else so the only time an internal fuse could probably blow is if the CPU malfunctioned or some other catastrophic event took place in which case simply replacing a fuse would probably be the least of the HO’s problems.
They also mention remote start capability for this unit, but they say the generator must remain plugged in for this function. Would it be a violation to keep a portable backup generator permanently connected with a cord and L14-30 plugs?

APC is a big supplier of Uninterruptable Power Supplies...

So a UPS can also be connected to this transfer switch.

I think the switch is OK...just not sure if some of the design is code compliant. Overcurrent devices for the most part should be readily accessible 240.24

Here is a link to a more informative video on the product...

http://www.hondapowerequipment.com/flash/hp2s/ml.rwp41t91.index.html

I see that for Legally Required Standby Systems, 701.25 Accessibility states that the branch circuit overcurrent devices shall be accessible to authorized persons only, but I don’t see anything at all mentioned in 702 for Optional Standby Systems, which is what a setup like this would normally be. So not sure, but maybe it is up to the manufacturer if they want the HO to be able to access them or not. I may have to flip through the UL white book later on and see if anything pops up.

The loophole in 240.24 is for supplemental protection. I suppose of the APC is monitoring current and holds it below 15 or 20 the fuse should not blow ... or at least that is the design that was presented to U/L.

Greg...the fuses inside the switch aren't supplemental when the unit is operating on generator power...right? So if there is a shortcircuit in a circuit fed by the transfer switch when on standby power, the cartridge fuse inside the unit will blow. Now the owner can't fix that without opening up the unit to replace the fuse. They will need an electrician to do this. Fine with me...I could use the work.

But I thought overcurrent protection should be accessible to the owner to fix/reset safely?

Also the owner can't shut off a circuit if they needed to?

shortcircuit

Well, I haven’t been able to find anything in the UL white book that refers to the overcurrent protection used with these transfer switch type panels and the UL 1008 standard that is mentioned by the manufacturer doesn’t seem to address this either.
Now I’m also wondering how this fancy type of UPS/generator backup transfer panel would handle the bypassing of AFCI and GFCI circuit breaker protection on generator power any different than a regular GenTran or Reliance panel would. This is another reason I generally prefer an interlock kit or dedicated generator backup panel.