I learned a new trick today.
Searching around for stuff Brian could use, the first thing I was looking for was a disconnect switch or load switch rated for his high voltage DC. I found quite a few, but they don't give that stuff away. Yikes$$$
Anyway, after reading a number of spec manuals from ABB, Allen Bradley, Square D... I came across some info on using these AC rated load switches with DC.
The pic is of an ABB 16amp 3 pole AC load switch. Designed primarily for 3 phase equipment.
Look at the top row of terminals marked 1L1, 3L2, 5L3, then the bottom row marked 2T1, 4T2, and 6T3.
Here's the LEGAL trick. If you bring your high positive VDC into 1L1 from the PV, then run a wire from 2T1 on the bottom to 3L2 on the top, and do the same and run a wire from 4T2 on the bottom to 5L3 on the top, then connect 6T3 to your load, which is the heater, the switch is now rated for 220VDC at 16 Amps. These are ABB's published ratings, and is legal to use in this manner per NEC code. If you just ran it thru 1 contact, it's only rated for about 48VDC, but series wiring the 3 contacts bumps it up quite a bit.
ABB does make a purely DC rated load switch for PV, but it's >4X the dollars.
You can use this as a disconnect and a means of turning on and off your heater as long as the load side from 6T3 is fused properly.
List price is $40.98 each from:
Kendall Electric There is some additional hardware you need and a NEMA rated enclosure to mount it in, if an inspector is on the prowl
We'll cover that later. I logged into our account at Kendall and it's like $9.00 cheaper, but I could just email it to our account manager for a quote and he'll get me a few more bucks off. Free shipping as well. (They deliver every day to the shop)
Also ran across that NEC2014 requires that every solar installation must have a means of disconnecting PV panels from the load they are supplying, and this fits that code for this application.
I'll have more later.
