DC Manual X-fer Switch?

[TwoBlocked]

The customers in the gas field sometimes have some odd ideas, which are then interpreted by salesmen. The requirements are to provide 40 amps 24vdc from either utility power or from solar/battery power. Am looking for a door mounted manual transfer switch rated for 24VDC and at least 40 amps. I can find many options for AC, but need something that is rated for DC on the spec sheet. Any suggestions?

Oh, and want it to be double pole, switching both the Pos and Neg

 

[coop3339]

You could maybe use AC breakers that is dual rated for DC like a Square D QO and install it in a small panel with a generator breaker interlock.

 

[solarken]

You could use something like a Schneider 199X-18 DPDT relay and a manual dc switch to operate the coil off the Solar/battery source, or wire the coil to the utility DC supply and have it switch on loss of power automatically.

 

[TwoBlocked]

Originally I suggested an ATS, but "they" wanted to keep it "simple." Later... "they" thought having a normally closed 120vac coil contactor that would open the battery/solar power when there was ac to the DC power supply would work. I talked "them" into also installing a normally open 120vac coil contactor that would open the power supply power when there was NOT ac to the DC power supply. (I don't like the idea of backfeeding a power supply.) And then I will slip in a timer relay so it doesn't bang back and forth if a recloser on the utility side is cycling. Hmmm, kinda like an ATS.

But seriously, I think a manual x-fer switch rated at 60A AC would hold up with a 40A DC load. Just couldn't find one where DC was listed on the spec sheet.

Funny thing is, there isn't utility power at the site, and haven't heard when there might be. We're planning on running a bunch of 240vac heat trace as part of the job...

 

[solarken]

But seriously, I think a manual x-fer switch rated at 60A AC would hold up with a 40A DC load. Just couldn't find one where DC was listed on the spec sheet.

Funny thing is, there isn't utility power at the site, and haven't heard when there might be. We're planning on running a bunch of 240vac heat trace as part of the job...

Midnite makes a transfer switch that is made from the Big Baby box, 2 DP breakers, and a sliding interlock. It comes with AC rated breakers but they have DC breakers that would probably fit. Maybe call them and ask.
https://www.midnitesolar.com/productPhoto.php?product_ID=416&productCat_ID=29&sortOrder=3&act=p

 

[PWDickerson]

You could maybe use AC breakers that is dual rated for DC like a Square D QO and install it in a small panel with a generator breaker interlock.

You should consider this option. It would cheap and easy to install. Lots of folks are not aware that Square D QO breakers up to 70A are dual rated for AC and DC. A breaker interlock in a small 100A 6-space QO panel might be a workable solution. I used a QO panel as a battery combiner panel once, and it worked quite well.