120v/240v Subpanel Transfer Switch

[mattT]

Hello,

I am planning a critical loads backup system from 200A main panel + 100A subpanel but need help understanding something fundamental about my situation. For budgetary reasons, my goal is to only backup 120v. I have critical circuits split between the two panels, the main being in the garage, where I would install the transfer switch, and the subpanel located in the basement. The subpanel is fed off the main panel by two 80A breakers and contains three non-critical 240v circuits.

I'm really struggling to come up with a solution that meets my 120v only goal. Is it a transfer switch at each panel + extension cord run to the subpanel? or a separate 120v panel off the subpanel? Any ideas would be appreciated, thank you in advance.

 

[42OhmsPA]

Diagram would be helpful.
I don't think you'll be able to make it work without pulling your critical loads wires from the sub panel back to the transfer switch location. Is everything ran in conduit?
Also 2 80 amp breakers to the sub is confusing, do you mean a double pole 80 amp?

 

[Mattb4]

Your present setup does not lend itself to an easy solution. Two transfer switches (one at each panel) with critical load sub panels or one of those generator transfer switches with load breakers, to each might be the only possibility. You would have to bring your backup power wires to both locations.

 

[OzSolar]

If I'm following you I can offer that did something similar with with one of these Reliance transfer switches installed on the main panel. Then I ran a circuit from this transfer switch to a new panel that I installed in the basement. It took some drilling and conduit but overall it wasn't that bad. Since the wiring in the basement readily accessible I moved the circuits I wanted to backup to the new panel.

 

[NEpowerandlight]

I'm doing something kind of similar but I'm a newb and not an electrician so I can't offer a solution. However your situation brings a couple questions to mind.


Is it possible to run the backup power to the sub panel equipped with an interlock to lock out power coming from the main panel? You'd have to manually shut off the 3 non critical 240 circuits in the sub panel before engaging the interlock.

Then run a 120v circuit from the sub panel back to a transfer switch at the main panel?



In my case I have split phase output from my inverter which will feed a sub panel. I'll run a 40a circuit from my sub panel back to my main panel equipped with an interlock to lock out grid power. I don't anticipate having my inverter power my main panel unless my generator stops working. My main panel is backed up by a split phase capable generator hooked to a transfer switch.

 

[mattT]

Wires from the main panel to the sub panel are not in conduit. Yes, double pole 80 amp is what I meant. ?

As OzSolar said, I'm leaning towards running a circuit from a transfer switch on the main panel to a new panel next to the sub panel to which I will move the critical loads circuits. This is a newer, well insulated spray foamed house but I think it will not be too difficult to run wires from the main panel in the garage through the subfloor to the sub panel location.