power transfer switch with circuit breakers

slyttle · 11-26-2012, 01:16 PM

Hi there,

I'm in the process of designing a battery backup system for critical circuits in my house.

I'm currently searching for the most appropriate automatic transfer switch and secondary breaker box.

Ideally what I would like to find is a combo ATS and breaker box all-in-one, but so far this has alluded me.

The transfer switch I have in mind is the Aimes 3-way transfer switch

http://www.aimscorp.net/transfer-switches/

This one can switch between a battery backup, and a generator, and of course grid power ... and switch within milliseconds so voltage levels don't fluctuate too much.

This is the primary goal of the whole system.

If anyone can recommend a transfer switch / breaker box that his these kind of features I would be most grateful.

thx

-Sheldon

joed · 11-26-2012, 03:39 PM

The proper solution is to always run the critical loads through the UPS so that power failure does not interrupt the loads. That is the purpose of the UPS(Uninterpretable Power Supply). Then the generator takes over the grid power to the UPS supply before the batteries run down.

slyttle · 11-26-2012, 04:45 PM

yes, but I am basically building the UPS and the transfer switch and breakers are part of that.

ie. I have 600 amp hours worth of batteries, a 3000W inverter and a separate charger that plugs into grid power ... now I need an transfer switch, and that will basically completes the 'UPS' ... but I would rather have the transfer switch built into the breaker box so I don't have to buy the two separately.

Maybe such a thing doesn't exist. ... not sure.

joed · 11-26-2012, 10:14 PM

Run the output off the inverter. The charger needs to be large enough to feed the inverter and charge the batteries. Power goes off and the batteries take the load instead of the charger.
You are trying to reinvent the UPS.

mpoulton · 11-27-2012, 12:32 AM

To clarify, you do not want or need a transfer switch. The transfer isn't fast enough to keep critical loads up. You run a subpanel off the output of the inverter at all times, and put the critical loads on that panel. When power fails, the only change is that the batteries stop charging and start discharging. Make sure your charger is capable of handling at least the average load of the inverter, plus about 50% minimum overhead (to account for the inefficiency of the batteries and the inverter). So if your average load is 2kW, you need a 3kW charger at the absolute minimum.

slyttle · 11-27-2012, 07:12 AM

Many thanks! Appreciate the advice, and this saves me some money!