Critical load panel & transfer switch?

[electro7]

Hi,
I am installing an interactive system with battery back-up. My customer wants a few of his shop circuits on the critical load panel. The issue I am having is his shop is 150ft+ away with 4/0 aluminum wire feeding his sub panel. I think it will be nearly impossible to pull new wire in that conduit to get circuits from there onto his critical load panel. I was thinking about using an automatic transfer switch between his feed from the service and the shop and adding the critical load circuit to the transfer switch. So when power goes out he has power from the critical load panel to his shop. The question I had was if the breaker from the critical load panel to the transfer switch was hot all the time if it would mess up the automatic transfer switch? I would rather set it up for him where everything is automatic. So when power goes out he does not have to go out to the critical load panel and turn on the breaker for his shop feed.

Hopefully this all makes sense.

Thanks

 

[BillK-AZ]

As I understand, your need is to be able to turn off the non-critical loads in the shop when on the backup system.

Suggestions:

1. Install a second, smaller UPS backup in the shop for those critical loads and do not power the shop when on main backup.

2. Put the shop on the critical load side of the transfer switch and use relays operated by a control signal to disconnect the non-critical loads. Problem is controlling the relay if you do not have any other lines running to the shop. Something like a X10 wireless remote switch might do the control of the relays.

 

[jaggedben]

... I was thinking about using an automatic transfer switch between his feed from the service and the shop and adding the critical load circuit to the transfer switch. ...

If it is possible to do this, then why is it not possible to simply feed the shop from the critical loads panel? I'm confused about the situation.

 

[tallgirl]

There's a lot about this that is seriously confusing. If the only thing connecting the battery backed system to the workshop is a set of 4/0 conductors, the only way to control what stays on when running on backup power is to run additional signalling conductors. They'd have to switch off all non-critical loads in less time than the inverter would decide it was feeding a short and shut down.

The "grid connected" conductors absolutely must be switched off when the grid drops because otherwise the inverters are likely to die from over-current before any amount of logic, including X-10, gets the loads switched off. I think my inverters will feed 70 amps for 6 cycles. I think anything much more than that and the inverter just plain gives up immediately. X-10 transmits one BIT each zero-crossing. I believe a complete message is 24 or 32 bits. That would be 12 to 16 cycles. WiFi faster for lots of data, but it starts off with a 3 packet handshake before a connection is even established, and that takes more than 6 * 16.7 milliseconds per cycle to establish a connection. That all tells me the ATS goes in the workshop and you run another set of wires for the backup power side of the ATS.

 

[ahmedats]

How to Wire an Automatic Transfer Switch to a Sub-Panel

How to Wire an Automatic Transfer Switch to a Sub-Panel

Hi,
I am installing an interactive system with battery back-up. My customer wants a few of his shop circuits on the critical load panel. The issue I am having is his shop is 150ft+ away with 4/0 aluminum wire feeding his sub panel. I think it will be nearly impossible to pull new wire in that conduit to get circuits from there onto his critical load panel. I was thinking about using an automatic transfer switch between his feed from the service and the shop and adding the critical load circuit to the transfer switch. So when power goes out he has power from the critical load panel to his shop. The question I had was if the breaker from the critical load panel to the transfer switch was hot all the time if it would mess up the automatic transfer switch? I would rather set it up for him where everything is automatic. So when power goes out he does not have to go out to the critical load panel and turn on the breaker for his shop feed.

Hopefully this all makes sense.

Thanks

I think you can use an Automatic Transfer Switch in your case. The following article will help you to Wire an Automatic Transfer Switch to a Sub-Panel.
I hope this is helpful for you.