Single phase 15A 120V Auto Transfer Switch

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faresos

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Does anyone know if there is a product such as a single phase 15A 120V Auto Transfer Switch to be used for a microprocessor control board for a CRAC unit (Computer A/C unit). The issue is the unit has a redundant feed (two 480V/3Phase circuits) but if the controller fails then the unit will shut down. My thought is to bring two circuits (120V) to the controller via an ATS, but not sure if they make such a product.

Thanks,
 
faresos said:
Does anyone know if there is a product such as a single phase 15A 120V Auto Transfer Switch to be used for a microprocessor control board for a CRAC unit (Computer A/C unit). The issue is the unit has a redundant feed (two 480V/3Phase circuits) but if the controller fails then the unit will shut down. My thought is to bring two circuits (120V) to the controller via an ATS, but not sure if they make such a product.

Thanks,
Click to expand...

You could easily do this with a double throw relay.
 
iwire said:
You could easily do this with a double throw relay.
Click to expand...

Thanks for your reply IWire. Is this relay very reliable? This will be used for a critical Mission projetct (Data Center), I just want to make sure this will be the best reliable option. Thanks again
 
The term "ATS" is used here in North America because it carries with it very specific requirements based on the NEC and UL that allow that term to be used. These requirements are intended for line feed systems where a back feed into a utility source can cause injury to line workers, things like that. This entire concept of special regulations is for the PURPOSE of not allowing people to use simplistic double throw relays or contactors to do this without oversight.

That concept does not apply to control circuits, at least from a regulatory standpoint, therefore the double throw relay is the commonly used method. It doesn't mean you must not be very careful about how you implement that, but it does mean that you don't need an official "ATS", which then also means that nobody it going to bother with the considerable expense to make, test and list one for something like this.
 
Is the control board powered by its own circuit, or is it fed via a transformer off of the unit?

If it's the latter, all you need is a small UPS to ride you through the blip during transfer.
 
I agree with Pharon. No need to make this complex. Feed the microprocessor control board from a UPS 100% of the time and you
won't have any problems. Could this be a solution to your problem?
 
That must be a crappy CRAC unit. If they have redundant 480V feeds to the unit, they should have the same redundancy for the control power.

Most equipment I have seen with a redundant supply has a control relay that switches control power to the other supply if the first supply dies.

Or maybe the control board is separate, and not part of the CRAC unit?
 
bob said:
I agree with Pharon. No need to make this complex. Feed the microprocessor control board from a UPS 100% of the time and you
won't have any problems. Could this be a solution to your problem?
Click to expand...

I don't see how a UPS is the solution to the OPs question.

It sound to me like he was concerned about supply one failing and automatically switching to supply two I assume until supply one is restored. A UPS is only going to last a limited time.
 
Does anyone know if there is a product such as a single phase 15A 120V Auto Transfer Switch to be used for a microprocessor control board for a CRAC unit (Computer A/C unit). The issue is the unit has a redundant feed (two 480V/3Phase circuits) but if the controller fails then the unit will shut down. My thought is to bring two circuits (120V) to the controller via an ATS, but not sure if they make such a product.
Click to expand...
I seemed to me that the OP wants to maintain voltage to the Microprocessor Control board. I am not familiar with this unit.
 
Bodine makes a cute little 20A 277V ATS that is in fact listed as a UL 1008 transfer switch. But you're gonna pay a whole heck of a lot more for it than you would for a DPDT relay in NEMA 4 box:
GTD20A.jpg
 
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