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#59709 - 12/13/05 12:51 PM Power Relay  
InspectorE  Offline
Member
Joined: Oct 2004
Posts: 51
Hudson WI USA
I need a 250 - 300 amp AC relay and have checked Allen-Bradley and a few others. Can anyone tell me where a high current AC relay can be obtained?


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#59710 - 12/13/05 02:34 PM Re: Power Relay  
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ


#59711 - 12/13/05 05:06 PM Re: Power Relay  
Dave T  Offline
Member
Joined: Jan 2005
Posts: 155
Waukesha, WI, USA
Lighting contactors are available up to 400a and diffinite purpose contactors shoulde be also. I'm assuming you're talking about 480vac. Usually when one inquires about a product one includes the voltage rating of the device in question, the numer of poles, the type of load, latching of magnetically held, coil voltage as will a the current requirement. Otherwise, should an answer be provided based upon limited information the answer is likely to be incorrect for the actual application.


#59712 - 12/14/05 12:35 AM Re: Power Relay  
InspectorE  Offline
Member
Joined: Oct 2004
Posts: 51
Hudson WI USA
Ask a general question, get a general answer.
My mistake, I should have given the application.

This is for a generator transfer switch. So it would be a double pole, double throw, and rated at preferably 250 amps continuous. Normal residential voltage 120/240.

Thanks!


#59713 - 12/14/05 02:53 AM Re: Power Relay  
mhulbert  Offline
Member
Joined: Oct 2004
Posts: 132
Anaheim, CA USA
Whoa...you're trying to build your own transfer switch??!! Whatever you build is not going to be listed for the application, and won't be as relaible as a purpose-built transfer switch. This is not something you want to mess around with! Besides, you will have a hell of a time finding a double throw, 250A relay!

May I suggest a real, listed transfer switch, a reliable company is ASCO, check out what they have here http://www.ascopower.com/Products/ATS/atsmenu.html

be safe!

mike


#59714 - 12/14/05 10:47 AM Re: Power Relay  
JBD  Offline
Member
Joined: Jul 2001
Posts: 599
WI, USA
FYI, relay contacts are usually limited to 10A and sometimes as high as 20A. Above that current rating the devices are usually called contactors. Normally closed contacts are not usually available above 100A.

For 300A non-life-safety semi-automatic transfer switches some fire truck manufactures use mechanically interlocked 400A contactors, one coil wired to the on-board generator and the other coil wired to shore power.

For home-built applications stick with a listed commercial transfer switch especially if you need engine start and exercise functions.


#59715 - 12/14/05 11:24 AM Re: Power Relay  
InspectorE  Offline
Member
Joined: Oct 2004
Posts: 51
Hudson WI USA
The service is 225 amps for the house. The generator/transfer switch are rated at 100 amps. Generator controlled circuit breakers will drop enough circuits in the house to keep the generator happy.

It sounds like a contactor rated for 225 amps would work to disconnect the mains service before the generator fires up, then let the transfer switch relay dump the generator to the house feeders once the warmup period has elapsed. I just thought an external relay (or contactor) rated for the full normal service current would negate the need for two separate electrical items.

The transfer switch has all the bell and whistles, it just isn't built into the generator as some are. I'm well aware of the safety issues! Thanks for the response!


#59716 - 12/15/05 12:17 AM Re: Power Relay  
Larry Fine  Offline
Member
Joined: Feb 2005
Posts: 693
Richmond, VA
It sounds like you want to use this relay so you can use a 100a TS instead oif a 200a one. I have a feeling that a 100a TS and a 200a contactor will cost more than the 200a TS will.

I suggest getting the proper TS and save the 100a TS for a 100a service.


Larry Fine
Fine Electric Co.
fineelectricco.com

#59717 - 12/15/05 09:23 PM Re: Power Relay  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,802
Brick, NJ USA
Sounds like what you are trying to accomplish with individual components is classic 'over-engineering'.

A manufactured transfer switch, automatic, or perhaps manual would be the 'preferred method'.

Your statement "The service is 225 amps for the house. The generator/transfer switch are rated at 100 amps. Generator controlled circuit breakers will drop enough circuits in the house to keep the generator happy."

Please explain what a 'generator controlled circuit breaker' is??

John


John

#59718 - 12/15/05 10:01 PM Re: Power Relay  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
Chief, you are looking for one of these.... http://www.asco.com/cgi-bin/redirect.pl?/product.html

I am afraid to think of what could go wrong in the possible reconnection of the POCO and your generator due to relay contacting at the wrong time. Unless you have a fool proof make before break circuit, I would not want the liability. Also what will you be doing with the neutrals?


Mark Heller
"Well - I oughta....." -Jackie Gleason

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