HVAC Contactor

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Old 11-09-07, 02:36 PM
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HVAC Contactor

Can i use a 35 amp contactor in place of a 40 amp??
 
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Old 11-09-07, 03:34 PM
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Where or what is this contactor used for??
 
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Old 11-09-07, 07:59 PM
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Its on my compressor unit outside. The unit was not turning off. I checked inside and the contactor was really old and points all burnt up. Everything is faded so i cant tell you much about it...make, amps, voltage, how many ton.
On th inside panel i can make out that its 40a and 24 volt but thats not listed on the schematic near where its showing the image of the contactor, its near some othe part... (capacitor??) but im assuming that applies to the contactor as well. It has a 2 pole contactor but somewhere along the line one side was burnt up, and the wires from that side were all grouped and conected with a twisty... so basically the contactor was only operating thru one side of the 2 poles... (one pole).
Those wires on the still connected side consist of a hot coming in, and 2 coming out to their designated componants. It also has the 2 low voltage wires operated by the thermostat.
I bought a replacement... the dude looked at the old one and gave me a single pole to replace it..., but its a 35amp instead of 40. I cant be sure 40 is correct as i said the marking on the unit are old, faded and arnt listed near the contactor in the drawing...

Basically the contactor looks like it will work fine...just want to be sure 35amp is going to be ok in the event it did have a 40amp in it...
 
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Old 11-09-07, 08:18 PM
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Wink

Need to know what size or tons the unit is . That will tell you what amp contactor you need there. But you say 40 amps you saw . Id say stay with a 40 amp then. Can be 1 or 2 poles thats ok.
 
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Old 11-09-07, 10:38 PM
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but will 35 work?
 
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Old 11-10-07, 04:54 AM
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It may work. but in the long run the contactors may weld shut due the higher current going over the contact points.

What is your unit tonnage?
 
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Old 11-10-07, 04:59 AM
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YES the 35 amp contactor will work (possibly however for a short period of time if it is overloaded) Any electrical device operated outside its design parameters will suffer from early failure rates well past the expected failure rate for properly sized devices. If you have one or know someone that has one, use an amp probe so the actual amp draw of your unit can be checked. Then you can make a intelligent decision as to the correct capacity of contactor. Keep in mind that the new contactor can fail at any time if overloaded and typically that time is not going to be convenient to you LOL
 
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