Determining amps on contactor


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Old 06-13-08, 03:10 AM
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Determining amps on contactor

Hi,
I need to replace my contactor but I can't determine the amps for the replacement. The current contactor only shows me 240 VAC 50/60 Hz. It appears to be a single pole contactor.

Any ideas on how I figure this out?

Thanks,
Erik
 
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Old 06-13-08, 03:21 AM
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With the unit up and running and a clamp-on meter set to read amps, clamp the meter around the wire connected to that pole. The reading you get is the RLA (running load amps). This is what is called an "inductive load". Armed with that info go to the place where you're planning on buying the contactor, tell them is for an hvac application and give them the value you just read.

You may also take the M/N of this unit (that tells its size) and give the counter person the info. They'll know what to give you.

Lastly, if you post the info on the MFR and M/N, maybe we'll be able to do a web-search and help you out with part number and specifications.
 
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Old 06-13-08, 04:06 AM
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Unfortunately I do not have a meter capable of reading amps above 10 so I'm wondering if there is a plan B.
 
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Old 06-13-08, 04:08 AM
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plan B is the MFR & M/N of your unit
 
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Old 06-13-08, 04:40 AM
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It's an Arcoaire

Here's an image of the sticker on the side:
 
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Old 06-13-08, 05:03 AM
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M/N: AH048G2
This is a 4-ton condensing unit

compressor running amps: 23.7
Fan running amps: 1.4

A 1-or 2-pole, 24V-coil contactor, with contacts rated for an inductive load of 30A or more (running amps) and 130A or more (Locked rotor amps) will do.
 
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Old 06-13-08, 05:20 AM
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I was going to get the part from Grainger but they seem a bit overpriced, so if you have any online resources that sell the part at a good price that would greatly appreciated.

Thanks for all of your help on this!
 
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Old 06-13-08, 05:24 AM
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Also, currently it is a 1-pole. If I were to get a 2-pole would the wiring be just the same?
 
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Old 06-13-08, 05:41 AM
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same deal. The only difference is that you will have an extra set of contacts instead of a flat metal jump bar across the contactor which your existing one has now.
 
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Old 06-13-08, 05:43 AM
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Is there an advantage to getting a 2-pole over a 1? Is a 2 safer?
 
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Old 06-13-08, 05:48 AM
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Originally Posted by TinLemon
I was going to get the part from Grainger but they seem a bit overpriced, so if you have any online resources that sell the part at a good price that would greatly appreciated.
How expensive?
I'm surprised. Graingers usually have good prices. This part should go for about $15 (maybe a couple of dollars more or so)

At any rate, if you call someone to do the job, expect no less than $100 for them coming...so if Graingers is charging you 20-or-30 bucks for this, you're still saving.
 
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Old 06-13-08, 05:54 AM
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Originally Posted by pflor
How expensive?
I'm surprised. Graingers usually have good prices. This part should go for about $15 (maybe a couple of dollars more or so)

At any rate, if you call someone to do the job, expect no less than $100 for them coming...so if Graingers is charging you 20-or-30 bucks for this, you're still saving.
Yeah... It was around $30 but I saw some up to $50. At the time I didn't know the amps so I don't know the exact price. I'll just go back to Grainger then since I can get it in-hand today.
 
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Old 06-13-08, 09:27 AM
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You need to replace the single pole with a single pole if that is what you had. I did not dig for the hour it would take to find out but if your unit utilizes a compressor heater it may not function correctly unless you do some rewiring. For a novice it is best to get a identical part and wire it up identically, that might save a bunch of problems down the road.
 
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Old 06-13-08, 10:03 AM
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I ended up getting a single pole from Grainger for only $16, which was 1/2 the price of a 2 pole.
 
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Old 06-13-08, 10:08 AM
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Good work tin man, let us know how it works out.
 
 

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