replace compressor or buy new ac unit???

Problems related to residential installations.

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replace compressor or buy new ac unit???

Post by oldmanbob » Thu Sep 08, 2011 8:55 pm

My home has (2) 3 ton carrier unit. Unit # 2 is problem unit. Yesterday the breaker for #2 was blown in garage. When reset, it immediately blew again.

Using the knowledge of my son, I think we have identified the problem. My son had a 3 years of HVAC repair in technical high school and actually even went to national competition for HVAC in the Skills USA competition, so he has some decent working knowledge of HVAC. But he does not do that for his occupation. But he still helped me ( actually I helped him) try and trouble shoot.

We first checked the capacitor and it is fine. Checked proper voltage via main line; ok. Checked contactor and all seems fine. Tested voltage from each lead on capacitor, and each wire connection screw on contactor; all seemed fine. I do not think there is a start or run capacitor, I think the triple lead capacitor we have does both functions.

We then disconnected the compressor leads from capacitor and then tried just the fan motor, it ran fine, no noise, and breaker did not blow. Then we disconnected the fan motor leads and tried compressor by itself. It tried to run, but made noise I would describe as very audible grinding for 10 seconds then breaker blew again. The noise made me think a fan blade was scraping something, but we had already removed motor fan from housing, the fan motor was d/c from wires, and noise was definitely from within housing.

As we tried this it was about - am in the morning, My son works weird hours and he just came home from work so we attacked the problem right away using numerous flood lights to illuminate the entire area to ensure safety. However. In a little semi darkness, my son said he saw a brief but noticeable electrical spark emit from compressor housing when we threw breaker on to see if compressor would turn on. I was standing50 feet away by garage to listen for the noise made if the breaker blew so I did not see the spark.

We reset breaker again and compressor ran another 10-20 seconds, again making loud noise, and breaker blew. Son hooked up his ammeter or ohm gauge ( i do not know proper name) and checked the three prongs on plug going into compressor housing. Two of the leads showed equal reading, one lead showed a lesser reading that he thinks is indicative of a problem (possibly electrical ??) within the compressor housing itself. Thus, we feel pretty confident the compressor went out on it.

So this unit # 2 is a 6 year 3 months old Carrier, 10 seer, 3 ton (carrier 38cks) unit that cools the upstairs bedroom and bonus room area. (Maybe 1500 sq ft.area to be cooled)
I have yet to have a professional HVAC company come on site. If possible, can anyone please give me a good guess-estimate of cost, including labor (including recovery and replacement of Freon) to reinstall a replacement compressor as opposed to the cost to purchase a newer more efficient ac unit, (maybe 14 seer 3 ton) and then have new unit installed to existing pad and connections. The unit itself only has a little rust so it may be worth replacing compressor, but I want to compare costs. Web search showed prices for compressor from 4 hundred to 19 hundred ( compressor is carrier p/n 739024-1602-00; model # H29B33UABCA oc-25 230/208v, 60hz, 1 ph lra 82)

If a new a/c is purchased, guess-estimate cost and will is cause any conflict/ problem with unit # 1, which is a twin carrier 3 ton, that is also 6 + years old that cools the downstairs of my home.

I appreciate any and all insights.

Thanks in advance,!!!!!

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Joined: Wed Jul 06, 2011 9:10 am

- replace compressor or buy new ac unit???

Post by heatseeker » Fri Sep 09, 2011 8:41 am

Your compressor is scrambled like broke internally. Electrical is in tact but mechanics are shot. compressors are about 1200.00 dollars.
Its up to you what you want to do.

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Joined: Mon Sep 12, 2011 6:36 pm

- replace compressor or buy new ac unit???

Post by newhomeowner » Tue Sep 13, 2011 5:20 pm

I have had many friends run into this same problem. I know 1200 sounds better than 6 or 8, but they always seen to end up replacing the entire unit down the road. If you have a very high quality system already, it may be worth trying to fix. If not, I would suggest getting a new one and getting a very high quality one. Another good thing to think about is using your system wisely. You will get a new Thermostat with your purchase, but you will want to upgrade to a programmable that allows the system to shut off when not needed. I found mine online. This will not only save you money, but it will also decrease the wear and tear on your unit.

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