JB4XX Posted June 26, 2006 Share Posted June 26, 2006 Background...New units on a new construction threes years old. The upstairs unit quit working a couple weeks ago. I called and the repairman replaced a switch in the outside unit that looked burnt. Three days after he came out, the unit for the main floor did the same thing. The inside unit and blower would run but the compressor wouldnt kick on. I took the cover off the corner of the compressor and found what looked like the same type switch burnt. The first one was replaced under warranty, but we had to pay for service call and diagnostics. I replaced the second one myself. What could be causing these switchs to both go out within ten days of each other? Quote Link to comment Share on other sites More sharing options...
JoWhee Posted June 26, 2006 Share Posted June 26, 2006 Background...New units on a new construction threes years old. The upstairs unit quit working a couple weeks ago. I called and the repairman replaced a switch in the outside unit that looked burnt. Three days after he came out, the unit for the main floor did the same thing. The inside unit and blower would run but the compressor wouldnt kick on. I took the cover off the corner of the compressor and found what looked like the same type switch burnt. The first one was replaced under warranty, but we had to pay for service call and diagnostics. I replaced the second one myself. What could be causing these switchs to both go out within ten days of each other? Looks like the relay isn't strong enough for the current draw the compressor needs. This could be caused by either your compressor is getting older (3 years it doesn't seem likely but you never know), and it's starting to pull more current, you could check this out with an amprobe and compare it to the tag on the equipment, but your service man should have already done that. Another possibility is it's a cheapo made in china switch that is only designed to last for the duration of the warranty, if you can buy a heavier duty relay, or just buy 2 other cheapies and replace them yourself every 3 years. Oh ya.. your compressor may be cupped Quote Link to comment Share on other sites More sharing options...
airborneXX Posted June 26, 2006 Share Posted June 26, 2006 Did you have alot of thunderstorms lately? Brown outs and brief power failures beat the hell out of compressors and related electrical components. Like Jowhee said check the compressor with an Amprobe. It should spike up breifly at startup the level off to about 60% of the RLA (Rated Load Amps) of the label on the condensing unit. PM me if you have any other questions HVAC is what I do for a living :icon_wall: Quote Link to comment Share on other sites More sharing options...
00XX Posted June 27, 2006 Share Posted June 27, 2006 How about the 24V transformer going bad that your thermostat uses to control the contactor (relay). Perhaps the voltage is low under load. The relay engages, but weakly, and the contacts burn. That would explain both going out. Quote Link to comment Share on other sites More sharing options...
xrated Posted June 27, 2006 Share Posted June 27, 2006 Contactors are made to carry a certain amount of current for a continuous period of time. For a contactor to burn up like the one that you have pictured required a fairly heavy overload of the current through the contactor. There are several possibilities for the overload. As mentioned, there is a possibility that the control voltage (24 vac) from the transformer is low. The operating coil of the contactor could have been going bad thus causing the main contacts to not fully close and "wipe" the contacts. There could have been lower than normal voltage coming into the house temporarily which would cause the compressor to pull more current than it normally would (lower voltage = more current to do the same work). If at one time the contacts got burnt a little, they usually will continue to worsen and the current will increase and finally the contactor will give it up. There is also a possibility that something is wrong with the compressor itself, but not likely, since the same thing happened to both contactors that are on separate units. Loose connections can and will cause higher than normal current flow and start the overheating and contact burning. Bottom line is that it probably should be checked out by someone that has a thorough knowledge of electrical components and their operation.............read a qualified Electrician. Quote Link to comment Share on other sites More sharing options...
JB4XX Posted June 27, 2006 Author Share Posted June 27, 2006 Did you have alot of thunderstorms lately? Brown outs and brief power failures beat the hell out of compressors and related electrical components. Several rough storms with no long power outages but several brief outages. Just enough to have to reset the time on the stove and microwave. The sales person at the A/C parts place said it looked like lightning hit nearby. They may have both been weak and just happened to go out with the recent storms. :icon_think: Quote Link to comment Share on other sites More sharing options...
beondwacko Posted June 27, 2006 Share Posted June 27, 2006 This posting may or may not be the reasons for the burning switchgear. Just a possibility. As refrig' compressors age, they sometimes require more current at start up. I've seen this happen a few times. There are for some peices of equipment an upgrade kit / replacement kit for the starters and cap's. The offer a higher supply of current at the start up of the compressor. I don't know if this would apply to your situation, but for other peices of equipment it is. Good luck. Quote Link to comment Share on other sites More sharing options...
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