Hi,

I have a Lennox Elite Series HS29-030-1P air conditioning unit and the compressor will not start. You will hear a buzzing sound then it stops, it about a minute it tries again then stops. What are the best ways to test the starter cap and the compressor to isolate the problem. The starter cap is a dual capacitor and the condenser fan fan starts right up, only the compressor is is not starting. Another question, if the freon was low, would there be a circuit to prevent the compressor from coming on like in this case?

Thank you :)

First check all electrical connections to the compressor from the contactor. The wires to the compressor are usually behind a cover on the compressor.

Without a capacitor tester/checker it is just about impossible to get a accurate test. If you have a ohm meter that might work but not be accurate.

Where is the buzzing sound coming from. Did you locate the exact component. It could just be the contactor pulling in to start the unit.

Some units have a low pressure switch that will hold compressor off if it is low on refrigerant but if the contactor is pulling in that is probably not the problem.

Check all the internal wiring and post back.

Thanks hvac1000,


I checked all the connections, cleaned them up. The buzzing/humming noise is coming from the compressor, not a contactor. There is only one contactor that I can see unless there is one in the compressor, the contactor stays closed the whole time once the system is kicked on.

I checked the continuity of the compressor windings, nothing was shorted to ground and I had a low resistance between the leads. The compressor is a scroll single phase (Copeland ZR30KC-PFU-230 if that helps any).

I still tested the cap with a digital meter, I see current flow between the common and fan poles but nothing between the common and the compressor poles.

I really don't know where a pressure switch would be unless it is built into the compressor, everything seems pretty basic and like I mentioned before the contactor stays closed when the system is on. So when the contactor closes, the compressor hums, then stops but the contactor remains closed at all times. A few seconds (30-45) it will try again. Is there some thermal overload in the compressor to cause it to stop. I'm thinking the cap is bad and I think that is where I'm going to start, what do you think?

Do you know where I can find a parts breakdown of this unit, seems like I am having trouble finding part numbers. I also attach a copy of the electrical diagram, this is what I have.

Thanks

It could be a bad capacitor but without a tester you will have to replace it to test.

If after you change the capacitor there is no difference I would feel then that the compressor is stuck.

Now you just might be able to rock it free by using a hard start kit BUT that would be another expense that may not work and a scroll compressor usually will not rock free if really defective.

Most service people have a hard start pack on the truck to test with and a capacitor checker. In your case you will have to purchase these parts and they might not be defective so you will loose a bit of $$ doing your own work.

I see no low pressure cut out on the wiring diagram so that shot that idea.

How old is the unit. Could it still be under warranty?

If not and all the above does not work I suggest you replace the unit. OUCH but it is a better deal than replacing the compressor.

Thanks hvac1000,

I removed the cap and took it to work to test it, we have a tester there. I did test it with a digital voltmeter and it tested bad, after testing with a cap tester, this confirmed it was bad. I replaced the cap, and fired it up, all seems to be working fine. I got off lucky I guess, it only ended up costing me about $18 for the cap. I will probably still have a professional AC person come out and tune it up etc...

Thank for your help

Next time you have this kind of problem look at the capacitor for any bulging of the top or bottom, Most of the time you will see something if the capacitor is bad.

Thanks hvac1000,

I removed the cap and took it to work to test it, we have a tester there. I did test it with a digital voltmeter and it tested bad, after testing with a cap tester, this confirmed it was bad. I replaced the cap, and fired it up, all seems to be working fine. I got off lucky I guess, it only ended up costing me about $18 for the cap. I will probably still have a professional AC person come out and tune it up etc...

Thank for your help

I am glad you got it going.

I have an HS29 Elite Lennox Condenser Unit Air Conditioner and it just stopped running altogether. The breaker did not blow and there was no freezing on the lines, the condenser is almost brand new and was replaced a year ago. Anyway, the AC guy came and changed the compressor contactor, but wired it wrong and when we started the unit up it blew the start capacitor. We finally figured that out after he charged me $180 for it and he wanted another $220 for the start capacitor. So I went to another company to get them to check my unit. Just so you know I had a service contract with the original AC guy. So the other guy came out and tested all the components of the unit and changed the wiring that was done wrong and put in a new
Start capacitor ($28) and it was still not running properly, so he added a booster to the dual capacitor and found that the compressor was gone. The unit was installed new June 2000. I found out that this unit has had lots of problems and that is why they do not warranty the compressor for more than 5 years. I would suggest anyone buying a new unit to stay away from this one. We will be going ahead now to purchase a new air conditioner. The Lennox Elite furnace on the other hand has been very good. I don't really have a question just words of experience. Before you spend too much money have them check the compressor.

Lennox Elite 11TM Condensing unit, HS29-036-9T has died. Compressor has seized. Thoughts on whether I should change the compressor only or replace the entire unit. Also is there are cheaper comparable unit on the market that I could replace the Lennox with?

We have six HS29 a/c units for our youth center that are paired with G51MP units. Yesterday the a/c on one of them was not working. In checking it out there was a bunch of icing on the interior of our building between the units. We changed the filter on the G51 and that did not solve anything.
Would appreciate any help in correcting this. We are a non-profit agency without tons of $$$ so would prefer to fix anything we can do ourselves if possible.
Thanks for any help.