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kfreeman 04-06-13 09:41 AM

Old Janitrol heat pump
I have an old Janitrol heat pump that keeps burning out the compressor start capacitor. I can replace and it will melt one of the red wires from compressor and damage the capacitor. What would be a good approach to troubleshooting this problem? Could I poosibly be using too small a capacitor. A service person from a local company replaced the first one and I have had trouble ever since.

AC_Hacker 04-06-13 12:00 PM

3 Attachment(s)

Originally Posted by kfreeman (Post 29327)
I have an old Janitrol heat pump that keeps burning out the compressor start capacitor.

NOTE: If you try to repair your own heat pump, you might kill yourself or destroy your heat pump... only a fool would proceed.

* * *

Before you mess with your heat pump unit, be absolutely sure that power has been cut. Turned "OFF" is not good enough.

The capacitor thing isn't rocket science. The capacitor is there to give the single-phase compressor an initial startup kick... after that, it does nothing. In general, all compressors of a particular Tonage rating (1/2-Ton, 1-Ton, 3-Ton, etc.) and the same voltage (110v, 220v) should be pretty much the same, so their starting capacitors will be pretty much equivalent.

If you can get hold of a parts list for your unit, it will spell out the correct part... that is the part it should have.

Otherwise, the capacitor specs are dictated by the compressor's requirements. That compressor would be used in many different heat pumps, all of them using pretty much the same capacitor. The capacitor call-out for any of them should do it.

In many units, the same capacitor will be doing double duty to help the compressor to start and also to help the fan to start, so it's really two separate capacitors of different sizes in one can. There is the possibility that your previous repairman switched the leads incorrectly. I would think that the smaller capacitance should go to the fan and the larger capacitance should go to the compressor. You could follow the wires to see where they go to. If you are sure that the capacitor was correctly hooked up correctly, copy that hook-up. If you are not sure, find a schematic.

As a last gasp, the cap will be specified by it's capacitance and also for it's voltage. you might get one for a higher voltage... the capacitance should remain the same (assuming your tech got that part right).

So, you really need to find out the correct part call-out before you start subbing in different parts.

Finally, and least likely, your compressor could be dying and drawing too much current... in which case, it should be given a proper burial...


NiHaoMike 04-06-13 03:58 PM

Replace it with one of the same capacitance and a higher voltage rating. Also check the start relay if there is one.

stevehull 04-07-13 12:41 PM

AC makes great points with excess current draw clearly causing the red lead to burn out.

I would certainly test the capacitor and this is where the "death head" comes up.

Capacitors store charge and a good capacitor can store a REAL hefty charge for several days (or longer). Before you do anything, remove the AC power and short the capacitor terminals to each other. You should see a big spark and the snap of a high current pulse.

When uou can't find the exact capacitance value, get two capactors and put them in parallel. This placement allows you to simply add capacitances. The voltage rating is not critical so long it is ABOVE the stated voltage on the original capacitor. In this application, it is NOT critical if the total capacitance is a bit larger, the key is not to have it be too small.

Now the interesting way to test . . . . yeah, not with small kids or animals around.

Disconnet the leads to the compressor and put main voltage (120 240, etc) on the unit. Most times this is via a circuit breaker. Just a minute or two is sufficient - then turn off power.

Now get an insulated screwdriver and short the terminals of the capacitor together. The louder the snap, and the vigorous the light pulse indicates the amount of stored energy. A VERY quick and dirty test, but if there is a weak spark, thern you know the capacitor is likely bad.

In enginering grad school, we would take a much smaller capacitor, wrap the leads around the non-metalic capacitor body (leads not touching) charge it up - and then toss it to someone who just walked in to "catch".

The auditory responses were quite impressive . . . . . :eek:


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