Heat Pump Help

Problems related to residential installations.

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Heat Pump Help

Post by AllenGentry » Mon Jan 31, 2011 10:57 am

Carrier HP R-22
Model 38YCC030340
Serial 4502E23719

Robertshaw 9420

Our home, of which we are the 3rd owners, is about 7 or 8 years old. To our knowledge, all equipment is original.

3 years ago, I got the bright idea to install a new programmable thermostat myself. My wife was having trouble reaching the old dial type, mechanical I believe, due to furniture placement.

I screwed that up, as apparently, the thermostat was defective out of the box. It was a Honeywell. My t-stat wiring is not fully to any code, and it appears there isn't a hard and fast code that is followed, mostly general guidelines. I apparently had the t-stat hooked up correctly initially, and when it didn't function properly, I started second guessing and switching wires around until finally nothing worked. Long story short, I blew a low amperage (2.5 if I remember correctly) ATC automotive type fuse in the air handler. A friend who is retired HVAC from the phone company came out, replaced the fuse, and installed the above thermostat which he happened to have on hand.

Everything seemed to be working just fine. AC worked, heat pump seemed to work, electric back up strips worked, unit would frost up in the winter, run through the defrost cycle, loud hisses here and there, and steam, life was good. I do say "seemed to work" because when the t-stat was replaced, it was spring, and since then we have had no complaints during winter, heat or comfort wise. Every observation I made when outside in the years since that thermostat issue indicated the system was running normal in the heating cycle.

Last night I noticed the outside unit cycling very rapidly, and shutting down rather harshly. The unit would shake slightly upon shutdown. Also, when cycling in this manner, upon start up (LRA 73), the breaker for the unit inside the garage buzzes. The breaker is not warm, but I felt it important to mention. In my opinion the unit is not starting as quickly as it should, and drawing high current for a second or two...

It seems to me the unit is "rapid cycling", which apparently my thermostat is supposed to prevent.

It does not rapid cycle all the time either. I noticed this morning the outside unit started and ran for a few minutes, then cycled. I have no idea how long it WILL run between cycles as I have the entire system shut down to prevent compressor damage. I tried searching the web for information that was specific to my model, and the only thing I ran across was someone with similar issues to mine that switched over to "E heat". After about 6 hours in emergency heat, something in his backup strip system malfunctioned and melted causing more issues and repairs. As such, it is completely off.

The only issue we've had in addition to my botched thermostat replacement was during an insane hot spell during the summer two years ago. Came home to no AC. Called my friend. The start up capacitor had exploded, or more correctly it was deformed and blew a bunch of oil out. He replaced it the next day and everything has been fine.

OAT is 36*, IAT is 68* and holding with the system shut off. The air handler seems to be functioning properly.

Finally, money is a huge issue. Both my wife and I are unemployed and we have two little boys. I really need to keep the repair costs to a minimum and do as much as possible myself.

I must also mention the lack of air handler information. To access the air handler, I must go outside and into the crawl space. It is basically a dirt floor covered in plastic. The floor starts out as a crawl space, but slopes upward as you head to the air handler. Up at the air handler it transforms into a lay down flat on your stomach and scoot space. Really stupid...

I am standing by with my multi-meter.

Where do I start?



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- Heat Pump Help

Post by nomadpeo » Mon Jan 31, 2011 11:28 pm

first of all, i must say, you tell a great story. ....'loud hissing here and there, steam, life was good'..... gotta love it.

let me reiterate the safety issue. you may know this, but i will say it anyway because i do not know your level of expertise around dangerous power. before handling any components, test the incoming power level with your meter. test each line to each other, then each line to ground. if you do not read less than 1 vac for each of the three readings, do not touch components. i recommend you have your system tested professionally.

your motors are psc (permanent split capacitor) motors. as such, they require run capacitors (the metal ones). if you have a black plastic one, it is a start assist. it may be a one peice or it may be a capacitor accompanied by a square relay. these components are not essential to the running of a psc motor, but could have been added. if these components fail in a certain manner, they can cause the symptoms you described (by the way, it sounds like the shortcycliing you are noticing is during a call from the thermostat. the problem is transparent to the thermostat). also, the run capacitor can go bad, but generally will just cause the compressor to quietly stall with a distinct intermitent hum. this is when it is pulling rla (locked rotor amps). energy that cannot be converted to mechanical is converted to heat and quickly overheats the compressor. an internal sensor opens the circuit to protect the compressor, then resets automatically, hence the intermitent hum. if the start kit is removed and the run cap is good, the problem may go away. a new start kit could be added again. also, the contactor, after all this upheaval, could be pitted and burnt and probably should be replaced.

(at the risk of contradicting myself) you may want to pull all of the aforementioned components and go buy new ones. the worse thing for a qualified technician to do is to start replacing parts until it is fixed, but given your appeal to save money, removing all the possible variables could be a good approach for you. the only thing left is the compressor. if you solve the problem, you have spent relatively little money and saved a lot. the best alternative is to have it serviced professionally. keep in mind that there could be other underlying issues that replacing these components does not address. often, defective components are symptoms, not the cause. good luck.

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