My house has a split heat pump system. The outdoor unit, a carrier 38QN-030, 2.5 tons, suddenly stopped operating a couple of days ago. The house is now getting heat from the inside unit(supplemental heat, not emergency heat).
Here are the things I have tried so far(with no success) to get the outdoor unit to operate:
a)I checked the breakers, they were ok(not tripped). b)The thermostat seems to work ok, it tells the indoor unit to operate and heat the house. c)I changed the main fuses for the outdoor unit(two 40 amp fast acting). d) I checked the indoor unit and seems to be ok, operational so far.
Upon further inspection of both the indoor and outdoor units, I do not see a reset button anywhere in sight ( for the compressor, condensor, pump, etc), to get the outdoor unit operational again. The outdoor unit does not emit any noise whatsoever as I turn up the thermostat to heat the house; which is the reason I thought the outside fuses were at fault.

My questions are:
a)Can the thermostat be damaged? ;i.e, the part that instructs the outdoor unit to come on.
b)Is there a hidden reset button somewhere that I might have missed?
c) Can the refrigerant be low, a cause that prevents the outdoor unit to come on?
d) Does anyone know of other problems(except being broken for good)that could be a cause for the outdoor unit to die all of the sudden?

This unit is old(from 1986), so it might be near the end of its life cycle. it could be a good time to invest in a newer more efficient heat pump system...I need to find the money first.
Any ideas?? Thank you all in advance!!

 

I'm no expert but...

Is the fan on the outside unit turning (I suspect from your comment that it isn't - just wanted to verify)?

If the answer is no, my first suspect would be the main contactor. Especially since your unit is fairly old. It controls the voltage to the fan and compressor. If it's stuck open, you've got your symptoms.

 

It's been 8 days since your original post. So, what was it? Are you still having the same problem?

 

Thanks for your concern...a tecnnician came by and said the thermostat was sending the signal correctly to the outdoor unit. He determined that the PC board(circuit board)in the outdoor unit was damaged. So he connected the unit directly to the thermostat, and it works ok. The problem now is that the outdoor unit does not enter the defrost cycle, and it freezes solid after operating a while, especially overnight. When it gets frozen solid, it still works but the air that it sends in is cool, and the system operates continously as you might imagine by now.
I guess I have four options :
1) buy a new heat pump system
2) buy a used circuit board somewhere
3) try to repair the old board
4) hose down the outdoor unit daily until old man winter is gone.

I am considering my finances for options 1 as we write. As for option 2, I have looked on the internet, but so far have not seen anything that would match my heat pump (carrier 38QN, from 1986), and to tell you the truth I dont know if there would be a similar circuit board somewhere at a reasonable cost. As for option 3, the technician said it might be better to purchase a new unit than to invest in repairing the old circuit board. Option 4 is not an option really, I still have to go out there everyday and hose down the old thing.

So that is the new situation...sorry it took so long for me to reply, but the technician came in just a couple of days ago(good thing it wasn't an emergency).

Any ideas out there???

Thank you again.

 

You should be able to get a defrost control.
I am shocked that the tech didn't offer you a replacement.
Call around they could be from 50.00-150.00 much less than a replacement.

 

You can just turn the unit to AC and it will get the ice right off for you. You dont say how old unit is. AC units are like good for 15 years Then heat pumps we put at 7.5 years.Then get new ones. Some of of them do run longer.

ED

 

Thanks for your prompt reply...a little while ago I was finally able to search on furnaceparts.com,heatcoolparts.com,and partsguy.com among others and found the exact(I hope) replacement part for the old, you're right, defrost board for my outdoor unit. They vary in price,from $60 to $95 or so, and they look similar to the one I saw outside in my unit. So, it looks like for now I will purchase a replacement board and install it a see what happens.

Meanwhile, I am still considering installing a newer more efficient system in my house because this current heat pump split system is from 1986 and I figure it has run its course(maybe not). I think I need to do the load calculations to figure out how big my new system needs to be. This one is a carrier 38QN-030 with 2.5 tons. Maybe the new system could be 2 tons or it needs to be 3 tons, I have no idea. That's why I figure the load calculation is a good place to start.

Any ideas?? Maybe I need to make buying a new system a new thread.

Than you again.

 

Stay in the same thread. That way we know what you have been doing As you say new heat pump yes for sure have a heatloss and AC load ran on the home . Be sure and get 3 bids for the job. Also new inside and out dont use the old coil and blower inside.
You want to look at some of the new units.They have a SEER 17.00 and a HSPF of 10.55 on the heat pump side. if you are going to be in the home for 10 years or more . You can get a 10 year warranty with it.
As I said for now go to AC and it will take the ice off for you.

ED

 

Thank you for your advice on the new unit. Yes I was thinking initially to purchase just the outside unit, but I have changed my mind cause heat pump systems nowadays are much more efficient than the previous ones(certainly much more than the ones from 20 years ago!!). I have only been in this house for two years, and plan to be here no more than 3-4 more, so I am hesitant to go for a high end system since I will leave it with the house. Some people have told me to go for a SEER 13 and above, but they tend to be expensive, especially the heat pump systems with the new refrigerant. I for sure will do a load calc on the house to see how big my new unit needs to be.

As far as running the heat pump in AC mode, I will do that today...I thought the reverse valve might be damaged if the AC runs in cold weather like we are having around the DC area. Today is a warm 30F outside, it will be 40F at noon or so, so maybe that will be a good time. I'll have to pull off the breaker for the fan(inside unit) cause the fan runs automatically with either heat or AC for my system. (I dont want the cold air to be blown into the house while the AC is on).

Any more ideas??

Again, thank you!

 

It dont care what the outside temp is just think it goes in to defrost all the time by it self.

ED

 

Hello there again...I have run the heat pump in AC mode, but does not seem to be defrosting the unit. Besides, with the fan on, the air that blows in the house is cold and the machine stops after a little while, not enough to defrost the unit. What is the technique here, if there is one at all. Just turn the machine to AC with a low setting for the Tstat and let it run? If I do that wouldn't the house get a lot of cold air all the time?
When the technician came to check out the unit, and found a problem with the defrost board, I believe he connected the unit in heat pump mode(bypassing the defrost board), so maybe the unit does not work in AC mode at all. I have no idea, I might have to call him and find out.

I have gone out and manually defrost the unit with a hose, but it gets frozen solid overnight again. So I have been doing that daily until I get the new defrost board. I ordered a replacement board online, and that should fix the problem(so I hope).

Any comments, ideas??

Thank you very much

 

The tech that came in the first place is not the tech to call. If he was worth his salt he would have fixed the thing instead of "jerry rigging" it. The guy could have gotten a replacement board if he felt like it. Instead he bypassed the problem and created a new one.

Call another dealer and give them the model number of the unit and tell them to bring a defrost board and the sensors that go with it. That will fix your problem and give you time to save up and have the whole mess changed out.

 

ICM makes a universal defrost board for lots of units. It sounds to me like the tech may have heard how much money you don't have to fix the unit and thought he was going to get stiffed and decided to cut his loss on labor only... Just speculating! Many HVAC companys won't do residential because of all the wining about how expensive it was....WAH!!!!!!!!!!!!!!!!!