Heat Pumps and Electric Heating - Outside unit keeps running.

:wall:

I have a problem with the outside unit continuing to run.

I believe it is a sticking load contactor because it will shut down if I cycle the system on /off with the thermistat.

I tried to lube it with some sillycone spray but it still sticks.

I guess that it is best to change it.

If I measure the coil resistance and know that it is 220V and twin contacts, is that good enough to tell a replacement ?

Maybe I can find a part number on it.

However that is not all of the problems I have with this unit. It is a Rheem with resistance unit emergency heat.

Last year I had problems getting it to reverse cycle (change mode from AC to Heat).

I suspect it might have something to do with what I consider to be a "Mode Relay" .

It is a plug in clear plastic relay with several contacts inside.

If I could change out this relay and my load contactor I feel that I could solve most of my problems.

There is also a circuit board which I cleaned and sprayed with silicone spray (hope I did not damage it).

Anyone have any help or comments or ideas ?

Anyone have any good links to parts sources like the relay and contactor that I need ? :confused:

David Haynes >>> Central Florida (hurricanes, no ice) :cool:

:wall:

I believe it is a sticking load contactor because it will shut down if I cycle the system on /off with the thermistat.

If all you have to do is turn the stat to off then it's not the contactor.

I tried to lube it with some sillycone spray but it still sticks.

This will not help a thing.

Last year I had problems getting it to reverse cycle (change mode from AC to Heat).

Did the heat pump work this season??

It worked in reverse mode to heat the home.

Then it fails to switch back to normal run mode (as a cooling unit).

In the past I have changed the mode switch several times in order to get it to switch to the opposite mode, which is why I am blaming the contacts on the "mode switch relay".

When the thing is in mode it sometimes leaves the compressor running (and the fan) when I move the tstat to change the temperature out of the "on" range.

Any help ?

:wall:

It worked in reverse mode to heat the home.

Then it fails to switch back to normal run mode (as a cooling unit).

In the past I have changed the mode switch several times in order to get it to switch to the opposite mode, which is why I am blaming the contacts on the "mode switch relay".

You have a lot of ifs here but first find out if the reversing valve is working right. on some you can change just the coil. Or is it in the tstat?

ED ;)

You have a lot of ifs here but first find out if the reversing valve is working right. on some you can change just the coil. Or is it in the tstat?

ED ;)

Two problems exist :

1) Failure to shut down the outside unit regardless if it is in reverse or normal mode

2) Failure to effectively and reliably go from normal to reverse mode

On this Rheem the reversing valve is selected through a relay mounted to the left of the load contactor.


My understanding of the problem is :

1) Failure of the mode relay contacts to allow a complete mode change

2) Failure of the load contactor return spring to pull off of the load contacts due to >>>> weak spring, dirt, pitted and sticking contacts

Not being an HVAC Tech, but an Electronics Tech, I do not have the real knowledge, training, and experience to fully understand how it works or how to repair it. I can tinker and hope not to destroy it and learn when to call in an HVAC Pro. I am also careful to only change out control circuits (or at least attempt to) and never mess with anything else.

I honestly believe that with a new control relay and a load contactor that I can fix it. If not I will call in a qualified service person.
:D :mask:

If while it's running when it shouldn't be, pull the disconnect outside. Then ohm out the contactor and if it is closed and no 24v to the coil then replace the contactor.

I have received your instructions and will now attempt to follow them.

It will be done on the weekend.

Where is the best place to find the manufacturers ID info on this unit ?

Is it possible to order a parts info sheet on this model ?

Where can I buy the parts that I need ?

When should I scrap an olde unit and buy a new one ?

Can I do a partial install of a new unit and pay someone to complete the installation, to save money, or is it not worth the pain ?

Am I asking too many qustions ? :rolleyes: :confused:

If the contactor is bad then take it out and go to a hvac supply house and they will match it up for you with a new one.

A tip before removing the old part is to take a digital picture for rewiring refrence. Or draw your own picture.


Replacing it depends really on how old it is and how well the install was and if it was maintained. You should usually get somewhere in the neighborhood of 10-15 years out of it. A lot of times less since a heat pump works double time.

It's not worth the hassle of trying to DIY it. You need special equipment to remove the old refrigerant and specialty tools for the install. Then if you did get your own equipment you wont find a quality company to do the tie ins for you and you wont have a warranty.

Waiting for the weakend. (in other words >>> if you expect a warranty, then let the company do an install that they know is done correctly, and stop trying to cut them out of a profit.

Also if you intend to sell the house in the near future , such a warranty is a very good selling tool, as the HVAC is a major part of the homes well being
and the creatures contained therein.

:D ;)

You can also go to graingers online to get parts to fix it.

Thanks :D :D :D


filler. (message too short, had to add some filler)

If while it's running when it shouldn't be, pull the disconnect outside. Then ohm out the contactor and if it is closed and no 24v to the coil then replace the contactor.

Well it was a nice 70 degrees F out in "almost paradice" >>> Central Floridas today, so I went out to tinker with the Outside Unit.

I pulled off the access cover to the control box (Rheem was good on this design) , and encountered wasp and a small snake. I don't care HOWSMALL the dern snakes are , I don't like snales. i let the critter slink off as we eyed each other with severe distrust.

I noticed the the clear cased control relay showed signs of over heating >>> slightly melted case and small burn. For this reason I did not fire up the unit
for the disconnect test. I went ahead and pulled the service disconnect anyway, then went in to trip modes from normal to reverse.

Apparently the reversing valve was working and the load contactor engaged and the inside plant blower kicked on as it should.

I turned off the tstat and went back out to check to see if the contactot had pulled off. It did not and was stuck down. I touched it with my meter
probe and it released to the off position. This tells me that I need to replace the contactor.

I will take the digital camera pictures and replace this contactor.

The other problem is the overheating and probably damaged control relay.
I may have a real problem finding a replacement for it.

This unit is dated (at least the pictorial drawing is) 8-17-84.

Drawing # 90-21970-01 .

Apparently a 24V contactor and control relay.

other numbers >>> PCB-024 (2ton , 7 KW ?)

other numbers >>> RCPB-B024 , RCPB-B027 ?

other numbers >>> 92-20477-56-00 ,,, 92-20477-34-01

Inside numbers >>> RHQA 1005 .

Anyone recognize these Rheem models. ?

:thinker:

(maybe I could rip out the defrost board, disable and rewire the reverse cycle mode, and turn the thang into a straight AC ONLY unit. Since I live in central Florida i do not NEED a heat pump, and for the few days it gets "cold" I can still use the backup resistance heater. :gespann: Plus I have a small stand alone "space heater")

Good find. You sure can wire that thing up to be straight a/c and it's a very simple task. You will want to get a regular t-stat when you do this. I am always armed with wasp spray when I open a unit up. The critters love the service area especially down south the ants will get in there.

You should have no problem getting that relay and contactor at any hvac supply house if they will sell to you.

:)

Grangers says that they will not sell to me direct , unless I am a business.

They did say that I could contact my local supply house and ask them for a list of resellers who I could go to for the parts. Of course that means more money, but if it is not unreasonable that's okay.

Due to the age of the unit I plan on replacing it soon anyway >>> for added efficiency and reliability, as well as resell enhancement to the new owners.

Thanks to all for your input and help.

(20 years aint bad service) :D

David Haynes