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gotoman for ac, HVAC Technician
Category: HVAC
Satisfied Customers: 5052
Experience:  51 years of experience install design and repair of all makes and models of AC
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My Ruud 2.5 ton Heat Pump Model UPKA-031JAZ (Serial# 6389M309912572)

Customer Question

My Ruud 2.5 ton Heat Pump Model: UPKA-031JAZ (Serial# 6389M309912572) has an Auto Defrost Problem. Last winter the outside coils were freezing up. The temporary solution was to periodically switch from heating to cooling mode. This heated the outside coils clearing the ice. The technician tracked it to a failed Defrost Controller. I now have a replacement controller board with sensor, Rheem P/N 47-21517-11 9928-09 DDL-013002-ORH. The original board and the replacement are NOT the same.

I need help performing the replacement and post installation prechecks and restarting/testing.
Submitted: 6 years ago.
Category: HVAC
Expert:  Douglas replied 6 years ago.
Hi, I'm Douglas and I am here to help you resolve problems with your heating and cooling equipment.

The board should wire up the same but let me verify the OEM part to this one while it may be laid out differently, the wires should still be the same. Do you have the the number from the original board? It should also start with 47-xxxxxx-xx

This is a demand defrost control board, the PKA-031 should have had a demand defrost in it as well.
Customer: replied 6 years ago.
Sorry for the delay in following up. Its been a while and I needed to open up the condenser to double check .
The original card was 47-21517-11.
The new card is Rheem P/N 47-21517-18

The new board has 2 different sensos on leads, not just 1. The first appears to be the same as the original but the leads are longer - this is not a problem, I can tywrap the leads somewhere out of the way. The second sensor is new, WHAT TO DO ????

Also, Any help on other help with the replacement and post installation prechecks and restarting/testing would be apreciated.

Thanx,
Chuck

Expert:  gotoman for ac replied 6 years ago.

One lead clamps to return bend on coil. The other is an ambient sensor just let it hang loose in the air below box that holds contactor. Just try system. No post checks needed. if it was the defrost board and Rheem has a lot of problems with them it will be fine. I have a RHeem and have replaced two board in two years. This accept goes to Doug. Russ

Customer: replied 6 years ago.
I have two remaining questions concerning this repair:

First is a longer term concern -future replacement. This Ruud seems solid but my research has uncovered a large amount of negative press concerning quality and longterm reliability. Is this true of all Heat pump systems, or has Ruud changed. You guys are in the trenches where the rubber meets the road. What would you consider for yourself?? Please, any input would be appreciated.

Second concerns testing (trusting my repair). It is summer and the defrost control system is dormant. this appears to be for 3 reasons:
1. The system is on Cooling.
2. Action is triggered by the Frost Sensor and there is no frost on the outside unit.
3. There is a sensor for ambient temperature (New???) does it prevent defrost operation above some preset temperature??

The first I can handle, Just switch to heating and set the thermostat high enough.
It's the last 2 that concern me.
The hardware for the defrost operation is currently working. The heat pump is in the AC mode thus in the defrost mode as it heats the condenser coils outside. If there was frost on them it wouldn't last long!
My real concern is that the defrost CONTROL SYSTEM works. I may be very dense, and I don't have an environmental chamber let alone one big enough to fit the outside unit in, but isn't there a way to cycle the CONTROL SYSTEM NOW rather than wait until winter to find out, when it's too late, that it still doesn't work??
Just exactly how do I "Just try the system" when the sensors are keeping it out of play???

PLEASE HELP
Thanx,
Chuck
Expert:  gotoman for ac replied 6 years ago.
I sell Trane equipment but have a Rheem heat pump outside. Just like the Rheem because of it simplicity and ease to work on. They are as reliable as the next unit. I live on the gulf coast and the Rheem can not take the salt air but I am about a 1/2 mile offcoast. That is an on demand defrost you cannot force defrost. If it is a new board you will be fine. This defrost takes into consideration outside temp,coil temp and length of running time. With these higher temps it would be 100 degrees inside before you could possibly check defrost. Russ
Customer: replied 6 years ago.

I'm still not comfortable with the Idea that "if it's new it's OK" and feel the need to confrirm before the middle of winter and I need to dig thru snow to get near the outside unit.

Check out this link I found: http://www.hvac.amickracing.com/Heat%20Pump%20Information%20and%20Data/Defrost%20Controls/Ranco%20DDL%20defrost%20control.pdf
Some of it I "think" I understand but am not positive what I am looking for example: How do I know wnen the reversing valve has reversed?. There is a big difference betweenbelieving I usnderstand a concept and KNOWING when it has happened - and happened properly.



Before I found it, I was considering the following test, can you possibly review it and fill in the blanks? Any other suggestions would also be apreciated.:

1. Get 2 styrofoam cups, fill the first with crushed ice and add a little water (a slushie) fill the first with very hot water.
2. If possible turn off the backup heating (deselect it at the control or turn off the power to the backup heating)

3. Before mounting the sensors place them both in the hot water.

4. Turn the system on to heat and set the thermostat
DO NOT RUN IN THIS MODE FOR AN EXTENDED TIME!!! (DO NOT ALLOW OPERATION IN DEFROST WITH THE SENSOR FUNCTIONS ALTERED LONGER THAN NECESSARY. WITH A WARM AMBIENT TEMPERATURE, HIGH PRESSURES CAN DEVELOP DAMAGING EQUIPMENT).

At the outside Unit I should notice???? 1.______________________________________________________________________________
2.______________________________________________________________________________
3.______________________________________________________________________________
4.______________________________________________________________________________
5.______________________________________________________________________________

5. Move the AMBIENT sensor to the "slushie".
The changes at the outside Unit I should notice are:______________________________________________________________________________
______________________________________________________________________________
This will take about________________ seconds / minutes But no longer than _________________ seconds / minutes

6, Move the coil sensor to the "Slushie".
The changes at the outside Unit I should notice are:______________________________________________________________________________
______________________________________________________________________________
This will take about________________ seconds / minutes But no longer than _________________ seconds / minutes
DO NOT RUN IN THIS MODE FOR AN EXTENDED TIME!!!

7. Move the coil sensor to the HOT water.
The changes at the outside Unit I should notice are:______________________________________________________________________________
______________________________________________________________________________
This will take about________________ seconds / minutes But no longer than _________________ seconds / minutes

8. Move the AMBIENT sensor to the HOT water:
The changes at the outside Unit I should notice are:______________________________________________________________________________
______________________________________________________________________________
This will take about________________ seconds / minutes But no longer than _________________ seconds / minutes

9. If all operations are normal, rreturn unit to normal operation and complete the installation:
Return unit to normal operating mode and reset thermostat.
Enable backup heating if turned off
Turn off unit.
Turn off power to outside unit
Install sensors in final locations. Replace covers etc.
Restore power to outside unit.
Perform final checks.
Customer: replied 6 years ago.
In my hast to get the last request out, I had some typos. here are the corrections.

Some of it I "think" I understand but am not positive what I am looking FOR - FOR EXAMPLE : How do I know wnen the reversing valve has reversed?. There is a big difference BETWEEN BELIEVING I usnderstand a concept, and KNOWING when it has happened - and happened properly.

1. Get 2 styrofoam cups, fill the first with crushed ice and add a little water (a slushie) fill the SECOND with very hot water.


Expert:  gotoman for ac replied 6 years ago.

You can use this but wait till weather cools a little. You will need to run several minutes but in this weather the unit will go out on high head pressure before you can check system. When the reversing valve switches you will know. The compressor will make a noise and you will here the valve switch. Russ

gotoman for ac, HVAC Technician
Category: HVAC
Satisfied Customers: 5052
Experience: 51 years of experience install design and repair of all makes and models of AC
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