Heat pump service gone wrong.

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  #1  
Old 10-09-18, 03:49 PM
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Heat pump service gone wrong.

Heat pump/ac unit that has been flawless for the 15 years I have been here. Nothing but yearly cleanings. Condenser is about 15 years old, air handler about 30.

We recently had a power outage for 12 hours. When the power came back on only the heat pump would work, setting thermostat to cool would only produce hot air. After some DIY troubleshooting it seemed to be the reversing valve not getting energized to make the switch to cold. Doing some further research it seems this is a common problem with Nest thermostats (which I have). Before I went too far down a rabbit hole I decided to call a tech to come look it. Prior to his arrival, we had the system set to off with the fan on running for about 6 hours without an issue. Here is what happened next:
  1. Set thermostat to cool, jumping reversing valve at condenser = cold air.
  2. Check air handlers wiring. Looks ok
  3. Sees Nest thermostat and says that is likely the cause. Doesn’t have replacement in truck. I dig out the original thermostat for him to use.
  4. Before swapping thermostat he attempts to jump reversing valve at thermostat connections. Reversing valve buzzes. Notes that is strange.
  5. Replaces thermostat, sets system to cold, blows transformer.
  6. Checks condenser wiring with meter. Checks ok.
  7. Replaces transformer.
  8. System set to cold and blows cold but transformer is getting hot. He ****s it down before it blows.
  9. Surmises there must be a short in wires out to condenser, will run new wire next day.
  10. I ask him to leave fan on for air circulation. System off, fan on (same condition as before he arrived). Transformer blows after a few minutes.
  11. Arrives next day and runs new wire to condenser and installs new transformer.
  12. Sets system to cold, reversing valve switches and blows cold air. Ran no issues for 5 minutes.
  13. Switches system to heat. Transformer now heating up. Reversing valve solonoid smokes.
  14. Says my problem is a shorted solonoid. Will only have heat and fan now. Had to disconnect 2 wires on circuit board to bypass shower.
  15. Locates part but says it is only sold with the valve, not separate. This is a 15yr old R22 unit and he doesn’t want to fix. Instead they come back with a recommendation to replace condenser and air handler at a considerable cost.

Questions:

A. Shouldn’t the shorted solonoid have presented itself sooner? Before I called him I had run the system in both heat and cool modes thinking it may have been a stuck valve, but had no issues in either.

B. I just have to think something was overlooked, because now the system is worse condition than before he arrived. Seems very odd that I cannot even run system in original condition without wires disconnected now.

C. What are my options here, other than getting a second and third opinion? Are there any checks I can do at this point? Could it be the wires between thermostat and air handler?

I’m sure a whole new system would be wonderful, but it seems like buying a new car because the old one needs the struts replaced.


Thanks in advance.

 
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  #2  
Old 10-09-18, 05:53 PM
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Welcome to the forums.

The defective reversing solenoid did present itself earlier. It blew out the nest O/B circuit.
The tech should have checked the resistance on it if was questionable.

Now you need a new reversing valve solenoid and most are replaceable without getting or changing the valve.

Post the full model number for the condenser.
 
  #3  
Old 10-09-18, 06:29 PM
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Thank you for the welcome! Not sure how I didn't find this place sooner.

Thanks for the quick response. I guess I (incorrectly) assumed that the solenoid was always good since it worked when he jumped it at the condenser. He did seem to check the condenser after the first transformer blew, but I couldn't tell what wires he was checking. Also, I guess my biggest question is if the solenoid was always defective, why did he have to pull 2 leads on the circuit board to stop the short when that worked fine before his arrival? Is this the difference between the circuitry on the Nest and a traditional (Honeywell programmable) t-stat?


As for the condenser it is a Carrier Model 38YCC018300

Jay
 
  #4  
Old 10-09-18, 06:54 PM
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That should use a common Carrier solenoid......EF19ZG034 / EF19ZG034A
He probably took the wires off the solenoid to keep from damaging the thermostat.

Solenoid link

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  #5  
Old 10-09-18, 06:59 PM
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Thanks for the link and helping me understand!

Jay
 
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