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Patricio

Lennox Heat Pump HP26

11 posts in this topic

My heatpump quit running.  I got it running again i don't understand.    It has a pressure safety switch circuit that after the 3rd instance that the unit goes off during one demand cycle, the defrost board will lock out the unit.  What causes the pressure to open the pressure switch?     How can I remedy the problem.    I reset the board by breaing the 24v hot lead from the thermost.    It is cold out there & momma does not like being cold.    

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You don't specify if the code is for a high pressure trip or low pressure trip. so here are some reasons for both. This is not a complete list

 

**** The below info regards heating mode only

 

High pressure trip: --- The evaporator coil inside is  the refrigerant condenser. Low airflow will cause high pressure trip. 

Look for dirty /restrictive air  filter , dirty evaporator coil, Closed vents , blocked return air. anything that can reduce  air flow. 

 

Low pressure trip. --- very Low refrigerant or

malfunctioning defrost cycle or defrost setting set too far apart and bad temperature sensor to start defrost. does the condenser(outside) coil ice up, and stay iced? most defrost cycles are no more than 90 minutes apart  when unit is operating at  very cold temps. 

 

Hope that helps shed some light on your problem. 

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LED 1 in the manual says pressure lockout does not distinquish between high or low.  Any way it worked overnight then shut out sometime early morning.   It is cold outside.   But no lower than 35 degrees.   The other night when it locked out it was in the upper 40's so I don't think I have a trouble with ice.   I will check everything you said about high pressure lock out.   Than you.

 I am going to open panel & do some more checking.  

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Wife turned the unit off this morning because blower was blowing with no heat & temperature in house dropped a few degrees.  I pulled service panel & the 2 LED's are flashing normal operation.   I turned unit back to heat mode & it is working now.   I am checking vents & air filter (it was changed last fall, the big accordion style).

 

Is it possible the control board is failing, The board failure code is not there.   

 

Now the thermostat is flashing a +2 next to the heat system.   I turned thermostat to off waited 5 minutes, turned back to heat system mode, set temperature 2 degrees higher.  Thermostat (electronic) clicked on & unit & blower energized.  Heat is coming out of ceiling vents.   I will monitor as I can, Have to go earn money now.

 

I checked venting all open & blowing,   Air filter was dirty but not blocked.  I vacuumed with brush nozzle, will get a new one today.

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The + 2 indicates a call for 2nd stage heating . This is usually electric resistance heat.  It is strange that the electric backup heat is not functioning  when  the HP stops working. You should almost not notice that the outside unit is not running . The 2nd stage " aux heat" usually kicks in when you get 2 - 3 degrees below setpoint . Do you not have electric backup heat, or is that broken ?  Or is something miswired perhaps. Heat pumps are alot more complex to wire and most installers do it wrong(scary no?).  

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Yes it has a heat strip,  it only works when I set the thermostat to emergency heat & when on this setting I get warm air but it does not shut off when the temp gets to the thermostat setting.  

 

I had a big AC & Heating company (they run several trucks) from this area install a new electronic thermostat last spring after the tech recommended a new stat was needed.     This is the 1st time I had to use the emergency heat that I can remember.   Since I am not a HVAC tech I have paid to have a professional tune the lennox up every other year.

 

I hesitate to call them back because of recent problems & word of mouth from others about poor performance & unnecessary charges.   I have been studying HVAC since the summer.

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Now the Heat pump worked without a hitch all night.  A balmy 74 degree.  Outside it is at the freezing mark.   Go figure.   Does the pressure switch resemble the pressure switch of a washing machine.  If it does may it be full of gookus that I could clean out?

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Now the Heat pump worked without a hitch all night.  A balmy 74 degree.  Outside it is at the freezing mark.   Go figure.   Does the pressure switch resemble the pressure switch of a washing machine.  If it does may it be full of gookus that I could clean out?

 

No, they aren't like a washer pressure switch.  They are hooked into the copper tubing inside of the outside coil. 2009-10-17_012629_pressure_switch.jpg

Edited by BryanS

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HVAC pressure switchws do fail.

If you read your pressures and know the pressures are good and consistent,you can bypass the pressure switch.

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Something I have not got into freon & pressure testing.  I have thought about it, have looked at the information for taking the exam & getting a license.     I think I would want some sort of accredited training.     But for now it is my heatpump, it hiccuped but seems to be working OK now & todays outside temps got close to 60.    I will continue to research & maybe come across something.   Just this posting has taught me a few things.   I am thankful that I am a member of Appliantology.

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jumptrout.....  "

 

HVAC pressure switchws do fail.

If you read your pressures and know the pressures are good and consistent,you can bypass the pressure switch.

 

Yes pressure switches do fail, but not often . they either work or don't in general.

AND the only  reason to ever bypass a pressure switch is an emergency,  with said pressure switch being replaced  ASAP.  Pressure switches protect the compressor. by removing a pressure switch you may very well be also removing 10 years from the life of the compressor if something tragic should happen like a catastrophic leak or fan motor failure.  :soapbox: 

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