Residential A/C Experts Help

[Runs2rch]

Have a Lennox heat pump with a scroll compressor. Tuned up last summer. New capacitor, fan motor, contactor, and defrost board. Freon level checked/verified.

Ran perfect all summer. Now switching and running heat it was fine for the last month or so. Noticed the fan/compressor not kicking on. Pulled panel. Diagnostic Led's show high psi lockout.

Flip Breaker to reset. Led's now show normal operation. Ran for the 5 times and locked out again.

Has High pressure switch only. I'm guessing the switch is bad.

Can I use a jumper wire to bypass the high psi switch?

I'm guessing the compressor has its own built in protection and the high psi switch is redundant?

 

[Riverbound]

Is the fan running?

 

[SoCalDave]

Is the fan running?

X2

 

[Shlbyntro]

Is it a thread on high pressure switch?? They're easy and cheap enough to change just to see... if you do it quickly you won't really lose any freon either. Make sure you get the correct switch for your type of freon

 

[Riverbound]

Is it a thread on high pressure switch?? They're easy and cheap enough to change just to see... if you do it quickly you won't really lose any freon either. Make sure you get the correct switch for your type of freon

View attachment 957843

It’s almost never the high pressure switch.

 

[TrollerDave]

Could there be a sensor on the indoor coil that could be tripping a “ high pressure” lockout?
Is your filter clean?

 

[Shlbyntro]

It’s almost never the high pressure switch.

I've had a rash on marine units as of late, especially the 410 units. Replaced 4 last summer. Agree that it could be another issue tho

 

[rrrr]

Can I use a jumper wire to bypass the high psi switch?

I'm guessing the compressor has its own built in protection and the high psi switch is redundant?

No and no. There's a reason the unit is tripping offline.

 

[jet496]

Verify that your indoor fan is running & the filter is clean (the indoor unit is now the condenser & the outdoor is the cooling unit). Make sure the indoor coil is clean and all your dampers are open at the registers or in the ducts (basically just verify you have normal airflow).

If those aren't it there could be be restriction in the refrigerant system or maybe they overcharged it if they added refrigerant during it's checkup. Or the fan could be on a lower speed for some reason.

DO NOT JUMP THE HIGH PRESSURE SWITCH. Put gauges on & that will tell you if the pressures are going up.

 

[Runs2rch]

Is the fan running?

Yes fan is running.

 

[Runs2rch]

Could there be a sensor on the indoor coil that could be tripping a “ high pressure” lockout?
Is your filter clean?

Filter is drawer style. It is clean. All registers open. Also condenser coils are clean.

 

[Runs2rch]

What would cause it to kick ass all summer with zero issues, and then only have the high pressure lockout in heat mode?

If it was overcharged wouldn't it have a high pressure lockout in cooling mode also?

 

[TrollerDave]

What would cause it to kick ass all summer with zero issues, and then only have the high pressure lockout in heat mode?

If it was overcharged wouldn't it have a high pressure lockout in cooling mode also?

Heat pumps reverse the flow of the refrigerant so the indoor coil, which is smaller, now is the hi pressure side. The exact refrigerant charge is more critical because of this. They have a little tighter parameters on how/when they work. "Kick ass" in the summer is easier to cover up an issue than in the winter with a heat pump.
The only way to tell if the switch is bad is to have gauges on it to see when it opens. If you bypassed, the problem could still be there and probably end up being A LOT more expensive.

It could be a lot of things. Might have to call someone out.

 

[TPC]

What would cause it to kick ass all summer with zero issues, and then only have the high pressure lockout in heat mode?

If it was overcharged wouldn't it have a high pressure lockout in cooling mode also?

No. HP switch is doing it's job correctly. It's working.
May need the charge adjusted, could be a solenoid,,, could be several things.
Ya need a tech to check it out. Don't mess with it you may toast the compressor with all the starts and stops and hard starts.
Call authorized Lennox.

 

[Runs2rch]

So the only other change is the defrost board. Lennox stopped making this part number. The new one is one they made for a bunch of different models.

Seems like the unit has never really run the same in the winter like it used to.

Tech came out and checked charge in September. Also verified all pressures.

 

[rrrr]

So the only other change is the defrost board.

Is this the first time you've run the unit in heating mode since the board was changed?

If so, something the tech did installing the new board is fucky.

If not, it's possibly a sticking reversing valve. When the HP cutout is reset, how long does it run before tripping? Seconds? Minutes?

Have you tried running it in cooling mode to verify that's OK? Have you tried cycling it between heating and cooling modes a few times?

Have you checked the defrost board terminal strip to make sure the wiring is firmly attached?

 

[Runs2rch]

This is the first time you've run the unit in heating mode since the board was changed?

Something the tech did installing the new board is fucky.

No last winter ran no problem. I double checked board wiring to the Lennox instructions. You are right though. Initial install of board was fucky.

Leads me to think with everything in check that the High psi switch is bad?

 

[rrrr]

Leads me to think with everything in check that the High psi switch is bad?

After the reset procedure is done, how long will the unit run before the HP switch kills it? Time it. Does the compressor sound like it's increasingly laboring under load before the trip occurs?

 

[Flying_Lavey]

No last winter ran no problem. I double checked board wiring to the Lennox instructions. You are right though. Initial install of board was fucky.

Leads me to think with everything in check that the High psi switch is bad?

Is the outdoor fan coming on? The defrost control board likely will control the outdoor fan to maximize performance in different conditions.

Also, was the coil temp sensor replaced with the board? If not, was it verified that the sensor is compatible with the new board (there are different resistor levels for different sensors and are not all a 'one size fits all' scenario)?

 

[Runs2rch]

After the reset procedure is done, how long will the unit run before the HP switch kills it? Time it. Does the compressor sound like it's increasingly laboring under load before the trip occurs?

It will run a few weeks.

Sounds completely normal. No laboring whatsoever.

 

[Runs2rch]

Is the outdoor fan coming on? The defrost control board likely will control the outdoor fan to maximize performance in different conditions.

Also, was the coil temp sensor replaced with the board? If not, was it verified that the sensor is compatible with the new board (there are different resistor levels for different sensors and are not all a 'one size fits all' scenario)?

Outdoor fan and compressor runs for a weeks. Then LED's show high psi lockout.

The DF sensor was not replaced. That makes perfect sense, and didn't cross my mind. I will verify that.

 

[rrrr]

It will run a few weeks.

Sounds completely normal. No laboring whatsoever.

I had the idea it was only good for a few minutes. With this information and the news the charge was adjusted in September, you should look there for an answer.

 

[Sherpa]

did OP reply how the indoor coil looks yet? air filters?? indoor fan motor?? any gauges been put on it yet?

 

[Runs2rch]

did OP reply how the indoor coil looks yet? air filters?? indoor fan motor?? any gauges been put on it yet?

Indoor coils clean, filter is new, Indoor fan motor running normal. No gauges yet.

 

[KMH]

A lot of heat pumps have a TXV in the condenser that works only during the heat mode. The unit will cool fine with out that TXV working properly. See if it has one and if it does check the cap tube from the valve to the sensing to see if it is broken.