High pressure warning AC

[Dan Leff]

40’ sedan bridge Forward stateroom unit keeps getting a high pressure warning. I have blown out the lines and get good water flow. I ran barnicle buster through the lines and it still is showing a hp warning. The other unit is working fine and has great water flow so the pump is working fine as it controls both units. I have reset the thermostat but still get the warning. Looking for any else I could try before calling in a pro. thanks

 

[ocgrant]

If it is truly going HP and the cooling is good do you have good air flow through the evap coil? Is the filter clean? Short of that the unit is done due to blockage

 

[GirlyGirl1999]

Is the sensor not replaceable? I’m spit balling here, not an A/C expert.

 

[Mark.60]

The high pressure switch is replaceable and readily available at any HVAC supply house.
If the original one is soddered into place just screw the new one on the high pressure schradder valve and connect the two wires.

 

[exsailer]

You might give Flight Systems, Mechanicsburg PA a call they have been very helpful to me over the years. They are mainly into the electrical/electronic side of AC never asked them about the "freon" side.
If you cleaned out the condenser sufficiently (recirculate for ~2 hours) with Barnicle Buster then I would be thinking low on "freon".

 

[ttmott]

40’ sedan bridge Forward stateroom unit keeps getting a high pressure warning. I have blown out the lines and get good water flow. I ran barnicle buster through the lines and it still is showing a hp warning. The other unit is working fine and has great water flow so the pump is working fine as it controls both units. I have reset the thermostat but still get the warning. Looking for any else I could try before calling in a pro. thanks

If it is truly going HP and the cooling is good do you have good air flow through the evap coil? Is the filter clean? Short of that the unit is done due to blockage

"HP" error is different than "HI PS" error. Which are you getting?
HI PS is related to the head pressure or the pressure switch.
HP from what I understand a loss of data communications.
I've had both. The new (2019) 27K BTU unit in the solon of my boat kept tripping out on both errors even with good water flow. As it ended up the HI PS was because the wrong pressure switch was installed. They had the older R22 refrigerant switch installed in a newer R410 system; different pressure ranges which made the system shut down when the raw water temperatures were higher. The HP error was from a bad data cable connection between the controller and display interface.

 

[km1125]

You also might try toggling into heating mode and running for a bit a few times to make sure the reversing valve is fully in the "cooling mode".

 

[ZZ13]

Hi PS comes from the refrigerant not absorbing enough heat in the evaporator to transition the refrigerant from a pressurized liquid (from the compressor) to a less pressurized gas (it’s normal state). As mentioned, poor airflow over the evaporator can cause this. Not sure what the temperature around that units evaporator was at the time but if it’s too cool you also won’t get any heat transfer into the refrigerant. I’ve gotten Hi PS when I’ve had the unit in humidity mode during cool fall/winter/spring days. I’ve had it try to cool in humidity mode when the ambient air was in the 50s (unintentionally of course). Doesn’t work. Ha!