Replyat all the things that could cause a high pressure situation and go from there. Did you put gauges on the unit? How clean is the outdoor coil? Etc, Etc, Etc.
Regular Guest
I'm not sure if I'm in the right forum area. I worked on a heat pump air conditioning unit the other day and the communicating control board was flashing a code saying it was on high pressure lock out. After checking all the basics nothing showed obvious as to what was the problem. I disconnected the power supply to the control board to see if it would reset and it did. I decided that it was the control board itself and replaced it. The person did not have the problem again before I changed it but just to be sure I replaced it anyway as it is under warranty. What do you think the problem is???
Professional Member*
at all the things that could cause a high pressure situation and go from there. Did you put gauges on the unit? How clean is the outdoor coil? Etc, Etc, Etc.
Regular Guest
The coils looked clean and the unit is no more than a couple years old. I noticed for a brief moment the compressor kicked on before the fan which suggested there was a problem with the fan but it checked out fine. The other tech was checking the inside unit and he didn't find any problems there. I did not put the gauges on it because I pulled the power to the control board and it reset with no problems. I'm pretty sure it's not overcharged. The person has not called back with any problems. I'm pretty stumped on this one what do you think some of the most common causes would be. It's a Trane a/c heat pump with the communicating board.
Professional Member*
operate the unit in both stages? What is the model # of the outdoor unit?
Professional Member
it probably got switched over into heat mode on accident
Professional Member
ive had something close to your problem could be a weak run capacitor, have you checked the play in the outdoor fan shaft , sometimes when bearings go bad it runs fine while youre their and when you leave locks up.It shouldnt move alot from left to right .
Banned
Always put your gauges on a system. You cannot begin to troubleshoot without superheat, subcool, temp diff across a coil, amp draws, static pressure and capacitor readings.Originally Posted by GSC
Regular Guest
I cant remember the model#. If I get a call to go back there I will have to check the run capacitor. The unit is pretty new so I dont think its the fan but I didn't check it. It was one of those situations were the problem was fixed quickly and then I moved on to the next call. I'll have to remember to ask the other service tech that was with me on some of these questions. My description is kind of vague. I was thinking it might have been the sensor malfunctioning but I'm not to firmiliar with these kind of units with communicating conrtol boards. Do any of you guy's know were I can get some literature on these type of systems?
Banned
Trans has a service manual on them. High superheat can cause a reciprocating compressor to go into thermal cutoff occasionally.
Regular Guest
I guess if Trane tests the control board I'll know for sure if that wasn't the problem. I'm a FNG in this field and I was with another service tech training me. I definitely agree on putting guages on at all times that will be kept on the top shelf when I get out on my own!!!!!!!
Banned
Sorry, your problem was high pressure lockout, not thermal cutout. Blocked txv overcharge,etc,etc fan motor .....at least you ruled out the board. Get all your measurements.
Regular Guest
If it had high superheat than that means it is low on refrigerant? There wasn't any signs of that but then again the systems was off long enough to avoid those signs. I think the other service tech asked if there was water around the furnace and she said no.
Regular Guest
The only reason I said low on refrigerant is because the outside coil was clean.
Banned
Thermal cutout (compressor overheat) could be caused by high superheat. High pressurelockout means the head pressure was too high more than once and the board locked it out from trying to start again. If your illustrious "teacher" is not going into these details but is rather changing random parts, you are in need of better tutelage.
Learn to take superheat, subcool, temp diff, amp draw, cap readings, static pressure readings and you will go far in your troubleshooting ability. Until you understand what these readings mean, it will be difficult to troubleshoot HVAC.
High superheat on a txv system could mean the txv is not opening enough.
Regular Guest
Do you think the fan was going on and off intermittently? I dont think it was the control board but wasn't sure. Its hard to determine the cause of a problem when the customer has had the system off for 24 hours and time is money you know!!
Regular Guest
Question for ChaseAir:
How do you do cap readings and static pressure readings? I know how to do the others.
Banned
Could be. Time is money so you ain't got no time to be guessing what is wrong with the thing.
Banned
a good multi meter has a capacitor tester. Magnehelic gauge is a pressure gauge for the ductwork. It helps evaluate airflow.
fieldpiece makes a good multi meter with an amp clamp temperature capacitance all in 1.
Uei makes a cheap digital manometer(another name for magnehelic gauge)
Professional Member
Testo 510 best for reading static in my opinion.
Regular Guest
What would i take a static pressure reading for? We just got a testo 510 at work i hope my boss let's me keep it in my truck. I used it once it is "VERY NICE" as we say in kazakhstanBorat!
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