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Thread: Stumped!

  1. #1

    Stumped!

    Help!! 2.5 Ton Goodman Heat Pump, when unit first turns on in cool, the suction psi is between 35-45psi, head pressure is between 125-150psi. These pressures hold steady at those psi's for 15-25 mins then both pressures slowly start rising and steady off at 70-75 low and 250-270 high depending on conditions. Problem is if pressures do not start rising fast enough sometimes unit will start freezing at evaporator. Unit does not freeze all the time just sometimes very infrequent. The air filter is clean, evaporator is clean, condensor is clean and evap. fan is running good on high speed. Could I have a restriction at the orifice, but usually the circumstances are the reverse of what i am finding. Any thoughts would be appreciated. The compressor was replaced in April 08 and has been running good up until about a week ago.

  2. #2
    Join Date
    Dec 2007
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    Kansas
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    Are you sure the indoor fan is coming on when pressure reagings are low?

  3. #3
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    Dec 2007
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    Ohio
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    2,875
    Superheat?
    Subcooling?

    Just because your fan in on high doesn't mean it's right. Have you tested staic pressure to determine CFM?

    Sounds like a charge issue to me but without more information, hard to tell.
    I need a new signature.....

  4. #4
    Yeah, indoor fan comes on every time.

  5. #5
    How do you test staic pressure?

  6. #6
    Join Date
    Dec 2007
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    Ohio
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    Jog.....don't take this the wrong way but if you have to ask, you may need to call a service professional out to evaluate your system. If you are a professional, get your post count up to 15 and apply for professional status on this site. There is a wealth of information on here, including step by step procedures for testing static pressure.

    We are not allowed to give out DIY advise on the open forums of this site but once you are professional, we can talk shop all day and night.

    I can tell you this....we test static pressure to get the amount of CFM a blower is moving. If you follow the 400 CFM per ton rule then your indoor blower should be moving as close to 1000cfm as you can get. After that is verified, then you can begin adjusting your refrigerant charge using superheat and subcooling measurements.
    I need a new signature.....

  7. #7
    O.K. thanks for the heads up. I am not a pro. just a maintenance tech at a n apartment complex, only been in the hvac/maintenace field about a year so this is really the first unit i have had that has given me a problem I couldnt figure out and my superiors think it is a bad compressor but i am not sure and dont want to just changing out parts if you no what i mean!

  8. #8
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    Jan 2004
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    Lancaster PA
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    66,818
    Was it the compressor that was changed out in April, or the condenser.

    What are the chances that someone has added gas to get the vapor pressure up.
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    How many times must one fix something before it is fixed?

  9. #9
    Join Date
    Jan 2005
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    Quote Originally Posted by Jogalloway View Post
    O.K. thanks for the heads up. I am not a pro. just a maintenance tech at a n apartment complex, only been in the hvac/maintenace field about a year so this is really the first unit i have had that has given me a problem I couldnt figure out and my superiors think it is a bad compressor but i am not sure and dont want to just changing out parts if you no what i mean!
    Still get your post count up and apply for pro status if you get it you will get all kinds of really good info from all of these great techs. Being a rookie does not mean that you are not a pro, it is defined by the way you approach problems and asking questions before making mistakes is the first step in the pro-direction. Good Luck
    "It's always controls"

  10. #10
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    Quote Originally Posted by skwsproul View Post
    Still get your post count up and apply for pro status if you get it you will get all kinds of really good info from all of these great techs. Being a rookie does not mean that you are not a pro, it is defined by the way you approach problems and asking questions before making mistakes is the first step in the pro-direction. Good Luck
    Agreed. If you are working on HVAC equipment as part of your making a living, have a cfc certification to work with refrigerants and are part of the daily HVAC industry, you qualify as a pro.

    Because of how long the system operates before the pressures change, there must be a change in the system operation. My guess would be that a refrigeration issue is causing an airflow issue later in the cycle.
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  11. #11
    Thanks guys, compressor was changed in april 08, no problems until last week, lady called office and said she had ice all over filter, another tech checked the first time and said filter was dirty and low charge, he changed filter and charged unit. Lady calls back to the office on thursday of this week and said it was froze again. i checked this time, let unit thaw, turned on cool, hooked gauges up and had 38psi low and 130 psi high, thought to myself we have a leak, walked to shop to get nitrogen etc and other tools, returned to unit about 20 mins later and i had 72 psi low and 250 psi high. Condensor was pulling some major heat out, i cussed to myself a little bit, evap. fan was set to run low speed, I installed black wire from motor to control board to run at high speed you could feel and hear the change in motor when I started back up, cleaned evap. coil and condensor, thought to myself that fan was on low speed was the problem. Turned unit back on, check gauges and it was doing the same thing as before. Been keeping check on unit since friday and it is cooling but just a matter of time before conditions are right to cause it to freeze up again and the lady can yell at me again. Ha Ha

  12. #12
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    Toledo, Ohio, United States
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    Twilli says whats CFC?
    No Heat No Cool You need Action Fast

  13. #13
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    Quote Originally Posted by Jogalloway View Post
    Thanks guys, compressor was changed in april 08, no problems until last week, lady called office and said she had ice all over filter, another tech checked the first time and said filter was dirty and low charge, he changed filter and charged unit. Lady calls back to the office on thursday of this week and said it was froze again. i checked this time, let unit thaw, turned on cool, hooked gauges up and had 38psi low and 130 psi high, thought to myself we have a leak, walked to shop to get nitrogen etc and other tools, returned to unit about 20 mins later and i had 72 psi low and 250 psi high. Condensor was pulling some major heat out, i cussed to myself a little bit, evap. fan was set to run low speed, I installed black wire from motor to control board to run at high speed you could feel and hear the change in motor when I started back up, cleaned evap. coil and condensor, thought to myself that fan was on low speed was the problem. Turned unit back on, check gauges and it was doing the same thing as before. Been keeping check on unit since friday and it is cooling but just a matter of time before conditions are right to cause it to freeze up again and the lady can yell at me again. Ha Ha
    Will need more info. Superheat, subcooling, static pressure, compressor amp draw. Do not get discouraged we all started somewhere too. Keep posting, get that pro status and you will get your answer and a wealth of knowledge at your finger tips. Understand that DIYers can be very dangerous with just a little information and that is the reason that this website screens for its members as well as protecting the industry. A lot of apartment techs (and many other general maintenance techs) just use high and low pressure to verify a charge but that is not the proper way, and do not waste your breath trying to convince them otherwise they are blinded by the ignorance of the reset and run way of fixing things, if you want to be anything other than a rent-a-hack you will learn the proper way to do it. Have patience the pro status has been invaluable to me and several of my co-workers and I am 100% sure that if you are as enthusiastic to do things the right way it will be invaluable to you too, not to mention your value $$$ as an employee.
    "It's always controls"

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