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  1. #1
    Join Date
    Dec 2007
    Posts
    6

    Waterfurnace - low output temp problem

    I have a Waterfurnace Primere open loop system that is about 16 years old. Overall it works pretty well. Over the past few years my output air temperature has dropped a few degrees each year. Right now I’m only getting about a 10 to 12 degree rise in air temperature, with a max output at about 80 degrees even on stage 2. My service guy suggested cleaning the water side heat exchanger by reticulating a mild acid solution. I did that and no change. I also cleaned the air side heat exchanger with a brush and vacuum, overall that looks good. The service guy checked the refrigeration and said that the charge looks good and the compressor seems fine. I have also checked the water input and output temperatures. My water input temp is about 49, and with the valves wide open the output temp is about 45. In the past I valved back the water so that the output temp was at lowest 35, assuming this was a waste of water to let the excess run out. Valving back the water did not change the output temp of the air. Even with the water running wide open the output temp never peaks much over 80. I also have the fan speeds set a bit below the manufacturer factory set up, so it does not appear to be an excess air problem.

    I don’t have a ton of confidence in my service guy – he is not a bad guy, he just seems stumped and I don’t have any other options for service in the area I live (extreme northern Michigan). Any ideas?

  2. #2
    Join Date
    Mar 2004
    Location
    Grottoes VA
    Posts
    5,856
    The water flow through the HX needs to be a precise GPM. Call someone who knows what they are doing with the geo-thermal and have it adjusted.

    After they adjust it do not mess with it.

    Too much water will not allow heat transfer, too little water will not allow heat transfer and possibly freeze the coil.

    There is a calculation that can be done that will tell you exactly how much heat is being extracted by the coax coil. The coil could still be scaled and plugged.

    Call a Waterfurnace dealer who knows what they are doing.
    Karst means cave. So, I search for caves.

  3. #3
    Join Date
    Mar 2004
    Location
    Grottoes VA
    Posts
    5,856
    Go to www.waterfurnace.com and input your zipcode and find a dealer. If that doesn't help, I'm sure the Territory manager will help you.
    Karst means cave. So, I search for caves.

  4. #4
    Join Date
    Oct 2005
    Location
    Pacific Northwest
    Posts
    2,266
    Quote Originally Posted by karsthuntr View Post
    Too much water will not allow heat transfer....
    Please explain how too much water flow in heating mode will not allow heat transfer.

  5. #5
    Join Date
    May 2002
    Posts
    287
    Are sure your compressor is going into second stage? Four degree drop on the water seems a little low.

  6. #6
    Join Date
    Jul 2004
    Posts
    109
    Because you are moving the water so fast it is not able to extract the heat. In order to figure out how much heat you are extracting use this formula. Flow X 500 X temp. difference = heat of extraction/rejection

    Flow would be the gallons per minute.
    500 would be the fluid factor. Different number for closed loop.

    This just gets you started on figuring out if it is performing within specs. I would find a dealer in your area. They are pretty strict about having properly trained techs work on their equipment. I just took a 3 day class earlier this year. We install their product with many happy customers.

  7. #7
    Join Date
    Mar 2004
    Location
    Grottoes VA
    Posts
    5,856
    Quote Originally Posted by crmont View Post
    Please explain how too much water flow in heating mode will not allow heat transfer.
    What prolinehtg said.
    Karst means cave. So, I search for caves.

  8. #8
    Join Date
    Jan 2004
    Posts
    48
    gallons/min X 8.5 Lbs/gallon X 1 BTU per Lb Per degree= heat extracted The first part of the formula is shortened to 500 As long as the fluid makes contact with the heat exchanger wall then the energy will be transfered, it would take an extreme velocity to negat this law of physics, On an open loop system of that age I would also suspect the exchanger, dirty or maybe even a bit leaky. Amp draw of compressor could give a hint.
    Class of 70

  9. #9
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    238
    How can you determine if a charge is correct if you know the unit is not moving enough heat in the first place? I would look at the compressor and charge again. +1 on the amp draw. Is this a Bristol Twin Single compresser unit. if so what tonnage?

  10. #10
    Join Date
    Oct 2005
    Location
    Pacific Northwest
    Posts
    2,266
    Quote Originally Posted by tuckerin View Post
    ...As long as the fluid makes contact with the heat exchanger wall then the energy will be transfered, it would take an extreme velocity to negat this law of physics.....
    Thank you Mr. tuckerin.

  11. #11
    Join Date
    Oct 2005
    Location
    Pacific Northwest
    Posts
    2,266
    Quote Originally Posted by prolinehtg View Post
    Because you are moving the water so fast it is not able to extract the heat. In order to figure out how much heat you are extracting use this formula. Flow X 500 X temp. difference = heat of extraction/rejection

    Flow would be the gallons per minute.
    500 would be the fluid factor. Different number for closed loop.
    All good stuff but not realevent to an open loop system in the heating mode. See previous post by tuckerin.

  12. #12
    Join Date
    Dec 2007
    Posts
    6
    Quote Originally Posted by tuckerin View Post
    gallons/min X 8.5 Lbs/gallon X 1 BTU per Lb Per degree= heat extracted The first part of the formula is shortened to 500 As long as the fluid makes contact with the heat exchanger wall then the energy will be transfered, it would take an extreme velocity to negat this law of physics, On an open loop system of that age I would also suspect the exchanger, dirty or maybe even a bit leaky. Amp draw of compressor could give a hint.
    Tuckerin,
    Which heat exchanger are you talking about, the water to refrigerant exchanger or the refrig to air? I’m guessing you mean the water side. Last night I acid washed the water side again. So far I have sent 4 batches of an acid mixture of “super iron out” and water (1 cup per gallon) through the water side. The service guy loaned me a recirculation pump and I ran each batch for about an hour. The spent acid was brown, but there didn’t seem to be excessive solids – no major chunks. Is their any way to test to see if the water side exchanger is bad?

    P.S. thanks a ton for all the help

  13. #13
    Join Date
    Dec 2007
    Posts
    6
    Quote Originally Posted by drsmith012 View Post
    How can you determine if a charge is correct if you know the unit is not moving enough heat in the first place? I would look at the compressor and charge again. +1 on the amp draw. Is this a Bristol Twin Single compresser unit. if so what tonnage?
    DrSmith,
    Not sure on the charge, the service guy hooked up a pressure gauge when it was running and said looks ok. He also checked the amp draw. Not sure on the compressor. It is a two stage reciprocating

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