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  1. #1

    Compressor Sizing

    I have an old WaterFrurnace Premier AT model ATV034 geothermal closed loop vertical well system
    The compressor is going out.
    The unit is rated at 30,600 btu
    The current compressor (not sure if original) is a Copeland Scroll 28,000 btu unit
    Copeland offers a 28,000 btu unit or 32,000 btu unit for my application.
    Can I upgrade to the larger compressor or will this cause me issues?

    Please note I will not be doing this work myself but having a friend who is certified do the work. I am just sourcing parts. He said the bigger unit would work and would not have to work as hard to cool the same.
    My friend is not a geothermal guy but has years of conventional experience. I thought I would ask here and get some additional info.

    Thanks for your time,
    Brian

  2. #2
    Join Date
    May 2006
    Location
    Philadelphia, PA
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  3. #3
    Seems to be leaking/bad valves in is his opinion. The unit has high suction pressure (110) and coil is only getting down to about 56 degrees. Head pressure is good(210). He replaced the expansion valve and drier last week. (reclaimed the R-22, sweated in new parts, pulled vac on unit, weighed in the new charge) But still not cooling properly. He put the sensing bulb thing off the expansion valve in a cup of cold water and the suction pressure went down proving the expansion valve was working and that made the coil get down into the 40's for a couple minutes then the compressor went into thermal cut off.

    The geo loop has proper delta of 9 degrees between input and exit from unit and it has the proper 50psi water pressure. He wasn't sure how to check/test flow rate but the pump was replaced 2yrs ago (a year before I purchased the house). So just guessing the flow rate is correct. Based off the paperwork I have on the unit and what he had the tools to test.

    I had 5 techs come out and look at this unit under the home warrantee and they were all completely worthless. So I ended up asking my friend to look at it once the home warrantee was expired as the unit has never worked well.

    Anyway not sure if I described this correctly as I was just his gofer and he was trying to help me out and I can only say what he told me about proper pressures and such.

    Anyway he said that the unit was rated @ 30600 btu and with conventional systems you could generally go plus or minus 3000 btu on the compressor from the unit rating and with the 2 size options he would go with the bigger one. But he said he didn't know if it was the same for geothermal but it should be fine. I was hoping to get a 2nd opinion here if possible before ordering parts.

    Current compressor installed (not sure if original) is a Copeland Scroll ZR28KQ-PFV-230

    Unit is 21 years old. I just can't afford the $10k for a new unit at this time and was hoping to throw a couple hundred bucks at it to get me through the summer.

  4. #4
    Join Date
    Jun 2011
    Location
    Central Indiana
    Posts
    614
    You really should find someone that is experienced and trained on geothermal. It sounds like you have some issues to address. First, waterside diagnostics need to be performed properly. You didn't provide enough info to make it clear if this was done properly. Some important numbers are missing. Proper water conditions must be verified before anything further is done.

    If nothing else, find a certified geothermal contractor and have them diagnose it. Replacing a good compressor will cost you more in the long run than having it properly diagnosed. Geothermal requires specialized tools and specialized skills. Not that your friend isnt a good tech, but this is a specialized situation.

    Check here for a dealer that specializes in Waterfurnace. http://www.waterfurnace.com/dealer_locator.aspx
    The only true knowledge is the pursuit of knowledge

  5. #5
    yeah have all (3) of the water furnace dealers in my area (within 75mi) sent someone out to my house in the last year. not a single one of them did anything with my loop. No temp test, pressure test, flow test, nothing. They all looked at the unit, slapped some gauges on it, and either put in Freon or took some out. Said the last guy who worked on this thing didn't know what they were doing. Charged my warrantee company a $ and said I needed to buy a new unit as this one was 20yrs old and they could get one installed for around $ after the government tax credit.
    There is no one else in my area to try. If paying out of pocket I would have been out over $ for all of nothing.
    One guy took a screwdriver to my duct work, ripped a hole in the side to see if the coil was dirty instead of taking 5 screws out and opening it at the seams.

    My friend has recently starting doing installs of new geo units for the company he works for but has very little experience servicing them.

    At least the first thing he did was check the static pressure of the loop, then the temp in and out of the unit, had me check it against the install manual. He checked several other things on the loop and desuperheater but my dog was harassing my kids so I was taking care of that when he was doing what he does. So I didn't want to post up info on what I didn't see tested or how he tested it.

    The expansion valve replacement fixed the extreme head pressure issue and the unit shutting off after running for an hour. But the low side is still not correct and he thinks that the valve issue probably caused compressor issues.
    The compressor sounds horrible and I don't really doubt it has an issue.

    I am simply wanting to know about the compressor sizing.
    Last edited by beenthere; 06-25-2013 at 05:13 AM. Reason: Price

  6. #6
    Join Date
    Jul 2011
    Location
    Nanaimo,BC, Canada!
    Posts
    346
    What compressor does water furnace list for your unit.. That would be a good place to start!

  7. #7
    as this system is over 20yrs old I have not been able to find any parts or documents anywhere online for this unit. Luckily the previous home owner had the original install documents or I wouldn't even have documents on the specs for the system I do have.

  8. #8
    Join Date
    Jul 2011
    Location
    Nanaimo,BC, Canada!
    Posts
    346
    Water furnace will be able to tell you.. Heck they can even recommend which compressor is the best fit for your unit..
    Geothermal units are sensitively balanced units.. Straying from the balance point will cause a lot of head aches! IMHO

  9. #9
    ok thanks will try to contact them directly tomorrow.

  10. #10
    Join Date
    Jun 2013
    Location
    NORTHERN
    Posts
    989
    This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary, or ask questions of the OP here.

    You can find the rules for posting and qualifications here.

    Further infractions may result in loss of posting privileges.
    Last edited by beenthere; 06-25-2013 at 05:18 AM. Reason: Non Pro * member

  11. #11
    Join Date
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    This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary, or ask questions of the OP here.

    You can find the rules for posting and qualifications here.

    Further infractions may result in loss of posting privileges.
    Last edited by beenthere; 06-25-2013 at 05:18 AM. Reason: Non Pro * member

  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,876
    GT1980, this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary or ask questions of the OP here.

    You can find the rules for posting and qualifications here.

    Your post has been deleted.
    Further infractions may result in loss of posting privileges.
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  13. #13
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    If it's over 20 years old, you might be best off replacing the unit with a new more efficient model A good geo controactor will evaluate the existing loop, do a load calculation to verify the equipment size, if hte ductowkr is adequate, and quote a couple difference optons.

    You could easily replace the compressor now and a couple months later the blwoer motor goes out, or worse, you get a coil leak. If the water coil leaks, there's a good change it will take out the compressor again.

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