geo thermo heat pumps
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  1. #1
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    Mar 2008
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    shamokin pa
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    Confused geo thermo heat pumps

    do they work good in the winter when temps go belo 20

  2. #2
    Join Date
    Feb 2006
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    91
    I live in Montreal where the daytime temperatures often go below 0F. I have a GSHP and it works fine at those temperatures. Like any HVAC system, a load calculation and proper sizing are required by a professional installer.

    Paul in Montreal.

  3. #3
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    Mar 2008
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    shamokin pa
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    Quote Originally Posted by pyropaul View Post
    I live in Montreal where the daytime temperatures often go below 0F. I have a GSHP and it works fine at those temperatures. Like any HVAC system, a load calculation and proper sizing are required by a professional installer.

    Paul in Montreal.
    thanks for your reply i was just woundering how they work in cold envirements . since i work on reg heat pumps. my employer had them installed at a building accross the way where the old heat pumps were 15 ton units and replased with the same btus made by florida heat pump. i wont be touching them for awhile till the begining of next year.

  4. #4
    Join Date
    Mar 2003
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    PA/DE area
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    LOOP sizing is key as well as equipment sizing,cold weather can run loop temps too LOW and put you on back up heat and all your savings gones out the window.
    It's NOT the BRAND,it's the company that installs it!!!!!

  5. #5
    Join Date
    Mar 2007
    Location
    Connecticut
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    104
    Quote Originally Posted by heatpumpguru View Post
    LOOP sizing is key as well as equipment sizing,cold weather can run loop temps too LOW and put you on back up heat and all your savings gones out the window.
    Actually duct size is more important - CFM capacity is the key to heat pump performance. Loops are important too, but I investigate GSHP problems all over the northeast and consulte on HVAC issues all over the US and airflow is the number one problem with heat pump performance across the entire US that we find.

    I've touched over 300 GSHP's and have only seen a few that had questionable loop sizing - and actually it turned out in most of these cases the loop installer didn't grout the loop properly or just lied about the amount/depth of loop installed.

    Do NOT design ducts to .1" of static. You must actually design them correctly. If attaching to existing ducts - you absolutely have to measure the static pressures and airflow of the existing system before you can determine how much duct modifications will be needed to make the system work correctly. .1" may actually work in a simple ranch, but most of the newer houses I've designed ducts for are coming in around .075" per 100'

    Heat pumps need around 450 cfm per ton of cooling capacity to work correctly. We typically design regular A/C systems for around 400 cfm/ton, yet rarely ever see more than 325 cfm per ton.

    In terms of performance, the colder the return air coming back into the heat pump air handler (condenser in heating mode) the more efficient they are. I am constantly dealing with customers who set their thermostats to 72 degrees because they think their GeoExchange systems are so efficient that they don't have to care. When the return air is around 70 degrees you can loose .5 COP or more from the rating! I wont mention the thermostat and control issues other than to say the electric resistence should be on it's own circuit breaker and turned off. WaterFurnace makes this hard with their standard wiring configuration, but can be done easily on most units.

    Typical field COP's are around 3.2 COP regardless of their rating. Best I've measured yet is 3.6. Yes they can get up over 4.0. but no one ever installs the ducts correctly - sadly.

  6. #6
    Join Date
    Feb 2008
    Location
    Waffleville
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    10,339
    Quote Originally Posted by hvac old guiser View Post
    do they work good in the winter when temps go belo 20
    OD temp doesn't have as much effect on a ges system because your using the stable ground temp to keep things going but it you may need some extra heat depending on the heat loss of your structure. here in NC geo systems do not need any supplementary heat
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  7. #7
    Join Date
    Mar 2003
    Location
    PA/DE area
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    Most of the one's we had trouble with around here were LOOP related,for the exact reason you stated.One person had that stuff that was made by Goodyear I think was recalled.One guy drove for PORSCHE Racing and had 3 in the home and HVAC guys kept selling him equipment.They put in 12 sytems in in 20 years and keep fixing them between,because he had money and did not think to question them,he kept writting check.With the LOOP cost to redrill,he went with 3 INFINITY air sources.
    It's NOT the BRAND,it's the company that installs it!!!!!

  8. #8
    Join Date
    Mar 2008
    Location
    shamokin pa
    Posts
    3
    Quote Originally Posted by heatpumpguru View Post
    LOOP sizing is key as well as equipment sizing,cold weather can run loop temps too LOW and put you on back up heat and all your savings gones out the window.
    thanks for your input this system is going to be vary interesting to see if its going to do what its supose to do. the old heat pump system had 3 phase back up heaters this one has 1ph. and using the old fiberglass ducting and there is some long runs. well just see what happens

  9. #9
    Join Date
    Mar 2008
    Location
    northern Indiana
    Posts
    114

    Duct sizing

    While I agree with the duct sizing issues, 60 degree RA
    would lead comfort issues especially with older people.
    Assuming 20 degree TD, supply air temps would feel cool
    also. Low loop temps lead to lower COP s also, so proper
    sizing of both is very important. COP and and comfort
    level is often a delicate balance. By the way that
    waterfurnace aux. heat can be turned off via dip switch
    if you choose to do so.

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