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geothermal assisted heat pump - warm air furnace

we require about 200 feet of VBH (vertical bore hole) for each ton of capacity. In your case, that would be 1200 feet of VBH.

Sounds like you are short hole to me..

It could also however, be an improperly set dip switch...



  • Sean Heath
    Sean Heath Member Posts: 1
    Geothermal assisted heat pump

    I have a 2,400 sf. brick bungalow in Chicago with a geothermal assisted heat pump connected to a warm air furnace with ductwork. The back up heat source is electrical resistance. The unit is a 6 ton Waterfurnace. Last winter the electrical bills were $800 or more. The fault light on the thermostat indicagtes that the back up heat kicked in. The installer put in 20 wells 40' deep each for the refrigerant loop. Given the size of the unit, is the loop circuit properly sized for Chicago's climate? What should I be looking for? I don't want a repeat of last year's heating bills. I wasn't even warm.
  • Nick S
    Nick S Member Posts: 62

    Sheesh, so much for energy savings, huh? The light on your thermostat is indicating the EMERGENCY heat is on. Judging by your electric bills, the electric back up heater was handling all of your heat. Call your contractor out there to see what is going on. You definately have a problem.
  • Glenn Harrison_2
    Glenn Harrison_2 Member Posts: 845
    You may have 2 issues...

    One, as Mark E said the loops may not be deep/long enough, unfortunately, I cannot help with that one as I am not up on the loop sizing for WaterFurnace.

    Two, a 6 ton heat pump will give you approximately give you 72,000 BTU's of heat, if the fluid in the loops is aroung 50*, and the capacity will drop as the fluid temp drops. Being in the Northwest suburbs, I know a 2400 sq ft house will usually require around 100,000 to 125,000 BTU's to heat in cold temps, depending on how well built and insulated the house is. A heat loss should be done to determine the true heat loss of the bungalow to determine what size heat pump and possible extra electric heat you need.

    You also may have problems such as the electric heater package being undersized, and/or not working correctly, the many dip switches in a WaterFurnace not set correctly, the loop pumps may not be the proper size, or may not be working correctly, the geothermal loop may not have enough pressure, which would also effect/prohibit the flow of the fluid through the loops.

    I would get the installing company back there to confirm the system is doing everything it is supposed to in the Heating modes. If you are not satisfied with them or there answers, Contact WaterFurnace and ask for Dave Buss, he is the Chicago and beyond area rep, and I'm sure he and/or tech services can help you out.

    By the way, If your wondering I have taken the WaterFurnace service and installation classes, and have worked on them many times. However I am no longer working for a WaterFurnace Authorized contractor. I am located out in McHenry County.
  • singh
    singh Member Posts: 866
    Sounds like

    you have a direct DX type of system. That is copper loops in the ground at shallow depths, inside of the copper is refrigerant.
    The plus side of this type of system is copper has better heat transfer between the ground, the negative is that copper is suspect to develop leak if soil is corrosive. It's possible the refrigerant leaked out, calling for the back up heat.

    Just a guess.

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  • Perry_3
    Perry_3 Member Posts: 498
    I second Glenn Harrison's comments

    I'm a homeowner sevearl hours north of you in Wisconsin.

    I also looked at using geothermal. I have about a 1300 Sq Ft house... and was looking at more borehole lenght than you have (and a direct HX system) - for about the same size unit you have (5-6 ton range).

    My heat loss calculated to about 55,000 Btu/Hr - after I had improved insulation and windows in the house.

    You really need to understand what your home heat loss is: There is heat loss calculator software available free from one of the boiler vendors on this site. Click on the appropriate buttons on top to find it (it will show up as a CD in the mail in about 2 weeks).

    Overall, I suspect that your geothermal system is well undersized for your house. I suspect that the amount of bore hole length is undersized for your system - in order for it to work year after year (too little bore hole and spaced too close and the ground temperature does not recover each year - and the system doesn't work after several years).

    All that explains why you have such a high electric bill.

    In the end; I personally chose to go with a new high tech boiler for my situation. I cut my natural gas bills by 45%.

    Of course, such efficiency improvements may not happen for a forced air system.

  • Not Waterfurnace but...

    I recently spoke to Econar about well sizing and they want a 170' well per ton here in CT. So even with those figures you come up a couple hundred feet shy on well.

    And I concur, if your heatpump is using crazy amounts of juice it's probably running the electric heat more than it should. The question is why.
This discussion has been closed.