Maryland 4 Ton Loops - 5 Ton System

Discussion in 'Maintenance and Troubleshooting' started by Garet Jax, Aug 21, 2020.

  1. Garet Jax

    Garet Jax New Member

    Hello all,

    I have been in my house for 8 years and have always had issues with the cost of heating. The first 3 winter months cost me almost $3000 until I figured out what was happening. From that point, I more or less shut down the electric backup heat. This controlled the costs. I installed a pellet stove to supplement the base heat.

    A few weeks ago, the coil ruptured in the geotherm unit. I refused to replace it without getting to the bottom of why the heat was unable to keep up without using the electric backup heat so much. I pulled the original permit and found there are two 320 foot loops. From what I am reading these loops are sized for 4 tons. My service company is telling me that my system is a 5 ton unit. Could this discrepancy be the reason why my electric heat is coming on so much?

    I am assuming it is because I had everything else checked out on the machine (by multiple service companies and the manufacturer) to make sure it was running to spec.

    The real question is what do I do? I really don't want to put good money after bad. I am looking at 3 real options:

    1) Add another 320 foot loop and fix the coil. This should provide the existing geotherm enough flow to correct the heating problem. I am not sure that this is the only problem and I am not sure how much life I am going to get out of the existing unit. The house is only 10 years old, but I have no way to know if running the system with too little flow for so long has caused damage elsewhere.

    2) I priced out adding another 320 foot loop and another 5 ton system and was shocked by the price (> $30,000). To be fair, this also involved changing the returns a little bit since the prospective installer thinks my unit is starving for air. The basement was finished by the original owners after the house was built and a return was never added.

    3) Go away from geotherm completely. I am very reluctant to do this since geotherm was one of the attractions to buying the house and I am convinced that I have 85% of a working geotherm system. I just want to finish the last 15%.

    Please help.
  2. ChrisJ

    ChrisJ Active Member Forum Leader

    Are the loops vertical? or horizontal?

    Adding a loop won't change the "flow", only the amount of pipe in contact with the ground. More flow would come from increased pumping.

    What pump or pumps are circulating fluid now?

    What was the entering and leaving water temps during winter? Supply and return air temps?

    Was the cooling working ok?

    How is the electric back up controlled?

    What is the size of the house?, insulation levels?
  3. Garet Jax

    Garet Jax New Member


    Flow was probably not the right term. When the system was heating, the water just didn't get restored quickly enough. It would constantly lose more and more heat until the circulating pumps would get frost on them.

    There are 2 pumps installed, but only 1 is running. My service company told me that is normal.

    Not sure - I am only going on what the service company has told me. The water should be mid to low 50s when coming from the ground. During winter it was much, much colder because the loops just didn't restore it to the proper temp.

    Yes. Other than significant cold wet air in the basement. I expect an extra return in the basement will help (maybe eliminate) this problem.

    Not sure I understand the question. It kicks on when the system feels it needs help. As I remember, I removed a jumper from the main board to disable the electric backup.

    It's about 3200 square feet. The basement was finished and an extension was added after the home was originally built. The original house was sized for 4 tons. I believe the finished basement and extension pushed it to 5 ton.

    I had a company in to evaluate the house for leakiness and was told it was very tight. I seem to remember 95%+.
  4. ChrisJ

    ChrisJ Active Member Forum Leader

    Well that's not really true, entering water temps (EWT) always trend downward as the winter goes along. That's why there needs to be antifreeze in the loops. The ground around the pipes becomes colder then average ground temp, it's normal for EWT's to get down to 30-35*F. The heat pump still makes rated BTU's.

    Usually the electric backup is controlled by the thermostat, for example when the temps in the house are 2-3* below set point, the system is losing ground and needs help, the backup comes on with the heat pump to bring temps up to set point.

    However, I have read about systems using a thermostat that uses outdoor temp to determine when the backup comes on. Which is all wrong for a ground source heat pump. Those tstat's are for air source HPs.

    5 Ton is about 60,000 BTU's, a tight well insulated house should not lose that much heat. Servicers need to test heat of extraction to tell if HP is working at capacity.

    EWT and LWT is important, the delta T, the difference between the 2 temps is going to tell us whether there is enough flow through the loops, and whether you need both pumps running. Using one when there are 2 is not a good idea, the unused pump restricts the flow.

    2 @ 320' loops, Do you know if the holes are 320' deep each or 160' deep for a total lenght(down & up) of 320'?. Rule of thumb...150'/ton, means 150' down & 150' back up. My other thought is that it's always possible the water is only flowing in one of the 2 wells.

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