Maryland Variation on Gas Boiler with Heat Pump

Discussion in 'Maintenance and Troubleshooting' started by Tanja, Mar 17, 2016.

  1. Tanja

    Tanja New Member

    We are having trouble with a geothermal system, could use comments/suggestions/criticisms for how to fix it. Thanks for your time!


    1. We have a 7 ton Waterfurnace split system in our house, 3 tons upstairs and 4 tons downstairs. Model and serial numbers are: NDV049A111CTR, serial no. 110400562, ND2038A11AC, Serial no.110401016

    2. A 4 ton system was installed underground (2x300 foot wells in Maryland). The HVAC contractor is bankrupt and the well driller knows nothing.

    3. We have an old house with approx. 4300 square feet, 1600 feet in the basement (somewhat heated), 1700 on the main and 1000 on the second floor. The house has good insulation in the attic and good crack sealing, but otherwise it is an old leaky house -no insulation in the walls and 50 leaky windows.

    4. Before we installed the geothermal system we had radiators with a gas boiler. As far as we know those systems are still functional. The gas boiler is 130,000 btu/hr input, Burnham model no. 205ncc-te12, serial no. 64881444, from 2006

    5. In the summer, the geothermal system works well. We set ac at 78, the system stays on phase 1 and our bills are $100-150 monthly. In the winter, the system works ok until mid-20s, at which point it freezes out and I have to reset. Winter bills are $200 in mild months and $400+ in the cold months (too high). Last winter in the cold stretch we could not maintain heat.


    1. Add 3+ tons of underground wells (clean fix, but expensive, ruins backyard landscaping, and may be more system than we need and could lead to short cycling)

    2. Use the gas boiler as auxiliary heat for the heat pump at phase 1 at 5 tons (cheaper, uses existing systems, but geothermal may not operate efficiently)

    3. Increase insulation (would help, but likely not fix problem)

    Any thoughts on these options or others? Which do you prefer? What should we watch out for, ask about? Thanks for your time. Tanja
  2. malatu

    malatu New Member

    I couldn't imagine spending one single cent on hvac without having an energy audit performed and then upgrading the shell of the home by additional sealing and insulation. Blowing in insulation into the wall cavities is a no brainier and is money well spent. Consider closed cell foam insulation for wall cavities.

    I don't know where you live in Maryland but I just had an outfit perform house sealing and insulation to my residence and three rental properties. They are called Seal Right Foam Insulation and are located in Newark, DE. I was greatly impressed with their operation.

    You also might want to check with your State to see if there are any rebate programs for insulation projects. In Delaware, there is a rebate program that reimburses costs of insulation projects at approximately 40-45%. In my opinion, it's money well spent.
    Last edited: Mar 17, 2016
    waterpirate likes this.
  3. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    How did I miss your post. If running I can ride the metro from your house to our daughter's home in DuPont Circle.

    I am braver than malatu. I fix stuff without spending money on blower door testing. If the door leaks who cares if you are cold.

    You know what to do already. Run the geo units when they offer the best bang for your comfort buck and then add heat. You can do this by turning switches on and off or get an automated control run from your smart phone or anything in between the two ideas.

    It sounds like you could run the geos year round and add gas hot water heat only as needed, since they are separate systems.

    Since you live inside the beltway you may need to import tech help. I could design and build your new control sub-systems.

    warm regards,

  4. malatu

    malatu New Member

    I have a similar set up. We have an existing hotwater baseboard natural gas fired boiler. We use it as aux heat. As a result, we didn't have any electric backup as part of the geo install. We love the setup. The control package and thermostat does all of the switch over automatically, of course.
  5. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I did not know that
  6. goochman

    goochman New Member

    I have a similar setup as you do in MD. After 6 years I believe I finally figured out my problem of a "flow" issue locking out my WF 5 series unit. The antifreeze mix in our loop was set for 25 degrees, these should be set for 15 degrees (21% mix for us, we had 10% mix).

    Below 20 degrees the Geo unit struggles to keep everything toasty so on my thermostats I had it set to switch to Gas once the outside temp drops below 20.

    We got our loop fixed in Mar so I wont be able to see if our lockout issue is 100% fixed but it should.

    I would go Gas under 20 and be done with it - hopefully your termostats have an outdoor sensor and can handle the transition. I have Honeywell prestige thermostats (the original release) and they work well.
  7. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    It is all about capacity. What does your old house need, and what did the previous hvac provide. Blower door with a independent manual J would be my first step. Fossil fuel furnaces are usually grossly oversized, so the btu;s there may or may not be useful.
  8. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    If you really only have 600' of wells, then you are likely correct that your capacity is going to be around 4 tons. So the easiest and most comfortable thing to do we be to try to get the home down around 60,000 btu's and you will just need the boiler to kick on once in a great while. Since you have multiple systems the easiest thing would be to continue with existing thermostats and set the boiler control 1 or so degrees lower than the other equipment.
  9. mrrxtech

    mrrxtech Member

    Adding another 3 to 4 Tons of loop capacity with 2 more wells or one deep well would keep your loop temperatures from going into the 20s allowing the Geothermal System to heat the house except for very cold days.
    My ground loop is undersized for my 4 Ton unit which shows up in the winter only, by loop temperatures being in the 20s.
    During the mild winter this year with very short periods of snow cover over on the fields, my ground loop stayed out of the 20s. I have additional loop piping that I'll be adding as soon as I can rent a trencher.

    The homes with no wall insulation aren't good candidates for geothermal if left as is. You need to insulate them as mentioned above. Drill holes along the top of the wall between studs inside the house, then blow in insulation to fill each wall section.

    Based on the type of windows, their operation (weights hanging in the walls in older homes) and installation, find how & where the air comes in and fill the gaps with foam or other insulating material. Fiberglass may not be a good choice for sealing around windows, due to the potential for the fiberglass to carry into the house with the air from the high winds we have been seeing lately that accompany the cold fronts. You may have to pull the trim from the windows to find & fill the gaps, then put the trim back up.
  10. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    How do we know that Tanja's loop temps have dropped in the mid 20s? I think she was referring to outside temps, that her system cannot keep up when it gets down to the mid 20s outside.

    Freeze up and lockout when unit is running more suggests a lack of antifreeze. Even if loop is cold, geo heat pumps do not lock out when entering water temp is in the mid 20s.

    Even homes without wall insulation are good candidates for geo, you just have to design and install enough capacity. Nevertheless, you should always try to apply as good of an performing envelope as practical possible. But the more a house is an energy hog, the more reason to use the most efficient heating system.
  11. mrrxtech

    mrrxtech Member

    Since a closed loop uses antifreeze, and most units have a jumper that you clip to set the loop temperature lock out from 32 degrees to 20 degrees, I'm sure from the above sentence the loop gets into the 20s.
    Also I see the same temperatures in the winter and my loop gets down to the 20s, so Tanja's undersized loop would do the same.

    As far as an uninsulated home goes, before my house was complete I had a lot of air infiltration causing my Unit to run 24 hours a day on very cold days. I was trying to keep the water line in the basement slab from rupturing, since I didn't live in the house yet. With the cost of electricity the house was expensive to heat using a 30degree air rise device that a heat pump is. I would have been better off with a propane furnace which produces much higher temperatures.

    From the electric bills that a few owners mentioned on this website like Maurice and the cottage owner on the lake, they didn't seem too pleased with the miracle of Geothermal.
  12. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    You have been wrong again, she is referring to the outside temp.

    You don't seem to understand the principles behind geothermal systems, or capacity, or building load.

    1) Just because your system's loop temp goes down, that must not mean that other people's loop tens go down...
    2) A propane furnace producing higher temperatures has nothing to do with the capacity of the units, namely the amount of total BTUs delivered to a given space.
    3) Your units capacity might was not enough to cover a given load (leaky house), the same would be the case with an undersized gas furnace.
    4) Capacity is delta T x flow. Capacity has nothing to do with the air rise. A 1 ton or a 5 ton unit operate with similar temp rise over the coil, the difference is the amount of air flow, 5 times as much for the 5 times larger unit.
    6) Not saying that geo systems cannot have inefficient design, the issue mostly is the amount of BTUs the house needs, and the price you pay for electricity versus gas/propane/oil. In other words while electrical usage and costs certainly can raise significantly, the cost with propane would likely to be even more.
  13. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    causing my Unit to run 24 hours a day on very cold days
    This is a misconception of many with new equipment. Wheter multistage or variable furnaces, boilers, heat pumps etc. Continuous operation during cold whether will soon be the rule, not the exception.
    New appliances are designed to use minimum energy to maintain set point, when they begin falling behind they "ramp up" and use more energy until they can "ramp down" to maintain desired parameters.
    before my house was complete
    This suggests your warranties would be considered void by the manufacturer if you used a geo as a construction heater.

Share This Page