Results 1 to 9 of 9
  1. #1
    Join Date
    Dec 2010
    Posts
    107

    Thinking of a Geothermal system w/hydronic gas backup

    I currently have a 3200 Sq. Ft. house with Natural Gas heat for first floor and a heat pump in the attic for second floor. House was built in 2002. HVAC is original and was never serviced by previous owners.

    Current setup: 2nd floor (1400 Sq ft) heat pump is a 13 Seer Goodman unit (2 ton) connected to a 2.5 ton attic air handler with 2 - 4.5KW strips backup. Honeywell VisionPro 8000 Thermostat.

    1st floor (1800 Sq. ft) is 92% Goodman gas furnace with 3 ton standard AC unit. Honeywell IAQ Thermostat.

    Current system handles house well (comfortable, keeps up fine). House is very well insulated for Maryland. (Heat pump looses refrigerant, gas furnace had a cracked secondary combustion chamber) - looking to replace both systems .... last month 3000KW electric usage, natural gas usage not that bad (also covers fireplace, hot water heater and stove).

    My yard size (4 acres - wide open) would support a Geothermal system (horizontal system may be preferred due to cost and efficiency). Soil is clay.

    I am considering a system with one combination geothermal unit/air handler for the 1st floor (~3 ton unit in basement) and a second split system with geothermal unit in basement (~2 ton) with air handler in attic.

    For backup, I am considering a high-effeciancy gas boiler that would be zoned and connected to a hydronic coil in the basement air handler and another hydronic coil in the attic air handler.

    Another option would be to install high efficiency gas furnaces as the backup to the geothermal systems (instead of the hydronic system).

    Looking for pros/cons of such systems.

    Our local HVAC company can install any/all of these (our choice).

    Current Heat Pump system w/electric backup is sufficient but expensive to run during December through February with the temps here in Maryland.

    Thanks in advance for suggestions/ideas.

  2. #2
    Join Date
    Dec 2010
    Posts
    107
    Accidentally and unintentionally somehow triggered a double-posting of this thread - my apology in advance .... edit/delete is not enabled for me as I just found out.

  3. #3
    Join Date
    Jan 2011
    Location
    Lancaster county PA.
    Posts
    34

    one mans opinion

    A properly sized and installed geothermal should not need much "back-up", so if you are only installing the furnace or boiler as back-up for geo systems, you are basically installing another whole heating system, which is an up front waste of money compared to standard electric elements. If you are going to use the boiler for some floor radiant heat or domestic hot water or some other purpose, then I can see also using it as back-up. I just serviced a 6 ton Water furnace with gas hydronic back-up today. This boiler has 4 radiant floor heat zones and does back-up for two geo-systems. And, basically his boiler never runs to back-up his 2 geos. Lancaster PA, so similar climate to yours. Good luck. Brian. 23 years of geo experience.

  4. #4
    Join Date
    Dec 2010
    Posts
    107
    I appreciate the information related to backup systems. In the Baltimore, MD area, electricity is expensive, natural gas is cheap (today ...), so I was under the impression that having the gas backup would eventually be a benefit, but you are right about the upfront costs .... I am learning.

  5. #5
    Join Date
    Dec 2010
    Posts
    107
    The more I read, the more I see large variations in installation/efficiency relating to geothermal systems in our area. From an efficiency standpoint, with a well sealed/insulated house, the gas/hydronic system alone may provide what I am looking for without digging in the yard ....

    That said, most of the geothermal companies in the area are well-digging companies. I do have the land for a horizontal system but am considering the long term work needed to restore the 4 acre lawn after all the work is completed. I would need to factor this into the upfront costs.

    Curious as to why I could have a septic field completed for much less than a geothermal horizontal ground loop system (not including the actual inside hardware) installed (digging is less with the geothermal system), no stones to buy, but pipe to purchase and connect ??

  6. #6
    Join Date
    Jan 2011
    Location
    Lancaster county PA.
    Posts
    34

    Hmm some thoughts

    Either you have cheap septic installers or expensive geo installers. Here in Lancaster PA, sand mounds run 6-15 thousand dollars and complete geo systems, including the wells go for around 20,000. The wells are usually 4-6 thousand of the installation.
    High eff gas boilers and radiant floor heat is wonderful for heating but it does not offer anything towards the air conditioning of your home. So now you need a separate cooling system if you go the boiler route. This is usually comparable to geothermal in cost and sometimes more. Both systems have their ups and downs. Only you can know what is right for you. It is hard to pass up on the geo because of the federal tax credit of 30% on the entire job.
    Last thought for know. There are a few geothermal systems that heat water for radiant heating, heat air for air heating using your ductwork, and cool air in the summer for air conditioning, all in one unit. Good luck with your decision.

  7. #7
    Join Date
    Dec 2010
    Posts
    107
    I know we are not supposed to talk prices, but based on what you mentioned above, a horizontal system (5 tons) would go for 1.5X what your well systems go for, and a well system would be 2X what you mentioned .... this is for 2 inside systems (one in the attic and one in the basement) that would handle heating and cooling.

    I was considering hydronic coils (with a gas boiler) in the air handler as a backup .... that adds about the same cost as a high cost well that you quoted above.

  8. #8
    Join Date
    Jan 2011
    Location
    Lancaster county PA.
    Posts
    34

    Smile more thoughts

    As you say, I should not talk about specific prices so I will not. Shop around and get at least 3 quotes. This way you will get some different ideas and prices from pros in your area. Ask them how long they have been installing geothermals and how many they have installed. We have been doing them since 1983 and have over 1500 in service. I am not wild about the idea of having water lines in the attic for back up heat. I have been lead service tech in an hvac company of 76 employees for 23 years. I don't know how many times I have had to deal with water through 2nd floor ceilings from condensate issues. Putting pressurized water lines in an attic is asking for problems you do not want. If you choose to go the boiler back-up route, I would counsel you to give up a little living space on the 2nd floor for the unit. Actually, attic installations of any kind are less efficient than having everything within the insulated shell of the home, so maybe now is the time to design the unit and ductwork into the 2nd floor rather than the attic. good luck again.

  9. #9
    Join Date
    Jan 2002
    Location
    East Grand Forks, MN
    Posts
    1,375

    Possible

    Quote Originally Posted by chloeourdog View Post
    Current setup: 2nd floor (1400 Sq ft) heat pump is a 13 Seer Goodman unit (2 ton) connected to a 2.5 ton attic air handler with 2 - 4.5KW strips backup. Honeywell VisionPro 8000 Thermostat.

    1st floor (1800 Sq. ft) is 92% Goodman gas furnace with 3 ton standard AC unit. Honeywell IAQ Thermostat.

    Current system handles house well (comfortable, keeps up fine). House is very well insulated for Maryland. (Heat pump looses refrigerant, gas furnace had a cracked secondary combustion chamber) - looking to replace both systems .... last month 3000KW electric usage, natural gas usage not that bad (also covers fireplace, hot water heater and stove).

    My yard size (4 acres - wide open) would support a Geothermal system (horizontal system may be preferred due to cost and efficiency). Soil is clay.

    I am considering a system with one combination geothermal unit/air handler for the 1st floor (~3 ton unit in basement) and a second split system with geothermal unit in basement (~2 ton) with air handler in attic.

    For backup, I am considering a high-effeciancy gas boiler that would be zoned and connected to a hydronic coil in the basement air handler and another hydronic coil in the attic air handler.

    Another option would be to install high efficiency gas furnaces as the backup to the geothermal systems (instead of the hydronic system).

    Looking for pros/cons of such systems.

    Our local HVAC company can install any/all of these (our choice).

    Current Heat Pump system w/electric backup is sufficient but expensive to run during December through February with the temps here in Maryland.

    Thanks in advance for suggestions/ideas.

    Questions:
    Is there any off-peak/off-demand services from your util provider?
    Did you say you have or not have a basement?
    Did you say the boiler would only operate the hydronic coils in the plenum?

    Ideas:
    If backup is a must (like for power outages); perhaps go with an indoor split Geo unit. These essentially replace your Heatpump's, AC's, or any mechanical cooling devices, but you can still keep your gas furnace/s.

    If you had or have a basement, you can always put both split units there!!

    In some locals; excavation can cost a lot and even add up to the cost of drilling bores (for close loop system), otherwise wells would be cheaper (open loop system)..

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event