New Geo or add ETS furnace to existing Geo?
jmmsailing
| Posted in Energy Efficiency and Durability on
I have an undersized ground source geothermal heat pump for my house. The heat pump is 5 years old and has struggled from year 1 to maintain heat on the days colder than 10 F. Yes, I have tried everything; finally determined that the install contractor (out of business) undersized it for our conditions here in Minnesota. So, do I add an ETS furnace to supplement the inadequacy of the existing heat pump; or, do I purchase the correctly sized system? The costs will be similar. Thanks, J.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Jaeson,
First of all, a new heat pump may or may not solve your problem. It's possible that your buried ground loop is too small or is buried in a trench that is too shallow -- or, if you have a vertical loop, it's possible that there was a sizing or installation problem connected with your vertical loop. Before investing in a new heat pump, you have to be absolutely sure that the cause of your problem has been nailed down. That may require the services of an experienced engineer -- not a contractor.
The second point: if your heating system can't keep your house warm when the temperature drops below 10 degrees, investing in more heating equipment may not be the best solution. It may be better to improve your heat distribution system (ducts? hydronic pipes?). If your heat distribution system isn't impeccable, your system might be losing tremendous amounts of heat.
Finally, the best solution (and the best investment of your money) might be good old fashioned weatherization: air sealing work and additional insulation for your home.
If you have natural gas, use it.
how much room do you have in improving your shell in a cost effective manor. That may be the best solution.
Martin & Robert are on the right path- first have the geo assessed by a competent contractor for any obvious system-design or implementation defects, but it may be cheaper to lower the heating load than replacing or upgrading the geo.
When all else is equal upgrading the building will CERTAINLY be more comfortable than upgrading the heating system. Blower door testing with aggressive air sealing is the first-most cost effective measure, followed by remedial insulation (where it's easy). Replacing windows with high-performance windows is a distant third in most cases, but sometimes makes the biggest difference in comfort if the existing windows are U0.50 or higher, or single-panes with clear-glass (rather than low-E) storm windows.
Thanks for kicking this around with me! I greatly appreciate your time, experience, and opinions! Here is some additional information that may be helpful: Because the install contractor went out of business, I was able to utilize the engineers of the manufacturing company (ECONAR) for troubleshooting; they are a high quality organization. What we essentially came up with was that the system is working as designed and is operating at 85% of heat supply for the house. This falls into the industry standard of 75 to 108% of heat production for a given property, heat loss, and available resources. Well, they may not live with the lack of 15 to 23% heating capacity in their homes-so, no longer their problem.
FYI: Open loop system w/ EWT of 51 to 54F all year. All Delta T's are within range or better than range calls for. We are on the schedule for an energy audit w/heat camera, hopefully this will address the insulation/windows/air leaks/etc. among other things. Oh, and the natural gas doesn't match my wind turbine out back, so I won't be using dino mud;). Thanks again, J-
>>the natural gas doesn't match my wind turbine out back, so I won't be using dino mud
You rock.
Installer out of business, "our expensive subsidized heat system, doesn't heat,our home. Lots of that near me in the past.
I like the warranty, we will provide 75% of your heat. I should have that for my projects, I will build 75% of your project right.... Pay 100%.
No non GSHP system could state such nonsense.
Jaeson, glad you are happy with your wind turbine. Residential wind power here is less cost effective than your GSHP. Superinsulated, small, low load, subsidized PV and or pellet stove assist, split air... seems to be the closest to green here... or just letting the home get cold and putting on layers. For grid use right now natural gas works at such a low price and makes sense if used by a family that drives four gas fueled vehicles.
Just watched a movie on a family living in ANWR (Arctic National Wildlife Refuge). Two people to survive need a thousand acres for hunting and gathering lifestyle, they rely on satellite radio for sickness, emergency, they have several factory made guns, thousands of rounds of ammo, and they have to rotate between three cabins to stay near food seasonally, and... they even have in place emergency shelters with emergency food rations. And they have two way radios, a generator, generator fuel, fuel for gas lanterns, flashlights. All this, for TWO people. I use less resources living a regular 2012 life in a just anywhere US town.
The day we are able to survive in the future like days of old in caves is never to be for billions of us anyway. Maybe a few tribes like five hundred years ago.
If it's measuring up-to-snuff for it's design output, then it's probably going to be easier to whittle away at the heat load with envelope upgrades. (TBD). If you're lucky there will be enough low-hanging fruit to make the difference, but we're not always that lucky... Fixing a 15% shortfall on peak loads with envelope upgrades often within reach without breaking the bank though.
But since you know the rough costs of the heat pump & ETS options, you should able to make rational financial decisions around it. Be prepared to spend a bit more for envelope upgrades, since unlike ETS furnaces or heat pump replacements envelope upgrades have no operating costs, as well a longer lifecycle.
We have the full report back from the energy audit. Well worth the investment! House size: 4000 sq ft. Air leaks: 1350 cfm. We could tighten this up but would then have to likely add an air exchanger at $2000. Windows/Doors/Insulation: All adequate with the exception to the leaks for our climate zone. Geo: 4T and working as designed. Undersized for home size; should be a minimum of 5 to 7T. Seasonal Heating Costs: 5000kwh @ $.04. = $200. Not bad for Minnesota. Neighbors are paying $350-500 a month for gas with similar homes. Heat Loss: 68,000 BTU.
Bottom line: We will adding 6 inches of attic insulation (blown) and purchasing the ETS system. This is not something that we are excited about; when considering Geo, have an energy audit done, heat loss calculated, and do not settle for less than 100% of your heat production from the Geo unit. Ask to see and have the numbers explained to you. Stay green my friends, J.