Has anyone had direct experience or heard of using a geothermal heat pump as the source for hot water under floor radiant heating. One heat pump manufacturer’s rep says the most heat that can be obtained from a heat pump is 120 degrees. Is this physics or just a limitation of his system? A design provided to me by Radiantec requires 130-150 degree water for a between the floor joist system.
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Replies
bump
r u a feckless dastard?
You may need to go with closer tube spacing, add aluminum plates, get the tubing closer to the finished floor surface (sandwich versus staple-up or embedded in slab or gypcrete) or add supplemental heat source for the coldest days. When thay come up with water temperatures they usually mean for the coldest day of the year.
In my well insulated and sealed 1600 sq ft house in a 7k+ HDD climate, I seldom need to go higher than 120*. Chances are if you have the capital for a ground source system, you have enough for a supplemental heat source.
120 to 130 deg is the max that I have read for geothermal. I used geothermal in my house and set it up so my max temp is 98 deg. I have no back up heat.
wyatt
My research on this led me to the same conclusion as JohnnyD's. You can use the heat pump for radiant floors but will need another heat source for the COLD days. I have also heard that radiant floors, regardless of heat source, require another heat source for the cold days- maybe a radiator or maybe a wood stove. there must be plenty of people out there with experience with this out there.
It would be expensive and a little redundant but you could use the heat pump as a preheater for a boiler, then the boiler would only kick in when you needed the extra heat.
How far north are you- that could make a big difference.
Allow me to quibble...If you insulate your home well, then the problem of supply temperatures goes away. We have Climate Panels in our home and never expect to crank the supply temperatures above 110°F during -15°F design days... our slope is 0.6 thanks to effective wall insulation.Doing Geothermal on a house that does not feature efficient emitters and effective insulation is throwing money at the wrong problem, IMO.
We are maximizing insulation and have replaced existing windows with energy efficient ones. Are you using a boiler or a heat pump?
We ended up using a Viessmann Vitola oil-fired boiler. It made the most sense for our low-temp system since it has no lower limit on the internal tank temperature... Where most systems use injection-mixing, 4-way valves, etc. to protect the boiler from low return temps, our system is the reverse - the 4-way protects the heating distribution system...
Memory jogged now....have an HVAC contractor in the area who did a gypcrete emitter system with a ground source heat pump run via peak demand electric. He did have a hard time keeping up with heat loss when peak demand shut his heat pump down. Burned alot of firewood in his fire place. Don't know what if any solution he put in.
That's one reason I gravitate towards alternate heat source to make sure you will make it through really cold spells or if your power is interupted.
New information from our electric co-op indicates peak-demand 35% electric discount will likely be discontinued. There goes my motivation for water source heat pump or electric boiler as the heat source for my radiant floor heating. In addition, I can't find a local HVAC contractor that wants to install a water to water geothermal heat pump. Trane makes one but I can't find a dealer to install. Not excited about propane but am back to considering a Polaris LP water heater for my heat source.
I'd seriously consider an inexpensive boiler like a T50 Munchkin instead of the Polaris. With all the things you have to add to a Polaris to make it safe as a hot water and RFH source, I doubt that it's worth it over the long haul. With LP prices directly tied to the price of hydrocarbons (and at a premium over them), I'd elect to go as efficient as the budget allows.
Thanks! I'll explore the Munchkin T50.
Have a look at http://www.ourcoolhouse.com/
I am in the western part of lower Michigan. Muskegon is the nearest big city.
Klamath Fall, OR and Harrison, BC use radiant heating with geothermal extensively.
I am not aware of any geothermal wells or springs in Michigan.
Do you mean ground source heat pump?
Have been considering "pump and dump" open loop system using well water.