Greetings! We just moved into a house that we built. It has a Geothermal heat pump. It uses 5 Geomax heat pumps that send warm water through a radiant heat system as well as through forced air. We've had some technical difficulties in getting it to work as designed due to the way it interfaces with the backup gas boiler which also handles domestic hot water. I'm trying to learn as much as I can so that I'm not so dependent on our installer so I'll probably be asking a lot of questions.
Canton, southeast MI. So I seem to be up and running now. So here's my setup: I have 5 Geomax 2-stage heat pumps. They're targeted at 120 degrees. The house uses radiant heat throughout as well as forced air via the Geothermal setup. The house uses a backup gas boiler which also takes care of domestic hot water (the geothermal doesn't handle the hot water, they said it would be very difficult to have the system do both radiant and domestic hot water). For the first month, it was not wired up right and so the boiler was used instead ($800 gas bill). But finally today it seems to be working. Does this sound like it's set up? 120 degrees doesn't seem very hot. The gas boiler heating water to 186 degrees by contrast.
120 is actually borderline high for radiant heat. Considerable savings might be had by dropping the 120*F setpoint down during mild weather via an outdoor reset thermostat
How are they set up.... to run at 120*F? Those heat pumps will lock out if they see 120* coming back from the floors. Any idea how many BTUH the machines produce? How big is the house? 5 units cost you a bunch of money.
The house is about 20k square feet. What temp do you think I should set the units to target? They are all geomax 2 units. Closed loop. Radiant throughout house w forced air too.
Nothing we think matters much...it boils down to the design of the radiant system. Room heat loads, floor compositions and coverings, tube diameter and spacing...all data we lack. I really really hope that for a 20ksf house there is a very well thought out design somewhere, and that it includes outdoor reset. It would be unfortunate if the system were designed to require 120*F water...that's borderline for geo heat pumps and costs considerable efficiency. Real money can be saved running with cooler water. I hope whoever put this in has more experience with geo and radiant than I (none)
Ahh yes. I heard about this job (I sometimes work in adjacent city's building department). Having just moved in system must be under warranty. Is there a reason your contractor can not answer your questions? Joe
I haven't asked him. I decided to start here so that I can ask more educated questions. So today I moved the temperature down to 115F. No problems. I don't want to change it further before I talk to my contractor to learn more about why. A lot of the challenge is that there aren't a lot of houses around this area that are this size and have geothermal. The main bummer I'm having is that the water isn't heated through geothermal but my understanding is that there was considerable complexity in having radiant heat and hot water heated through geothermal though I am not sure why that would be. Overall, I'm pretty happy with the system so far. It's working quite well. It'll be interesting to see how well it all works in terms of cost savings.
Mixing Hot water is potable water. Radiant water isn't. The added complexity comes in preventing the two from mixing.
Load temps For radiant? A water temp of 85 to 100f is what I aim to design for. But, what has been hinted at, this depends on your design information that we don't know. Outdoor reset that will control these operating temps based on outdoor air is also a nice control to be considering.
draginol, Thanks for the video. Do I understand correctly? You have s 20,000 square foot house and there are 30 vertical loops installed?
RE educated questions....key is education, since there are design variables we don't know..... I would definately get whatever radiant design info you can it may be needed for future service work. RE big house with geo, that is true. It also occured to me that there are few companies experienced enough for that job. Of those that come to mind, most are affiliated with one of the lables, not installers of over the counter Geo Max. While there is not anything wrong with Geo Max, it implies your installer may not do a lot of Geo. There are exceptions however (M. Custis among them). I would be curious about the pedigree of the installer and presume you looked into it. If they are not an everyday geo company, they can certainly keep your system working, but not necessarily at the best efficiency. j
