Has anyone ever used gas fired backup for geothermal? Is it possible? I’ve got a new Waterfurnace geothermal unit that is often calling for backup heat (though not at full power) and it’s only been in the 30s.
We used the backup heat coil for a day when we were drying the walls, it produced very little heat and I’ve never seen the power meter spin so fast. Seems a small gas unit would be much more efficient, AND produce more heat.
That coil just makes me nervous!
Thanks,
Bill
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Replies
It is not unknow to have gas backup on air-to-air heat pumps. They are called dual fuel systems. So I don't see any reason that you could not do this on a geothermal system.
However, I am surprised that aux heat is coming on at 30 degrees with a geothermal.
It makes me wonder about the installation or sizing of the system.
I would have the installers check out the operation of the equipment and to also show you the sizing calcualtion and your design temps using manual J.
If that does not lead anywhere I would contact waterfurances tech support.
I agree with the other Bill that something isn't quite right about the sizing or install if you need backup so soon. Call the installer and have it explained.
We almost did gas backup, but found out that a problem with one of the rfh loops was keeping the slab from being heated.
Did the heat coil thing, too. OH MY GOD! Pulled that plug real fast. Checked some figures. The heat pump drew 13.9 amps and generated 54000-ish btuh. The coil added 12000 btuh and drew 19 amps. Hmmmm, don't like THOSE numbers.
What temp you running in the GSHP (geo)? We actually have better results with the set point at 103 than at the original 115.
Since I don't use the backup anymore, I can't remember how it was triggered. I think it was just the regular water heater temp setting on the storage tank. That sound right?
Hi Bill 487
Sorry I can't answer your question. I am interested in the approximate area you live because of the water furnace efficiency. I am building in the western U.P. of MI and I know of one person that has "geo-thermo" and he professes that it works really well and has low energy bills. I have been trying to decide for myself about an installation in a house I am building in that area.
I hope you can get some improved results with your system.
Regards,
Virginbuild