Do you like Geothermal with low temp radiant?

Rich L.

Hi Kevin,

I installed a system much like your describing when I built my house 2 years ago, 2200 sq ft plus full basement, and am very happy with the results and economy of operation. Like most radiant applications the comfort is second to none!

Geo with radiant is a perfect combo. The manufacturers claim you can reliably deliver 120 degree water. In my experience I shoot for lower temps, 115 max, which can generally be done with tube spacing in Gyp-Crete. Be sure you adequately size a buffer tank, 10 gals per ton, to prevent short cycling when small zones call. I also recommend outdoor reset for this application.

As far as domestic goes you can gain some efficiency by preheating water with a desuperheater option on the GSHP. If you want and the budget allows you can dedicate a small water to water unit specifically for DHW production. We have one of these in a business we service and it works great.

You can tie in a gas or electric boiler to boost the temps in extremely cold weather but I prefer to get in early enough to design around it if possible.

With the Gyp-Crete you should try to convince your customers to go with lots of ceramic floor tile. It’s a great match and you really notice the nice warm floors.

Good luck, Rich L

Kevin O. Pulver

Geo or No?

We are going to do a 5000 square foot residence with basement. Gyp-Crete overpour. All low temp radiant. Warmboard not an option. The homeowner has asked about a groundsource heat pump. I don't do that part, but told him if it's in the budget he'll get a lot of efficiency for the extra dollars.
My understanding is that geothermal will only provide so much temperature and then an electric coil will make up for any possible temp deficiency on colder days. Is that correct? Can it be done with a boiler also or is that bad engineering?
What about domestic hot water? We were going to do an indirect if we used a boiler. Do you ever tie in a boiler with Geo? Can the geo provide DHW?
What are your reccomendations? The geo would be subbed out, but the customer is looking to me for advice, and I'm admittedly ignorant but told him this is the place to ask.
Thanks in advance, Kevin

bobbyg_10

In my area in SW Indiana, there have been many jobs using ground source heat pumps to heat up a electric water heater (used as a buffer tank) and utilizing one of the elements as a backup or additional source when outside design temp. is met. If your heating load is much larger than cooling load, then definitely you can use a boiler. I would think about using a outdoor temp. stat to kick on the boiler when outdoor temp. dropped to low.

Some heat pumps have an additional isolated dhw tappings (totally isolated from the heating part). I don't supply the heat pump.

There are limitations on maximum temp. that can be achieved. I try to keep the system at 120 max. (the lower the better). You may have to bring your tubing spacing closer to achieve this.

From experience, I prefer the Rheem super-duper wtr htr tank (not sure of the name - maybe marathon) because in cooling mode, the moisture coming from uninsulated pipes/tank can make the job look nasty very quickly.

Hope this helps.