High-temperature options for geothermal for radiators/convectors?

frogpond

Hi all. I currently have a gas boiler, which heats the water to 180F for my convectors. As far as I can tell, there are only two high-temperature options.

Nordic has a water-to-water heat pump up to 160F: https://www.nordicghp.com/product/nordic-products/high-temp-water-to-water/

WaterFurnace can get up to 150F: https://www.waterfurnace.com/residential/products/geothermal-heat-pumps/504w11

Are there any other options? Any higher temperatures available? Thanks!

Ironman

The problem is that you'll need 180* SWT in cold weather if that's what the system was designed at.

You need to do a Manual J heat loss calculation to see exactly what your load is and then a radiation survey to determine what the needed SWT will be at design conditions to meet that load. If the house has had substantial envelope improvements, then it's likely a lower SWT can be utilized. Be aware though that convectors have about 1/2 as much output at 150* SWT vs. 180*.

Also be aware that those output numbers for WTWHPs are best case, ideal scenario and may not be what you actually get all the time in your application.

I would keep the gas boiler as a backup and/or add more radiation such as Smith's Heating Edge low temp radiators.

hot_rod

as @Ironman mentioned, the better approach is to lower the load, and required SWT to match what Has are capable of.
I would say below 140 SWT on design day would be the goal, even 120F!
The best money you could spend would be to first upgrade the building envelop, lower the load.
Have you performed a blower door test? A large portion of the heat goes out of a building through cracks, infiltration. That is usually low hanging fruit. Cans of spray foam can make a big difference.
https://www.caleffi.com/sites/default/files/file/idronics_25_na.pdf

frogpond

Thank you both. I separately posted asking if someone could help me identify the EDR for my convectors so I can figure out if they can put out enough heat at a lower temperature. The heatload calculations suggest I need to hit around 75,000 BTU. https://forum.heatinghelp.com/discussion/comment/1614442#Comment_1614442

We have done all of the upgrades we reasonably can (and yes, have had a blower door test and energy audit!). But we want to get off of fossil fuels altogether.

So, back to my original question - do you happen to know whether there are any other high-temperature water-to-water heat pumps out there? Thanks!

Jamie Hall

First off, "get off fossil fuels altogether" isn't happening. A heat pump uses electricity. Electricity is, mostly in the US, generated from fossil fuels. If, however, you can find a heat pump with a COP of at least 3 in the temperature ranges you are working with, you would at least not be using more fossil fuel...

hot_rod

Nordic and Arctic claim 160F, but capacity and efficiency would take a hit at high delta like that. It’s common to use a back up if you cannot get required SWT lower. I would also look at weather data to see how many days per year you are at design condition. If it is a week or less you would pencil out how much it would cost to have electric resistance help.

hot_rod

some add some additional info here
https://www.caleffi.com/sites/default/files/file/idronics_27_na.pdf

frogpond

Thanks, hot rod. I'll consider that.

Jamie - we'll be getting solar panels to cover the electrical usage, so, at least in theory, it'll be a beautiful outcome and free us!

Jamie Hall

Uh huh. Unless you are using a very efficient heat pump, have you figured out how many square meters of panel you need? And how many batteries?

One of the places I care for has three acres which could be used for panels, and the owner has the capital to install them and the associated batteries -- but simply won't do it, as the return on investment is some horrible negative number. Do your math homework (for that place, it would take about 2 acres of panel area on an averagely sunny day to produce enough kilowatts to make it through the night for straight electric).

hot_rod

If you have power near the convectors you could add a row of muffin fans to greatly increase output and allow lower SWT operation. A few of the panel rad manufacturer offer retrofit kits for that purpose. Jaga promotes them for heat pump systems.


Here is an example of days of occurrence BIN files. You can easily look over say 30 years of weather data to see % of the year at different "bins".

With this info, your load calc, required SWT and A2WHP test data you could determine how well a heat pump will match your needs.
You are not alone in this quest, them info is available to make good decisions.


https://www.jaga.com/en/products/horizontal/dbh-upgrade.html

hot_rod

If you have power near the convectors you could add a row of muffin fans to greatly increase output and allow lower SWT operation. A few of the panel rad manufacturer offer retrofit kits for that purpose. Jaga promotes them for heat pump systems.


Here is an example of days of occurrence BIN files. You can easily look over say 30 years of weather data to see % of the year at different "bins".

With this info, your load calc, required SWT and A2WHP test data you could determine how well a heat pump will match your needs.
You are not alone in this quest, them info is available to make good decisions.


https://www.jaga.com/en/products/horizontal/dbh-upgrade.html