How long into winter can we run our Heat Pump with our Legalett System
We have a Legalett slab on grade radiant air system powered by a gas boiler and an electric Mitsubishi heat pump system. With gas prices so high in Ontario, we want to run our Mitsubishi heatpump for as long as we can before turning on the Legalett system. The Mitsubishi is easily keeping the air temp in the house between 15C and 18C. Temperatures outside are now well below 0C. Will keeping the air temp at 18C with the heatpump still meet temperature requirement for the Legalett system or does Legalett system have to be turned on and warming the slab as well?
This is a good idea, as heat pumps can be up to 3 times more efficient that other heat sources. We consulted with a Legalett engineer to be sure, and they would like you to run your Legalett air-heated floor system at least a bit to inject some heat for proper frost protection. In order for it not to compete with the heat pump, you could set the floor at a higher temperature just to activate it, just be sure to set a reminder somewhere to turn it off again so you don't overheat. This is something you could do for a few hours every few days perhaps. That way you can use your feet as a judge for when the temperature has risen slightly. It doesn't need to be run so much as to heat the air of the house {the heat pump can do that) but enough so your feet are a bit more comfortable.
Legalett has required minimum operating temperatures for each custom design, either 18C, 15C or freezable like in the case with an unheated garage, and freezable slabs have significantly more skirting. Do you know the base operating temperature? If not you could email us your address (info@ecohome) and the Legalett engineers have offered to confirm if you aren’t sure.
Thank you Emmanual, that is great news. Our Legalett system's minimum operating temperature is 18C. We anticipate that using the heatpump as long as we can will save us close to one full propane tank a year.
Always happy to help, and even better than setting a reminder is if you have a programmable thermostat, which I'm sure you know is better programmed to run off peak hours :)