GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Will I have to be concerned with pipes freezing when I install a Mitsubishi Hyper heat system?

carnut442 | Posted in Mechanicals on

I have oil heat with forced hot water presently in my home in NH. The house is 5 years old and very well insulated. I want to add the Mitsubishi hyper heat to our house. It will have two indoor units one on each floor of our home. We are not putting a unit in the basement. It is primarily for cooling, but would like to use it to maintain the home at 55 degrees when we are not there. This is a vacation home so we are there mostly on weekends. My concern is that the oil burner will only be running to maintain hot water. We have a tankless unit off the boiler. In the past, the boiler would add some radiant heat to the basement, so we never worried abut pipes freezing. My concern is, will I have problems with pipes freezing in the cellar and the walls since the oil burner will only be running to heat the hot water.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. GBA Editor
    Martin Holladay | | #1

    Q. "Will I have problems with pipes freezing in the cellar and the walls?"

    A. Probably not -- but the answer depends on how well you have addressed air leaks in your home's thermal envelope.

    You wrote that your home is "very well insulated," and that's good, as far as it goes. But pipes don't freeze because of a lack of insulation; they freeze because they are located near an air leak. Even a small hole can freeze a pipe when the outside temperature is at -20F.

    If you've done a good job of air sealing your basement, I wouldn't worry.

  2. carnut442 | | #2

    Thanks Martin

  3. charlie_sullivan | | #3

    When I read your question title, I thought your question was going to be whether the mini-splits would be reliable enough to count on to not fail while you are out of town. Martin has answered the question you actually asked well, so I'll answer the question I thought you were doing to ask.

    Having two mini-splits is pretty good redundancy, better than many heating systems. It would be good to know if one fails, in case it gets very cold and the other can't keep up. You could also run into trouble with snow clogging the outdoor units or the grid going down. So you might want some kind of remote monitoring system even though your redundancy is better than many people's heating systems.

    My personal experience includes a ground-source heat pump failing in NH in January while I was out of town. I cam home to find the indoor temperature at 28 degrees and several pipes burst. Fortunately, the water leaking somehow re-froze and sealed the leak with ice before too much damage was done.

    Another question you didn't ask is whether the mini-split thermostat can be set as low as 55 F. I recall another thread in which that was discussed for the same purpose and I think the answer was that the lowest setting was 60 F. At the time I suggested a hack to put the thermostat in a box with a very small heat source (maybe a 0.5 W LED night light, for example) that keeps the interior of the box 5 F warmer than the room, and put the thermostat, set at 60, inside that box. I'm not sure whether anyone tried and or whether anyone came up with a better idea.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |