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Q&A Spotlight

Giving a Heat Pump an Occasional Boost

How to solve a two-week-a-year performance problem

This heat pump can't quite keep up for a few weeks of the year, and tight quarters will make it difficult to add auxiliary heat strips. Is the answer improved ductwork, improvements to the building enclosure, or supplemental electric heaters? Photo courtesy Irene3.

Writing from the temperate Pacific Northwest, Irene3 describes an unanticipated problem with a Mitsubishi heat pump installed just a few years ago.

“We had the impression that it would be easy to install heat strips later if it turned out it couldn’t keep up during the coldest weather,” Irene says. “We are in Seattle and generally get only a couple of weeks below freezing, if that. The last couple of years we have had a few uncomfortably chilly weeks in January or February, so we decided it was time to spring for heat strips.”

And that’s where she ran into trouble. It turns out that the strip heater compatible with the system’s air handler goes on top of the unit rather than inside, and the original installer is not sure he can make it work with the available clearance. The heat strip add-on is 6 in. tall, and there’s only 9 1/2 in. to work with.

“It seems to me that for something we really only need a couple of weeks of the year, if we can’t have a centralized solution, it would make just as much sense to use good quality portable heaters,” Irene says. “My husband thinks a centralized solution has to be possible and we should look for a different Mitsubishi specialist. What say you all?”

That’s the issue for this Q&A Spotlight.

There’s plenty of room…or not

At first, Akos Toth thinks that with 9 in. of room for a 6-in. auxiliary heater there’s plenty of room. What’s the problem?

“The heater can be installed farther downstream in your main trunk as well,” he says. “It doesn’t have to be right by the air handler.”

But after looking at two photos that Irene provides, Toth changes his…

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  1. newbiemike | | #1

    We recently installed a properly-sized, cold-climate "HyperHeat" Mitsubishi system in our home in NE Washington, Climate Zone 6. In the past month we have seen 6 to 9*F and the system put out plenty of heat without using resistance/strip heating. Is the system installed in the Seattle home not a HyperHeat version?

  2. acckze | | #2

    Re: Aux. Heat:
    I use the Envi plug in 120 convection wall heaters- recommended in this article by Malcolm Taylor. I love them. Your expert recommends Stelpro- who also has a plug in 120 convection heater, but this costs more ($419 vs $279 for Envi). Can someone compare/contrast these two products? I'm about to buy a few more for a different property. They are used as Aux heat only.

  3. user-5311948 | | #3

    I am in Wa climate zone 5 and was told that heat pumps don’t work very well during freezing fog which is fairly common here. How much decrease in efficiency can one expect and is it enough that you would have to have a backup heating system.

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