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Community and Q&A

Minisplit base pan heater

Andy CD Zone 5 - NW Ohio | Posted in Energy Efficiency and Durability on

I self-installed three Fujitsu minisplits, and had them commissioned by a dealer’s service tech in the hopes of maintaining the factory warranty.  All three (AOU9RLFC outside units) have worked better than expected through several CZ5 winters.  In researching for future installs, I now see third-party websites stating that a base pan heater must be part of any installation to prevent ice-up of the outside unit in cold weather, a recommendation that seems to be repeated across all their brands.  Neither the manufacturer’s installation instructions I worked with nor my dealer ever mentioned this.

In the Mitsu literature, I see that their Hyperheat outdoor units have a built-in pan heater.

In northwest Ohio, is it possible that I’m right on the line where a pan heater is not really needed?  Is the third party reseller just upselling expensive accessories?  Or is this a judgment call, based on my willingness to invest in reliability and performance at the bottom end?

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  1. Expert Member
    Akos | | #1

    A pan heater is a good idea in most colder climates, definitely a good idea in snow country.

    Most cold climate units come with one, I would look for a unit that has it built in. Adding it on as an accessory tends to cost more than the proper cold climate unit.

    In Toronto, the pan heater is definitely needed for about a month out of the year, lot of ice melt under the unit when it starts going into defrost often during a cold spell.

    1. cbut8995 | | #9

      Hi Akos,

      Those base pan heaters that are part of the unit. I am assuming they are automatically turned on and no need for any manual configuration etc?

  2. Drew Baden | | #2

    Andy - I know this isn't the best place to reach out to you but I don't know how to otherwise. Are you a builder for hire in NW Ohio? I'm looking to build and searching for help!

    1. Deleted | | #4


  3. Trevor Lambert | | #3

    It was explained to me that the pan heater was not necessary if you're willing to periodically check for icing and take corrective action, if required (melt it with a heat gun or hair dryer). I elected to get the pan heater model, which was only about a hundred dollars more, if I recall correctly. The only thing that made it a tough choice for me is the pan heater model is slightly less efficient.

    But, as they say, the proof of the pudding is in the eating. If you've gone through several winters with three units and no pan heaters, with no problems, it would appear they're not necessary where you are. That is unless most of those winters were unseasonably warm.

  4. Josh Durston | | #5

    The decision is made tougher by the fact that nothing on the market really compares to the 1:1 Fujitsu slim ducted units. To get a base pan heater I think you have to switch to a multizone outdoor unit which has considerably less overall efficiency.

    There are things like electrically heated thermal tape that could be used to fashion a pan heater.

    I have one on mine, but have been wanted to add a toggle switch to the heaters I can disable it until the daily temperature highs for the week stay substantially below freezing.

  5. Jay Thomas | | #6

    What Trevor is says is correct. If you watch the ice build up once a day you really don't need a pan heater in your climate zone. Last year I had some ice build up I melted with water.

    That being said, (on the advice on this forum) I did add an engine block heater to my split. It seems to more or less avoid defrost cycles close to zero even at 20 degrees F. I only turn it on about 5-6 days of the year, but it's good to have to increase overall heat capacity.

  6. Joe Braun | | #7

    It would be helpful to know the models of the units you used. For all you know, you may already have one with a built-in pan heater. The Fujitsu XLTH are rated to work down to -15F. From other posts I've seen around the net, people have said they work great down to -30F.

  7. Matthew Michaud | | #8

    How is it that a pan heater (engine block DIY or otherwise) prevents a defrost cycle? Isn't the defrost cycle clearing ice from the coils while the pan heater is clearing ice from the pan? Unless the pan ice is high enough to block the coils, it seems like these two would be separate problems. What am I missing?

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