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Mini Split Condensate Pump

We had Mitsubishi mini splits installed last September and one of our units has a condensate pump. It sits in our attic just above it and not one of the ones that’s right below the unit.

We already had to have the first pump replaced and last night when running the ac, the new pump was going off multiple times per minute in short few second bursts when we had the unit set at 67 degrees. It was the first real humid night with this new pump.

Is this how to supposed to work or do I need to get my hvac company back out to fix or replace this one too?



    HVACNUT Member Posts: 4,856
    Is this for a ceiling cassette?
    Model of unit and pump?
    Keep in mind the basin in a ductless condensate pump is extremely shallow and will discharge frequently.
    Can you hear it from the living space?
  • NJHomeowner
    NJHomeowner Member Posts: 61
    It’s for a wall unit that had to be put on an interior wall. Don’t have the model for the pump but the unit is a MSZ-GL09NA.

    I can hear it from the living space.
    HVACNUT Member Posts: 4,856
    The condensate pump is in the attic above the wall unit?
    Shout out to Mitsu installers.
    I know some cassette types can utilize a pump that mounts above the unit. Not sure about a wall mount but I'm not too familiar. Have you checked the I&O manual?
  • ratio
    ratio Member Posts: 3,331
    I might expect somewhat longer run cycles, but it's possible it's running normally, that unit's smaller than what I usually install.

    Can you see the discharge? How loud is it? They're not really silent, but what I'm hearing in my mind is loud enough that it might warrant a call, as long as you don't mind being known as One Of Those Customers.

  • DJDrew
    DJDrew Member Posts: 69
    Does the pump look like the one attached? Three of our units are on interior walls and had to have the pumps. The one in the photo is installed in the attic above one of the heads.

    Our installer suggested we pour a 1/2 cup of water in the pan of the mini-split to flush out the dust and give it a good run before turning AC mode back on after they sat unused all heating season. I usually also go outside to where the lines drain to make sure everything is draining okay and the lines didn't get kinked or clogged.

    If the pump looks like the blue one in my photo, it is an Aspen Mini Aqua 230 83812. https://www.rectorseal.com/asp-ma-230sp/

  • pecmsg
    pecmsg Member Posts: 3,529
    I hate wire ties on Armor-Flex!
  • NJHomeowner
    NJHomeowner Member Posts: 61
    edited May 2019
    Ok the pump is a saurman si30. They flushed it already this spring when they came for service. It’s not particularly loud. Just a quick hum.

    Also pics of the run out. Goes through one more small room before reaching the exterior.
    HVACNUT Member Posts: 4,856
    If the black tubing is the discharge, I would run it up at least 12 inches before any turns. And long sweeps at any turns. It could be the pump is meeting too much resistance.
  • hvacfreak2
    hvacfreak2 Member Posts: 500
    edited May 2019
    The problem could be that the controller portion is not level causing it to turn the pump on with very little water in the collector. The pump pulls it out fast and the float drops turning the pump off again ( repeat ). The controller / collector is crammed in the space on the bottom of the unit along with the refrigerant piping , electrical , and the drain tubing. More often than not the guy is just happy he got the cover to close on the unit with all of the stuff crammed in the small space. Someone will need to spend some time and effort to get everything to fit perfect or install a pump that fits outside of the cabinet ( Aspen white ).

    Mechanical Enthusiast

    Burnham MST 396 , 60 oz gauge , Tigerloop , Firomatic Check Valve , Mcdonnell Miller 67 lwco , Danfoss RA2k TRV's

    Easyio FG20 Controller

  • NJHomeowner
    NJHomeowner Member Posts: 61
    Just took a video of it but doesn’t look like I can post it? Pump going off 3 times in 2 minutes. Each time it goes off lasts only about a second.

    Guys coming today in a few hours to take a look. Let me know if anything else I should bring up. Again it’s a sauerman si30 pump which is sitting in the attic above it.
  • Zman
    Zman Member Posts: 7,433
    In some installations the uphill discharge pipe has a volume almost the same as the reservoir for the pump. The pump will turn on and fill the pipe, when the pump turns off, the water goes back into the reservoir causing short cycles.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • pop
    pop Member Posts: 1
    @Zman or whoever?

    "In some installations the uphill discharge pipe has a volume almost the same as the reservoir for the pump".

    I know this is over a year old, but I have a new, first time, install with 2 cassettes which are tied into the same drain pipe, one is cycling and the other is not. I think this may be part of my problem, so what's the solution? Raise the pipe a little higher close to the cycling cassette? I don't have much of a slope if any for almost 20 feet, plus the other cassette ties into it at about 5' before it heads down and out.