Is there anything that can be done to mitigate the effects of a floor humidifer on ice formation gumming up various systems in the house? I have learned that even RO water is not pure enough to prevent our AC system from freezing up (unit close to air intake duct, HEPA filter, etc.) so am switching to distilled water.

But I'm also concerned about how I can mitigate the formation of ice in our refrigerator. We have already had a repair person come out due to the fridge side not cooling and the ice maker not working, and after about half an hour of taking things apart (it's not a cheap unit!) pulled out a huge chunk of ice from the internal ducts. At the time I didn't associate the possibility of this ice formation with running a humidifier but now I'm starting to suspect a connection. However, unlike the AC where the easy fix is to switch to distilled water, the fridge doesn't have a filter that can clog or simply be replaced. How I can mitigate ice buildup when a humidifier is pumping water into the air 24/7?

Not running the humidifier is not a good option either, as there are allergy sufferers in the house and it struggles to even maintain 40% RH in the summer.

  • I understand that not running the humidifier is not a good option, but perhaps it could be done as an experiment? Both refrigerators and AC units have systems to shed condensation, but it sounds like they're not working properly.
    – Aww_Geez
    Jul 14, 2020 at 18:19
  • Just to be certain, you're actually adding to humidity in the house in the summer? On purpose? Air conditioning helps reduce humidity. Humidity leads to ice formation on all sorts of cooling equipment, and it usually leads to the growth of undesirable things in the house, many of which can cause allergies...
    – FreeMan
    Jul 14, 2020 at 18:20
  • @FreeMan Correct. Adding humidity. The air conditioning removes humidity, but I already live in a very dry climate (<20%). Indoor humidity is around 30%, trying to raise it to no more than 40%. In the summer even with a tank a day we aren't quite hitting that.
    – Michael
    Jul 14, 2020 at 20:12
  • Is there any way you can back off on how much A/C you are using? A/C by nature dehumidifies... so you are doing this... youtube.com/watch?v=Sv0O6b65o3U Jul 15, 2020 at 12:50

2 Answers 2


Ice in your fridge with a RH of 40 is not because of your humidifier, unless you stand with the door open for long periods of time.

I would expect your defrost timer in the fridge was not is not functioning or a fan was not properly moving the air.

Any moisture you put in the intake of an ac system it should by design take out l. Don’t introduce into the intake , the purer water is the faster it will freeze.

If you want to humidify air the moisture should be introduced after the air is chilled.

dehumidification Is a side effect of air conditioning this may be why you are struggling to get the Humidity up all the moisture you add is being removed with each pass through the evaporator (cooling coils in the air handler). Try adding moisture at the vents so the moisture air is pushed around or add a humidification system after the coils then all the vents will vary the humid air.

One thing I almost forgot to add the type of humidification can cause worse allergies if there any impurities in the water I would call good RO water the same as store bought distilled probably 19 meg ohm per centimeter.

  • My understanding was under normal conditions the condenser coils shouldn't freeze anyway unless there is reduced air flow which could be caused by fine particulates from the water (we do see a white buildup on the base even with RO). Unfortunately this is a floor unit and all the outflow vents are up near the ceiling, so I will need to think a solution to this further...
    – Michael
    Jul 14, 2020 at 21:02
  • Normally the coils will not freeze unless the refrigerant charge is low but an excessive amount of moisture could cause icing, the problem then is tha air flow drops the exposed coils get colder and it turns into a brick of ice. In some cases with multi speed motors we run ac at a higher speed but that may compound your issues as the air would pass over the coils more often taking out the moisture faster.
    – Ed Beal
    Jul 14, 2020 at 21:23
  • I haven't run the humidifier for 24 hours and I just checked the coils right after the unit shut off after having run for a substantial period of time. No traces of ice and the coils don't feel overly cold, so I think at this point we can rule out low refrigerant.
    – Michael
    Jul 14, 2020 at 22:27
  • Can you move the humidifier away from any intakes ? With ceiling level vents you probably have a large floor grill as the intake, this is usually located centrally and makes it hard to humidify the bedrooms and the living kitchen area with 1 unit.
    – Ed Beal
    Jul 14, 2020 at 22:54
  • Yeah I would like to move it away from the intakes... there are actually three intakes spread across the house. They are grills unobtrusively set into the wall right above the baseboards and beyond the grill in the wall is a vent hole that goes down into the slab and under the house to the AC unit.
    – Michael
    Jul 14, 2020 at 23:09

The humidifier had nothing to do with your fridge problems

The refrigerator has a hot side, and a cold side. The hot side is outside the fridge proper, where humidified air might matter. Since it’s hot, condensation and freezing is impossible.

Condensation from fridge operation, and freezing, can only happen on the “cold side” - the inside. Where would this water be coming from? If the room humidity were high, it might come from room air interchanging in and then condensing. But your room air is low humidity. The more likely possibility is, first, an icemaker leak. Second, efflorescing from the ice in your ice bucket, or other unsealed packages. And third, vaporizing from water or food left open in the fridge. Fourth, something malfunctioning in the defrost cycle.

Any way you slice it, a fridge that is icing like that, in such a dry space, is malfunctioning.

Humidifying and A/C are fighting each other

It is the nature of air conditioning that it wrings water out of the air. It is, inherently, a dehumidifier, and this function cannot be turned off because that’s simply how the gas laws work. It’s not possible to cool air without dehumidifying it.

So, the humidifier is fighting the “dehumidifier”, and you are in a vicious circle.

So you might want to look at how much you are air conditioning. Lower humidity reduces the need for A/C, because your sweat glands work better, and your body runs cooler. So if you are running your A/C at the “conventional” settings of 68 or 72 because of a held belief about normalness, I would revisit that. Generally aim to set the A/C as high as is physically bearable. Summers are summers, and they’re supposed to be warm.

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