Question about Aprilaire 550 Humidifier

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Aprilaire 550 has exploded with water

Have been having problems with my furnace itself for a while running cold air. While that was happening, the carbon monoxide detector was beeping every 15 sec. Its been going on for about 2 months, every couple of weeks. The other night woke up to the carbon monoxide detector beeping and furnace was running cold air. My humidifier is set at 25%.  Later that day came home to my furnace area under water. It looked like it came out of humidifier. There was at least a gallon of water on the floor. Shut the whole system off and been living in cold since. Does the water just sit in the unit if not heated up by hot air? Can I drain the unit myself?

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  • anastasia802 Feb 11, 2009

    What might be the reason for that much water to gather in the unit and spray out 2 ft in the air?

  • anastasia802 Feb 11, 2009

    Is it safe to open the humidifier if its on top of the furnace? If that much water sprayed out of it, and I remove the cover, would it possibly flood the furnace below it?

  • anastasia802 Feb 11, 2009

    Thank you:)



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No water should not just sit there in the system. It is supposed to recirculate itself. You should really call a tech out and have them check your system.

Posted on Feb 11, 2009

  • 1 more comment 
  • Jeremy Reddick
    Jeremy Reddick Feb 11, 2009

    Sounds like the coil broke inside the humidifier. You can look in there and see what is going on. Just make sure you unplug the unit. Also just check the water supply going into your humidifier. Just to make sure that did not happen

  • Jeremy Reddick
    Jeremy Reddick Feb 11, 2009

    Yes that is true. That is why I say that you should get a tech out there, if anything happens to the furnace it is on them to repair and replace not you

  • Jeremy Reddick
    Jeremy Reddick Feb 11, 2009

    Welcome have a good day



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1 Answer

We have a Aprilaire 550 that have been overflowing via the bottom of the unit & down the line. It seems as if there is a gooey build up after a few days/weeks in the outlet drain that inhibits flow...

Yes, it happens fairly often. The solution is to flush the system with a 50/50 solution of White Vinegar and Bottled Distilled Water. And clear the outlet line, running from the bottom of unit.
Also check any opening to the tank that would allow dust and lint to enter the tank and seal them, if necessary with duct tape. If the furnace is in a dusty area, do the best that you can to eliminate the dust.

Hope this helps you to solve the problem.

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Hope this solves your problem, look for the humidistat, it should be located on cold air return duct near furnace, make sure it is not set in the on position, if it is, then this is why it is staying on, please set humidistat any where from 20 to 35%, never over 40%. If the humidistat is set properly and is still running, you may have a electrical problem, humidifier circuit should only receive power(24 volts) when the indoor blower motor of furnace receives power, also if you have galvanized plumbing in your home, you may have a piece of rust or lime deposit in the humidifier solenoid valve preventing it from closing, turn water off to humidifier and disconnect water supply line entering solenoid valve inspect & clean protector screen. Good luck.

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Feb 03, 2010 | Aprilaire 550 Humidifier

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I have an Aprilaire 550 hooked up to my furnace,

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Jan 31, 2010 | Aprilaire 550 Humidifier

1 Answer

How much water should be draining from Aprilaire 550?

thats too much.. and a waste of water... you should install a good ball valve water shutoff inline and let it trickle.. ideally, it should be net zero water wastage but there's always a bit.. my water take-off drain runs about once every 5hrs and its about a litre (its siphoning water out of the combustion chamber as well as the waste water from the humidifier.. (you can get those ball valves at homedepot for about 6bucks -- they're usually compression fittings as well)

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My Aprilaire is connected to the Hot water line and it stops working in approx 1 month. I just had plumbing work done and my new plumber said the problem it that it should be connected to the Cold Water...

Your plumber is correct your unit should be plumbed with cold water.
Easy fix if you need to do it yourself.
More than likely they have a 1/4 inch line taped into a 1/2 inch copper line near your furnace.
Simply shut off the tap on the undesired line and disconnect the 1/4 inch line.
Install a new tap on the cold water side and reintall supply line to the unit.

Do not remove the old tap on the hot water line simply shut it off because it puctures the line, hence the tap.

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yes it should be bypass but solenoid could be trying to open but the voltage to it may be to low if you have 24v ac power at the 2 small wires. but to change shut down power to furnace and water to loosen the 2 compression nuts unwire they cant be reversed so dont worry then 2 mounting screws then reverse to install

Dec 17, 2009 | Aprilaire 550 Humidifier

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Cold air and smell

replace the humidifier pad every season you may also want to install UV lights

Apr 02, 2009 | Aprilaire 550 Humidifier

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It could be that the humidistat is not calling for humidity. Make sure that you have the dial turned up all the way (as far as it will go, just to test it) and that the blower on the furnace is running - if the unit is properly wired, the water will not run unless the blower on the furnace is running. This should do the trick. If not, the only other thing would be a bad humidistat. Good Luck!

Dec 14, 2008 | Aprilaire 550 Humidifier

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