# Humidifier pounding noise.



## wrj47 (Dec 22, 2010)

I have an Aprilaire 700 humidifier on my furnace. In order to increase the level of humidity in my house to 30-35% I was told by Aprilaire to disconnect the humidifier cold water line and connect the humidifier water line to my hot water line. When I did that it stated toi make a pounding noise when it it cycles off. I can hear this sound throughout the house. What can be done to rectify this? Thanks


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## hvaclover (Oct 2, 2008)

The water line opening is partially blocked at either the valve or the solenoid.


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## wrj47 (Dec 22, 2010)

Thanks for the reply.

I removed the water line and checked for blockage and could not find one. I bled the valve and the line. When I reconnected it it still made noise when shutting down.

Is there anything else I should do?

Thanks


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## Jackofall1 (Dec 5, 2010)

Switch it back to the original line and see if it still does it.

I am wondering if the seals on the solenoid valve are rated for hot water? Usually not, sounds like you are experiencing water hammer, caused by the solenoid closing too fast.


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## wrj47 (Dec 22, 2010)

I'll try connecting to the cold water again to see. 

I called Aprilaire and they said to install a shock arrestor in the 1/4" line. Would that get rid of the hammering?

Thanks again


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## hvaclover (Oct 2, 2008)

Jackofall1 said:


> Switch it back to the original line and see if it still does it.
> 
> I am wondering if the seals on the solenoid valve are rated for hot water? Usually not, sounds like you are experiencing water hammer, caused by the solenoid closing too fast.


 Aprilaire requires a hot water hook up per the instructions.

OP, have you checked to see if the supply line opening is not out of round and the copper has been de-burred?


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## hvaclover (Oct 2, 2008)

wrj47 said:


> I'll try connecting to the cold water again to see.
> 
> I called Aprilaire and they said to install a shock arrestor in the 1/4" line. Would that get rid of the hammering?
> 
> Thanks again


 If that's what they said take it as goepel.


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## Jackofall1 (Dec 5, 2010)

What is the humidifier putting out as far as RH to the house?

Is the bypass damper open? 

Install manual calls for cold, hot, softened or unsoftened water. Hot water (Max 140 degF) will provide the best evaporation rates.

As for the hammering, try and dial back the supply flow through the valve as an experiment. If this works you could add a small inline valve to regulate flow to the humdifier.

A shock arrestor should work, but so will regulating the flow rate to the unit.


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## beenthere (Oct 11, 2008)

Jackofall1 said:


> Is the bypass damper open?


The Aprilaire 700 is a power humidifier, so it doesn't have a bypass.


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## hvaclover (Oct 2, 2008)

beenthere said:


> The Aprilaire 700 is a power humidifier, so it doesn't have a bypass.


 
hhhmmmmm...i was just about to tell the OP to check the by pass damper.
Sometimes the damper can come loose inside the by pass and the supply air can slam the damper around..BUT NNNNNoooOOOOooOOOO... Been blew that idea to hell be cause he knows EVERYTHING about humidifiers:laughing::jester:


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## beenthere (Oct 11, 2008)

hvaclover said:


> hhhmmmmm...i was just about to tell the OP to check the by pass damper.
> Sometimes the damper can come loose inside the by pass and the supply air can slam the damper around..BUT NNNNNoooOOOOooOOOO... Been blew that idea to hell be cause he knows EVERYTHING about humidifiers:laughing::jester:


Or maybe its because I've installed 700's and know the difference between a bypass and power humidifier. :whistling2: :laughing:


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## TJW1112 (12 mo ago)

wrj47 said:


> Thanks for the reply.
> 
> I removed the water line and checked for blockage and could not find one. I bled the valve and the line. When I reconnected it it still made noise when shutting down.
> 
> ...


You should definitely RE connect it to your cold line. I have aprilaire 800 and the install manual specifically states not to connect to hot. Also the 1/4” nut and ferrule connection at the unit says ‘cold water only’
I am an insured master plumber, gas fitter and HVAC technician.


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## beenthere (Oct 11, 2008)

TJW1112 said:


> You should definitely RE connect it to your cold line. I have aprilaire 800 and the install manual specifically states not to connect to hot. Also the 1/4” nut and ferrule connection at the unit says ‘cold water only’
> I am an insured master plumber, gas fitter and HVAC technician.


Thats because the 800 is a steam humidifier. The 700 however, is not. And works best when connected to hot water. As recommended by Aprilaire.


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