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Heating, Air Conditioning, Fridge, HVAC/Install of Aprilaire 700 humidifier



I'm planning to install this humidifier in my system but I ran into a small snag during the planning. The diagram says to install the unit on the supply plenum (ideally) and, if there's an a-coil in there, to install it on the side where the coil panel is angled away toward the center. On my system, access is limited to the side where the coils form the A shape right next to the plenum wall. It's blocked by the return plenum on one side and the utility room wall on the other. My questions are:

1. Is it completely out of bounds to install it on that side, provided I'm exceedingly careful not to saw my coils in half? I can see it blocking some of the moist air, but are there other reasons this is a bad idea?

2. Is it worth putting a non-bypass type humidifier on the return side given the extra expense of this fancy unit? The house is 1991 construction, about 3500sf. and reasonably tight.

3. Is the saddle valve they included in the kit as big a piece of garbage as it looks? What's the best way to tee off from the water supply for a project like this?

Thanks for your help,

Dirk Koenig
Shorewood, MN

Hi Dirk, Aprilaire always recommend's putting the humidifier on the supply duct. In most cases that's not possible. It's perfectly acceptable to put it on the return duct.

I would recommend installing the bypass humidifier. Don't worry about the saddle valve I have installed many of them and never had a problem.


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Jim S.


I can answer questions on gas or electric furnaces, ac units and heat pumps. I don't work on boilers,chillers,or home appliances.


I have been in the HVAC trade for over 35 years. For the past 15 years I have owned my own business. I am semi-retired so I can answer questions in a timely manner.

I attended trade school for 5 years on weekends and evenings. This was very hard to do, but well worth it!

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