Q&A / 

Install Humidifier on Return or Supply

Larry Clifford had a humidifier install at his Richmond, KY home. He's now wondering if it was done wrong because it doesn't seem to be working right. Let Larry lay it on you:

"I have a heat pump that came with the house. I am the original owner.

A few years ago I had a HVAC company install a Bryant HUMBBSFP humidifier.

It was installed BEFORE the heat pump as the air flows. I believe it does not add humidity to the house because the heat generated by the heat pump immediately dries out all of the moisture.

I believe it should be installed AFTER the heat pump so the air will retain the moisture.

Am I correct saying the location is critical? Should it be before or after or does it not make a difference?

Also, this is a very bad design. I have replaced the pad, but it took an hour. It took a technician about 1/2 hour. That is too much time."

Here's my answer: CAPS below for emphasis, not SCREAMING. 🙂

Larry, I know you may think I'm being a smart A * *, but it doesn't matter how I feel it should be installed, nor any other person at any other website. I do know the answer, but what I'm going to recommend is that from now on you don't ask folks like me.

If you want to know exactly the best way to install any product, you do but one thing.

You READ the written installation instructions that come with the product. Period.

If you want to make sure you discover the BEST COMPANY or TECHNICIAN or CARPENTER or PLUMBER or ROOFER to install products you buy, you READ the written instructions BEFORE you GET BIDS. Why?

You want to be able to ask questions of the bidders to see if THEY KNOW the RIGHT WAY to install the product.

Yes, this is work. Yes, this is a royal PIA. Yes, you would think that you can TRUST the mechanics to do it right.

But you CAN'T. You need to do your due diligence if you want to make sure things are done right.

Here's another reason why you have to do it this way.

Most product warranties are VOIDED if you don't follow the instructions!

Okay, here's your answer. My guess is the written instructions will show it's best to put that humidifier on the SUPPLY SIDE of the ducting system. Why?

Warm or hot air can absorb MORE MOISTURE.

Finally, you want to make sure the idiot installer didn't tap a nearby water line with one of the USELESS saddle valves. NEVER use one. Currently your humidifier could be starved for water because of the horrible saddle valves.

You want to install a proper tee fitting in the water line, put in a ball valve shut off and then the reducing fittings for the 1/4-inch soft copper or other supply line to the humidifier.

I hope this helps you.

If you're a person who bet me on whether you'd know my exact answer and got it wrong, it's time to PAY UP. 🙂

I say this especially if you discovered something here in this post that will save you a TON of money in the future.

CLICK HERE to avoid being labeled a bet welsher.


6 Responses to Install Humidifier on Return or Supply

  1. My HVAC guy says furnace mounted humidifiers should not be used as they cause corrosion in the plenum or supply lines.. He recommends portable room humidifiers instead.

  2. Hot air furnace has Electronic air cleaner installed up stream with optional wheel-type humidifier on exhaust side.
    No sign of corrosion after plus 10 years, "knock on wooden head" but my ELC has stopped "zapping" !

  3. I'm going to have to disagree with you on one point. Yes, you should read the manual thoroughly, but sometimes the people who write these manuals don't know much. My humidifier manual says it can be installed in either the return or the supply. (It's a bypass unit, not fan driven. And it came with a saddle tap,lol). So I don't quite trust these guys. Why install it in the return? It seems inefficient to me.
    Funny-ish story, mu husband and I have been bickering for years, over the return vs. supply debate, lol.
    So, my husband had it installed in the return, because the manual said it was ok, and because a local hvac instructor told him to do it that way. I tried telling him it would function better in the supply, the hotter air from the furnace would hold more moisture, and the condenser sucks all the moisture out of the air. Then he told me the humidifier isn't wired up to run with the ac (but it can be). So I told him that running the humidifier with the ac would help alleviate the summertime bloody noses and sore throats and dry itchy skin, shrinking wood, etc. And he tells me, you don't run humidifiers with the ac, because all the humidity would get sucked out by the condenser.
    That's when I said.... DUUUUHHH! That's why the humidifier goes in the supply, not the return! But he went through hvac school, and I'm just a dumb housewife, so surely I can't actually know what I'm talking about here right?

    • Good for you. Thinking is sometimes/always? better than being educated. My HVAC guy said install the humidifier on the return side. Doesn't the air filter become wet?

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