How not to install a whole-house humidifier

Hurumph. I didn’t get to sub on Friday. It was a snow day. The snow was absolutely beautiful. It was about 25 degrees, very little wind, and big fluffy beautiful flakes covered everything. The tops of all the tree branches were covered in an extraordinary way.

We put in a whole-house humidifier today. After only a few hours we could all feel the difference in the house. It feels warmer and cozier! The coziness is quite palpable.. in exactly the same way that a room in summer can be stuffy. Now our house is 3 shades closer to stuffy and 3 shades further away from bone dry.

When putting one in, you’ve got to watch out that you don’t encourage mold growth in your ductwork. I did a little research on the topic. Here’s some tips:

Think very carefully about using one if you have insulated ductwork. You can get into trouble with this. I didn’t follow up on this angle but it looks important.

The guys at Lennox said that you have to make sure the plenum is at least 120 degrees. (plenum is a $5 plumber word for “duct-work”… actually, it refers to any space pressurized by air. Your ducts are pressurized by the fan in the heater so that the air gets pushed around the house) This means that (according to our installer) you shouldn’t install it on a Lennox pulse-fired heater because the output air isn’t hot enough…. but I don’t have much faith in what he says; he installed our humidifier incorrectly.. I’ll tell you about that later. It also means that you shouldn’t run the humidifier while the heater isn’t running. As an example, you should recall how in room humidifiers, the filters often advertise how they are impregnated with silver to keep the mold at bay. Well, imagine if there wasn’t any silver and the mold had free reign of all your duct-work. Bad. The idea is that the 120 degree air in the plenum keeps the mold at bay.

In our installation, our guy incorrectly wired the motor on the humidifier to the 24 volt “ACC” accessory tie in. So the humidifier wheel would run whenever the blower in the furnace was on. I had him rewire it so that it was attached to the wires for heat (green and white wires, I think) going between the furnace and the thermostat. So then the humidifier only comes on when there is a call for heat… and the plenum is hot. We’ll see how well it goes.

I was a little disappointed with their choice of humidifier as well. A Lennox WD 15 Humidiwheel. Even though the guy swore up and down that it didn’t have any trouble with lime deposits, I don’t believe him. There are several newer models that go to special lengths to flush lime out of the system… I mean, this thing evaporates 15 gallons of water a day of pretty hard water… The lime has to go somewhere! I’ve got a feeling that I’m going to be self-installing my own unit in a few months. It’s good that I watched him install the unit.

Next time, I’ll definitely install the things myself. The average HVAC technician just doesn’t have the brain-power to get it right.

There was this other issue about a hot water heater safety valve that I spoke to him about… The conversation we had bothered me. He sounded more intent on replacing parts and charging us than fixing the problem. You see, 2 months ago we had asked him to fix a problem with a leaky safety valve on our hot water heater so he replaced the valve. He was pretty sure it wouldn’t fix the problem (and it didn’t) but did it anyway because we had told him “that valve leaks, fix it.” Duh, I’m not a plumber but I’m smart enough to say, “Hey, there’s water on the floor, I should call someone that will know what to do.” If they’re not smart enough to know what to do, then I should call someone else! Or… learn how to fix it myself. Grrrr.

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