Since becoming a first-time homeowner nine months ago, I’ve had to figure out how to maintain, adjust, and upgrade the inner (and outer) workings of our old house. From dealing with electrical and asbestos issues to pruning our shrubbery to installing a new smart thermostat, it’s been an adventure! Today I’m sharing another project I took on recently: replacing our old whole-house humidifier.
Now that we are well into winter and our furnace is working hard, we’re noticing how drafty our 92-year-old house is. Sealing all the windows and cracks in the stucco exterior this past spring did not completely stop the cold winter air from pushing its way inside (though it did help). And even though our new Ecobee thermostat is keeping our home’s temperature comfortable, the air has still been unbearably dry. I took a look at the thermostat and saw that the humidity was 24%, below recommended levels for inside the home.
I did some research, and found the Home Energy Resource MN website that discusses the optimal humidity levels to have in your home in winter and summer. According to this info, the air inside our home during the winter months should be about 35%. That’s an 11% difference from what we were experiencing.
So I went into the basement to investigate our existing furnace and humidifier, both of which are around 20 years old. Since we don’t want to replace the furnace quite yet (that’s expensive!), I wanted to see how the humidifier was holding up. Maybe I could fix it or adjust it to help it run better.
Hopeful, I opened up the service panel on the humidifier…and saw this mess.
This humidifier used water sitting in a tub at the bottom of it and pumped the water up and over the evaporating media. As the water sat and evaporated, it left sediment, minerals and who knows what else that also was again cycled over the media. Yuck! It was too old and built-up with residue to salvage. So, for the health of our family and for the house itself (super dry air is bad for plaster and wood too, the primary make-up of its structure), I decided to do some research on new humidifiers.
I looked at three types of humidifiers:
- Evaporative Bypass Humidifiers (the furnace blower pushes warm air through water evaporating media)
- Evaporative Power Humidifiers (a powered fan pushes warm air through water evaporating media)
- Steam Humidifiers (a container boils water and makes steam that is released into the air ducts)
At first, I thought a steam humidifier would be the right choice for us, because the water would be sterilized and not promote the growth of any funky microbes. But they are really expensive, and some reviews said that condensation can still build up inside the ducts, where those microbes could grow out of sight. And the evaporative bypass humidifier was going to be much more work because it required a new duct connecting from the humidifier to the return air duct, and we just had no room for this.
So I looked at the evaporative power humidifiers. I decided to go with the Aprilaire 700A Power Humidifier, due mainly to Aprilaire’s history of strong performance and good reviews. The 700A Power Humidifier seemed to be a good fit for our current system – it’s the same size as our old humidifier and would not require major modifications to ductwork. Also, it does not cycle water sitting in a tub – instead, fresh tap water trickles over the evaporative media and down into a drain. This cleans the evaporative media as it flows over it when the furnace fan is running. (We’ll see how this affects our water bill over the next few months.)
The first task was to remove the old humidifier. And before I could do that, I needed to shut off the power to the furnace. On the day I was installing this new humidifier, the temperature was 17˚F outside, so I was very motivated to work as quickly as possible so that the house would not become crazy cold inside (especially in the basement where I was working).
Removing the humidifier was pretty simple – it was just held together with screws. But every piece I took off revealed more of its poor condition.
And it seemed like something was missing here that would have sensed humidity levels. Basically, it all looked very old and clunky.
The removal process took about a half hour, and then the furnace was ready for the new humidifier. The temperature inside the house was dropping fast, so I focused on getting the unit installed on the furnace so that I could turn the power back on and run the furnace for a little while to get the house warmed up again.
The new humidifier required a larger opening into the furnace than the old one had, so I expanded the old opening, first using a level to size it, and then a reciprocating saw with a metal cutting blade to cut the ductwork. (The saw cutting into the duct was very loud – I would strongly recommend using ear protection when doing this step.)
And finally, I was left with a perfectly-sized opening for the new humidifier.
The humidifier attached to a bracket that fit right into the opening. I fastened the bracket to the duct with sheet metal screws, then attached the humidifier to the furnace itself.
I was able to turn the power back on temporarily to run the furnace for a bit, so I could warm up while taking a lunch break. Luckily, during the two hours I’d been working so far, the temperature inside the house only dropped about 10 degrees. No icicles forming on my nose yet, but I still wanted to get this project completed ASAP!
After the house warmed up a bit, I turned the power off again and began to prepare the wiring and plumbing. Our old humidifier was hard-wired to the 120V AC, but the Aprilaire 700A has a plug that requires a standard outlet and also a 24V converter with constant power (included with the humidifier), so I needed to rewire the switch at the furnace to accommodate these connections. I was able to get all the needed electrical supplies for this wiring with a quick trip to Home Depot. The rewiring was as simple as following the instructional schematics provided with the humidifier. I used the leftover wires that I had saved from our thermostat project this past summer.
With the plumbing already in place from the old humidifier, I just trimmed off the end of the existing water line, cleaned it up a little, and attached it to the new humidifier. I used a clear drain hose (I wanted to see if the water would flow properly) and routed it into the furnace’s condensate drain.
Installation completed, it was time to turn the furnace back on and program the humidifier. The Aprilaire 700A is an automatic humidifier, meaning it will adjust the inside humidity based on outside temperature. This is important for regions (like ours) where temperatures drop below freezing – condensation or frost can develop on windows and inside the walls that can cause mold to grow (even leading to rot and structural damage).
I set the humidifier at the highest setting at first, with a plan to adjust it if we saw condensation on our windows. Within a few hours, we saw on our thermostat (and felt in the air) that humidity levels were increasing to 37%. The temperature outside was 20˚F – I checked our windows, and did note that condensation and frost were developing.
A quick adjustment to the humidifier’s settings, and the condensation disappeared. And what’s great about this new humidifier is that it will automatically adjust from here on out. We’ll keep an eye on the windows (especially during extreme temperatures) to make sure nothing is amiss, but so far, so good.
And we are breathing much easier – literally! Which is good, because this winter – with its dry air and polar vortex and 900 inches of snow – has been a little challenging to keep up with.
What are you doing to keep your home feeling comfortable this winter?
(Update: Read about how our furnace actually died shortly after writing this post. Luckily, we’re able to keep and use our humidifier with the new heating and cooling system!)