Central humidifier works well

Faced with maintaining humidity for the Steinway Grand Piano in the living room. Humidity during the winter months dropped to about 18% RH; Way too low for the piano wood. Was considering room-level humidifier but decided to try this house-wide humidifier that attaches to the central heating/air conditioning system for the entire house. I figure not only the piano wood won't crack but I won't get shocked when petting the cats as well lol.

This unit is based on evaporation for humidification as most are these days. It has the unique feature of a built-in fan to circulate air from the exhaust plenum, through the evaporative mesh, and back into the plenum, whereas other units, including some from Honeywell, have ductwork to attach to the return plenum. Thus, other units rely on the system blower to move air through the evaporative mesh while this one has a built in fan. I am not sure if this is really "better" since the fan is one more thing that can eventually break....it may not matter.

The main kit consists of the humidifier housing, the evaporative mesh, a humidistat (thing that senses RH), and the fan. HOWEVER, the sail switch -- which detects when your main blower is running -- is supplied in the separately purchased "installation kit". The installation kit also includes water supply tubing, drain tubing, mounting hardware, and a few other things. This installation kit is MANDATORY and I'm surprised it's not included with the purchase of the main unit. The installation kit also has a VHS video which is helpful.

The exercise of mounting this unit to your central system can be a NIGHTMARE. Installation video suggests about 1 hr, but please plan on spending many hours. In my case, I had to move the natural gas exhaust ductwork to make room for the humidifier. The humidifier takes up a sizable portion of the exhaust plenum -- installed, it measures about 14" wide, 17" high, and 10" deep -- so make sure you have room for it in your heating setup.

I believe cutting the hole in the plenum -- for the humidifier, the sail switch, and the humidistat -- is the most challenging aspect of installation. Forget about a manual hacksaw. Forget about trying to use tin snips. I was only successful using a hand-held jigsaw with a metal cutting blade. Make sure you wear ear-protection if you do this as the sound emitted from the plenum when using the jigsaw is quite intense. Also, heed the warning in the documentation to make sure you don't cut your air conditioning condenser coils since units (including mine) may have the coils occupying a portion of the exhaust plenum. After drilling an exploratory hole in the plenum, I found I had to move the humidifier unit upward about 8 inches to avoid interference with the air conditioning condenser coils.

You need to tap into a water supply nearby using the saddle valve that came with the installation kit. I used the nearby water heater "cold" intake for this purpose. The tubing supplied in the installation kit feels like a teflon-like material (not sure exactly what it is), but it works well and does not leak and can withstand the water pressure.

The water supply attaches to a solenoid valve on the humidifier unit. The water is allowed to flow into the humidifier when BOTH the sail switch AND the humidistat are "on" -- indicating the system blower is on AND the house humidity is too low, respectively. This makes sense, since you only want to operate the humidifier when the blower is on (as sensed by the sail switch) and when the house needs more humid air (as sensed by the humidistat).

Per the recommendations, I mounted the sail switch and the humidistat on the RETURN plenum, which is sensing return air FROM the house....before the system blower. I mounted the humidifier on the EXHAUST plenum, which is after the blower and is using warmed air from the heating means -- in my case, natural gas.

When the water solenoid is ON, water passes through the humidifier evaporator mesh to keep it moist. Since an excess amount of water is used, water WILL drain out the bottom of the unit, and this must be directed to a floor drain or equivalent water removal technique. In my case I did not have a floor drain nearby, so I used the condensation pump that is also used to pump out condensate from the air conditioning coils.

I believe there is a need to have water flow through the unit to avoid contamination of the humidifier mesh. Essentially, the continuous flow of water effectively cleans the mesh so deposits don't build up as is the case with other wicking-style humidifiers.

BUT, there is a downside.....the unit uses MUCH more water than what is required for the humidification action itself. The specs don't state this, but I would guestimate about a gallon of water is wasted every 15 minutes !!! That's about 100 gallons per day if the unit is constantly on.

I figure my house is about 4000 sq ft with 3 meter ceilings. This comes out to about 1100 cubic meters of air volume in the house. At 100% RH, the water content of air at 1 atmosphere and 22 degrees C (72 degrees F)is about 20.6 grams/m3. This translates into about 6 gallons of water contained in the air of the house to bring to 100% RH. So I believe the advertised 18 gal/day capacity of this humidifier is more than enough to control the humidity to the degree I desire.

ISSUE 1: The sail switch broke after a few hours of operation. The springy metal that held the plastic sail in place broke due to "fatigue" same as if you flex a piece of wire -- it breaks eventually. Apparently the intense airflow through my system was too much for the sail design. I replaced the plastic sail with a piece cut from sheet metal that was removed from the plenum to make the hole for the humidifier and it works OK now.

ISSUE 2: The humidifier can only be "on" when the blower is blowing. The blower turns on based on heating needs of the house. So, humidity may not be controlled as desired if heating of the house is not needed at the time. I set my thermostat fan to "on" instead of "auto" so that air is constantly flowing through the system regardless of heating demand. The downside is the blower is always on. It might be possible to turn on the system blower when EITHER humidification is needed OR house heating is needed, but that requires taping into the heating thermostat,etc...a bit advanced; a successful circuit may require a relay. The instructions suggest a variety of control circuits, but you need to know what you are doing here to get something working. I just did the recommended series circuit consisting of the humidistat, the sail switch, and the water solenoid -- the simplest (and minimally required) installation and the one I think you should try to get working first.

The unit was purchased at my local Home Depot for $179 for the humidifier and $47 for the installation kit. Periodic maintenance is basically replacing the evaporation mesh which is easily done in this unit; at least once a season. Notwithstanding the installation hassle, I am satisfied with the value and operation of this unit and I think it's much, much better than trying to use room humidifiers. I feel comfortable in recommending this product for yet another DIY project....but you need skills, tools, and patience to install this one!!!!