A Fall Furnace Primer Part 2 of 2 - Humidifiers
The outside winter air is cold and dry. The inside winter air is dry. Our chapped lips, dry skin and static zaps from doorknobs remind us of that all season long. Homes like the dry environment, but dry air makes people uncomfortable. While an ideal humidity for homes can be as low as 5%, people prefer about 60% humidity. And because people are more powerful than homes, we add humidifiers to have it our way. Physics
101 The interesting part is that if you cool down the air in a room but add no more water vapor, the relative humidity goes up. And, if you warm the air, the relative humidity goes down. This is important because the winter air outside is very cold and dry. When we bring the winter air into our homes and warm it up, we get really dry air in our homes. For example, outdoor air with 80% relative humidity at freezing temperatures will only have 20% relative humidity when we warm it to room temperature. Do
I need a humidifier? Do
I have one? A drum type humidifier has a tray of water with a sponge barrel or drum rotating through it. The tray is kept full with a float switch, which allows water from the house plumbing to enter the tray when the water level drops. When the humidistat is turned up or the humidity level drops, a small electric motor rotates the sponge drum through the tray, absorbing water. Some of the air moving through the ductwork blows across the sponge, picking up moisture. This moist air moves through the ducts and into the rooms. Cascade type humidifiers
have no tray of water. A small electric valve at the top controls the water
supply to the humidifier. When the humidistat calls for water, the valve
opens, trickling water down a honeycomb-like metal pad. Air blows across
the pad, picking up moisture. Excess water is drained through a hose to a
floor drain, laundry tub, or condensate pump. If you have a cascade style unit, turn off the water supply and turn the humidistat to OFF in the spring. Before use in the fall, remove and soak the pad in de-scaling solution. If it is damaged or too clogged to clean, the pad can be replaced. Once the pad is back in place, the water supply pipe valve can be turned back on, and the humidistat set to 35%. This unit will not need cleaning again until next year. How
much is too much?
Keeping an eye on the amount of condensation on your windows is another great way to gauge your house humidity level. You can also track things with a room temperature and humidity monitor, available at hardware and building supply stores. Contents
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