??? about central air humidifier

We built our new home a few years ago. This is the first time we have lived with central air and heat. We have a high energy unit and are happy as clams and warm. The question I have is about how the humidifier control works. It is made by General Aire model 1137. It has a control box that sets beside the furnace thermostat. It works independent of the furnace thermostat. Should this thing be hooked into the furnace control some how? It seems to me that it would do a better job if it only came on when the furnace is on. You can turn it on and it seems to have to run all the time to get the humidity from say 24% to 28% humidity. I don’t see how this humidifier unit can push that humid air thru all the heat ducts by its self. Is this normal? Water is on to it and the filter gets changed each spring.

Just a guess but it should turn on your furnace fan when it wants to add moisture.

The humidistats that control your system are very unreliable in measuring the humidity. Go to a large store and look at the cheapest stats. Line them all up. Set aside the ones that read high and low. Buy three or four that are about the same and in the middle. Put one in the kitchen and one in the bedroom and one in the living area. Monitor and learn.

Middle twenties is the correct humidity level depending on where you live. Never in thirties or teens.

Most modern homes have to much humidity. How big it is , how many people live there, how you cook, how many plants you have, play a LARGE part on your levels. The largest variable is your air exchanger. How fast is it running?

Not sure if yours is like the one I have, but it is not connected electrically to the furnace at all, other than low voltage power to the water valve/solenoid. Basically the humidifier unit is a small branch on the positive pressure side of the furnace which (in my case) has a damper I switch manually from summer to winter, with the winter setting diverting a small amount of the outbound air through the unit which is simply a water spray over a wet media (replaceable filter basically). The humidistat you describe which is mounted near your thermostat simply turns off and on based on humidity in the room. When humidity is needed, it closes the switch which is wired in series with the low voltage of the blower relay, so that when the furnace blower switches on, it also switches on the water valve to the humidifier (if humidity is needed). When blower turns off, so does water flow to the unit. Works very well. There are two items I have that I would not be without - central humidifier, and water softener. It might take a bit of adjusting of the humidistat to get it correct, but it actually works out, in that the more your furnace blower runs, the more moisture is placed into the air, which is usually the case anyhow. In my case, I noticed the first year that we had fewer colds, etc due to the increased humidity in the air.

In most new construction if you use that type of system under many conditions I describe below the furnace may not run enough to maintain humidity desired. The trend is systems that turn on the furnace fan .

Makes sense, but with my situation it would not work as I have an outdoor wood furnace circulating to a hot water heat exchanger in furnace duct above the furnace, using same blower. I have a second thermostat which simply turns on furnace blower when temp calls for heat. Works very well maintaining within 1 degree. I use my gas furnace as a backup, and that thermostat is normally off. This setup also heats my hot water, using the water heater for storage with burner off during winter.

kswillie, your refer to your system as a "high energy" system...I'm assuming you mean high effeciency system?? If so it either has to be a gas furnace with condensing capabilities OR heat pump with staged electric backup...

Either way, the humidifier should be interconnected to the central system in a way that only allows water to drop across its evaporator pad when the blower is running. The vast majority of gas furnaces, propane or natural gas, have a terminal on their circuit board marked "HUM" for humidifier or "EAC" for electronic air cleaner. The 24v humidifier circuit should originate at the HUM terminal, pass through the humidistat then the water solonoid and then terminate on the 24v Common terminal on the circuit board.

IF your solonoid is of the rare 110v variety, a 24v relay has to be wired in as above described to switch the higher voltage to and through the solonoid.

If its a heat pump it may or may not have the HUM terminal, but a simple universal control is available that merely slips over the wire going to the motor speed selected for the heat mode. Anytime amperage is flowing through that speed, the relay (sensing amperage) closes and energizes the humidifier circuit.

That too however, becomes complicated because a lot of systems now utilize the same speed for heating as well as cooling, necessitating a physical turn off of the humidistat when in cool mode.

I know this is an older post, but I've been away and am catching up.....

Many new furnaces have a place on their circuit board to hook a 24V humidifier.
If yours does not, you can get a small pressure switch that will turn on from the pressure the fan creates in the warm plenum.
I think Grainger has them.