Where to install the humidifier

Usually, humidifiers are installed in the main distribution duct. It would make no sense to install it in the return duct.

Here is a link on humidifiers http://www.iallergy.com/humidifier_answers.html.

If the humidifier has a 6" duct on one side, this must be open in winter you should find a handle, if there is not any label, move it so the handle is parallel to the ductwork.
If the humidifier do not have a duct on one side, it must have a fan, if you can't hear it working, probably is time to get a new humidifier, and make sure contractor check furnace heat exchanger for CO2 leaks.

Humidifiers are installed in the return air unless they are a forced (uses a fan) type of humidifier.

Evaporative should be in the return plenum and steam in the supply plenum.

Hello Which came first the chicken or the egg?The unit will operate perfectly in the supply OR return as I have installed in both.If there is more room & easy service access put it in there.

Hope this helps, check and see if humidistat is set to 35% humidity and that bypass damper on humidifier is in the open position or winter position.(humidistat is usually located on cold air return duct near furnace). Next, replace humidifier media pad, remember to replace media pad (filter) annually, you also may want to clean any lime deposit out of humidifier housing with a solution of warm water and white vinegar before installing your new media filter.Remember to turn power off at side of furnace when cleaning humidifier and replacing media. Before installing new media turn power back on to furnace, set humidistat to the on position, turn furnace thermostat above room temp., and inspect humidifier to see if water is running from top,(you may want to have a bucket under humidifier when checking for water), if you see water running, turn power back off to furnace, properly install new media filter, reconnect humidifier cover & set humidistat to 35%. If you do not see water present, check water supply valve to humidifier and make sure its turned on. If water supply valve is open, then check water supply tubing for blockage.And the last things to check is to make sure all registers through out your home are open and not blocked by any objects, also make sure furnace filter is cleaned, if none of this works refer to installation manual to see if humidifier was sized and installed properly, Good luck.

thanks for your question,
you have to install the bypass humidifier on the supply side of your heating system, (hot side) and run a bypass pipe from the return side, (cold side), it does matter which side it goes on, you do not want water vapor going directly into your furnace, as this can damage it and shorten the life of it, your humidistat is installed on the return side of your duct work, this will allow proper operation of the unit as the humidistat senses the moisture in the air and brings on and shuts down the humidifier as needed. hope that helped to answer your question, please let us know what you think, again thanks, mr.grzz

you are ok. this way humidity will get to whole house if your supply duct splits off. done this way often.

THE MOTOR ONLY TURNS THE SPONGE DRUM AT MAYBE 10X'S PER MINUTE. THIS IS A BY-PASS TYPE HUMIDIFIER THAT RELIES ON YOU FURNACE BLOWER MOTOR TO SUPPLY AIR ACCROSS THE SPONGE MEDIA. NOTICE THE 5"-7" ROUND HOLE MUST BE DUCTED TO THE PLENUM OR RETURN AIR. (IF MOUNTED ON THE PLENUM, THE HOLE HAS TO BE DUCTED TO THE RETURN AIR, AND VISA-VERSA.) CAUTION!!!IF YOU HAVE CENTRAL AIR? A "DAMPER" MUST BE INSTALLED AND KEPT CLOSED THROUGH-OUT THE "COOLING SEASON". SERIOUS DAMAGE TO YOUR COMPRESSOR CAN RESULT FROM TOO COLD OF AIR ... CIRCULATING AND "BY-PASSING YOUR EVAPORATOR COIL".