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Whole House Humidifier Installation
Honeywell HE240A

whole-house humidifier system installation - RF CafeA large portion of the U.S. has experienced prolonged periods this winter (2014) with temperatures substantially below long-term averages. That means heating systems have been running much more often than usual, and if you have a forced hot air system, that means the indoor humidity level has been much lower than normal. In northern areas like where I live, humidity can easily drop to near zero. Because of that, triboelectric charging to high voltage potential occurs merely by walking a few steps across a carpet, resulting in a sometimes painful discharge arc when a metal object is touched.

The only way to mitigate low humidity conditions is to add water back into the air. One way is to use a free-standing humidifier that either evaporates water back into the air or to use an ultrasonic humidifier that blows a fine water mist into the air, which then evaporates. Ultrasonic types tend to put more water back into the air, but if you have a high chemical content in your water - such as lime or calcium - you will soon find a layer of dust deposited on everything in your house. It lays on top of horizontal surfaces and electrostatically clings to the sides of glass and plastic - an utter mess!

Evaporative humidifiers do not have that problem since the heavy, non-evaporative elements never leave the unit. Instead, they collect on the filter/dispersion grid. Cleaning or replacement is needed, but at least the crud is not all over everything else.

You can buy free-standing humidifiers of both types that have water supply line hookups with valves that regulate water inflow, but you need to have them located near a supply line. Regardless of the type, you will be listening to fans blowing all day and night long.

The preferred option, IMHO, is to install a whole-house humidifier that resides on the furnace ductwork, has its own regulated water supply, and is controlled by a humidistat. After a couple weeks of refilling three free-standing humidifiers two to three times a day and listening to the fans, I decided it would be worth the expense and effort to install a whole-house humidifier. The free-standing units cost $60 at Walmart ($180 total), and the Honeywell HE240A whole-house humidifier with a couple additional parts cost a total of around $225 at Home Depot. I already had the small sump pump to handle the water drain, so that saved me $40. I could have run the drain line into the garage floor drain, but that would have looked bad. So, after about six hours of installation time and an additional $50, I now have an automatic humidifier that waters itself and probably adds at least $225 of resale value to my house. The three free-standing units, which would have no resale value, were cleaned and returned to Walmart for a full refund.

Installation is very simple if you have all the needed tools, which I did. Instructions called for a 3/4" diameter metal drill, but I instead marked off a 3/4" hole and drilled around the perimeter with a 3/32" bit and filed the edges smooth. Because of the vertical downward flow of my furnace, I needed to mount the humidifier unit on the return air duct. Here are a few photos of the installation in case you want to try a similar installation for yourself. I'm guessing anyone who reads this, being an RF Cafe visitor, will have no problem.

Note: High efficiency fuel-fired furnaces generate water in the exhaust due to condensation from the air. It is the same process that condenses air in your air conditioner. It needs to be drained properly. Mine originally drained into the soil under the house, but I re-routed it into the sump pump used for the humidifier drain.

BTW, my furnace uses natural gas - the cheapest of all fuel sources these days. I pity those who use oil, LP, or propane!

whole-house humidifier system installation - RF Cafe

Here is the completed whole-house humidifier system installation. My house is only 960 ft2, so the Honeywell model HE240A, which handles up to 1,500 ft2, has plenty of capacity to spare.

Hang the humidifier body on the bottom of the duct opening - RF Cafe

Hang the humidifier body on the bottom of the duct opening.

Mark and cut hole in duct for 6" diameter duct tap - RF Cafe

Mark and cut hole in duct for 6" diameter duct tap. Pressure switch tap requires 3/4" hole with a grommet and nipple for hose.

Insulation wrapped around duct and water line - RF Cafe

Insulation wrapped around duct and water line.

Whole-house humidifier installation front view - RF Cafe

Whole-house humidifier installation front view.

Use a level to mark a reference line - RF Cafe

Use a level to mark a reference line. Don't measure relative to the duct because it might not be level or plumb. The humidifier body needs to be level to assure proper drainage.

Level before installing screws - RF Cafe

Level before installing screws. I needed to swap the left and right sides for my configuration.

I looped the water line around the heat duct the pre-heat the water - RF Cafe

Although not required, I looped the water line around the heat duct to pre-heat the water before entering the humidifier. 

pneumatic, hydraulic, and electrical hookups - RF Cafe

Details of pneumatic, hydraulic, and electrical hookups.

Drill 1/2" holes at the four corners and use metal snips - RF Cafe

Drill 1/2" holes at the four corners and use metal snips to cut the hole, then use pliers to flatten the edges where the snips curled them.

Mark and cut the humidistat hole - RF Cafe

Mark and cut the humidistat hole.

Tap installed on cold water supply pipe - RF Cafe

Tap installed on cold water supply pipe (same type as for refrigerator ice maker).

Whole-house humidifier installation overhead view - RF Cafe

Whole-house humidifier installation overhead view. The sump pump has a 1/2" hose running over to my washing machine drain pipe (about 20' away).



Posted August 5, 2021
(updated from original post on 2/20/2014)

KR Electronics (RF Filters) - RF Cafe

About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024


    Kirt Blattenberger,


RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

Copyright  1996 - 2026

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