Thread: Hot water line to humidifier

Can a hot water supply line be connected to a humidifier, never seen this one before.

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Another case of "Check the manufacturer's installation instructions".

Honeywell and and Generalaire allow it, and Aprilaire actually recommends it for some installations, see (8) here:

Frequently Asked Questions

and AFAIK no manufacture prohibits it, and I've not found any that specifically recommend against it.

Matt, you really need to work on your technical knowledge. When you supply the HUM with hot water it becomes a whole house sauna unit. Very nice to have after a long day of swooshing the slopes.
Seriously though, I don't know of a specific requirement against it. The Manuf. Spec's probably don't even say anything because who would think someone would be dumb enough to do it.
From a user standpoint it is a bad idea of course. HUM's are notorious for clogging up. Imagine what the inside of the HUM will look like with hot water. I also doubt that the insides are designed for hot water which could cause major malfunction. Then of course there's the utility cost.

Originally Posted by Markus Keller

Then of course there's the utility cost.

Which can add up, one estimate I've seen is that a average flow-through humidifier discharges between 5,000 and 8,000 gallons (668 and 1069 cubic feet) of water annually, assuming a 17 week heating system with a call for heat 50% of the time, in the city where I live (Evanston, IL, which charges $5.46/100/cu/ft) that translates to $36 and $58 a year.

Aprilaire makes a humidifier that wicks the water up thru a softer pad from a very small reservoir and uses substantially less water than waterfall or drum type units.

as a rule, any humidifier is a potential mold factory and should be labeled as such. Adding moisture to ductwork is just a bad idea. Now I know many folks don't think the same and that's their perogative. In my reports, i point out the possibilities.
And Hot Water? well that adds to the 3stooges factor for sure.

Aprilaire instructions

Your humidifier is designed to operate using hot, cold, hard or mechanically
softened water. (Hot water is required for Models 350 and 360.)
Water contains varying amounts of minerals. The residue remaining as a
result of hard water evaporation is primarily calcium and magnesium
components and is usually quite hard, scaly, and dense.
Residue from softened water tends to be soft and fluffy and has a greater
volume than hard water deposits. In either case, the service life of aWater
Panel evaporator will be the same. The Water Panel evaporator should be
changed at least once a year with the exception of Models 400A and
400M which should be changed at least twice a heating season. In the
drain-equipped models, most of the mineral solids are controlled by
flushing them down the drain.
Hot supply water, 140°F maximum, is recommended with drain type
humidifiers for increasing capacity and is required for heat pump and air

handler applications.