Got a Total Line Whole House Humidifer today
- Thread starter jjj70095
- Start date
saber1
Active member
Hooking a whole-home humidifier to a hot water line increases efficiency and output because hot water evaporates faster than cold water
ddhanna
Active member
AI says cold water is preferred for most furnace (whole-house) humidifiers.
Why cold water is typically recommended
Most furnace humidifiers (bypass, fan-powered, and many flow-through units) are designed to operate with cold water. Using hot water can:
Increase mineral buildup (hot water leaves scale faster)
Shorten pad life (evaporative media clogs sooner)
Increase energy costs (you’re paying to heat water unnecessarily)
Void warranty if the manufacturer specifies cold supply
When hot water can make sense
Some manufacturers (for certain models) allow either hot or cold water. In a few cases, hot water can:- Slightly increase evaporation rate
- Help during very cold climates where humidity struggles to rise
- The air moving across the pad does most of the evaporation work
- Water cools quickly once flowing through the unit
What most pros recommend
For common units like those from Aprilaire or Honeywell Home, installers typically use cold water unless the manual specifically calls for hot.Best practice
- Check your humidifier’s installation manual.
- If it says “hot or cold,” cold is still usually the better long-term choice.
- Use a saddle valve or proper shutoff with a humidifier-rated supply line.
- Replace the water panel annually (more often if you have hard water).
dfattack
Well-known member
AI is wrong.AI says cold water is preferred for most furnace (whole-house) humidifiers.
Why cold water is typically recommended
Most furnace humidifiers (bypass, fan-powered, and many flow-through units) are designed to operate with cold water. Using hot water can:
When hot water can make sense
Some manufacturers (for certain models) allow either hot or cold water. In a few cases, hot water can:
But the improvement is usually modest because:
- Slightly increase evaporation rate
- Help during very cold climates where humidity struggles to rise
- The air moving across the pad does most of the evaporation work
- Water cools quickly once flowing through the unit
What most pros recommend
For common units like those from Aprilaire or Honeywell Home, installers typically use cold water unless the manual specifically calls for hot.
Best practice
- Check your humidifier’s installation manual.
- If it says “hot or cold,” cold is still usually the better long-term choice.
- Use a saddle valve or proper shutoff with a humidifier-rated supply line.
- Replace the water panel annually (more often if you have hard water).
in the 70's the recommended hook up was hot water, then energy crisis switched "recommendation" to cold water. I have a house that has a tankless water heater and the volume of water does not call for the heaters to kick on so cold water is being fed to the humidifier and that location cannot maintain the humidity levels that similar houses are with hot water being fed through a traditional water heater. Thats a short quick answer but I have a real world comparison to prove the AI recommendation wrong. When connected to cold water humidifier manufacturers are relying on the heat to run to help to humidify. the newer furnaces are so efficient and newer homes are insulated so much better than they used to be decades ago that they don't run as often as they used to. I have spoken to tech support at these companies and they will all tell you that hot water gets better results (unless they are commie libbies).
They told me to turn off the humidifier when shutting over main water valve before leaving in spring.
jime
Active member
can you run the fan sans heater, on a timed schedule instead of heat schedule alone. i do this in summer to distribute ac cold
dfattack
Well-known member
Not sure what you are getting at. maybe clarify if you can. For example, you do you mean run the furnace blower without a call for heat?
I run my blowers constantly since I use a device called an ERV. This changes my air in my house approximately every three hours without opening windows and in the winter. With the blower running 24/7 the humidifier can cycle on and off based on the call for humidity. THIS is the reason why hooking up to hot water is better since the humidifier doesn't need to wait for a call heat for better efficiency. Hot supply water with a blower only condition is still producing good humidity.
ddhanna
Active member
AI did say MOST humidifiers which probably includes the OP's. Your ERV situation is not common and is a likely exception. The difference in evaporation for hot vs cold is not huge. My 10 year old 97% furnace with Aprilaire works perfectly using cold and saves energy doing it.
dfattack
Well-known member
Didn’t say it wouldn’t work. I’m saying it shouldn’t be the preferred setup. Hot water will give you better more effective results. That’s all I’m saying. In the end will probably use less water since humidity set point will be reached sooner. Im speaking from experience
jime
Active member
yes, AI is not to be trusted.
i misunderstood and thought your furnace did not run long enough to produce higher levels of humidity. when i run the blower fan, humidifier is on call. when the blower does not run neither does humidifier. hot or not, don't care that was HVAC install.
i do enjoy jjj questions by the way, i've heard hot water freezes faster than cold!