Humidifier - Hot vs Cold Water Experiment

e humidifier with hotter water. What surprised me is that the drain temper ature wasn't much hotter. To me this says that you aren't really "wasting" the energy by using hot water. You aren't putting more BTU's down the dra in.

ed me to go ahead and use hot water. I run an ecobee thermostat that is se t up to periodically run the blower to keep house air mixed even if no heat is needed. I was worried about how to make this work with the humidifier but now I'll just tie in to the hot water and use a current sensing relay t ied to the blower.

Well, usually when someone replies to a six year old post, people here jump on them, saying things like "that guy died 5 years ago from too little humidity". But here I am, still here.

If it were me, I'd probably rig it up to run when the burner is on. That's what I did with mine. At the very least you're going to use more water running it without heat. And while you get much of the heat from the hot water into the house, if the incoming cold water is 40F, you're not going to get whatever heat it takes for the WH to raise it up from 40F to around room temp, so the more water it uses, the more energy is wasted. Running with heat on will minimize the water and energy usage. How much of a difference it makes in the grand scheme, IDK.

You're safe probably because you don't have gerbils. There seems to be a strong correlation between death and gerbil ownership.

Interesting and well thought out experiment IMO. It seems to be a good guess according to theory, but it's nice to get actual data as opposed to guesses.

I wouldn't call it "wasted".

It takes energy to evaporate water no matter what.

If you want to add X gallons of moisture to the air, it's gonna take Y BTUs of energy no matter what.

The only issue is where those BTUs come from and how much they cost.

If you are using a gas water heater and gas furnace, there is not really any difference.

Consider two methods of adding 1 gallon of water to the air:

If the incoming water is 40F, you're wasting the energy used to raise the water from 40F to 80F, its going down the drain.

In general, I agree with you, and that was my key point from my post years ago. The key is that assumes the run time of the humdifier is about the same. He is proposing to let the humidifier run whenever the blower is on, including when there is no heat. Doing that, the humidifier will be running part of the time with no furnace heat. That means it will take much longer to put X amount of water in the air and while it's running, you have water that's comining into the WH at ~40F going down the drain at ~70F, which is additonal energy that's wasted.

In the grand scheme of things, ID?K how much diff it makes, but the effect is there.

the humdifier will USE more energy because of the longer run time of the humidifier

but I would not say it is wasted because he will also get more moisture in return for that energy.

It's wasted energy if the humidifier can keep the humidity of the house at the desired level by just running when the heat is on, which everyone I've ever seem will.

replying to trader4, SomeGuySomewhere wrote: Were you able to raise the humidity level after switching to hit water then?

replying to SomeGuySomewhere, Tim Barnes wrote: I respect

replying to HeyBub, Hvac doctor wrote: I have same set up and use hotwater as well i throttled down water usage using hotwater

hot water versus cold water in a furnace humidifier makes a difference in the amount of water that evaporates, I did the actual test on my unit. Here's exactly how I did it and the results.

test, I made sure to keep everything constant except the incoming water temp. My unit is connected to hot water, so to change the water temp, I turned off the water heater and used up the hot water through normal household use. I got the hot water tank temp down to 51F. The house humidity was 37% at the time of the test and the temp was 67F. I routed the humdifier drain hose to a location that I could put a gallon container under it and remove it without disturbing the hose. I placed a temporary container under the running hose to catch the water. I then started the furnace with the humidifier set high enough to be running constantly. I let the system stabilize for 5 mins to get to a steady-state. Then I quickly replaced the temporary container with another empty gallon container and started a stop watch. During the 5 min period, I also measured the temp of the water exiting the drain hose. At precisely 5 mins, I removed the container and used a measuring cup to determine the volume of water. I also shut down the furnace.

a higher temp to see what happens with medium temp warm water. I then turned the water heater off again. That temp turned out to be 102F. I then repeated the process of starting the furnace, letting it run for 5 mins to stabilize, then measuring the drain water output for another 5 minutes. Next, I fired the water heater up again and allowed it to come up to normal temperture. And again, I turned on the furnace, let it stabilize for 5 mins, then measured the water output for 5 mins.

connecting the drain hose directly to the water tube where it would normally drop onto the distribution tray at the top of the panel.

incoming flow: 73.0 Oz

mesurement and confirms why Aprilaire says you get higher output with hot water.

I am responding to Frank's comment. I too have been vacillating on whether to switch to hot water because thermodynamically it just does not make sense. In the case above, the energy required to heat the water to 135F from 51F is

Despite the increased humidification efficiency you may achieve by using hot water in your central heating humidifier, there are two considerations that would cause me to think twice before doing that.

1. The concentration of dissolved minerals may be higher in the water coming from a hot water heater for 2 reasons (1) if the water source is relatively high in mineral content, i.e., "hard" water, and (2) the lining of the hot water heater, sediment in the heater, and pipe inner surfaces may leach minerals that dissolve in higher concentration in hot water. In those cases, the evaporation media, solenoid valve and all other humidifier surfaces will clog faster with scale, reducing the evaporative efficiency of the humidifier medium and increasing overall maintenance time and lifetime humidifier cost.
2. From a health standpoint, hot water hold less dissolved chlorine, increasing the risk for the growth of bacteria in household hot water (assuming the output temperature is below about 165 (which it certainly should be!!). If those bacteria include the species that cause Legionnaire's Disease, you run a real risk of serious illness for all inhabitants and visitors at your home.

For me, the disadvantages outweigh the advantages and I wouldn't do it.

Question:

I assume then that the device that feeds the water INTO the humidifier is a fixed orifice so the same amount of water is flowing in no matter what else is happening? i.e. it is not a float valve?

Yes, the Aprilaire I did the experiment on uses an orifice that determines the flow rate.

replying to Peter, Mike K wrote: Good point unless you are using a tankless hot water system (like me :)

If you have a gas water heater set to 130F, the chances of legionaires being a problem is extremely remote. The bacteria can't multiply at that temperature and at slightly higher temps are dead within hours. I've seen quite a few stories in the news of people catching legionaires disease, but it's never been from a residential water heater. NYC had a bunch of cases last few years, all from AC cooling towers on roofs that sent droplets of warm water into the air. I'd be perfectly fine living with 120F, but 130 is better for clean dishes.

I'm sure you'll be hearing from the folks that will tell you that lower than 130F will kill you from Legionnaires. The Legionnaire's risk is not limited to when it's used for a humidifier. I suppose if 130F is so dangerous, they should stop selling water heaters that can be set to not only that, but a lot higher. Put a low limit on it like they did with hot tubs, now people come here complaining they can't get a hot tub/spa hot like they enjoy it. Like I said, I'm happy with 120F myself. Pick your risk. And I never suggested anything about needing to set the water heater to any particular temperature for use to feed a humidifier.

I haven't distorted anything.

I never said

A totally unproven anf false assertion. If anything, hot water at 130F could reduce the chances of Legionnaires, by raising the temperature on the upper parts of the media. This is a total nit. The media is exposed to hot air at an ideal temperature to grow legionnaires whether using hot or cold. The water exiting the humidifier is essentially the same whether using hot water or cold water. The media quickly drains and dries out in the typical modern design, Legionnaire's can't grow on a dry media that quickly cools to room temperature or lower. If you're using some old crap humidifier that has standing water in it, which no one uses because it can grow all kinds of bacteris, that tepid water will be at the ideal temperature to grow legionnaires, regardless of whether it's fed with hot or cold water. But if it were fed with 130F water, it would tend to kill Legionnaires, not promote it.

It is highly unlikely that the temperature

Per the above and the results of my actual experiment, the temperature of the water rapidly declines as it travels from the top of the media, to the bottom. The exit temp is about the same whether using hot water or cold water. It's all a nit, because the water is only there briefly and then the media dries out. There is ZERO evidence this has ever been an issue with Legionnaires disese.

I never said that the bacteria

I have mine at 130F.

Yup, when the environmental pond-huggers took the phosphates out of dishwasher detergent I had to crank the water heater temp up to 145F