Figuring out a "point of use" water heater for my Aprilaire 360 humidifier

[Melissa2007B]

We're in Denver and have had the Aprilaire 360 in the wall of the laundry room, humidifying the whole house, since 2005. It's even running now, as we have asthma and use it all year, due to the dryness here.

It's a great unit, but it causes "stacking" in the gas water heater and we've already had to replace one. It manifests as very hot black water coming out, so that's apparently the water heater tank eroding from too much burn time. ( it doesn't happen when the humidifier isn't in use )

So I's like to add a "point of use" water heater and move the humidifier water line from the hot side to the cold side. That would eliminate the problem.

So I just asked Aprilaire about how much water this humidifier uses per hour, and they replied:

Hello Melissa,
The 360 uses about a tenth of a gallon of water a minute (rated at 6 gallons per hour).
This means the flow rate of the humidifier is usually not enough to trigger on demand water heaters to heat the water. ...
Thank you,
Eric

So if I move the line from hot to cold, and install one of these, and set the temp to the 140 degrees suggested by Aprilaire, what type would I need, what capacity, and what amperage? I'm looking online, searching on: point of use water heater 120vac

Do these small units use phased heating instead of on/off? I'm asking because it may have to be plugged into the washer/dryer 120VAC circuit and if one of those is on, we don't want it tripping a breaker if it draws 1400 watts.

It SOUNDS like, if t uses phased heating, it might never need that much.

I need to plan this and buy the minimum unit necessary - not just from a cost perspective.

Thoughts?

 

[Jadnashua]

I've not had any issues feeding my humidifier from the cold water line for decades (it's also an AprilAire). Any 'instant' hot water source is going to use a lot of power. A small electric tank will, too.

Adding a hot water recirculation system to your tank would probably overcome the stratification issue and provide the convenience of having hot water throughout the house instead of needing to run the tap for awhile for it to arrive.

 

[Sponsor]

 

[Melissa2007B]

I've not had any issues feeding my humidifier from the cold water line for decades (it's also an AprilAire). Any 'instant' hot water source is going to use a lot of power. A small electric tank will, too.

Adding a hot water recirculation system to your tank would probably overcome the stratification issue and provide the convenience of having hot water throughout the house instead of needing to run the tap for awhile for it to arrive.

Thanks jadnashua. Interesting. I tried it on a cold line, per suggestion from someone here, a few years ago, and it used a LOT more water, as cold doesn't evaporate as well as hot does? Adding a recirculation system sounds expensive as heck. Isn't that where you make a loop to the other end of the house ( at least 80 ft in this modular house of ours ) and then it loses lots of heat on the way? And I'm doubtful that there's even a loop existing under there, as this is a modular house and has plastic sheet covering the bottom, even though it was put on a foundation, so there's no way to tell.

Or maybe some way of doing it internally to just the water heater tank, but that sounds expensive and risky?

 

[Bannerman]

And I'm doubtful that there's even a loop existing under there

When a home is not equipped with a dedicated hot water recirculation return line, a thermostatic valve may be installed in the furthest washroom which will use the cold water piping as a recirculation return line back to the water heater.

The thermostatic part of the valve will stop allowing hot water to pass when the arriving water temperature is about 100 degrees. When a hot water faucet is opened anywhere along the recirculation path, hot water will arrive more quickly as opposed to wasting a larger volume of water to clear cold water from the hot line.

There are various brands of recirculation valves offered including Navien, Watts, Grundfos, Taco etc. Here is a link showing Navien NaviCirc.
https://www.navieninc.com/accessories/navicirc

A recirculation pump will be also needed but some pump models may be installed within a vanity below a remote sink and will function as both a pump and a recirculation valve. Some pump models are also equipped with a timer so you may program the pump to run only when hot water is usually needed. https://homeinspectorsecrets.com/hot-water-recirculating-pumps/best-under-sink-recirculating-pump/

 

[Melissa2007B]

I've heard that's a huge waste of heat under the house - especially with central AC?

 

[Reach4]

I need to plan this and buy the minimum unit necessary - not just from a cost perspective.

https://www.supplyhouse.com/Bradfor...-Saver-Electric-Residential-Water-Heater-120V is the smallest I found.

https://www.supplyhouse.com/AO-Smit...sidential-Electric-Water-Heater-6-Yr-Warranty is a little bigger and cheaper.

https://www.homedepot.com/p/Rheem-P...t-Of-Use-Water-Heater-XE06P06PU20U0/204318372 is bigger.

 

[Melissa2007B]

https://smile.amazon.com/Bosch-Elec...ords=point+water+heater&qid=1597901782&sr=8-2

 

[Jadnashua]

The water lines by today's codes would all be insulated. If yours are, or you can insulate them, the energy losses aren't huge. Heat loss depends on the difference in temperature of the pipe versus the surrounding area. If, say, your WH is set to 120-degrees, most of the recirculation systems at the sensing location turn off when the water there gets to somewhere in the area of 95-105 degrees (depends on the brand and model), so not all that much difference, so the drive of the energy loss is low, especially if the pipes are insulated. In the winter, it (very slightly) augments the heating of the space.

The convenience of having hot water without having to run the tap for maybe a minute or two, and solving your water stratification issue seems worth it to me. The pumps used in these things are quite small, often not much more than a nightlight. The one on mine only draws around 9W when running.

Air leak sealing of the building might resolve the need for constant humidification, and save lots of money in the long term. Many utilities will do some of that work for free, depending on your income level and situation. The utility did about $4500 worth of work on my mother's house, and it didn't cost her anything. All she had to do was apply for it (well, I did it for her, but that's irrelevant!).

Any point of use water heater will need its own circuit. Depending on the location and how your home is arranged, that may not be a big deal, but it could be expensive.

Many retrofit recirculation systems are simple to install and may not require any special skills or tools. If you can run a dedicated return line, that can be better, but the disadvantages of not doing that, IMHO, aren't huge...the cold line becomes a little warmer. With a dedicated return line, that doesn't happen. I've found that the way mine is hooked up, flushing the toilet will clear any (slightly) warm water out of that line, which often happens prior to wanting to wash my hands or brush my teeth.

 

[wwhitney]

The 360 uses about a tenth of a gallon of water a minute (rated at 6 gallons per hour).
[. . .]
Do these small units use phased heating instead of on/off? I'm asking because it may have to be plugged into the washer/dryer 120VAC circuit and if one of those is on, we don't want it tripping a breaker if it draws 1400 watts.

Say your incoming water is 50F and you want to heat it to 140F, 6 gallons per hour. That's 50 pounds of water raised 90 degrees F, or by definition 4500 BTUs/hr. 1 Watt is 3.4 BTUs/hr, so you'd need about 1300W. You'd be adding 30 kWhrs/day to your electric usage. You'd definitely need to run a dedicated circuit for this, or possibly install some switching so that when you use the washer/dryer the humidifier is turned off.

I agree that figuring out a way to accommodate the hot water draw from your gas water heater without causing the stacking is likely a better solution. I see that the Aprilaire 360, as a standalone unit, is designed to work with hot water, not cold water. I'm wondering exactly what effect is causing the problem from the 6 gallons/hr constant draw, and whether changing how the hot water line to the humidifier is connected at the water heater would help.

Cheers, Wayne

 

[Melissa2007B]

Thanks jadnashua! I'm going to schedule someone to evaluate this. The loop sounds great, but this is a modular house that was built in 2004 and has pex lines, so I don't know if they're even insulated. Plus the stupid plastic sheeting that was left under there, by the crook builder. ( long story ) My only concern is heat rising up from under there, in air conditioning season. But will get it considered by someone. Thanks!

 

[Melissa2007B]

Say your incoming water is 50F and you want to heat it to 140F, 6 gallons per hour. That's 50 pounds of water raised 90 degrees F, or by definition 4500 BTUs/hr. 1 Watt is 3.4 BTUs/hr, so you'd need about 1300W. You'd be adding 30 kWhrs/day to your electric usage. You'd definitely need to run a dedicated circuit for this, or possibly install some switching so that when you use the washer/dryer the humidifier is turned off.

I agree that figuring out a way to accommodate the hot water draw from your gas water heater without causing the stacking is likely a better solution. I see that the Aprilaire 360, as a standalone unit, is designed to work with hot water, not cold water. I'm wondering exactly what effect is causing the problem from the 6 gallons/hr constant draw, and whether changing how the hot water line to the humidifier is connected at the water heater would help.

Cheers, Wayne

It's been very clearly illustrated over the years. The humidifier runs for about a half hour, then the water comes out of the tap at WAY hotter temp than the 117 degrees I set the water heater at. And then later, we see black water coming out, when starting to run hot water for a shower. If I turn the humidifier way back, like now, it stops the whole process, but then it gets too dry in here. We both have asthma, AND there are two things that are the greatest enemies of all electronic devices; heat and static. We keep the house below 72 all year around, and a little moisture ( enough so there's no static ) and the TV's and computers last forever.

 

[Reach4]

It's a great unit, but it causes "stacking" in the gas water heater and we've already had to replace one. It manifests as very hot black water coming out, so that's apparently the water heater tank eroding from too much burn time. ( it doesn't happen when the humidifier isn't in use )

I suspect that the black is caused by SRB reducing sulfate to a sulfide, with the magnesium or zinc-aluminum or water heater iron anode providing the metal for the sulfide. Additionally, if this were well water (don't think so), rather than city water, the iron could be coming in with the water. This would be accompanied by hydrogen sulfide (H2S) generation.

Do you get a "sulfur" (H2S) smell with your hot water, especially after being away for a while?

Now why would running the humidifier increase this effect? I guess it would allow a slow flow.

You did not cite the commonly described symptoms of stacking.

If it is SRB/SRM reacting with sulfate, there are ways to prevent that reaction from happening. Pure AlS, MnS, ZnS are white, but in impure form they can be brown to black. I also wonder if there could be a reaction that causes some other product involving sulfur to be produced that is black.

https://en.wikipedia.org/wiki/Sulfate-reducing_microorganisms

 

[wwhitney]

What's the water heater make and model number? I don't know much about the spatial water flow through gas water heaters, and where the thermostat is located, perhaps someone more knowledgeable can explain what's going on.

With the water being too hot after the humidifier runs, it almost sounds like the constant low flow is bringing incoming cold water to flow across the thermostat, causing the burner to be constantly on, but that the water heater recovery rate is higher than the hot water draw of the humidifier, so it ends up raising the water temperature. In which case the behavior could be changed if there is an alternate place to draw the hot water from for the humidifier only, that won't immediately trigger the burner firing. [I think for normal hot water draws, usage rate exceeds the recovery rate, so immediate burner firing would be a good thing and part of the design.]

Cheers, Wayne

 

[Melissa2007B]

I suspect that the black is caused by SRB reducing sulfate to a sulfide, with the magnesium or zinc-aluminum or water heater iron anode providing the metal for the sulfide. Additionally, if this were well water (don't think so), rather than city water, the iron could be coming in with the water. This would be accompanied by hydrogen sulfide (H2S) generation.

Do you get a "sulfur" (H2S) smell with your hot water, especially after being away for a while?

Now why would running the humidifier increase this effect? I guess it would allow a slow flow.

You did not cite the commonly described symptoms of stacking.

If it is SRB/SRM reacting with sulfate, there are ways to prevent that reaction from happening. Pure AlS, MnS, ZnS are white, but in impure form they can be brown to black. I also wonder if there could be a reaction that causes some other product involving sulfur to be produced that is black.

https://en.wikipedia.org/wiki/Sulfate-reducing_microorganisms

No, our water comes from mountain rain and snow runoff and has VERY low mineral content. It happens because the trickle of hot water from the top of the water heater brings cold water into the bottom and triggers the burner, but very little hot is getting used. I asked about it here, years ago, and was told it's called "stacking" effect?

Wayne: Exactly. This is why we need some pumped circulation, either inside the water heater, or in that loop idea. I'll check into it. Thanks guys!

 

[Reach4]

No,

Is that No sulfate, and therefore no H2S smell? Denver water has sulfate. Not a lot, but how much does it take?
https://www.denverwater.org/sites/default/files/2017-05/water-quality-report-2017_0.pdf

Can anybody explain stacking causing black water? If the tank is eroding, that would put iron into the water, right? Iron sulfide is kinda black looking.

 

[wwhitney]

Perhaps a crazy idea, but if I understand the geometry correctly (hot and cold attachments at top, cold has a dip tube down to the bottom, thermostat is on the bottom), then you could modify the dip tube by drilling an appropriate sized hole near the top or middle of the tube. The idea would be that low rate hot water draws would primarily get makeup water through the new hole, but at higher draw rates, the new hole wouldn't be enough and you'd get flow out the bottom of the dip tube to trigger the burner.

I have no idea how to calculate the proper hole size, or if it would really work. It might also just cause the water heater to be permanently thermally stratified between higher rate hot water draws, perhaps to detriment of the humidifier's function. Is there any strategy for intentionally destratifying a water heater?

What you'd really like is a method to convert the constant 0.1 gpm draw of the humidifier into a periodic draw, say a 2 gpm draw for 3 minutes every hour. I can't think of any passive solution for that.

Cheers, Wayne

 

[Jadnashua]

A blower door test and subsequent air leak sealing may resolve a lot of your need for the humidifier altogether. It should also make the place more comfortable and save energy to both heat and cool. It will also likely help to cut down on dust infiltration.

For first use in the day, how long does it take to get hot water at the furthest point? Consider that the water coming out of the WH you paid to heat, is just going down the drain, plus, it's being wasted. So, recirculating hot water would mean much less wasted water (that still costs money) along with energy to heat it. A showerhead's max flow is 2.5gpm. Say 2g of that is hot and it takes 90-seconds to get hot before you get in there. That's 3 g of hot you paid to heat that is not doing anything, means you've just added 3-gallons of cold to your WH, making it now hold less hot water, and thus shortening the time you'll have hot water. So, the energy to recirculate the water isn't a total loss, plus, you'll have the convenience of warm/hot water in seconds rather than minutes whenever you wish. It should also solve your water stacking issue as it will create some flow through the WH, and result in some mixing.

 

[Fitter30]

A 3-5 gallon electric water 120volt at the humidier would give you all the hot water u need.

 

[Melissa2007B]

Is that No sulfate, and therefore no H2S smell? Denver water has sulfate. Not a lot, but how much does it take?
https://www.denverwater.org/sites/default/files/2017-05/water-quality-report-2017_0.pdf

Can anybody explain stacking causing black water? If the tank is eroding, that would put iron into the water, right? Iron sulfide is kinda black looking.

I cant tell. From years of allergies, my sense of smell is partially kaput. I can barely smell my own sh@t.

 

[Melissa2007B]

Perhaps a crazy idea, but if I understand the geometry correctly (hot and cold attachments at top, cold has a dip tube down to the bottom, thermostat is on the bottom), then you could modify the dip tube by drilling an appropriate sized hole near the top or middle of the tube. The idea would be that low rate hot water draws would primarily get makeup water through the new hole, but at higher draw rates, the new hole wouldn't be enough and you'd get flow out the bottom of the dip tube to trigger the burner.

I have no idea how to calculate the proper hole size, or if it would really work. It might also just cause the water heater to be permanently thermally stratified between higher rate hot water draws, perhaps to detriment of the humidifier's function. Is there any strategy for intentionally destratifying a water heater?

What you'd really like is a method to convert the constant 0.1 gpm draw of the humidifier into a periodic draw, say a 2 gpm draw for 3 minutes every hour. I can't think of any passive solution for that.

Cheers, Wayne

No actually, the cold comes in the bottom, and the hot goes outa the top. But thanks.