Need Help With Whole Home Humidification System Control

[superskaterxes]

so the previously owners of our house had a honeywell TruSteam humidifier installed in the supply duct of our HVAC unit because their kids had asthma but we never really turned it on until recently. Our T-stat has a separate page for humidity control which is just a setpoint adjustment and a humidity readout.

without the humidifier on we were seeing ~15% RH in the house so we turned the system on and it seems to be working ok with a setpoint of 30% but it never seems to go above about 27% RH. The heat will cycle on separately and maintain SP just fine but the blower is basically constantly running while the humidity is trying to reach SP.

Is this normal? i dont see any errors on the unit itself and the reservoir is nice and hot so i know its working. If the blower never stops running its going to run the electricity bill way up and i would really like to get some humidity in the house if i can because everything i touch is followed by static discharge lol.


this is the unit i have

https://yourhome.honeywell.com/en/products/humidifier/truesteam-humidification-system

 

[superskaterxes]

so i tracked down the installer manual and apparently theres a function that lets you turn on humidification only when heat is applied. I think i will try this and see if it retains humidity levels as needed.

 

[peter2772000]

Sorry, only just saw this.

Two things;

Your steam humidifier needs to be feeding steam to the supply-air duct, not the return. And especially with steam, I can only imagine what it's rusting up in the blower compartment. By feeding the return, you also reduce the effective amount of humidity because the now-humid passes thru your heater and evaporates. Very inefficient

On a half-decent t-stat with incorporated humidity control, you should have a few choices about when the humidifier will operate.

A: Any time the blower is operating
B: Only with a demand for heat
C: The humidistat will energize the blower & humidifier to allow for humidification when there's a demand

B is my favorite because air that's just been humidified but not heated will feel like a draft in colder weather. But for maximum efficiency or if your humidifier is sized tight to begin with, C is your best choice

Let us know what you found!

 

[Trey T]

Since you have a humidistat to control the humidifier w/ blower separately from the heater, then the control is normal but there's something wrong w/ your TruSteam. Check the current draw on the system is a way to determine the effectiveness of the steam generator. The inefficiency of that steam humidifier design is well known. Many people either throw it away or sell it on ebay to get a canister-and-probe type steam humidifier.

Honeywell has a new system that utilize canister-and-probe to generate steam, but I don't recommend it and I definitely do not recommend the pass-thru humidifier (non-steam type) either. IMO, steam is the way to go and I like the Aprilaire 800, which I own, along w/ a Nest (3rd gen) to control it.

 

[justinjoyal]

Sorry, only just saw this.



Two things;



Your steam humidifier needs to be feeding steam to the supply-air duct, not the return. And especially with steam, I can only imagine what it's rusting up in the blower compartment. By feeding the return, you also reduce the effective amount of humidity because the now-humid passes thru your heater and evaporates. Very inefficient



On a half-decent t-stat with incorporated humidity control, you should have a few choices about when the humidifier will operate.



A: Any time the blower is operating

B: Only with a demand for heat

C: The humidistat will energize the blower & humidifier to allow for humidification when there's a demand



B is my favorite because air that's just been humidified but not heated will feel like a draft in colder weather. But for maximum efficiency or if your humidifier is sized tight to begin with, C is your best choice



Let us know what you found!

Exactly what he said ^^^

Steam humidifiers are known to be unreliable and costly to operate (and purchase!)

 

[walta]

When I read the Honeywell TruSteam humidifier manual I thought it required annual maintenance that amounted to replacement of the steam generator about $100 part.

Walta

 

[peter2772000]

I have a Carel steam humidifier with a disposable cylinder. I run on city water and my cylinders usually last about two winters. $150 + tx at my cost, I'm an HVAC contractor

 

[Trey T]

Exactly what he said ^^^

Steam humidifiers are known to be unreliable and costly to operate (and purchase!)

reliability is questionable but I agree ... they can be costly to operate. Depending on the home build and demand, it can add $50-100 to your electric bill every month during winter. Water is cheap everywhere in the US, so that's not a problem.

I can walk around in the house my underwear during winter, not that I do but I can. You can't say that with every home because as you increase the room temperature with heat to something like 76degF w/o RH >30%, it's unbearable.

Before I had the humidifier, we couldn't crank it above 72degF because the RH would drop and the air coming out of the registers would be too dry.

 

[larry4406]

As a builder, the steam humidifiers have been a real PIA over this past 1.5 years as we have transitioned to them. In all honestly, the issues I have had to deal with are all installation related. I guess the technology is/was too new to the service techs that installed them.

Just today had a service issue. HVAC tech determines the sail switch was wired wrong. Unit sees demand from humidistat, yet no fan operation, so unit dumps steam into the ducts. No air flow, steam condenses in duct, duct leaks, drywall damage, carpet wet, and carpet pad soaked. Then when there is air-flow, the humidifier is locked out.

Wrong set of contacts (NO/NC, etc) used on the sail switch.....

 

[tdkkart]

Am I the only one that wonders about spraying water mist or steam inside ductwork that is most likely filled with a quarter inch of dust throughout the house.

Does anyone else see the huge possibility for mold growth?

 

[larry4406]

Am I the only one that wonders about spraying water mist or steam inside ductwork that is most likely filled with a quarter inch of dust throughout the house.

Does anyone else see the huge possibility for mold growth?

+1!!

 

[Trey T]

It's all in the control. I don't know any steamer unit that have humidity sensor/switch, you have to add it to ensure that the humidifier isn't on if no fan on.

If it's operated correctly, there shouldn't be any liquid in the air stream to cause mold build up. Indoor RH should be <60% to prevent mold growth.

 

[u3b3rg33k]

Sorry, only just saw this.

Two things;

Your steam humidifier needs to be feeding steam to the supply-air duct, not the return. And especially with steam, I can only imagine what it's rusting up in the blower compartment. By feeding the return, you also reduce the effective amount of humidity because the now-humid passes thru your heater and evaporates. Very inefficient

On a half-decent t-stat with incorporated humidity control, you should have a few choices about when the humidifier will operate.

A: Any time the blower is operating
B: Only with a demand for heat
C: The humidistat will energize the blower & humidifier to allow for humidification when there's a demand

B is my favorite because air that's just been humidified but not heated will feel like a draft in colder weather. But for maximum efficiency or if your humidifier is sized tight to begin with, C is your best choice

Let us know what you found!

This is completely false. heating humidified air IN THE HVAC SYSTEM does not reduce effective humidifier output or RH% in the home. The water from a steam unit should be completely evaporated within a few feet of the nozzle bar.

If there is sufficient straight duct length after the humidifier nozzle bar, the steam will evaporate entirely and there won't be condensation on equipment. 12GPD is a very small unit.

Given that it's a steam unit, there's no penalty to moving the output to the hot side of the system. you should do this. having it in unfiltered air means there IS dust buildup on it. clean HVAC gear is happy HVAC gear.

you should check for the service light / make sure the canister isn't full of sediment. that will reduce it's performance.

if 12GPD is not enough for you to meet your target humidity, then your home is over-ventilated, either by excessive exhaust fan/air exchanger use, having ducts leaking outside the envelope (puling in cold air from outside or pushing hot air out), or by having a leaky home. try looking around for doors or windows that have cold breezes around them.

I've been installing Field Controls S2000 model units in houses behind RO systems. so far I've had zero complaints of low humidity (and no issues with RO water despite claims that it will cause sensor issues), and due to the use of RO water, examining them with a scope camera shows no need to clean them after 2+ years of operation.
in a 3600 sqft house, it took the 16GPD system about a day of continuous operation to bring the house up from 15% to 40% RH. that 16GPD system doesn't have any trouble holding the humidity at the setpoint.

My house came with a bypass system rated for 17GPD - but since my heat never runs 24/7 that number isn't possible to reach. sealing up air leaks has made a huge difference in my comfort, and I've not completed my list of doors/windows to fix.

 

[superskaterxes]

Sorry, only just saw this.

Two things;

Your steam humidifier needs to be feeding steam to the supply-air duct, not the return. And especially with steam, I can only imagine what it's rusting up in the blower compartment. By feeding the return, you also reduce the effective amount of humidity because the now-humid passes thru your heater and evaporates. Very inefficient

On a half-decent t-stat with incorporated humidity control, you should have a few choices about when the humidifier will operate.

A: Any time the blower is operating
B: Only with a demand for heat
C: The humidistat will energize the blower & humidifier to allow for humidification when there's a demand

B is my favorite because air that's just been humidified but not heated will feel like a draft in colder weather. But for maximum efficiency or if your humidifier is sized tight to begin with, C is your best choice

Let us know what you found!

So after doing some reading online i found the installer manual which has all the access codes i ACTUALLY needed to adjust this thing. I did find the option B above which seems to be working well. I also edited the OP as i really meant to say it was installed in the supply duct (derp).

This is completely false. heating humidified air IN THE HVAC SYSTEM does not reduce effective humidifier output or RH% in the home. The water from a steam unit should be completely evaporated within a few feet of the nozzle bar.

If there is sufficient straight duct length after the humidifier nozzle bar, the steam will evaporate entirely and there won't be condensation on equipment. 12GPD is a very small unit.

Given that it's a steam unit, there's no penalty to moving the output to the hot side of the system. you should do this. having it in unfiltered air means there IS dust buildup on it. clean HVAC gear is happy HVAC gear.

you should check for the service light / make sure the canister isn't full of sediment. that will reduce it's performance.

if 12GPD is not enough for you to meet your target humidity, then your home is over-ventilated, either by excessive exhaust fan/air exchanger use, having ducts leaking outside the envelope (puling in cold air from outside or pushing hot air out), or by having a leaky home. try looking around for doors or windows that have cold breezes around them.

I've been installing Field Controls S2000 model units in houses behind RO systems. so far I've had zero complaints of low humidity (and no issues with RO water despite claims that it will cause sensor issues), and due to the use of RO water, examining them with a scope camera shows no need to clean them after 2+ years of operation.
in a 3600 sqft house, it took the 16GPD system about a day of continuous operation to bring the house up from 15% to 40% RH. that 16GPD system doesn't have any trouble holding the humidity at the setpoint.

My house came with a bypass system rated for 17GPD - but since my heat never runs 24/7 that number isn't possible to reach. sealing up air leaks has made a huge difference in my comfort, and I've not completed my list of doors/windows to fix.

I definitely need to check my envelope for leaks. My house is relatively new (1987) and the previous owner installed all new windows and doors which should help my case but i have noticed alot of rooms that do not get adequate heat and i really need to seal some windows that never get opened.

thanks for all your help guys!!!

 

[peter2772000]

This is completely false. heating humidified air IN THE HVAC SYSTEM does not reduce effective humidifier output or RH% in the home. The water from a steam unit should be completely evaporated within a few feet of the nozzle bar.

If there is sufficient straight duct length after the humidifier nozzle bar, the steam will evaporate entirely and there won't be condensation on equipment. 12GPD is a very small unit.

I stand corrected. The only people who don't learn something new every day are dead ones

From the ACHR site:

As for humidity being lost when it passes through the furnace, this is simply an urban legend. The heating system is warm, and the only way the moisture can be subtracted out is by condensing on a cold surface. Since the surfaces are all warm, the air is going to be able to absorb even more moisture than it’s currently carrying, so it’s not going to condense on anything. It’s going to be carried on into the home and dispersed throughout.

 

[Trey T]

Peter: It's not an urban legend and the context is spoken in relative or non-precise manner. To be precise, we don't want to say that the moisture content drop as the air passes thru the furnace, we want to say that the RH% drops as temperature increase; those two are different things. In a minor case, the moisture drop could be due to combustion of the intake air (from the house) and fuel; some of that moist intake air will turn into vapor and vented off.

If anyone wants to learn more, do some google on sensible heat and latent heat. Also why machines can't "sense" latent heat but human can "feel" the latent heat.

 

[finn]

If you dump a fixed amount of water into the heating system, it doesn’t matter if it’s before or after the heat exchanger.

It all evaporates and comes out through the heating ducts.

 

[Trey T]

Sh*t, I don't even know where to start, finn.

 

[u3b3rg33k]

If you dump a fixed amount of water into the heating system, it doesn’t matter if it’s before or after the heat exchanger.

It all evaporates and comes out through the heating ducts.

hahaha

Sh*t, I don't even know where to start, finn.

not quite true finn. this is true for a steam system that doesn't leak. for a bypass or fan system, it's not at all true. media based systems evaporate a small fraction of the water input and waste the rest. I tried running my bypass on fan-only, and with a temp/humidity gauge on the supply vents, there was zero increase in humidity.

doing the same with the heat on yielded lower RH from the vents, but when corrected with psychrometric tables, there was actually measurably more moisture in the supply air than the house air.
save the fan power and water - only operate your bypass/fan humidifiers when the heat is on.

as for "dumping" in water - i wouldn't do that. your furnace might cry.


for steam systems, the benefits to putting your humidifier on the hot side are twofold:
1: it stays clean. clean is good. we like clean.
2: you increase the water output per kWh of energy (aka $) input into the humidifier. the nozzle bar being cold increases condensation inside the system, which means you don't get as much delivered humidity for your dollar.

having it on the hot side also means if it drips a little bit, that moisture will be carried away much faster by hot dry air than it will be by cool dry air.

similar benefits from the open pan style that I like better - less heat loss to the system that's unproductive.


Personally, I'd never install a steam system without an RO filter ahead of it. if you're a builder, you can include one for drinking water, and tap off it for the humidifier. some steam systems come with them, and you can get low conductivity canisters if you find it necessary. float systems should like RO (no minerals to gunk it up), and elements don't burn out when caked with nothing.

 

[u3b3rg33k]

Peter: It's not an urban legend and the context is spoken in relative or non-precise manner. To be precise, we don't want to say that the moisture content drop as the air passes thru the furnace, we want to say that the RH% drops as temperature increase; those two are different things. In a minor case, the moisture drop could be due to combustion of the intake air (from the house) and fuel; some of that moist intake air will turn into vapor and vented off.

If anyone wants to learn more, do some google on sensible heat and latent heat. Also why machines can't "sense" latent heat but human can "feel" the latent heat.

I take issue with the common claims that XYZ hot air /oil fired /etc style heat "pulls the moisture out of the air while ABC type of heat doesn't."

heat pumps/forced air have no effect on the RH% other than lowering it slightly by bringing the temp up to the desired temp. doesn't matter how you do it (excluding unvented heaters. that's bad, mmmkay?). yes, exhausting indoor air for combustion use will pull in cold dry outside air. so will running your dryer. or your bath fan.