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Old 01-02-2009, 01:06 PM   #1
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Integrated Thermostat/Humidistat


I've got a York Diamond 80 nat.gas furnace controlled by a Honeywell 97-4730 thermostat and a York 1042 duct humidifier controlled by a GeneralAire "HUMIDISTAT". The humidifier's water line is already hooked up to hot water.

The house is a constant 35% humidity which is too low. Everyone feels very dried out in the morning and the hardwood floors have large gaps. My daugter has a bad cough unless we run a small humidifer in her room.

The problem is that based on GeneralAire's humidifier capacity planning formula I need 16GPD for 68F/50%. This means my blower needs to run about 83% of the time. I estimate that the blower currently only runs about 33% of the time. So this means that I'm only getting about 6.3 GPD (19.2GPD x .33%)

It seems to me that all I need is a proper thermostat/humidistat that can run the blower and solenoid for the humidifer independently of the furnace. I estimate that the blower would run 83% of the time with the furnace running 30% of that time and the humidifer running by itself (without the furnace) 50% of that time.

First of all, am I right about all this?

Second, can I get some recommendations about good integrated thermostat/humidistats?

Thanks,

Paul

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Old 01-03-2009, 01:17 AM   #2
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Integrated Thermostat/Humidistat


need hot air to evaporate the water. Can't do that running fan only.

With a steam humidifier it is possible however.

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Old 01-03-2009, 03:24 AM   #3
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Integrated Thermostat/Humidistat


You shouldnt have to run the blower that much nor should you need a 16 gpd humidifier to meet your demands. Thats seems like alot. Sounds like you need a better humidifier. Also honeywell makes a nice thermostat/ humistat that will control both. It also depends on how you wire it weather it will turn on the blower. You can wire you current humidifer to run the blower while your humidifier is on.
Have both come on at the same time is all on how you wire them, but yes your thermostat now might not be able to control both.
Can you give some more specs on your house. Size, insulation, indoor and outdoor climate temps and humidity. Blower CFM.

I would recommend a TrueSteam by honeywell. Thye have up to 12GPH which shows it will well cover a 3000 sq foot house. Heres some info on it.
http://customer.honeywell.com/Honeyw...CFB4218DD64%7d

And I would recommend a Honeywell YTH9421 thermostat. This part number comes with the modual, but you will still need an outdoor sensor inorder for the humidifer to work. Its a very nice setup. It will display outdoor indoor and humidity levels, all touch screen. It will rasie humidity levels inside, but it will monitor outdoor temp to make sure the humidity level inside the house isnt to high where the windows it fog up. This also might be a problem with your idea of high humidity levels in your house. In the cold of winter if your inside temp is high and humidity level is high you will fog up your windows inside and have condisation all over. This thermostate will keep the humidity level up as much as possible with out foging the windows. I'm not sure if youll be able to reach the humidity level you want tho.
I would check that before you spend all this money on new equipment and find out you cant do it no matter what equipment you have.

Heres the link to the thermostate. Ignore the list prices you can find them for almost half online searching google.
http://customer.honeywell.com/honeyw...x/YTH9421C1002
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Old 01-03-2009, 03:33 AM   #4
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Integrated Thermostat/Humidistat


Heres some good links to what Im talking about. The 2nd one has this chart in the link. I live in sunny California so I'm 70-80 degrees all year I'm not sure how cold it is outside your house at night but heres the chart. Unless your outside temp is over 50-55 degree's at night, I dont think youll be able to get to your inside temp to 68f and 50% humidity without waking up to dripping water and wet floors.

The Chart is Based on a 70F interior room temperature.
Outside Temperature Inside Humidity
20 to 40F Not over 40%
10 to 20F Not over 35%
0 to 10F Not over 30%
-10 to 0F Not over 25%
-20 to –10F Not over 20%
-20F or below Not over 15%

http://www.askthebuilder.com/B103_Ho..._Balance.shtml

http://www.home-smart.org/how_your_h...ef=795:HYHW_LN

Last edited by integlikewhoa; 01-03-2009 at 03:46 AM.
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Old 01-03-2009, 10:49 AM   #5
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Integrated Thermostat/Humidistat


Quote:
Originally Posted by integlikewhoa View Post
You shouldnt have to run the blower that much nor should you need a 16 gpd humidifier to meet your demands. Thats seems like alot. Sounds like you need a better humidifier. Also honeywell makes a nice thermostat/ humistat that will control both. It also depends on how you wire it weather it will turn on the blower. You can wire you current humidifer to run the blower while your humidifier is on.
Have both come on at the same time is all on how you wire them, but yes your thermostat now might not be able to control both.
Can you give some more specs on your house. Size, insulation, indoor and outdoor climate temps and humidity. Blower CFM.

I would recommend a TrueSteam by honeywell. Thye have up to 12GPH which shows it will well cover a 3000 sq foot house. Heres some info on it.
http://customer.honeywell.com/Honeyw...CFB4218DD64%7d

And I would recommend a Honeywell YTH9421 thermostat. This part number comes with the modual, but you will still need an outdoor sensor inorder for the humidifer to work. Its a very nice setup. It will display outdoor indoor and humidity levels, all touch screen. It will rasie humidity levels inside, but it will monitor outdoor temp to make sure the humidity level inside the house isnt to high where the windows it fog up. This also might be a problem with your idea of high humidity levels in your house. In the cold of winter if your inside temp is high and humidity level is high you will fog up your windows inside and have condisation all over. This thermostate will keep the humidity level up as much as possible with out foging the windows. I'm not sure if youll be able to reach the humidity level you want tho.
I would check that before you spend all this money on new equipment and find out you cant do it no matter what equipment you have.

Heres the link to the thermostate. Ignore the list prices you can find them for almost half online searching google.
http://customer.honeywell.com/honeyw...x/YTH9421C1002
Damn skippy. You have to run that furnace more than what 68* will give you . A lot of mfgs spec are a little optimistic for the way most folks run their heating..
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Old 01-03-2009, 01:08 PM   #6
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Integrated Thermostat/Humidistat


Don't bet on the Truesteam 12GPD being able to humidify a 3000 sq ft house.
Unless its real real tight.

Might want to get another hydrotherm or 2.

35%RH shouldn't be too low, unless your outdoor temps are above 40F.

What RH are you trying to reach.

The YTH9421, is the stat that will do what you want.
You may need to increase your water temp to 140F to get to 40%RH with that Generalaire.

You'll need a mixing valve to temper the water that goes to teh faucets though.

If 140F water won't get you to 40%RH.
Then you might want to consider a EWC Autoflow S2000, or S2020.
The 2000 is a 16 gallon a day.
And the 2020, is a 22 gallon a day humidifier.
The 200, is 120 volt, the 2020 is 240 volt.


PS: Reduce use/on time of bathroom exhaust fans, and range fan, if its ducted outside.

If your furnace has a fresh air intake, reduce its volume.
If you have an open combustion air intake, see if its allowing fresh air into the rest of the house.
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Old 01-03-2009, 06:07 PM   #7
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Quote:
Originally Posted by beenthere View Post
Don't bet on the Truesteam 12GPD being able to humidify a 3000 sq ft house.Unless its real real tight.
That might be true, but Im not thinking his house is 3000 sq ft. Im also thinking his outside temp is Probley very low. With some more info from him we should see where he is standing.
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Old 01-03-2009, 10:56 PM   #8
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Integrated Thermostat/Humidistat


I bought a Venstar T1900 this past summer to allow me to do the similar thing you want to do.

http://www.venstarthermostats.com/Re...duct_info.html
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Old 01-05-2009, 11:28 AM   #9
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Integrated Thermostat/Humidistat


Thanks to all for the time, thought and consideration of my questions. Here is some follow up info as requested.

The house is 4 years old, average "tightness" and 2600sf and I live in Zone 5a. During the three coldest months the average lows are between 19 and 24 F.

I don't believe I need a bigger humidifier as mine is rated at 19.2 GPD. The problem is that with an average 30% duty, I'm only getting 6.3GPD from it.

The 16 GDP figure comes from GeneralAire's own capacity calculator for my SF + average insulation and 68F/50% RH.

I don't believe 50% is too high or that it will cause any serious condensation problems as I've been running 50%RH in our master bedroom with the help of a small cool mist portable humidifier and the only condensation I've seen is minimal.

I don't believe that hot air is required to evaporate water from the duct humidifier for several reasons. First, the cool mist portable unit I have evaporates water fine with 66F temp air., second, the water for the duct humidifier is already heated, third, the higher air volume from by furnace's blower should compensate for the lower temperature air. No doubt the evaporation rate will be higher with heated air, but it's not zero with 66F temp. air.

Along these lines, running the humidifier without the furnace should have a mild cooling effect from evaporative cooling. This in turn will necessitate a little more nat. gas to compensate. But I don't see any other alternative except running the furnace at a higher temp to increase the run time, but that will just dry out the air more, not less.

The only other alternative to consider is installing a new humidifer with 48GPD (16GDP x 3) capacity so that a 30% duty will produce the required 16GPD. But a 48GDP unit seems too large and expensive. I still believe this is just a control problem.

I found at least one control from Carrier called the "Thermidistat" which seems to meet my requirements.

I'll try calling GeneralAire and see what they say about the whole capcity planning issue.
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Old 01-05-2009, 12:32 PM   #10
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The Thermidistat, and the Honeywell IAQ both will control the humidifier and blower the way you want.

However. Trying to use 66F air, to humidify your house, greatly lowers the capacity of the humidifier.

Its GPD is figured out with a 120F air temp.

If your furnace only has a duty cycle of 30% when its 20 degrees outside. And your outdoor design temp is 0F.
Your furnace is oversized a lot.

Take a hydrotherm, and place it in a corner of the room that is on the outside wall in your bedroom. See what %RH it says it is.
Quite often it 10 and even 15% higher then the rooms RH on an inside wall.
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Old 01-05-2009, 12:34 PM   #11
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After talking with two HVAC contractors and GeneralAire's technical support it's become pretty clear that I don't think this solution will work. The reason being that my HVAC does not have an HRV, instead it has a 10% fresh air intake. So running the fan 85% of the time will draw in more cold dry outside air which will only make the problem worse.

Other concerns expressed were that running the humidifer without the burner on could shorten the life of the heat exchanger in the furnace from extra moisture. I don't know if I agree with this concern, but it at least sounds plausible.

GeneralAire stated that the 1042 is too small for my house and recommended installing a second 1042 or higher capacity unit.

I believe a better solution might be to simply get a large capcity console humidifer, preferrably one with a water line hook up.

Installing a HRV would be another possible solution, but those run about $1800.
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Old 01-05-2009, 12:46 PM   #12
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Actually, an ERV would be better.

An HRV would also pull the humidity out of your house.
An EFV would only remove 50%.

If you have a 6" fresh air intake. And it has a manual damper, throttle it back to only 50% open. If a motorized damper, most of them can be set to only open 50%.
That should still get you enough fresh air.

With the damper full open, on a 6", you could de drawing in anywhere from 100, to 160 CFM depending on how long the pipe run is.

Also, no harm will come to your heat exchanger. As long as its temp is above dew point.
Which is 48.6F when your indoor temp is 68F and 50%RH.
With the blower running, the HX won't drop to the dew point.

The humidity would have to reach 90%RH at 68F, before you were in danger of condensation happening.
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Old 11-04-2009, 09:00 AM   #13
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Integrated Thermostat/Humidistat


I currently have a Honeywell RTH8500D - which looks very much like the YTH9421.

anyone know if I can get the humidistat module for this to make mine an all-in-one panel? or do I need to go out and buy a new YTH9421?

also - any opinions on the Air King Wait 5000 Flo-Thru humidifier?
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Old 11-04-2009, 11:03 AM   #14
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The RTH8500 is a down graded Th8000 series thermostat.
There is no way to upgrade it to a YTH9421
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Old 11-04-2009, 11:41 AM   #15
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You can buy a new 9421 for about 150 shipped (buy-it-now) on Ebay. There are also some auctions cheaper, but don't know what they will end for.

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