Humidifier runs only when furnace runs

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Old 11-21-08, 06:56 PM
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Humidifier runs only when furnace runs

My new house has a model Carrier 58MCB furnace. I had a Bryant (Model HUMBBSBP2312) bypass humidifier installed to keep the humidity up in the winter so as to protect the hardwood floors. When the outside temperature gets down to 20 degrees F, the humidifier will not maintain the inside humidity above 35%, no matter how high I set the humidistat (installed in the cold air return). First, is 35% high enough to keep the floors from contracting and separating? Second, can the furnace controls be modified (rewired) to force the humidifier (when turned on and humidity level set high) to run when the furnace fan is in the ON mode regardless of whether the furnace burner is on or not? Currently, the humidifier runs only when the furnace burner is on (furnace fan in AUTO mode).
 
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Old 11-21-08, 08:16 PM
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Originally Posted by Elmer View Post
the humidifier will not maintain the inside humidity above 35%, no matter how high I set the humidistat (installed in the cold air return).
Do you have fresh air tied into the return, or have HRV system?
First, is 35% high enough to keep the floors from contracting and separating?
Yes, I have hardwood floor, and had no issues over the winter months we have here... My t-stat will lower the humidity set point when it gets colder out to help prevent frost on the windows.

Second, can the furnace controls be modified (rewired) to force the humidifier to run when the furnace fan is in the ON mode regardless of whether the furnace burner is on or not?
The control can't be changed but it can be rewired, and add a transformer.


Currently, the humidifier runs only when the furnace burner is on (furnace fan in AUTO mode).
I had mine set up in the past to run any time the blower was running, it never really stayed ahead, I think more water was wasted, so I switched it run with the heat only, and it keeps up just fine.
 
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Old 11-24-08, 12:33 PM
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Always connect the humidifier to hot water if possible. This will give you much better evaporation and allow you to set the humidistat as high as you want. Also it will reduce your heat cycle since cold water will suck all the heat out of your air supply.

I have no trouble maintaining 50% RH even on cold days.
 
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Old 11-24-08, 12:37 PM
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Originally Posted by zoneout View Post
I have no trouble maintaining 50% RH even on cold days.
Yikes, must be down south? There's no way you can do that up here in Minnesota!
 
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Old 11-25-08, 07:37 PM
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Humidifier receives cold water...

Originally Posted by Jay11J View Post
Do you have fresh air tied into the return, or have HRV system?

Yes, I have hardwood floor, and had no issues over the winter months we have here... My t-stat will lower the humidity set point when it gets colder out to help prevent frost on the windows.


The control can't be changed but it can be rewired, and add a transformer.



I had mine set up in the past to run any time the blower was running, it never really stayed ahead, I think more water was wasted, so I switched it run with the heat only, and it keeps up just fine.

Yes, I have fresh air tied into the return. Also, the water supply to the humidifier is from a cold water source, rather than a hot water source. Maybe that is my problem?
 
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Old 11-26-08, 05:57 AM
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Yes, both of those will keep the humidity lower.

Fresh air, there a couple of things you can do, You can add a damper that you can close it down some what to cut down on the air flow, or remove it from the duct, and just have it go into the furnace room itself.

Or, get a fresh air damper, the damper will be tied to a control that can control the amount of fresh air being brought into the home. I have the fresh air damper on mine, and humidity stays with in set point with no problem.

Hot water will help also.
 
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Old 12-03-08, 02:53 PM
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More questions on low humidity level

Thanks for your suggestions regarding hot water supply and fresh air damping. I'm thinking that if I tap into a hot water supply for input to the humidifier that it will run cold a long time before getting hot, since the water heater is on the second floor and the furnace is in the crawl space...maybe never get hot before the t-stat cuts the furnace off. Is that a possibility? Also, I'm wondering if the fact that my furnace is 90% efficient and doesn't run long at a time is not allowing enough moisture to be injected by the humidifier so as to bring the humidity level up? Another factor may be that my house is 2-story with a separate furnace for the second floor, and I have a humidifier only on the first floor furnace. Does the moistened air distributed on the first floor tend to rise like hot air does or stay on the first floor?
 
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Old 12-03-08, 04:02 PM
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Originally Posted by Elmer View Post
I'm thinking that if I tap into a hot water supply for input to the humidifier that it will run cold a long time before getting hot, since the water heater is on the second floor and the furnace is in the crawl space...maybe never get hot before the t-stat cuts the furnace off. Is that a possibility?
Yeah, if it has that far of run, not worth while doing.

Also, I'm wondering if the fact that my furnace is 90% efficient and doesn't run long at a time is not allowing enough moisture to be injected by the humidifier so as to bring the humidity level up?
What is avg run time? What do you have for t-stat?

Another factor may be that my house is 2-story with a separate furnace for the second floor, and I have a humidifier only on the first floor furnace. Does the moistened air distributed on the first floor tend to rise like hot air does or stay on the first floor?
Humidity travels to dry air, and will go up with the warm air going upstairs.
 
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Old 12-04-08, 01:13 PM
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My thermostat and furnace run time

I have a Honeywell VisionPro Touchscreen thermostat (TH8110U1003); normally set on 68F in the winter. I will have to wait til it gets in the 20's to get a fix on the avg run time for the furnace.
 
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Old 12-04-08, 02:29 PM
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on the VisionPro, I suggest to go into the Installer set up menu, #240.

If it's set on 5, then I would suggest to change it to 3, With 3, you get a longer run time.
 
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Old 12-10-08, 09:29 AM
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Furnace run time concern

My VisionPro does not have a function #240. I cycled thru the functions on the display and there are no functions between #160 and #320. The operating manual says the same thing. I checked the run times (over several cycles) when it was 30F outside and t-stat set at 68F. The avg. furnace run time was 6 min, 11 sec and was off 5 min and 50 sec, and then repeated. Is this reasonable? I haven't had a chance to time it at 20F outside. Also, I'm wondering if my inexpensive hygrometer is reading low. When I checked the furnace run times, the hygrometer (inside the house) read 36% rel humidity when the TV news said it was 41% outside. My intuition tells me the rel humidity inside in the winter should always be higher than outside..... is that correct?
 
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Old 12-10-08, 09:53 AM
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Elmer.....
What Jay was saying has come up before. Do you have the "Installers Manual" available?
Or just the "owners manual"? There are functions available that aren't listed in the owners version.

I tried looking for the Installers manual online, but no joy. I'm sure Jay will post a link next time.
 
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Old 12-11-08, 08:31 AM
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Elmer,

The humidity in the winter months in homes are going to be lower than what it is outside.

When you warm up the cold air from outside at say 41% at 20˚, and bring that air to 68˚, the humidity will drop down to about 25% (This is a guess since I cna't find my chart)

so that's why I was asking about fresh air tied to the return.

The menu is in the installer set up menu.

Here is the manual.
 
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Old 12-12-08, 01:28 PM
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VisionPro Installer Codes

Thanks again for you help. Following the Guide I easily got into the setup functions and found #240 set to 5, so I changed it to 3. I will check the furnace run times again and report back.
 
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Old 12-12-08, 08:44 PM
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With it set to 3,it may run about 15 to 20 minutes.. When it's colder it will run longer.
 
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Old 12-13-08, 10:19 AM
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Furnace Run time with VisionPro Function 240 set to 3

I checked the run time of my furnace this morning when it was 28F outside (t-stat set to 68F) and found that it was longer, as you suggested, when func 240 was set to 3 over what it was when func 240 was set to 5. Averaged over 3 cycles, the ON time was 12 min, 6 sec and the OFF time was 11 min, 42 sec in today’s test. This about double what it was with func 240=5. Of course this is very approximate since the outside temp was 28F today and was 30F during the test with func 240=5. The run time very likely will be 15 min or more, as you suggested, when the outside temp is 20F or lower. Even though the run time per cycle doubled, the percentage time the furnace was burning during each cycle stayed about the same ( 51.5% when func 240=5 and 50.8% when func 240=3). Bottom line: The furnace burned longer during each cycle with func 240=3, but over an extended period, the furnace burns about the same aggregate length of time with func 240 set to 3 or 5. I will keep an eye on the inside humidity level for a while with func 240=3 to see if it improves (minimum humidity level increases).
 
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Old 01-17-09, 09:42 AM
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Furnace run time at 20F outside

I answered a question in the first post from Jay11J incorrectly (regarding HRV and fresh air tied into the return): I definitely do not have a “Heating Recovery Ventilation” system, nor do I have fresh air tied into the return duct. There are 4-inch PVC pipes going into and out of the burner compartment of the furnace. It appears one is for pulling air into the burner and one for exhaust. The input pipe is only a few feet long and pulls air from the crawl space. The exhaust pipe runs through the exterior wall to the outside. These seem to be for operation of the burner only and are not connected to the ductwork. Does this make a difference in any diagnoses you (Jay11J) made in earlier posts on my topic?

I checked the run time of my furnace this morning when it was 20F outside (t-stat set to 68F) and found that it was about the same as it was at 28F outside - about 11 min on and 11 min off. However, I had the foundation vents closed this time. Vents were open when earlier run times were captured. Rel Humidity was about 30% outside (at 20F) and inside (at 68F). Two questions: Is this what you would expect? In Charlotte NC area, when should foundation vents be open and when closed -- I have heard conflicting advice on this?
 
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Old 01-18-09, 05:44 AM
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I'd say close up the vent in the winter if the floor above it is a living space... I'm gussing on this since it's is something we don't have around here.. Almost all of the homes has basement, and area that are crawl space are all sealed up, no vents at the outdoors.

The run time may be OK since you may have a large system.
 
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Old 01-27-09, 01:51 PM
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FYI...if you need to close off your crawl space vents manually...it is recommended that all crawl space vents be closed anytime the outdoor temp is 40 degrees of lower! The automatic closing vents are designed to close or open at the 40 degree number. Living here in NC I notice a lot of folks don't take the precaution to close these vents when the temp drops and find themselves with frozen pipes.

So the magic number is 40 degrees or less...
 
 

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