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Old 04-01-2013, 07:04 PM   #1
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Humidity question


Hi,

I have a quick question. I have a whole house humidifier and have turned up the humidity but I don't seem to be getting any condensation build up on my windows like I did during winter. I even had to turn the humidifier off for a couple of days because frost developed on one of my doors. Can I assume I am having a hard time feeling the moisture or seeing condensation on my windows because the temperate outside is not as cold as it was during winter?

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Old 04-01-2013, 07:54 PM   #2
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Humidity question


When is the last time you changed the element in the humidifier? Is it all calcified, or blocked up? Furnace filter clean?

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Old 04-01-2013, 07:57 PM   #3
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Humidity question


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Originally Posted by jagans View Post
When is the last time you changed the element in the humidifier? Is it all calcified, or blocked up? Furnace filter clean?
I change the pad every month. Am I correct about the outside weather in relation to this?
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Old 04-01-2013, 08:20 PM   #4
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Humidity question


Of course. Its all about dew point, and differential temperature/humidity. When its colder out, the cold is breaching the dead air space in your windows, and the inside glass is becoming cold enough to allow condensation. You may have air leaking around your door, or you may have thermal bridging in the door, causing frost.

Do you have a Hydrometer in the home to tell you what the internal relative humidity is?

Something else: Furnace mount whole house humidifiers only put moisture in the air when the main furnace blower is running. If you have the blower set to auto, it only runs when there is a call for heat. If you turn it to fan, the humidifier will be infusing the air with moisture all the time. If the house is too dry turn the fan to ON.
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Old 04-01-2013, 08:24 PM   #5
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Of course. Its all about dew point, and differential temperature/humidity. When its colder out, the cold is breaching the dead air space in your windows, and the inside glass is becoming cold enough to allow condensation. You may have air leaking around your door, or you may have thermal bridging in the door, causing frost.

Do you have a Hydrometer in the home to tell you what the internal relative humidity is?

Something else: Furnace mount whole house humidifiers only put moisture in the air when the main furnace blower is running. If you have the blower set to auto, it only runs when there is a call for heat. If you turn it to fan, the humidifier will be infusing the air with moisture all the time. If the house is too dry turn the fan to ON.
The one door has poor weather stripping and metal framing. Its just not a very energy efficient door. So, basically since its not as cold as it was before then moisture build up is less? Right now out humidity level is 50 percent. Were in Michigan.
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Old 04-01-2013, 08:50 PM   #6
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Yes, I suspect You have two things going on, less moisture and less vapor drive. If you want more moisture, again, turn the furnace fan to on. (I am making some assumptions here, one being that your whole house humidifier is attached to a Forced Hot Air furnace. You never said so I am speculating) If your "Whole House" humidifier is a cabinet type, turning the furnace fan to on will not help with humidity, but will keep recycling and filtering the air.

The door with the crappy weatherstripping is a whole different issue. It is suffering from air leakage.

I personally have a cabinet type humidifier, and I prefer it to the furnace type, as I run it all the time in the winter. I have chronic Bronchitic, and if the air gets too dry, I start hacking, need to go on steroids yada yada yada.

Hope this helps.
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Old 04-01-2013, 11:32 PM   #7
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Originally Posted by jagans View Post
Yes, I suspect You have two things going on, less moisture and less vapor drive. If you want more moisture, again, turn the furnace fan to on. (I am making some assumptions here, one being that your whole house humidifier is attached to a Forced Hot Air furnace. You never said so I am speculating) If your "Whole House" humidifier is a cabinet type, turning the furnace fan to on will not help with humidity, but will keep recycling and filtering the air.

The door with the crappy weatherstripping is a whole different issue. It is suffering from air leakage.

I personally have a cabinet type humidifier, and I prefer it to the furnace type, as I run it all the time in the winter. I have chronic Bronchitic, and if the air gets too dry, I start hacking, need to go on steroids yada yada yada.

Hope this helps.
If I run just the fan on my furnace, which is a forced air furnace, it would just be blowing basically slightly warm air into the rooms since its not heated air and the burners not running. Would the humidifier even be able to evaporate that air to create the moisture. I have mine mounted on the hot air supply plenum. It has a 6" in round duct running from the supply to return. Is that just so some moisture can be added to the return side as well?
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Old 04-02-2013, 05:52 AM   #8
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Humidity question


You have a bypass humidifier. Air must go through it and into the return in order for any moisture to be added to the air.

Without the heat being on. The only way the humidifier can add moisture to the air is if it is connected to the hot water line.
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Old 04-02-2013, 08:58 AM   #9
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You have a bypass humidifier. Air must go through it and into the return in order for any moisture to be added to the air.

Without the heat being on. The only way the humidifier can add moisture to the air is if it is connected to the hot water line.
Ok mine is connected to a cold water line so just running the fan is pointless then? If supply air passes over it collecting moisture why do you also need that bypass duct going to the return side as well?
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Old 04-02-2013, 11:39 AM   #10
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Humidity question


You have a round duct that goes from the supply side plenum to the return side intake. You need that to have air flow. There is a honeycomb type of grid through which water flows in the return side end of the bypass tube. When the main blower is on, which occurs when the burners are lit and the furnace is calling for heat, OR when you have the thermostat set to FAN ON air is blowing through that grid, and picking up moisture, as long as your humidification unit is wired to allow water flow over the honeycomb with fan on.

The cabinet type humidifiers do not use hot water, they use cold water, and paper filters wick up water, then fans blow over the filters, adding moisture to the air. I guess hot water might work better, as Beenthere said, but cold water works too. Evaporation happens due to vapor drive, otherwise, we would never have Fog

Beenthere forgot more than I will ever know about HVAC, but in this case I think I am correct. Again, the valve has to open with the stat set to fan on. So your unit has to be wired to open the supply valve to the humidifier with fan on.
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Last edited by jagans; 04-02-2013 at 11:45 AM.
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Old 04-02-2013, 05:02 PM   #11
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Ok mine is connected to a cold water line so just running the fan is pointless then? If supply air passes over it collecting moisture why do you also need that bypass duct going to the return side as well?
Because that unit is designed for the hot supply air to blow through the pad and into the return. If the damper is closed, air will only blow by the pad, not through it.


Unless you have very hard water(or an Aprilaire 400), the pad only needs changed once a year.

Yep, without hot water. Its pretty useless to run the humidifier with the fan only. And if you have leaky duct work in an unconditioned space, it can actually lower your humidity.
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Old 04-02-2013, 07:53 PM   #12
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Humidity question


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Because that unit is designed for the hot supply air to blow through the pad and into the return. If the damper is closed, air will only blow by the pad, not through it.


Unless you have very hard water(or an Aprilaire 400), the pad only needs changed once a year.

Yep, without hot water. Its pretty useless to run the humidifier with the fan only. And if you have leaky duct work in an unconditioned space, it can actually lower your humidity.
Are you an HVAV Professional? Do you do work in the field? I am in HVAC at school starting out and would love it if I could get your assistance on any questions I might have.
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Old 04-02-2013, 08:33 PM   #13
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Humidity question


Yep, been in the trade 38 years.

There are several HVAC tradesmen on this forum. We will all help if we can.
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Old 04-03-2013, 10:01 AM   #14
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Yep, been in the trade 38 years.

There are several HVAC tradesmen on this forum. We will all help if we can.
I have another quick question. There is a clear vinyl tube coming from the return duct to round device. I believe its a pressure switch. What is that for? Also, when you increase the relative humidity on the humidistat does more water get produced for the evaporator pad or what actually happens when you turn the dial to increase humidity?
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Old 04-03-2013, 10:06 AM   #15
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Humidity question


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Originally Posted by beenthere View Post
You have a bypass humidifier. Air must go through it and into the return in order for any moisture to be added to the air.

Without the heat being on. The only way the humidifier can add moisture to the air is if it is connected to the hot water line.
How come the humidifier air has to pass through the return side if the supply side air is what is being blown into the rooms? Reason I ask is because the return air is obviously cold.

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