2nd Floor Humidifier

JohnL_2

My home has 2 forced hot air furnances, one in the basement which services the 1st floor and one unit in the attic which services the 2nd floor.  I had a contractor install an April Aire bypass humidifier (model 600) for the 2nd floor unit.  They informed me that they couldnt put water lines in the attic due to freezing, so they put the humdifier in the basement with a duct feeding up to the Attic furnace's return.  The intake for the humdifier was settup on the basement unit's supply duct.  So basically the intake comes from the 1st floor supply and puts it up to the 2nd floor return duct.  I measured the air coming from the 1st and 2nd floor vents, and only noticed a small jump from 20% RH on the first floor (no humidifier) and 24-26%RH on the 2nd floor vents.  The problem I see is that if the basment furnace is not on, the humidified air will not run up to the attic.  Any advice on this situation?  Should I just switch the humidifier to be used on the basement unit?  Thanks

BillW

Humidifier

Humidity tends to diffuse evenly thru the entire structure.  If supplied by a humidifier, or by showers, cooking or laundry drying, it's the same.  Your contractor was right about the bypass unit freezing in the attic, a better choice would have been a steam humidifier, mounted remotely, with an insulated line running up to the attic ductwork.  That duct work MUST be well insulated. Sizing of the humidifier might be an issue as well; it may not have the capacity to handle both systems.  You can increase the output of a bypass unit by running hot water thru it rather than cold.  Your target range is between 40 & 60% humidity, below 40 is too dry, above 60 is too wet. 

JohnL_2

Humidifier

Bill,

Thanks for the quick response.  I am going to check tonight to see if they used hot or cold water for the humidifier, I can easily fix that if its not hot water since the water heater is right there.  The problem I see is that if the basement unit is not on (the blower is not running) I cant imagine the attic unit pulling the air all the way upstairs.

BillW

Humidifier

Usually, a bypass humidifier is set up to start before a heating cycle begins, so the pad is wet when the heat exchanger warms up and the fan starts.  The solenoid water valve is wired to the humidistat, or the home control unit.  Unless your upstairs unit is wired to the humidifier, it can't open the solenoid.  Does the humidifier run when the upstairs unit is running, and where is your humidistat located?

JohnL_2

Humidifier

Bill,

The humidistat is up in the attic in the return duct for the 2nd floor furnace.  The humidifier is working when the 2nd floor furnace kicks on.  The problem is that the upstairs and downstairs furnaces are on different thermostats, so they dont always run at the same time.  So if the upstairs one is on, the intake into the humidifier is not forcing air through, it is only pulling from the upstairs, which in my head, is not enough to pull the moist air upstairs.

BillW

Humidifier

I recommend that humidistats be located in the occupied space.  If water is flowing thru the pad, when the upstairs unit is running, but the downstairs unit is off, I don't think enough water will evaporate to do much on the top floor.  Bypass units need very warm air flowing thru the pad to evaporate the water.  Typically, most bypass units are mounted on the return, with the hot air coming off the heat exchanger ducted directly to them.  They only operate on a call for heat.  As I mentioned in my first post, a remote-mounted steam humidifier is your best solution for your 2nd floor unit, but they do require a water supply and a drain, and electrical service.