Truesteam and Variable Speed Blower

[lifelongstudent]

We recently had a Trane XC95/XL16i furnace/heatpump combo installed along with a Honeywell HM506 Truesteam humidifier. After several issues with the installation the humidifier is finally working. However, it is unable to raise the humidity level. There looks to be a sizing issue (based on Honeywell documentation and our house size of 2500sf), but I'm also curious as to the air flow of the furnace blower when the furnace is not running and if it is sufficient on low speed to deliver humidity into the house. I've been searching online without success but did notice a Honeywell sail switch for use in similar installs (S688A1007). I'm thinking this switch would turn on the humidifier only when the blower is at a higher speed, but doesn't seem like this would do anything for moisture delivery, only reduce the times the humidifier is running to only when the furnace is on. So my question would boil down to: will a variable speed furnace running on the lowest speed push enough air flow to carry moisture from a steam humidifier into the house or would the furnace need to ramp up to a higher velocity to accomplish this?

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[Tony Hwang]

Hmm, Typically humidifier and EAC run only when blower is on. That sail switch may not be sensitive enough when blower speed is low. My humidifier(Aprilaire) and Honeywell EAC are connected to blower power terminals. If blower is on, they are on. My house is little bigger than yours. I can maintain proper RH during season.

[Stormin Mormon]

Call a heating technician.

Size matters.

[Mike Hunt]

Probably.

[0815]

Just a few thoughts: The steam also gets moved at lower fan speeds, so it is not required to run full speed which is the case with conventional pass through humidifiers. Tranes XL Series have a setting as to how much air they move when they run on the lowest setting without call for heat or cooling. While this is a very limited setting it can be configured via a jumper on the main unit on the air handler.

In my house the entire setup (duct work is not ideal) and when we use our fireplace insert the thermostat does not initiate a call for heat so the house gets cooler in some areas since the low fan speed is not enough to even it out.

So back to the Truesteam, if you got the setup with the Vision Pro IAQ you actually have a programable fan mode caled 'circ'. When you program 'circ' rather than 'on' or 'auto' you will have the fan randomly run 35% of the time in addition to calls for heat and cooling. This will help to circulate the house temp and the humidity accordingly.

At 2500sq ft it depends how tight your house is, meaning doors & windows with draft, insulation in general how many recess lights etc... total volume also matters (ceiling height....). So I am almost certain 6GPD is not cutting it. 9 might be better, but even a 12GPD could be to small depending on your house tighness, volume and temperature you set and your outside temp in your area.

[0815]

Just a few thoughts: The steam also gets moved at lower fan speeds, so it is not required to run full speed which is the case with conventional pass through humidifiers. Tranes XL Series have a setting as to how much air they move when they run on the lowest setting without call for heat or cooling. While this is a very limited setting it can be configured via a jumper on the main unit on the air handler.

In my house the entire setup (duct work is not ideal) and when we use our fireplace insert the thermostat does not initiate a call for heat so the house gets cooler in some areas since the low fan speed is not enough to even it out.

So back to the Truesteam, if you got the setup with the Vision Pro IAQ you actually have a programable fan mode called 'circ'. When you program 'circ' rather than 'on' or 'auto' you will have the fan randomly run 35% of the time in addition to calls for heat and cooling. This will help to circulate the house temp and the humidity accordingly.

At 2500sq ft it depends how tight your house is, meaning doors & windows with draft, insulation in general how many recess lights etc... total volume also matters (ceiling height....). So I am almost certain 6GPD is not cutting it. 9 might be better, but even a 12GPD could be to small depending on your house tightness, total volume, target temperature and your outside temp in your area.