Humidifier control with Honeywell DG115EZIAQ
#1
12-15-16, 05:39 PM
Humidifier control with Honeywell DG115EZIAQ
I installed a Honeywell DG115EZIAQ to control a Skuttle steam humidifier on a forced hot air furnace. This was a replacement for a failed Skuttle humidistat that has no replacement. The Skuttle operates independently of the furnace and turns on the furnace blower when humidity is called for. I am using the IAQ ONLY for humidifier control. I connected 24VAC, the outdoor IAQ temperature sensor and the Skuttle to the HUM terminals. The IAQ HUM contacts don't close when the humidistat is set higher than the detected indoor humidity level (confirmed with an ohmmeter). The IAQ properly displays both indoor and outdoor temp and humidity. I confirmed the Skuttle works properly and responds to shorting it's control input, which is normally connected to the IAQ HUM contacts.
#2
12-15-16, 05:46 PM
Group Moderator
Welcome to the forums.
In my installations... I don't allow the humidistat to turn on the blower as the cooler air doesn't carry moisture as well. I guess with a steam unit you could let the hstat turn the blower on if you needed a lot of humidity.
You have the R and C connected to the furnace and what other colors ?
In my installations... I don't allow the humidistat to turn on the blower as the cooler air doesn't carry moisture as well. I guess with a steam unit you could let the hstat turn the blower on if you needed a lot of humidity.
You have the R and C connected to the furnace and what other colors ?
#3
12-16-16, 08:29 AM
Heating and cooling are controlled by a Nest thermostat that uses the Y, G, W(1) and R(H) connections. There is an AUX relay installed to allow the humidifier to control the furnace blower independently of the thermostat control. The rationale is that the humidifier takes a short time to reach steam temperature, which then triggers the blower. This results in a more constant home humidity level. The heat cycle is often too short to keep the humidifier ON sufficiently if the blower was only controlled by the heat thermostat.
Thank you for your attention. I still have not figured out why the IAQ unit won't activate it's HUM output needed to turn on the Skuttle.
Thank you for your attention. I still have not figured out why the IAQ unit won't activate it's HUM output needed to turn on the Skuttle.
#4
12-16-16, 11:04 AM
Group Moderator
R and C won't activate the hstat. That's why I asked what other wires you have connected to it.
I believe you would need both G (fan) lines connected for total automatic operation.
I believe you would need both G (fan) lines connected for total automatic operation.
#5
12-16-16, 06:42 PM
I don't understand why the IAQ HUM terminals output state will not be "closed" when detected humidity is lower than the IAQ set humidity level. This control state should be independent of whatever the furnace thermostat and furnace blower are doing. A simple manual humidistat works this way by closing a set of contacts when humidity is called for. The contact closure is then used to turn on a humidifier. That's exactly what I expect the IAQ to do. It is powered and has humidity set higher than indoor ambient.
#6
12-16-16, 11:08 PM
Group Moderator
Ok... I see what you're asking.
Did you program the advance function 25 to #3 for independent operation ?
Did you program the advance function 25 to #3 for independent operation ?
#8
12-24-16, 09:27 AM
PROBLEM SOLVED
My diagnosis confirmed a defective Honeywell IAQ unit. The dry contact Hum relay failed to close when humidity was called for. Supply House sent me a replacement unit, which was installed, reprogrammed and worked perfectly.
Supply House was very accommodating and handled my replacement promptly. I definitely will choose Supply House for future HVAC related products.
My diagnosis confirmed a defective Honeywell IAQ unit. The dry contact Hum relay failed to close when humidity was called for. Supply House sent me a replacement unit, which was installed, reprogrammed and worked perfectly.
Supply House was very accommodating and handled my replacement promptly. I definitely will choose Supply House for future HVAC related products.
transformer:
When we purchased a new furnace, the installer neglected to re-wire the Nest to the humidifier, and then was unable to do so. I'm willing to concede there may be something wrong with the nest, the tranformer, the relay or the wiring, but if anyone has any insight it would be greatly appreciated.
I tried to use this, the nest detected the wiring, but the solenoid did not switch when tested:
I believe the original, successful, installer, used this relay, but I have no idea whether it would make a difference:
If anyone has any advice, I'd appreciate it.