Humidifier control with Honeywell DG115EZIAQ

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Old 12-15-16, 04:39 PM
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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.
 
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Old 12-15-16, 04:46 PM
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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 ?
 
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Old 12-16-16, 07:29 AM
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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.
 
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Old 12-16-16, 10:04 AM
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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.
 
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Old 12-16-16, 05:42 PM
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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.
 
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Old 12-16-16, 10:08 PM
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Ok... I see what you're asking.

Did you program the advance function 25 to #3 for independent operation ?

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Old 12-18-16, 10:24 AM
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yes, #25 was set to 3
i also reset #20 to 80% so i could be sure that the set IAQ trip point was well above ambient humidity, which is unusually high now.
 
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Old 12-24-16, 08:27 AM
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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.
 
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Old 12-24-16, 10:48 AM
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Thanks for letting us know what you found.
 
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