Thread: Control

Honeywell Humidity Control. Found this control on wall in hall. Roof mounted evaporative cooler vents into this hall near control. House is all electric heat and has always been electric heat. What could this control? Cooler has it's own controls, I have never seen an evaporative cooler with this added. Can see nothing at duct in attic or anywhere else. Homeowner has no idea what it does. Any guesses?

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Originally Posted by Tom Rees

Honeywell Humidity Control. Found this control on wall in hall. Roof mounted evaporative cooler vents into this hall near control. House is all electric heat and has always been electric heat. What could this control? Cooler has it's own controls, I have never seen an evaporative cooler with this added. Can see nothing at duct in attic or anywhere else. Homeowner has no idea what it does. Any guesses?

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My SWAG Anatomy of the Home Furnace Humidifier - How a Humidifier Works
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TrueEASEâ„¢ | Whole-House Evaporative Humidifier
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Billy, No furnace all electric radiant heat.

Was there a humidifier installed on the ducts near the air handler? If I see a control like that, then I look for the humidifier.

In southern coastal regions it is popular to install a humidistat in parallel with the AC thermostat to keep the indoor humidity at an acceptable level when the house is not occupied. E.g., the homeowner sets the AC thermostat for, say, 80 deg (to save energy) and the humidistat to, say, 65%. If the humidity exceeds this set point the AC operates even though the temp is below 80 deg to dehumidify. Sometimes called "overcooling", sophisticated thermostats like the Honeywell Prestige and Eccobee Smart provide this capability.
I don't know how much dehumidification a swamp cooler will provide but any cooling device will cause the humidity to condense from the air if the humidity is high - near dew point.

Jeff's RnR

Hi Jack, Never say that on a plane. Evaporative coolers like this generally have one central duct that comes straight down from the roof mounted cooler. It's a sheet metal duct about 3 feet square. I could see nothing in it or on it in attic. I'm originally from back east and had never seen one of these (evaporative cooler) until I moved west. They don't work in humid climates. The thing is most humidifiers I see here are for use in the winter months. They should not be run when running conventional A/C with compressor/condenser and coil at furnace. The homeowner seemed to think it was to condition air in winter??? I'm hoping someone has seen this control before, my hunch is it has/had something to do with the cooler. I'm stumped.

Tom,
This looks like an old version of the Honeywell single stage humidistat that can be used to control either humidification or dehumidification. Given that the house is in UT, it was likely for humidification in winter when the air is very dry. Since it is old, the system it controls may no longer be installed. Try tracing whrere the wires lead to see if you can find it.

Around here, that control would simply be wired to the nearest bath exhaust fan.

Originally Posted by Jeffrey Maul

I don't know how much dehumidification a swamp cooler will provide but any cooling device will cause the humidity to condense from the air if the humidity is high - near dew point.

Not a swamp cooler- they actually *increase* humidity.

That's in fact how they work... outside air flows across a damp medium into the house, causing water to evaporate. Because evaporation is endothermic, the air is cooled (proportionally to how much water evaporates - hence why it only works effectively in arid climates).

Unlike conventional AC, both the water and air parts of the cycle are open-ended. You have to keep adding water and fresh air at the inputs rather than recirculating as you would with refrigerant-based cooling.

As for the humidistat, it's either got to be a high-limit cutoff for the swamp cooler, or a control for a (now-missing or well-hidden) wintertime humidifier.

As for the humidistat, it's either got to be a high-limit cutoff for the swamp cooler, or a control for a (now-missing or well-hidden) wintertime humidifier.

My thinking exactly.

Looks like a typical mold farm control...

I agree with one of the above - in UT, it was probably a high humidity cut off for the evaporative cooler. Probably no longer connected.