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laurawr · Jul 4, 2008, 11:27 AM

I have a small house and don't need a whole-house sized dehumidifier. I'm thinking that I'd like to run a portable dehumidifier that gets power through an external dehumidistat switch. That switch would also turn on the house fan, to circulate the dry air, when the dehumidifier is turned on.
Somebody told me all this switch needs to do it to connect the R and G terminals on the thermostat. If there's central AC you have to have a relay to avoid backfeeding power to the Y terminal. I don't have central AC but I might get it, so I'd want to put the relay in.
I have a good electrician who would do the work, but I don't know if he's familiar with HVAC controls. So I'm trying to confirm if this is right. And if anybody knows what kind of relay would be needed I'd like to know.
To do this with a portable dehumidifier you need to get one with mechanical controls, so it remembers its settings when the power is interrupted. Its control is set to continuous dehumidify or to a very low humidity threshold.
Comments?
Thanks
Laura

hvac1000 · Jul 4, 2008, 11:48 AM

Originally Posted by laurawr

I have a small house and don't need a whole-house sized dehumidifier. I'm thinking that I'd like to run a portable dehumidifier that gets power through an external dehumidistat switch. That switch would also turn on the house fan, to circulate the dry air, when the dehumidifier is turned on.
Somebody told me all this switch needs to do it to connect the R and G terminals on the thermostat. If there's central AC you have to have a relay to avoid backfeeding power to the Y terminal. I don't have central AC but I might get it, so I'd want to put the relay in.
I have a good electrician who would do the work, but I don't know if he's familiar with HVAC controls. So I'm trying to confirm if this is right. And if anybody knows what kind of relay would be needed I'd like to know.
To do this with a portable dehumidifier you need to get one with mechanical controls, so it remembers its settings when the power is interrupted. Its control is set to continuous dehumidify or to a very low humidity threshold.
comments?
thanks
Laura

Try these

laurawr · Jul 4, 2008, 04:17 PM

Wow. Thanks. So you would not directly connect the R and G terminals. It's more complicated than I realized!
The blower motor only has one speed and I'm not sure what happens to the diagram in that case. Does that simplify the relay? You have two wires coming from the relay to high and med. Speeds of the blower.
I suppose if I were using a wall-mounted dehumidistat, it would close a 24-volt connection. I was thinking that the dehumidistat, when the switch is closed, would activate a wall outlet which the portable dehumidifier is plugged into. Would a relay be needed for that?
I don't have AC right now, if the AC isn't in there terminal 3 of the relay is still connected to the C terminal on the thermostat?
Maybe I should just leave the relay out until I got AC. In that case you could just connect the R and G terminals with the wires coming from the dehumidistat?
The other choice of dehumidistat switch is something that controls an interrupter plug. You plug the interrupter plug into the wall and the dehumidifer into the interrupter plug. But that doesn't seem suitable.
:o
Laura

hvac1000 · Jul 4, 2008, 05:27 PM

Actually I just plug the dehumidifier in at my camp and leave it run all year. The dehumidifier has its own built in control and a percentage level you can set.The drain is set up to go out the wall and drip on the ground so there is no bucket to empty

The diagrams above are usually reserved for a HVAC system. The lower blower speed causes the moist air to hang at the coil longer and pulls out more moisture. I use that system at my regular home to stay comfortable.

There are many options.