I’m looking to buy a pressure switch to sense airflow for my humidifier. Can someone give me some typical WC numbers for a residential supply air plenum? It’s a variable-speed fan, and I’d like to pick up the low speed, if possible.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. –James Madison
Replies
Maybe try this?
Soldered a 4 inch square piece of copper shim stock to a microswitch lever. Stuck it in the duct with a 90 degree rotation capability. Rotated till it switched where I wanted it to, no numbers needed .
Why?
Fighting Ignorance since 1967
It's taking way longer than we thought
Why do it the hard way?
Almost all modern furnaces have a "HUM" terminal that provides some voltage for humidifier operation. Some manufacturers provide 24VAC, others 120VAC. It only comes on in the heating mode. Check the schematic on the door.
If you don't want the board to provide the voltage, use it to drive a Relay in a Box. RIB has one that will work on 24VAC or 120VAC. Connect the relay to the voltage needed to drive the humidifier. The only reason to do this is to isolate the humidifier from the furnace board so there is little chance of a humidifier problem taking out the furnace board.
You can buy a sail switch new in the humidifier installation kits offered by the big box stores. Cheaper than a pressure switch. You would need to measure the wc" of your supply plenum to get the right switch.
If you use a sail switch and you have your variable speed furnace set to continuously circulate air on low, then the humidifier will come on at any time.
Using the EAC terminal on the board will allow your humidifier to operate at any time. Check voltage and specs on the schematic and wire accordingly.
If you allow the humidifier to operate at any time, make sure that the AC (dehumidifier) and your humidifier don't get into a little competition.
If you have the cycles per hour set right on your digital stat, then you don't need to worry about that. Hopefully you got a nice two stage stat to work with that VSD furnace.
Edited 4/9/2006 8:05 am ET by danski0224
You only use the hum terminals if you don't know the words.Yeah, I'm trying to get the humidifier to work full time. Will have the humidistat turn on the fan, but the fan stops anyway for about 3 minutes if the heat comes on. Hadn't thought of using the EAC terminal, but on my unit it's 120V, so I'd have to use a relay or another transformer if I used that.A pressure switch is about half the price of a sail switch, and involves less duct surgery.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
>>Yeah, I'm trying to get the humidifier to work full time. Again, why?Too much humidity can cause mildew and mold growth and is not a good thing.If you have a dryness prolem, work on weatherization: reduce the air changes and you (i) keep moisture produced through normal household activities in the house and (ii) reduce your energy bills.
Fighting Ignorance since 1967
It's taking way longer than we thought
Because in the spring and fall the furnace doesn't run enough to keep the humidity up.House is about as well weatherized as one can do without ripping out the walls and starting over.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
you can wire that off of the control board...
the prescribed terminal to jump off of is listed in the paper work..
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
you can also wire it thru the call side of the thermostat...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!