On Jan 2, 8:31*pm, Nate Nagel wrote:
Nate Nagel wrote:
Pete C. wrote:
Nate Nagel wrote:
Hi all,
I have an old Aprilaire powered humidifier connected to my furnace,
which is an old Ruud 90+ gas unit. *Currently the humidifier is enabled
whenever the fan is running. *I assume that there is a terminal on the
board that goes hot when the fan runs, intended for this connection.
Here's the issue - it's cold enough here and the insulation in my house
is uneven enough, that currently I have the fan manually turned on low
speed all the time to provide circulation. *Otherwise my bedroom gets as
cold as 62 degrees when the downstairs, where the thermostat is located,
is 67 degrees. *This allows the humidifier to operate when there is no
heat call. *What would be the best approach to change things around so
that the humidifier operates only when the furnace is actually firing?
I bet I could come up with something that works by looking at it myself,
but I figured I'd throw this out there in case there were any "gotchas"
that I might overlook.
While you could simply reconnect it so that the burner firing enables
it, I'd suggest connecting it to a humidistat, so that when the fan is
running *and* the humidity is low it will run, and of course not run
when the humidity is high.
It's already got the humidistat control, the problem is that it gets so
dry indoors when it is cold out that it's calling for it to run near
continuously. *This means that when the fan is running but the furnace
isn't firing, there's still water flowing through the humidifier which
is likely mostly going down the drain rather than into the air. *I'd
rather fix it so that it only runs when the furnace is actually firing
so most of the water gets into the air and then it shuts off when it
goes back to the low speed circulation fan.
I suppose I could also move the humidifier feed over to the hot water
line, but I don't know if that would still work well when the furnace
isn't firing.
Nate
Follow up: *I started looking at what I have closely, and the only
"control" wiring from the humidifier is to the humidistat itself. *So I
figured that it must be controlled by cutting power to the receptacle
that it's plugged into. *Unplugged it, powered furnace back up, 120V at
receptacle. *Waited for heating cycle to finish. *0V at receptacle
(which is mounted on the outside of the furnace) *OK, so there's a relay
inside there that is cutting the 120V to the humidifier to shut it off.
* Powered furnace back down again, opened up control box. *I see that
there is a "HUM" terminal but nothing is connected to it. *There is a
pair of black and white THHN entering the area the white is connected to
neutral and the black is connected to "EAC." *Not sure what that stands
for - but I suspect that that is somehow controlling the humidifier
because it's obviously field wiring (looped 14AWG rather than a stranded
wire with a factory crimped end.) *I can't see where it goes, but am I
on the right track?
Main questions:
- What does "EAC" mean on a furnace control board?
- What are the typical voltages on the "HUM" and "EAC" terminals?
120VAC? 24VAC? 24VDC? *I'd check 'em myself but it's kinda hard to keep
my thumb on the pin switch, hold a multimeter, *AND* operate the
thermostat upstairs 
*I guess I'm wondering if that's just taking
120VAC direct to the recep or if there's a relay hidden somewhere in
there that I need to dig deeper to find and verify. *It's pretty hard to
pull the cover on the recep box too, once it's warm I really need to
relocate a lot of this stuff to make it more user friendly (one screw is
partially blocked by a drain line, etc.)
thanks
nate
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Since you have a voltmeter, you chould be able to poke around and find
some point that is only energized when the gas valve is energized.
That may be the primary of the transformer that feeds the gas vavle.
If the thermostat and other controls are all on the 24V side of the
trransformer, you are SOL unless you want to buy a transformer and
wire it backwards to develop 120 V from some point in the 24V control
circuit. Can't you throttle down the water flow slow not so much goes
down the drain on a continual basis?