Pat Coghlan wrote:

I used to have an Aprilaire bypass unit at our previous house. I liked
it very much, but they are only available through contractors. Our last
one cost about $450 installed.

I just purchased a Honeywell HE260 from Home Depot for $199 (there is a
$30 rebate offer in effect until Nov.). It's quite similar to the
Aprilaire in styling etc. I've got it bolted to the furnace (Lennox G2
- I believe) and the water supply connected.

Problem: The HE260 comes with a big honking 30VA transformer and a
kludgey "sail switch" (relay with a big "sail" that floats in the cold
air return and closes when air is flowing...Honeywell's way of sensing
blower activity). I want to avoid installing the transformer (24V) and
sail switch and, instead, just power the 24V solenoid water valve from
the furnace itself.

I doubt the solenoid draws more than about 500 mA. Is there any reason
I should NOT try to power it from the Y/T terminals (compressor
contactor) at the furnace's low-voltage terminal strip, which provides
24VAC when the blower is on?

-Pat

Well, the technically correct way to get the answer is to see if the
present xformer in the furnace has a current (or VA) rating marked on
it, then measure the current that transformer puts out when it is
driving all loads which can possibly be placed on it simultaneously. If
that shows that the transformer has power to spare, then you could then
add on the humidifier's solenoid valve and see whether the current
drawis still below the xformer's rating.

But how about this? If the blower motor runs from 120 volts you could
just wire the primary of that "big honking" transformer across it and
power the solenoid from that transformer. The contacts which control the
blower motor must surely be robust enough to take a little additional load.

HTH,

Jeff

--
My name is Jeff Wisnia and I approved this message....

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"