Well, running an outlet to the transformer is one thing, but there is
also the sail switch which requires another hole to be cut in the cold
air return.

I e-mailed Honeywell, but there reply was "oh, then you're touching the
furnace, we can't help you there". I wonder if they take the same
attitude towards defence contractors: "oh, then you're interfacing to
the jet engine, we can't help you there".

The wires to the solenoid are hanging right by the low voltage strip, so
I'm really tempted to just wire it to the Y/T.

Jeff Wisnia wrote:
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