On Oct 24, 4:12*pm, dpb wrote:
On 10/24/2011 11:20 AM, N8N wrote:
...

There is a mechanical humidistat, but it seems to me that the flow
rate of the water is such that it might overpower the drain if the
water isn't actively evaporating off the panel....

The solenoid should shut off the water when there's no demand...tied w/
the sail switch since you have one or from the HUM contact on a furnace
w/ that logic on the board.

Generally, the old Honeywell sail switches I'm familiar with were
dual-function humidistat/flow switch using a humidity-sensitive
lever-connection that stretched/shrunk as humidity went up/down that
controlled the contacts.

As noted, replaced both w/ the solid-state humidistat and the new
furnace has the HUM logic onboard so all is much simpler that way.

I thought you said you do have a solenoid; doesn't it shut the water off
when not demanded? *If not, what _does_ it do? *


Right, I wanted to interlock the valve to something other than *just*
the sail switch and humidistat - because all the sail switch does is
detect airflow (this one appears to be a simple sail switch) to
prevent the humidifier from running when someone manually turns on the
fan just to circulate air and/or the A/C is running.

I think after thinking this over I will go ahead and get a MR-101 or
similar relay unit to provide me a set of dry contacts that change
state on a heat call and leave everything else substantially the way
it was (re-running the 120V feed to the sail switch though so that it
a) doesn't lay on top of the supply plenum and b) will be cut off by
the furnace cut off switch, so that it doesn't require shutting off
the breaker for maintenance.) I suspect that the reason that this
wasn't done is that like my last house, the humidifier was installed
prior to the installation of central air and/or a thermostat with a
switch that could manually force the fan on without a call for heating
or cooling, so no thought was given to interlocking it (or in other
words, if air was flowing in the return plenum, it was a pretty safe
bet that the furnace was operating at that time.)

nate