Humidifier cutting out furnace burner

[cofloater]

I have two new Honeywell TrueEASE HE200 humidifiers on my two older SnyderGeneral furnaces. They are simple humidifiers with the only electrical component being the water solenoid. One humidifier works fine. The second one works but consistently cuts out the furnace burner before the blower even comes on (less than minute). So there is a never-ending short cycle of one-minute burner only (with humidifier solenoid energized), two minutes fan only, everything off for two minutes, then gas valve and humidifier solenoid both energized again until the gas valve prematurely closes and the burner turns off, etc. As soon as I disconnect the solenoid to the humidifier, the furnace will run normal cycles of 5, 10, 15 minutes or whatever it takes to satisfy the thermostat. I have 27.2 volts to both gas valves when calling for heat. Both humidifier solenoids cause about a 1.5 voltage drop. The problem furnace's 24 volt circuit (gas valve and water solenoid) pulls a little more amperage than the combo that works well but ohms law tells me I am still only using about 14 watts between the valve and solenoid on the problem furnace and the 40VA transformer should handle that fine. Why will the gas valve not stay open when sharing its 24 VAC with the water solenoid? Am I barking up the wrong tree by thinking it is an electrical problem?
thanks,
cofloater

[HayZee518]

ohmslaw

basically in ohm's law the voltage in a parallel circuit is the same and the total amps is the sum of the individual current devices. volt/amps is watts in a raw sense. a 40 va should be enough, but take toll of the current draw of each device and see what the total draw is.
is the humidifier motor 24 volts or 120 volts?
if its 120 volts is there an interposing relay between the control circuit and the belt rotating motor?

[cofloater]

furnace humidifier

thanks HayZee518. But as I stated, the solenoid is the only electrical component in this simple humidifier -- no blower and no relay. I understand Ohms Law . . . the gas valve is pulling .2 amps and the solenoid is pulling .33 amps. Their total of .53 amps X 27.2 VAC = my rough approximation of 14 watts (yeah, I know it is not a purely resistive circuit but rather an inductive circuit so we are bending Ohms Law and bit and saying approximate). Anyway, the 40 VA transformer should be able to handle 2-3 times that load. So I am puzzled as to why the gas valve drops out after being in parallel with the gas valve for less than a minute. And again, the other matching furnace and matching humidifier work fine.
And again, this furnace works fine without the solenoid wired in. I have also checked air flow (new furnace filter and no blocked vents) and all else appears OK on the furnace so the high limit is not taking it out. From a cold start, I loose the gas valve in less than a minute if the humidifier solenoid is wired in.
cofloater

[HayZee518]

humidifier

ok, let's try this. disconnect the humidifier circuit and start your furnace. leave the wires where you can get to them. now establish a fire and wait until the furnace is in full cycle.
when its cooking, reconnect the humidifier circuit and see what happens. if it drops out the furnace, then you must have a grounded solenoid coil. if that be the case, leave one wire connected and try to start the furnace again. if there is in fact a ground through the coil, then it'll do the same again, dropout. if it doesn't then try the other lead and start the furnace again. something in that part of the circuit is drawing down your applied voltage. if you can, leave your meter connected across the solenoid leads and see what happens to the voltage.

[cofloater]

humidifier

HayZee518 -- thanks for sticking with me.
Hope I am not duplicating this post -- my last one seems to have disappeared after submitting but I am new to this site and perhaps there is a delay.

I have tried every which way. Regardless of where in the furnace cycle or if before the cycle, disconnecting either lead to the solenoid allows the furnace to cycle properly upon a call for heat. Connecting the solenoid leads (before or after furnace is running) will result in losing the burner in just under a minute.

Voltage on problem circuit is 27.2 without solenoid and but with gas valve on and drops to 25.9 with the solenoid energized. Combined amperage of gas valve and solenoid is .44 on properly working furnace and .53 on problem furnace. A difference there but well under what the 40va transformer can handle. The solenoid appears to be the guilty party but everything appears within tolerance. The 25.9 voltage with the gas valve and solenoid energized drops to zero after a minute of the burner firing.

thanks, cofloater

[HayZee518]

solenoid

ok, change out the solenoid. because its on the water side, it could be waterlogged AND part of the magnet wire insulation has broken down.
a typical water solenoid like ASCO or PARKER-HANNAFIN has a removable epoxy sealed coil. the coil mounts onto a stainless steel "core" nipple. Inside is a spring and an iron valve piece with a silicone seat on one end. It could be a flow through or a pressure assist type of valve.

[cofloater]

humidifier cutting out furnance burner

It turns out it was that the heat anticipator on the old mercury thermostat did not like having the solenoid added to the circuit along with the gas valve. I changed it out to a digital T-stat and the furnace now cycles properly. The second furnace-humidifier combo is also acting up a bit; I will be changing that T-stat to a digital soon also.
thanks, cofloater

[HayZee518]

furnace

well, I'm glad things worked out. And thanks for the follow-up. It's odd that the thermostat would act up like that. Usually you don't think the "stat" would be at fault but I guess anything's possible.
I got some problems here. Snow and ice came crashing down off my roof and dented the roof panel on my ford sedan. After searching come to find out the roof panel is abs plastic and is replaceable with suitable adhesives. It's just glued to the roof headers.
Now to find out how to remove the headliner and change out the roof panel.