Old Honeywell Humidistat help

pharmerphil

After many years the I thought solenoid had quit functioning. I could not make out the info, so went with a 24V. thinking that was what I had 'read' on the worn out solenoid.
Wired replacement in-No Go.
Any information will help, what should the voltage be where it attaches to solenoid, how to test control, Thanks in advance, photos attached

mattmia2

When was the last time you serviced it?

EBEBRATT-Ed

it probably is 24 volt. Disconnect the two wires going to the solenoid and ohm out the coil you should have some resistance. Then hook it back up put the power on and see if you have 24 volts. If not check the voltage at the transformer If you have voltage and it still will not open try jumping the humidstat terminals or wires

JUGHNE

Often the 24 vac is not supplied unless the blower is running and/or heat is on.

Sometimes a sail switch was used to power the stat which in turn would power the solenoid.
Solenoid and or nozzle can be plugged.
Or water supply valve off or corroded shut.

This is fairly old??

EdTheHeaterMan

That was not the best design for the life of anything metal that was just below it. I prefer the media type humidifier, over the spray nozzle type. Many a heat exchanger has failed the was below that type humidifier. It is time to consider replacing it IMHO.

EBEBRATT-Ed

I remember those Lennox humidifiers. They were not the best that thing has to date back to the 70s. Can't beleive it lasted this long must be good water

pharmerphil

mattmia2 said:

When was the last time you serviced it?

Every year

pharmerphil

EBEBRATT-Ed said:

it probably is 24 volt. Disconnect the two wires going to the solenoid and ohm out the coil you should have some resistance. Then hook it back up put the power on and see if you have 24 volts. If not check the voltage at the transformer If you have voltage and it still will not open try jumping the humidstat terminals or wires

I will check for resistance, where would one find the transformer? I have wires leading to the solenoid, and one that disappears into the duct work above furnace, where would I jump the humidstat terminals?

pharmerphil

JUGHNE said:

Often the 24 vac is not supplied unless the blower is running and/or heat is on.

Sometimes a sail switch was used to power the stat which in turn would power the solenoid.
Solenoid and or nozzle can be plugged.
Or water supply valve off or corroded shut.

This is fairly old??

Yes that is the way it operates, Fan on, power to solenoid. Sail Switch? The water supply, nozzle and shut off all good, water up to solenoid, but no power to solenoid

pharmerphil

EBEBRATT-Ed said:

I remember those Lennox humidifiers. They were not the best that thing has to date back to the 70s. Can't beleive it lasted this long must be good water

Amazing isn't it! But I maintain it every heating season, have replaced the spray nozzle once

pharmerphil

EdTheHeaterMan said:

That was not the best design for the life of anything metal that was just below it. I prefer the media type humidifier, over the spray nozzle type. Many a heat exchanger has failed the was below that type humidifier. It is time to consider replacing it IMHO.

At my age I just need to EEK it out for a couple more years

pharmerphil

Thanks everyone for your replies, Keep em' coming I would settle for a solution to bypass the old and go from the control (which may be at fault) to the solenoid. Is there a way to test the control?

JUGHNE

You should hear a mechanical "click" when rotating the knob back and forth.
As you raise to a higher setting that first "click" should be the approximate humidity of the sensor. The second click is the differential for the control.

Perhaps if you pull the knob off there are screws behind it that hold the cover on.
The terminals are obvious under the cover.
If duct mounted there may be a hole in the ductwork for sensing air.

Early humidistats were a little wonky in operation, they are simply a switch.
If you jumper the screws with the wires or put both wires on one screw then that takes the switch out of the equation.

Transformer might be in the blower compartment, or mounted on the disconnect switch, or on a ceiling box. Sometimes the furnace transformer is used.

mattmia2

If i recall the sensing element in those is a strip of cellophane. Perhaps it disintegrated.

And yes, there should be 2 screws under the knob that hold the cover on.

EdTheHeaterMan

Depending on how the original technician installed the humidifier, your problem may be in several locations,
In the wiring diagram 5 below, the 24 volt transformer that operates the humidifier is wired to the blower motor heat speed. This way the transformer only gets power when the fan is operating. On the High temperature system wiring diagram, there is a thermal switch that limits the power to the solenoid in the event the fan is operating but the furnace is not operating.

So the sequence of operation is:

1. Call for humidity from humidistat (no spray yet)
2. Call for heat from the thermostat (no spray yet)
3. Furnace lights and flame is proven (no spray yet)
4. After the fan switch, or fan timer turns Furnace blower on heat speed, the 24 volt transformer is powered. (no spray yet)
5. The thermal switch in the humidifier closes when the duct is hot enough to evaporate the spray from the nozzle (now the spray is on)
6. Solenoid is powered and opens the valve to spray water.
7. Any of the following will stop the humidifier
a. Humidistat is satisfied
b. Thermostat is satisfied and the blower eventually stops
c. Thermal switch opens as a result of low air temperature in the supply plenum
d. Defective part: Humidistat, Transformer, Thermal switch, Clogged nozzle, Solenoid valve, Just to name a few.

If for some reason the transformer was not connected to the Heat Speed on the blower motor, (the 24 V is always on) there is an alternate wiring diagram that will prevent the humidifier from operating if the fan is not operating by measuring the air current in the duct using a Sail Switch

Sequence of operation is almost the same

1. Call for humidity from humidistat (no spray yet)
2. Call for heat from the thermostat (no spray yet)
3. Furnace lights and flame is proven (no spray yet)
4. After the fan switch, or fan timer turns Furnace blower on heat speed, the sail switch is activated. (no spray yet)
5. The thermal switch in the humidifier closes when the duct is hot enough to evaporate the spray from the nozzle (now the spray is on)
6. Solenoid is powered and opens the valve to spray water.
7. Any of the following will stop the humidifier
a. Humidistat is satisfied
b. Thermostat is satisfied and the blower eventually stops
c. Thermal switch opens as a result of low air temperature in the supply plenum
d. Sail switch contacts open
e. Defective part: Sail switch, Humidistat, Transformer, Thermal switch, Clogged nozzle, Solenoid valve, Just to name a few.

EdTheHeaterMan

If you are able to follow the wiring diagram that best matches your humidifier then you will be able, through the process of elimination, to determine where the 24 volt electricity to power the valve has been interrupted. or if the 24 volts is getting to the solenoid valve you can determine if the coil is defective or the valve is stuck or the nozzle is clogged.

If all this is beyond your DIY comfort zone, then you may need a professional.

I hope this helps. If you have any questions on this information, feel free to contact me here, or by direct message. I'm retired and have nothing better to do. LOL

Mr. Ed

pharmerphil

JUGHNE said:

You should hear a mechanical "click" when rotating the knob back and forth.
As you raise to a higher setting that first "click" should be the approximate humidity of the sensor. The second click is the differential for the control.

Perhaps if you pull the knob off there are screws behind it that hold the cover on.
The terminals are obvious under the cover.
If duct mounted there may be a hole in the ductwork for sensing air.

Early humidistats were a little wonky in operation, they are simply a switch.
If you jumper the screws with the wires or put both wires on one screw then that takes the switch out of the equation.

Transformer might be in the blower compartment, or mounted on the disconnect switch, or on a ceiling box. Sometimes the furnace transformer is used.

There were no screws behind the control knob, just an arrow and directions to pry tab at bottom to open. will check everything out this weekend

pharmerphil

EdTheHeaterMan said:

If you are able to follow the wiring diagram that best matches your humidifier then you will be able, through the process of elimination, to determine where the 24 volt electricity to power the valve has been interrupted. or if the 24 volts is getting to the solenoid valve you can determine if the coil is defective or the valve is stuck or the nozzle is clogged.

If all this is beyond your DIY comfort zone, then you may need a professional.

I hope this helps. If you have any questions on this information, feel free to contact me here, or by direct message. I'm retired and have nothing better to do. LOL

Mr. Ed

Thank You and I will get after this on the weekend, and I will message you if I get in over my head, Thanks again

pharmerphil

EdTheHeaterMan...Well I followed the best wiring diagram, wiggled this and that...And the worst thing happened, it now works, and don't know what I did to get voltage to the solenoid valve, However, once I did, it tested out at 12 volts, the old valve (which leaked) worked, the 24V. only hummed a bit. So I ordered a 12V. solenoid valve, all should be good, will go back and make sure all wiring connections are good. I should say that the transformer (found in the furnace housing, was taken off the old oil furnace (which the service man said the furnace was so old, that it came across on the Mayflower ) and installed on our 5 year old Lennox, I will keep You informed, Thank You Sir, for your help