Troubleshooting the solenoid and humidstat

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Old 01-19-15, 02:33 PM
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Troubleshooting the solenoid and humidstat

Hi, I'd like to help my neighbour with is White-Rodgers (HFT2100) Central Humidifier.

I noticed there is no water coming thru even if I turn the dial on the Humidstat and I do hear the click.

Next time I go over I will verify the incoming water line, if not clogged, but my questions are:

1. Can you please tell the steps on how to test the voltage and continuity on the solenoid.

2. Can I test the Humidstat with a multi-meter, i.e. voltage and continuity ?

Your help would be greatly appreciated. Thanks!
 
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Old 01-19-15, 02:39 PM
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Both can be checked with an ohmmeter. The solenoid should show a low resistance.....probably under 100 ohms and the humidistat should show near 0 ohms when calling for humidity.

The solenoid needs 24vac to open.
 
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Old 01-19-15, 07:53 PM
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Thanks for the info. Excuse my ignorance but can you please be more specific on the steps.

Here is how I would do it, correct me if I'm wrong:

1. Solenoid continuity testing:

- turn off furnace power supply
- disconnect the wires in between Humidistat and Solenoid
- put each probe of the multi-meter on each of the 2 solenoid's wires
- verify resistance (number) on multi-meter
- should show a low resistance (per your previous entry)

2. Humidistat continuity testing:

- turn off furnace power supply
- disconnect the 2 wires from Humidistat and Solenoid
- put each probe of the multi-meter on each of the 2 terminals of the Humidistat
- verify resistance (number) on multi-meter

I believe before I turn the furnace "off", I have to make sure the humidistat dial is at the "on" (on going) position and that the furnace was working (heating), otherwise I think the Humidistat would be in an "off" state, is this correct ?

Thanks!
 
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Old 01-19-15, 09:47 PM
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You are correct. The humidistat is a basic switch. It doesn't require any power to operate. It doesn't matter if on or off when turning furnace off.

You should hear a distinct click when turning the h'stat to max humidity.
 
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