How do you test a solenoid valve ? - Aprilaire 550 Humidifier

The solenoid valve unit will work upside down however, I am concerned that the tech that installed the unit might have installed it backwards. Look on the side of the valve the solenoid is connected to and you should find an arrow. Thats the direction of the water flow.A strainer helps keep the valve clean however if there is dirt in the valve it would be stuck opened not closed. Make sure the solenoid is getting power via float valve. If the solenoid is getting power you can tell by touching the top of the solenoid with a metal non magnetic screw driver. It will pull the screw driver like a magnet. Good luck

Did you just install this unit, or has it been working for a while and just stopped?
1. If you just installed it, the solenoid wires (yellow) must be hooked up to switch in when you have a call for heat.
a) use a current sense relay OR
b) connect 120V & neutral to "HUM" terminal and neutral on heater control board.
2. If it has worked before, maybe the saddle valve is plugged. Turn the "T" handle all the way clockwise, then all the way out CCW. You can hear the water start flowing. Loosen compression fitting at solenoid valve to make sure water is getting there.
3) Also, you must supply 24V to the circuit to open the solenoid valve. Check your wiring. It depends on the model what way to wire it and I cannot go into that here.
4) Testing: Turn off humidistat control. Turn on heat, wait for blower to come on. Turn humidistat control to test posn. Solenoid valve should click. This will put water into top of Aprilaire tray, after few minutes it will dribble out bottom clear vynl tube to the
drain.

May be an issue with the solenoid valve. check for voltage at the valve. if there are error codes check the owners manual for cause. I am providing a link to the manual if you don't already have one. the last thing to check would be the control itself. the control and the solenoid valve are the 2 main items for the unit. hope this helps.
http://www.aprilaire.com/themes/aa/en/manuals/AA-Humidifier-Owners.pdf

It sounds like you got it...

The solenoid will not open with only 13 volts to it. Jump or apply the full 24-27 volts to the solenoid and see if it clicks and opens and allows water to flow.

If the valve still won't open or pass water, start looking for a plugged inlet solenoid inlet screen or a faulty solenoid valve as well as a faulty humidistat.

Turn off the water to the humidifier

Disconnect the water line to the inlet water valve (the solenoid), catch any excess water or drips in a small container

Turn the water back on slowly and see if water flows through the open line (the one you just disconnected - catch the water in a small bucket)

If you have water to the valve, it's probably the solenoid valve - you can test this by reconnecting the water line and turning the humidistat all the way up. You should hear a click as the solenoid tries to open. If it clicks and no water comes out it's the valve. If there is no water to the valve, you'll need to determine the reason(s). Although not every water valve has one, check for a plugged inlet screen at the entry to the water valve (solenoid)
Sometimes the small line tap valves commonly used with humidifiers can plug up or malfunction. If you try to repair or replace the tap valve, make sure the water is turned off.
If no click, it could be the humidistat or there is no power to the unit.
If the humidistat is bad, you won't hear any click and no power will be sent to the solenoid valve. In that case, the humidistat may be defective.

Depending on your comfort level and knowledge, you can try applying power directly to the valve by bypassing the humidistat, but only try this if you are comfortable working with electricity. The voltage should be around 24 volts (in the USA) , which is low, but requires some knowledge.

Most likely you have crud buildup in the solenoid valve. But first make sure that you test accross the solenoid connections for voltage when the furnace is OFF. Put your meter to AC volts and see if you see 24 Volts when furnace is ON and 0 Volts when furnace is OFF. If you get those readings then you need to replace your solenoid valve.
Available from mfg for about $55-60
or on ebay for about $40 shipped.
search for Aprilaire 4040 Solenoid

If the above tests fail, you will need to ensure that the wiring is correct and not shorted, but is probably your valve. Install a fridge water filter in the water line to help prevent this in the future.

the change water panel light is just a timer. it does not sense that the water panel actually needs to be replaced. sounds like you have a solenoid issue. if you have water to the solenoid and are certain you are getting 24v to it, the solenoid is ethier bad or plugged with calcium. most likely calcium. sometimes you can take them apart and clean them. so, it you can hear clicking at the solenoid when you turn the humidstat up and down. try cleaning it.

That is not a 'motor' on the side of the humidifier housing, it is a solenoid valve. The water feeds in to one side and exits the other side to a tube that feeds in to the top of the humidifier unit. The valve opens and allows water to flow when electrical power is applied to the valve

The valve electircal requirement may be either 120 vac or 24 vac. Power typically is switched on and off by a Humidistat control. The power feed to the Humidistat may come from a small transformer if the valve is a 24 vac unit, or directly from a furnace connection if the valve is a 120 vac unit. There are many variations, though.

A qualified licensed eletrician should check the power feed to the valve. If there is no power feed to the valve then he can trace back to the point of failure and correct the issue ... but he must also check for additional issues with the valve itself, as noted below.

Other possibles reasons for solenoid valve failure:

If power feed to the valve tests ok, then the coil inside the solenoid may be 'open' (bad, no continuity). The electrician can test the coil by checking resistance or continuity of the coil.

A non-electrical problem is that the valve path may be blocked by hardwater mineral build-up or other foreign material that flowed through the water line.

The solenoid valve must be replaced if either of the above is true with your valve.

Remember, use only a quailified licensed electrician!

Hello All,

Was having a similar problem. Disconnected the source line and opened saddle valve. I was getting water to the solenoid but nothing out the other side. My humidistat doesn't have a "test" setting, it's either off or the highest humidity. I held the outbound line in my hand and experimented with adjusting both sadlle valve and humidistat. I didn't get any water until I opened the saddle valve MUCH further than I thought was necessary and turned the humidistat to near the highest setting. Once I had water coming though I experimented with the setting on the humidistat, turning it off and then slowly increasing the humidity until the solenoid clunked and water started coming out. I would recommend anyone having this same problem to open the saddle valve all the way (I was surprised how many turns that took) and set the humiditstat to it's highest setting.

Randall

Have you checked the position and function of the floats in the pan?