Background / Motivation:

Like many people my furnace runs much the winter,  so I need a humidifer to keep the air from getting too dry.  When the furnace runs a lot, the humidifier needs to be re-fill every day, sometimes twice a day. 

My humidfier is located in the utility room and there's a faucet nearby  - so all that was needed was a way to automatically refill the humidifer from that water source.

Basic Idea:

With just a few basic components it was surprizingly easy to create a simple auto-fill system. 

1) An electric solenoid valve & power supply - commonly used for irrigation systems and readily availabe at a Home Depot or Lowe's. 

2) A DIY float and a limit switch, this energizes the solenoid valve to refill the humidifer tank if it's low.

3) Common lamp / appliance timer (the kind you might use to turn the lights on and off while on vacation).   With this you can scheudle a few "fill check & re-fill if needed" cycles each day.

4) A few hose and electical connectors. 

You should be able to get everything locally except prehaps the limit switch, total cost should be < $50.  Say goodbye to manual refilling !!

Another Option
- Of course the best solution, allbeit at more cost and complexity, is a whole house humdifier that attaches to a forced air furnace. 


Step 1: Will This Work for My Humidifier ??

The first requirement is that there be a COLD WATER source near  your humidifier.  I my case, there was an utility room faucet available. 

If you can locate the humidifier near a sink you may be able to "tee into" the water line feeding the sink. 

Secondly, check that with the humidifier's fill tank removed, you have a clear line of sight to water reservoir (see photo).  This is to accomodate the float and limit switch hardware you'll need to install. 

If space is tight, the solenoid valve can be mounted somewhere other than directly onboard the humidier itself - just route the outlet line from the solenoid valve to the humidifier water reservoir.

The instructions that follow at specific to my model humidifer, you may need to make some adjustments to suit your humidifier.

This is a great project! I had been thinking about something like this but you saved me some work! I used a Lasko 1128 9-gallon humidifier which I got on Amazon for $79. http://www.amazon.com/gp/product/B000VP7FWA/ref=oh_details_o00_s00_i00 <br> <br>I made some mods. I used a pill bottle instead of the light bulb for a float, and screwed a dowel on top of the bottle lid that rises up and activates the limit switch. Mounted the valve and transformer externally. I had to Dremel away the inner plastic ledge at the bottom of the tank to allow enough room for the float to operate, and used eye bolts to guide the dowel of the float. <br> <br>I would add that the appliance timer adds the important feature of hysteresis to the system, which lets the valve turn on and off once a day, rather than constantly be switching every time the water level drops a little bit. <br> <br>Very clever! <br>

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