We had an Aprilaire humidifier (600 model) installed in a new house 2.9 years ago. About a year ago, the humidifier began leaking water all over the basement floor. This has happened 3 times with 3 visits from a heating a cooling company tech to fix the problem. We just had the biggest flood yesterday - water was literally pouring out of the I think the front of the humidifier. I need to know what to ask the h/c technician who will come again to fix the problem. Doesn't it seem that there is broken part that should be replaced to stop this from happening? I know nothing about humidifiers and neither does my husband and we're about ready to toss it out. Any tips would be appreciated.
Here is a diagram of that model from Aprilaire. The drain tube (#9 in the diagram) might be clogged. Look on page 11 section 9 for further instructions about the drain tube. Also, check the main water outlet where the tube connects to the bottom of the pan to make sure drainage isn't restricted. Check the pipe that the drain tube is connected to. It could be clogged as well.
Humidifier is a simple device, you need a new heating guy. 3 visits and he can't solve it. Not good. A handy friend should be able to identify the problem in a matter of minutes. Clogged drain, misaligned pad, cracked or dislodged 1/4 " water supply. Even if the solenoid was stuck open it should not leak.
The problem I have seen is a small chunk of scale or sand blocking the valve from closing. I started installing mesh screens prior to these valves similar to what is used in washing machines. The screens do need to be cleaned when they plug up with scale and debris, but this is better than a flood. Depending on your supply line, a small inline filter may be a good choice, but this has been the cause for several leaks that I have found. With both the mostly plastic valves and the more expensive brass and stainless models, I have disassembled the valves and been able to clean them. When the valve gets ~8-10 years old the diaphragm needs to be replaced. On the brass ones there are rebuild kits for ~$15. The plastic ones I just replace.