HVAC Overflow Flood Detection and Preventative Shutdown
Saturday, October 12, 2013 at 8:39AM
Robert Savage in Home Appliances, Home Automation, Home Security, Home Systems, automation, flood, home, sensor, water

This summer I was confronted with an air conditioner evaporator drainage problem.  My air conditioner's primary drain line became clogged and the air conditioner began draining into its overflow pan and draining to an outside location.  I was fortunate that the system worked as designed and thus there were no leaks in the house, but this may not always be the case.  When I was younger, I used to work in home repair and received numerous calls from customers with this same problem except in many cases their overflow drains were also clogged and their overflow pan would spill over resulting in water damage to ceilings and sheetrock (not to mention personal property in the path).  It is surprisingly common for the emergency overflow drain to get clogged with insulation from the attic as well as cobwebs from spiders and other insects that nest in the pipe.     

The overflow drainage lines are typically designed to drain in a place where they will be noticed by the homeowner.  Commonly this emergency drain is located in either above bath/shower location (common for apartments/townhouses) or outside back porch.  The intent is to draw attention to the problem.  Unfortunately many homeowners are not aware that seeing water drain from these locations represents an underlying problem that needs immediate attention.   

Homeowners are also instructed to routinely clean the primary and overflow drain lines using a bleach/water mix. But in reality your average homeowner is not performing this maintenance. 



So there has to be a better way ... right?  I want a more proactive means of getting notified in the event of a leak/drainage problem.  In case I am not present to address the issue, I want the system to shutdown to prevent any damage until the issue is corrected.  I want a "smarter" solution than the passive overflow drain which is not a fool-proof solution.

So after a bit a research (that is what I like to call shopping on Amazon and reading product reviews) I found a variety of solutions.  Some involved modifications to the drain lines and others were simply alarms to help draw attention to the problem, but most of them didn't do anything to stop potential flooding.  However the solution that I found that best suited by needs, goals and budget was the:


Diversitech® WS-1 - Wet Switch Flood Detector


The Diversitech® WS-1 - Wet Switch Flood Detector is placed directly in the overflow pan and upon water detection it shuts down the HVAC system.  This is a simple solution that can be easily installed into any existing system without further modification.  This solution proactively shuts down the HVAC system to prevent continued water spillage into the overflow pan.  When you notice that your HVAC system is no longer cooling, you can inspect the The Diversitech® WS-1 - Wet Switch Flood Detector and overflow pan to see if there is a problem with your AC system.   

Apart from simply noticing that the HVAC system is not cooling , the Diversitech® WS-1 - Wet Switch Flood Detector also includes additional wiring leads that can be connected to you central alarm system or other device for alert notifications.  You can optionally purchase the Diversitech Universal Alarm UA-1 accessory which can be connected to provide an audible alarm.  (I have mine connected to my Ecobee HVAC thermostat system for alert notifications --- I'll be posting a follow-up article detailing that installation.

What's In The Box

The Diversitech® WS-1 - Wet Switch Flood Detector comes with wiring nuts, instructions, and a warning label to affix to the HVAC unit.

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Installation Instructions

The installation instructions provided with the Diversitech® WS-1 - Wet Switch Flood Detector are provided below.  (You can also download a PDF file including these instructions here.)

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Installing the Diversitech® WS-1 - Wet Switch Flood Detector is actually pretty simple.  If you have basic electrical skills or have ever replaced a thermostat then installing the Diversitech® WS-1 - Wet Switch Flood Detector will be a snap.  If you are not comfortable installing this on your own, any HVAC professional should be able to install and fully test the wetswitch in under an hour.  

Once the installation is complete, make sure to place the wetswitch in your overflow pan.  You should place it close to the drain pipe as the drain pan may be contoured or leveled to force overflow water to flow towards the drain pipe.



You should test your wetswitch by placing it in a small container of water to make sure the wetswitch trips properly and shuts down the HVAC system.  The wetswitch should have the green LED illuminated before you place it in the water.  After placing it in water, the wetswitch should illuminate the red LED indicating a TRIPPED condition.  While tripped, the HVAC system should remain off.  If wired as described above, the wetswitch opens (disconnects) the common lead to the thermostat, thus powering off the thermostat which in turn should power off the HVAC fan and condender/compressor.   (You can alternatively wire your system to only disable the compressor if you prefer to keep the thermostat and blower fan working during a tripped condition.)

Note:  You can also use the TEST button on the wetswitch; however, I prefer a real world test with water.  

You can press the RESET button to reset the wetswitch.  Please note that the wetswitch must dry out before the RESET will work.  This could take in excess of an hour to dry out.  

Green LED when NORMALSaturate the WetSwtich in waterRed LED when TRIPPED

Here is a short video demonstrating a test of the Diversitech® WS-1 - Wet Switch Flood Detector.

Below is a video from the manufacturer:

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