Auxiliary Drain Pan Switch Testing

[Robert Foster]

I'm interested to know how many of us check the cut off switches installed in auxiliary drain pans for proper function.

If you do check them, can you share your process and what you consider proper function, as in do you think the whole system should shut down or just the exterior coil.

Thanks

[David Bell]

It's best to wire those to break R so the occupants will be aware the is a problem right away.

[Scott Patterson]

I'm interested to know how many of us check the cut off switches installed in auxiliary drain pans for proper function.

If you do check them, can you share your process and what you consider proper function, as in do you think the whole system should shut down or just the exterior coil.

Thanks

If it turns off the condenser unit then that is all that is needed. Once that compressor is off the system will stop producing condensate, the temperature in the home will rise and it won't be long before the occupants realize that something ain't right.

I look at the switches but I do not test them. Most I see are float type switches and some work on contact with moisture. If the float type switch is all cattywhompus I will note that it looks like it needs adjustment for it to work properly.

The ones I see are low voltage and if you want to pull and use the "I'm not required to inspect low voltage equipment" card I guess you could get away with it.

[Rod Butler]

If you have a condensing furnace you would want the switch to shut the system down.

[Robert Foster]

I'm surprised how little response this has generated considering the ramifications of an overflowing pan.

Thank you to those that did respond.

[Jerry Peck]

I'm surprised how little response this has generated considering the ramifications of an overflowing pan.

Thank you to those that did respond.


If it turns off the condenser unit then that is all that is needed. Once that compressor is off the system will stop producing condensate, the temperature in the home will rise and it won't be long before the occupants realize that something ain't right.

Most that I saw were wired to shut the condenser down, thus testing the float switch while in the attic does nothing because you cannot hear the condenser unit running or turning off, and there is no reason to report the switch as not be good when, in fact, it did shut the condenser unit off.

A reason for shutting down the air handler instead of the condenser is that if the auxiliary drain pan is already full (I've found this many times), shutting down the air handler keeps the coil iced up. It still gets hot inside the house, but if the float switch shuts the condenser down and leaves the air handler running, then the block of ice on the evaporator coil will begin to melt ... and there is no place for that water to go as the auxiliary pan is already *full*.

I would write them up if, as Scott said, the switch was not installed properly and if the switch was one of the old types which was a micro-switch with the lever resting on and aspirin tablet. The theory was that when water gets in the pan the aspirin tablet dissolves and the switch shuts off - good theory and it worked, the problem was that humidity in the air, at least in South Florida, would basically 'dissolve' the tablet with no water in the pan, only air pressure (it seemed) held the aspirin tablet together, one slight bump and the aspirin tablet would crumble into powder ... now the unit is off and what do you do because you caused it to shut down? Those were an automatic write-up for me.

Robert,

I think there were few replies because Scott covered it pretty good with his reply.

[Robert Foster]

Thanks Jerry.

Climbing out of the attic to go check the outdoor coil is a PITA...maybe I'll reconsider this whole process, could sure use the time saved for other things.

[Rod Butler]

So "what-if" you have a condensing furnace producing condensate and for whatever reason the aux pan fills? The float switch shuts off the condensing unit, which hopefully is not on because the unit is in the heating mode, and the unit continues to produce condensate.

The only time you'll know is when the gyp ceiling becomes saturated and comes crashing down.

Also if the unit is properly installed the furnace fan shutting down should also shut down the condensing unit.

[Jack Feldmann]

To the original question...I do not test them.
To Jerry.... how does shutting down the air handler keep the coil iced up?

[Jerry Peck]

To the original question...I do not test them.
To Jerry.... how does shutting down the air handler keep the coil iced up?

The compressor keeps running and no air is blowing over the coil. The block of ice just gets bigger.

However the a/c technician connected the float switch is what it will turn off. I found many which turned off the air handler (presumably turned off the condenser unit too, but I did not check), and many which did not turn off the air handler (presumably, the condenser unit turned off, again, I did not check).

Being as there is no reasonable way for one person to see if the compressor shuts off, I stopped checking those switches. I did look to see how they were installed and wrote the ones up which did not look like they would properly activate based on their installation. Typically, there were plenty of things for the a/c technician to check out and repair, the float switch was just one more item on that list to check and properly install.

For inspectors who work tag-team with another inspector, as some do, then one person could be in the attic and the other person could be outside at the condenser units.

[Paul Kondzich]

A few years ago I was in an attic checking out an air handler. The float switch was laying in the auxilliary pan. Like an idiot (maybe I was in a good mood), I mounted the switch back on the side of the pan where it had been before. I made sure the condensing unit and air handler were operating when I left. Everything was working fine. (This is South Florida, no furnace) About 4 hours later I got a call from the tenant that there was no A/C. I went back and laid the overflow swith back in the pan, took a picture, and simply reported what I saw. Just like I was taught !!!!