Air Conditioning - float switch on A/C?

Hi there,

I have a central air conditioning unit in the "attic" (I put that in quotes because there's barely room up there to wriggle in on your belly next to the A/C unit). Recently, the condensation drain line clogged, leading to an overflow down into the wall and out into the carpets on the 2nd floor. I wriggled in there and snaked out the drain line, which fixed things.

My father-in-law suggested that I have a float switch installed, so that when the drain gets clogged again, the float rises and cuts off power before the water can overflow. However, our unit does not have an obvious drain pan, so I don't even know where the float switch would go, exactly. The condensation drips down inside the unit, and the condensation drain line is attached to the side of the unit. There is also a small hole, maybe 1 cm in diameter, next to but slightly above where the drain line is attached to the A/C unit - you can see the condensation through this hole, and it's through the hole that the water overflowed when the drain line was clogged.

There appears to be a switch on the outside of the unit which can be used to turn it off.

So, given this:
1) Is it even possible to install an aftermarket float switch? All the ones I've seen are built-in to the particular A/C model.

2) If so, how much, ballpark, does it usually cost to have one installed?

Thanks for your help!!!

Regards,
Bill

p.s. Unfortunately, I don't have the brand + model of the A/C unit...

The first thing you need is a secondary drain pan which goes under the entire air handler. The drain from this secondary pan must be isolated from the primary drain. Float switches are very inexpensive & easy to install in the secondary pan.

Like Grady said you really really should have a secondary pan up there. If that's just not possible there are safety switchs that install on the condensate line.

Copy and paste this into your browser and this is one type.

http://www.grainger.com/Grainger/items/4NY29

Another which is a great unit is made by EZ Trap

http://www.eztrap.com/documents/products/S1D-Product-overview-220series.pdf

Thanks for the great info and links to the float switch products!! When I get home tonight, I'll crawl up there and see if it's possible to put in a secondary pan, but I must admit it doesn't seem likely. I don't know how I can lift the unit in the confined space (I can't even kneel, let alone stand up in the cramped space). Maybe I'll try and take a few pics and post them so you guys can see what I'm talking about.

As an aside, how does that first float switch (the one listed on Grainger's site) work? It looks like you just put it in-line with the condensation drain line, but I don't understand how the water level goes up in the vertical piece, even if the drain is clogged. I guess it has to go at a lower level than the connection of the drain to the A/C unit?

The secondary pan can be very shallow and doesn't really need to have a drain, they make a very cool little device that you will find at most parts houses that senses moisture and trips a relay. I put one in my attic and when my drain line air locked the secondary pan barely had a puddle in it when the relay tripped. I wired the relay up normally closed to the line going to the condensing unit. You could also wire the normally open side to a 24vac light so you would catch the alarm before the house got warm.

Check local regulations regarding the secondary pan. Here, the pan must have a drain, it must be totally separated from the primary drain, & drain to a place readily visible to the residents of the dwelling. When I can, I like to terminate that secondary drain above the front door of the house. By doing so, if the homeowner walks out & gets dripped on he knows that is the "emergency" drain & he'd better find out what's going on.