Condensate float switch (safety switch) question

[Git]

So back in April we had a new Lennox HVAC system installed to replace our 17- year old system that had just failed (problem with the condenser and it was R22)

A couple of weeks ago, the thermostat went completely dead. It is one of those iPad looking devices and I did some initial troubleshooting, determined everything was getting power on my end and then called the contractor. It took them a couple of days to come out (non emergency) and the technician said he found the problem - a loose wire in the thermostat wiring where a wire nut had come off...

Everything was fine until yesterday when it happened again. Everything was dead but this time the overnight temps were going to be in the upper 30's. I got the contractor to send out a tech and they were able to find the problem - a faulty 'float switch' in the condensate line.

Now this is where my question comes in. It appears to me from googling around that there are two ways to wire in these float switches. One way is to break the thermostat wire which provides power to the thermostat which in effect kills the entire system (which is how my contractor did it). The other way would be to break the wire which would just turn off the outdoor condenser leaving the rest of the system to function, like the heater...

(I did find some Lennox literature that indicates 'wire kit to shut down compressor per instructions' - see pic)

I see mixed opinions about this on the internet. From a homeowner's point of view, I think the second way is better since it would have allowed us to run the furnace. But is there a specific reason why not to do it this way?

I should add there were zero problems with our condensate drain line - the problem was completely with the switch which was replaced

 

[yeldogt]

if you have a high efficiency furnace they condense as well

 

[Git]

You bring up a good point - my salesman mentioned that when I asked him about it, although it is hard to say how much condensation is produced when the furnace is running.

This morning I called Lenox and they put me in touch with another local dealer and they said they wire the switch to only kill the compressor

 

[brewchief]

The furnace will make a lot of condensate, is the switch mounted at the A/C coil? If so it's pretty much only going to be useful if the A/C drain plugs anyway so better to just kill the A/C.
If it's a furnace in an attic and the switch is in a pan under everything then I want it to shut everything down.

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[LS6 Tommy]

You bring up a good point - my salesman mentioned that when I asked him about it, although it is hard to say how much condensation is produced when the furnace is running.

This morning I called Lenox and they put me in touch with another local dealer and they said they wire the switch to only kill the compressor

A typical 100k condensing furnace makes about 8/10 gallon of condensate per hour. If the float switch is on the outlet of the evaporator drain, only break the "Y" cirtcuit. If it's in the condensate pump or if the furnace drain shares a trap with the evporator, break the "R".

Tommy

 

[Git]

Thanks for the info guys.

Not sure what they did, this is the only pic I have at the moment, and I don't feel like going up into the attic right now... You can just barely make out the edge of the drain panel under the coil and the float switch in front of it. Furnace is installed on it's side, and I don't think there is a pan under it, per se. That pvc pipe running across the floor gets plumbed into a bathroom sink plumbing and is the main drain line. There is also a secondary drain line that runs out to the eaves over one of the windows

If the furnace makes that much water, it sounds like it would be best to shut down everything then. I am just surprised that in 2020, and with a top of the line Lenox unit there is not some way to throw a code, sound an alarm or something to indicate there is a problem with condensate drain, instead of just shutting down everything dead. After all, the first tech that came out apparently missed it.

Edited to add - for other people reading this, just something else to look for in case you AC does not start up when it should. Along with checking the capacitor, maybe look for a tripped float switch. Before this happened to me, I would have never thought/know about it to check

 

[brewchief]

That's an 80% furnace so it won't make condensate, I would wire it to only kill the A/C. If it's a communicating system( XC 20 or XC 25) then you want it wired to break the red wire going to yhe outside unit.
One would think that they would have a simple way to add a condensate safety switch and have it give a code to the thermostat when tripped but they don't, don't get me started on the extra **** you have to do for utility load shedding either.

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[Git]

That's an 80% furnace so it won't make condensate, I would wire it to only kill the A/C. If it's a communicating system( XC 20 or XC 25) then you want it wired to break the red wire going to yhe outside unit.
One would think that they would have a simple way to add a condensate safety switch and have it give a code to the thermostat when tripped but they don't, don't get me started on the extra **** you have to do for utility load shedding either.

You would think... I dug through the installation manual tonight. Almost 6 pages of error codes.

Yes, it is a XC25 outdoor unit with the SL280NV series furnace that has an 80% efficiency rating, so I will keep it in mind about the wiring. Nothing in the SL280NV installation manual about a condensate trap or drain plumbing, yet their SL297 series (97% Efficient) clearly indicates the requirement.

Still waiting to hear back from the installer why the felt it was better to shut down my entire system instead of just the outdoor unit. At least I am better informed now - thanks

This is from the SL297 series manual showing the drain pan under both units as well as two drain lines

 

[nadogail]

There is no way I would want condensate forming in my attic without a float operated safety shutoff.

After my new furnace and AC were installed, and the drain pan overflowed, my HVAC contractor was out here twice to repair the ceiling. I am sure they lost money, but gained a loyal customer, on that job.

 

[LS6 Tommy]

Call your contractor back. They need to install an emergency pan under the unit. It's required by code. It also must have its own drain, it can't be tied into the existing condensate drain.

I'm sorry to say it, but the "octopus" flex duct setup speaks volumes to me about the quality of the installation. There's a lot of "wrong" going on there...


Tommy

 

[Git]

Unfortunately, that ductwork you see is pretty standard in S Cal. There is a drain pan under the coil - the furnace doesn't need one because like brewchief mentioned, it is an 80% efficient furnace and does not produce condensate

 

[brewchief]

Call your contractor back. They need to install an emergency pan under the unit. It's required by code. It also must have its own drain, it can't be tied into the existing condensate drain.

I'm sorry to say it, but the "octopus" flex duct setup speaks volumes to me about the quality of the installation. There's a lot of "wrong" going on there...


Tommy

Code here in MI allows for a switch to be installed in the secondary drain line opening in the coils drain pan, I prefer a separate pan with a wet switch. I personally don't like a seperate secondary drain instead of a switch because people will continue to run the equipment until that drain plugs up as well and the secondary overflows.

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