Lennox Heat Pump Overflow Switch Wiring Confirmation

[rob_in_fla]

I'm concerned the Safe-T-Switch SS2 (original version) on my interior unit was wired incorrectly. The drain line recently clogged, and the switch shut it off...more or less. Nest showed error E74 - no power to Rh wire.

However, the interior unit was "humming" (sounded like a motor that was energized but unable to turn), and the copper refrigerant tube was very hot. Is this normal when the overflow switch turns it off?

The SS2 is connected to the R wire. Should it be connected to Y1 (compressor) or another wire instead? The installation manual for my unit doesn't specify, but the one for a similar but newer model specifies that it should shut off the compressor.

I opened the cabinet, vacuumed the collected water, and cleaned the drain lines and the SS2. Everything then operated normally. I can recreate the humming by manually sliding the float to simulate water in the line. I did not check if the exterior unit continued to run, but I could easily test it.

The HVAC system is original to my house (16 years old). It's obviously been repaired at least once prior to me buying the house 11 years ago. The original transformer has been bypassed to another transformer with cut wires and splices everywhere. I wouldn't be surprised if a "tech" screwed something up based on other messes I've uncovered.

Equipment list:

• Interior - Lennox CB28UH-018/024-230-01
• Exterior - Lennox 12HPB24-10P
• Tstat - Nest 3rd gen

Thanks in advance.

[Bazooka Joe]

Lift up the switch, if blower shuts off then have someone check to see if the outdoor unit shuts off for starters.

Run in cool mode and if the larger insulated line is hot to the touch then your outdoor unit is running in heat mode when it should be off when overflow switch is tripped?


Check when your unit is running normally in cool mode to the smaller and larger insulated line then compare when you simulate a plugged line and the float switch is energized.

https://www.lennox.com/lib/legacy-re...cb28uh_iom.pdf

Looks to have the PSC blower motor by looking at wiring diagram so if the motor actually shuts off and you hear a humming noise, possibly that is the transformer. Is the humming noise by the Air Handler present when system is off?

[garyed]

There is more than one way to wire a float switch but the one thing that is crucial is that the outside unit shuts off when the switch is tripped.

[rob_in_fla]

Thanks for the feedback.

Lift up the switch, if blower shuts off then have someone check to see if the outdoor unit shuts off for starters.

I plan to do this later today.

Says you have a Heat Pump, so if your running in cool mode and the larger line is hot then your running in heat mode.

Check when your unit is running normally in cool mode to the smaller and larger insulated line then compare when you simulate a plugged line and the float switch is energized.

Yes, it's a heat pump running in cool mode. It's the liquid (smaller) line that was hot. This line is normally cool when running in cool mode. I didn't check or don't remember if the suction line was warm or cold. The blower turned on and the liquid line immediately began to cool once the drain was cleared and the float dropped on the switch. When I simulate a plugged line, the blower stops, the liquid line starts to warm up, and something hums.

For reference, this is the Nest wiring:

Y1 - Heat/Cool		W1 - empty
Y2 - empty		W2/Aux - Aux Heat
G - Fan		C - 24V Common
O/B - Heat Pump		* (star) - empty
Rc - empty		Rh - Power

[Bazooka Joe]

“It's the liquid (smaller) line that was hot. This line is normally cool when running in cool mode.”

If the liquid line was hot ( not warm to the touch but actually hot ) then chances it went to heat mode, as if you loose your blower fan in cool mode ( while in cool mode ) the indoor coil starts to ice up and even the larger line ices up to the compressor and the liquid line starts to feel cooler.

Again when the blower motor stops running and you hear the hum, it could be the transformer, as that’s energized 24/7. Do you hear the transformer humming at the Air Handler when the system is completely off, no blower, no outdoor unit running?

[rob_in_fla]

Looks to have the PSC blower motor by looking at wiring diagram so if the motor actually shuts off and you hear a humming noise, possibly that is the transformer. Is the humming noise by the Air Handler present when system is off?

No, it does not hum when the power is off. I have a new original transformer that I intend to replace the generic one that was previously installed.

[rob_in_fla]

If the liquid line was hot ( not warm to the touch but actually hot ) then chances it went to heat mode, as if you loose your blower fan in cool mode ( while in cool mode ) the indoor coil starts to ice up and even the larger line ices up to the compressor and the liquid line starts to feel cooler.

Why would it switch to heat mode? I live in Florida. It's still summer. And, yes, it was hot, not warm.

[Bazooka Joe]

Why would it switch to heat mode? I live in Florida. It's still summer. And, yes, it was hot, not warm.

Again you need to verify if the outdoor unit is running ( when float is energized ) when the liquid line is hot, how hard is that to do? if it is when you lift the plunger of the float, chances it’s in heat mode, the larger insulated vapor line should be hot also if it’s in heat mode. Check that also.

How about being more detailed oriented, as an example I lifted the plunger, and set it to where it stayed energized, the blower motor stopped, I went outside and the unit was/was not running. I felt both lines, I couldn’t tell if it was in heat or cool mode. I touched both the liquid line and vapor line and both where extremely hot to the touch.

Or I think it was in cool mode as the discharge ( rejected ) air temperature from the outside unit was hotter than the inlet temperature ( ambient surrounding air ) entering the coils. Or I noticed the discharge temperature at the outdoor unit was cooler than the ambient surrounding temperature ( which would indicate your in heat mode )

Heard here that nest are garbage thermostat, maybe you got gremlins in your system due to your thermostat?

Why not call for service if you have issues?

[rob_in_fla]

Again you need to verify if the outdoor unit is running when the liquid line is hot, how hard is that to do? if it is when you lift the plunger of the float, chances it’s in heat mode, the larger insulated vapor line should be hot also if it’s in heat mode.

Why not call for service if you have issues?

It's only hard because I'm 50 miles away at the moment. My arms simply aren't that long. I'm going to check this as soon as I get home in a couple of hours.

Since cleaning the drain and switch, I've had no issues at all. I just wanted to know if the other symptoms (humming and hot liquid line) would be expected when the switch shuts off the unit. I suspect they're not normal, but as long as I maintain the lines, they shouldn't be an issue.

I've also read different opinions as to whether the switch should be wired through R/Rh, Y1, or common. There's really no consensus other than it should shut off the outside unit, too. Again, I'll check this when I get home.

I'm now curious as to how it could switch to heat mode, if it is. The thermostat shouldn't be sending that signal. The wiring seems to be correct: it cools my house on hot days, warms it on cold days, and the auxiliary heat kicks in on colder days.

I call for service when the issues exceed my abilities. I may be near my limit here. I want to be more educated if/when I call. I don't like getting screwed.

I sincerely appreciate your feedback and tips on what to check. Thank you.

[rob_in_fla]

How about being more detailed oriented, as an example I lifted the plunger, and set it to where it stayed energized, the blower motor stopped, I went outside and the unit was/was not running. I felt both lines, I couldn’t tell if it was in heat or cool mode. I touched both the liquid line and vapor line and both where extremely hot to the touch.

Or I think it was in cool mode as the discharge ( rejected ) air temperature from the outside unit was hotter than the inlet temperature ( ambient surrounding air ) entering the coils. Or I noticed the discharge temperature at the outdoor unit was cooler than the ambient surrounding temperature ( which would indicate your in heat mode )

All good advice, and I would normally do all of those things. 11:30pm on a Tuesday night after a 12-hour day, trying to not disturb my neighbors, and 3 weeks after my dad died...well, I wasn't firing on all cylinders.

Heard here that nest are garbage thermostat, maybe you got gremlins in your system due to your thermostat?

I'm not exactly impressed with them, but they're what I have at the moment. Can you recommend a better alternative?

[Bazooka Joe]

I'm not exactly impressed with them, but they're what I have at the moment. Can you recommend a better alternative?

I’m old school, I don’t like over the top more complicated bells and whistles thermostats. A simple Honeywell Focus Pro 6000 series as an example only or something like that in those tier line works for me with a emergency heat setting.

Others here can recommend their favorite Heat Pump rated stat.

[HVAC_Marc]

Nest is really poo. If you want a smarter more reliable stat try Ecobee. If you want just plain reliable almost anything Honeywell is fine.

The small line will be hot in heating mode, condenser fan failure mode, or dirty condenser mode.

[pecmsg]

The NEST is a bigger issue

[pacnw]

Why would it switch to heat mode? I live in Florida. It's still summer. And, yes, it was hot, not warm.

NEST "thermostat".

[mgenius33]

NEST is the only thermostat I find fails by randomly energizing half of the proper signals. Most other thermostats have better redundancy, meaning they either work or they don't. That's why NEST is garbage.