LD1
Epic Contributor
Having some issues with my HVAC unit. Looking to see if any knowledgable folks have ever had similar issues like this before.
The unit is a 4-ton Geo-cool geothermal unit, with a Pro1 digital t-stat.
There are 4 diagnostic LEDS on the front of the furnace. High pressure, Low pressure, Auxiliary, and float switch (for condensate).
What happens, intermittently (like once a week) is the t-stat will call for heat, and the fan will kick on, but the compressor (and pumps that run off that same contactor) never come on. So it isnt until its ran awhile that I think " boy its been running awhile and still not up to temp". So I walk over and feel a register vent.....sure enough, no heat. SO I walk to the basement and see all the LED's flashing. Simply turning the unit off via the t-stat, waiting a few minutes, and trying again solves the issue.
I spoke with tech support, they said all the LED's flashing is an indication that the 24v transformer is either putting out too much voltage, or not enough. I "think" he said is +/-20%, but that was a week ago.
This morning I finally got around to prodding around with the meter to dig a little deeper into this issue. At a resting normalized state, I am getting 245.2v on the incoming power (that supplies the 24v xfmr). The xfmr is putting out ~32.1vac "eek". but once the fan and compressor and everything are running, xfmr voltage is a steady 25.9v. and with the load of the fan and compressor and pumps etc, the incoming line voltage is 241.4v. So that mere 1.5% voltage drop on primary is causing a ~24% fluctuation on the secondary.
This was never an issue in AC mode all summer. But I suspect thats the way the unit operates. In AC mode, the compressor will kick on first and run for ~30 seconds to cool the coils down before kicking on the fan. So the voltage readings go like this.....32.1v >>> compressor kicks on and secondary drops to 27.1v >>>>>>fan kicks on and secondary drops to 25.9v. In heat mode though, the compressor and fan both come on at the same time. So it goes straight from 32.1v to 25.9v when that happens.
So, my though is either 1. Too sudden of a voltage change triggering the alarm/fault condition. 2. The circuit board is set to sample the secondary once the fan is ready to kick on. And in cooling mode, with the compressor already running, its a nice 27.1v so the board gives the green light to run. Whereas heat mode, both fan and compressor come on at the same time, so the board sampling would show 32.1 and say....nope not today.
Last week when I had tech support on the line, (when they finally called back), I explained I had the t-stat set to 2h2c mode, as I didnt have any backup heat tied to this unit. And had a jumper between W2 and Y2 terminals to get both stages in heating AND cooling mode, since in 2h2c mode, w2 is used for the second / emergency heat. He thought this could be the issue and advised to go to 3h2c mode, get rud of the jumper, and just dont use w2 terminal.
I did not believe this to be the issue. Because who cares what terminals or how the t-stat is set. as long as it sends the signal to the correct inputs on the furnace. But I had to please him. So , I set it to 3h2c mode and removed my jumper. Issue is still present.
So what do you guys thing is the cause of the voltage fluctuations on the secondary. I have not added ANYTHING to the secondary. This unit is factory wired. The only thing I have done is connect the t-stat, and hooked the loop pumps to the compressor contactor outputs. Faulty transformer?
This was never an issue with
The unit is a 4-ton Geo-cool geothermal unit, with a Pro1 digital t-stat.
There are 4 diagnostic LEDS on the front of the furnace. High pressure, Low pressure, Auxiliary, and float switch (for condensate).
What happens, intermittently (like once a week) is the t-stat will call for heat, and the fan will kick on, but the compressor (and pumps that run off that same contactor) never come on. So it isnt until its ran awhile that I think " boy its been running awhile and still not up to temp". So I walk over and feel a register vent.....sure enough, no heat. SO I walk to the basement and see all the LED's flashing. Simply turning the unit off via the t-stat, waiting a few minutes, and trying again solves the issue.
I spoke with tech support, they said all the LED's flashing is an indication that the 24v transformer is either putting out too much voltage, or not enough. I "think" he said is +/-20%, but that was a week ago.
This morning I finally got around to prodding around with the meter to dig a little deeper into this issue. At a resting normalized state, I am getting 245.2v on the incoming power (that supplies the 24v xfmr). The xfmr is putting out ~32.1vac "eek". but once the fan and compressor and everything are running, xfmr voltage is a steady 25.9v. and with the load of the fan and compressor and pumps etc, the incoming line voltage is 241.4v. So that mere 1.5% voltage drop on primary is causing a ~24% fluctuation on the secondary.
This was never an issue in AC mode all summer. But I suspect thats the way the unit operates. In AC mode, the compressor will kick on first and run for ~30 seconds to cool the coils down before kicking on the fan. So the voltage readings go like this.....32.1v >>> compressor kicks on and secondary drops to 27.1v >>>>>>fan kicks on and secondary drops to 25.9v. In heat mode though, the compressor and fan both come on at the same time. So it goes straight from 32.1v to 25.9v when that happens.
So, my though is either 1. Too sudden of a voltage change triggering the alarm/fault condition. 2. The circuit board is set to sample the secondary once the fan is ready to kick on. And in cooling mode, with the compressor already running, its a nice 27.1v so the board gives the green light to run. Whereas heat mode, both fan and compressor come on at the same time, so the board sampling would show 32.1 and say....nope not today.
Last week when I had tech support on the line, (when they finally called back), I explained I had the t-stat set to 2h2c mode, as I didnt have any backup heat tied to this unit. And had a jumper between W2 and Y2 terminals to get both stages in heating AND cooling mode, since in 2h2c mode, w2 is used for the second / emergency heat. He thought this could be the issue and advised to go to 3h2c mode, get rud of the jumper, and just dont use w2 terminal.
I did not believe this to be the issue. Because who cares what terminals or how the t-stat is set. as long as it sends the signal to the correct inputs on the furnace. But I had to please him. So , I set it to 3h2c mode and removed my jumper. Issue is still present.
So what do you guys thing is the cause of the voltage fluctuations on the secondary. I have not added ANYTHING to the secondary. This unit is factory wired. The only thing I have done is connect the t-stat, and hooked the loop pumps to the compressor contactor outputs. Faulty transformer?
This was never an issue with
