Trane XL16i/XV80 DIP Switch Setting (S5-2) Question
I have the following system that has been installed for about 3 weeks:
- Trane 4TTX6060E1000B (XL16i) condenser
- Trane TUD2D120B9V5VB (XV80) furnace
- Trane 4TXCD063BC3H evaporate coil
- Trane TCONT802AS32DA (802) thermostat - recently changed to a Nest 2nd generation
I know that a common problem with the XL16i is incorrect wiring. As such, I reviewed it in-depth and made sure that the wiring, switches (settings), etc. all match what the installer guides call for to match the equipment. The first and second stages are wired correctly to the XL16i using the BK terminal in the furnace.
We do have Comfort-R enabled via the dip switches, air flow at 400 CFM/ton, 5 ton, etc.
The one setting that is different than what the manuals seem to call for is dip switch S5-2. The switch is currently set to ON (which translates to De-Humidifier is Not Installed) on my furnace. We do not have a de-humidifier so this makes sense at first glance. However, the XL16i manual says switch S5-2 should be OFF. Additionally, there is Note 9 of the furnace installer guide that references that S5-2 must be OFF when the BK terminal is being used for an airflow command signal.
My questions are:
1) Should switch S5-2 be ON or OFF for this setup?
2) When they are saying OFF, are they referring to the physical position of the switch (OFF as printed on the circuit board) or OFF as in de-humidifier is not installed (which really is ON on the switch)?
3) Can anyone explain what the difference is the different settings of this switch (e.g. if has supposed to have been OFF all this time, then what has having it ON been doing)?
Can anyone assist with answers on this?
First off, are you having any issues with the system at all? If not, you shouldn't change a thing. That switch is for an external dehumidifier. It allows the dehumidifier to send a command to the blower so it can operate without a call for heat or cool. Its set the way it needs to be.
The only true knowledge is the pursuit of knowledge
S5-2 needs to be off, or the system will always run in 2nd stage cooling whenever the thermostat calls for 1st stage cooling.
Having the S5-2 switch on is like having a jumper between R and BK.
I am not having any specific issues with the system that I know of. Rather I was verifying that the system was installed correctly since I have read that the XL16i condenser is improperly installed many times (believe it stems from the use of the BK terminal which is not common among other systems). The key item is that we do not have an external dehumidifier, so the switch makes sense to be ON. However, the installer guides for both the XL16i and the XV80 state that the switch should be OFF in this setup.
Originally Posted by 5thRoot
Since this was the one item on my system that did not match the installer guides, I was raising it as a question.
Thanks for the answer. I thought that might be the case, since the manual also references removing the R to BK jumper if it had one (older models) or setting the DIP switch to OFF on the newer models.
Originally Posted by mark beiser
The only puzzling thing was that I did check with my voltmeter and did not see 24V on the BK terminal until the thermostat actually called for 2nd stage cooling. Does that sound normal? I would have thought that with the switch ON, I would see 24V on the BK terminal at all times since it should behave like a jumper to R.
Based on some other items I read about the switch being used for a dehumidifier setup, the other idea was that the DIP switch being ON would trigger the blower to run slower when second stage was activated by the thermostat (e.g. thermostat calls for second stage, puts 24V to BK, condenser runs goes to second stage/step, and the blower speed slows down). I have not noticed that however.
Hmm, I'll have to play with one the next time I'm working on one.
The older boards had a jumper, that made a connection between the R and BK terminals on the board, that had to be cut.
I thought the switch on the newer board still made that R to BK connection, but if you were not reading 24v to BK, maybe it doesn't.
It could just be telling the board to ignore in BK, and run at 100% when the switch is on.
The way the system is supposed to work is that when the thermostat is calling for 1st stage cooling, Y and G should be energized, and the blower will run at 80% of its cooling airflow setting.
The contactor in the outdoor unit will be energized, but the compressor unloader will be deenergized, so the unit runs in 1st stage.
When the thermostat calls for 2nd stage cooling, BK on the furnace control board gets power applied to it, causing the blower to ramp up to 100% of its cooling airflow setting, and the compressor unloader gets energized, causing it to shift to 2nd stage.
With the S5-2 switch in the on position, the blower will always ramp up to 100% of its cooling airflow setting when Y and G are energized. Since you have Comfort-R enabled, it will take the blower 8.5 minutes to ramp up to 100%, but it will do the same thing regardless of if the thermostat is calling for 1st or 2nd stage cooling.
On the older control boards, failure to cut the W14 jumper would result in the indoor blower always ramping up to 100%, and the outdoor unit always running in 2nd stage with any call for cooling.
On the newer boards, with the S5-2 switch, it would seem that the outdoor unit would operate normally, switching between stages with thermostat calls, but the indoor blower will always run at 2nd stage(100%) airflow.
I have tried the 5-2 switch in both the ON and OFF positions. The second stage (BK terminal) does not appear to be affected by the position of the switch. From what I can tell, it sounds like the blower is running slower when the switch is OFF vs. when the switch is ON. I don't have a way to measure this that I know of, so this is based purely on listening to the sound as we go through the cycle.
Originally Posted by mark beiser
Is there a way to confirm the actual blower speed (e.g. via the LEDs)? I am not sure if the LED on the board indicate what it is set at, or what it is actually running at.
I appreciate the input and help.
When the switch is off, and there is no 24v to BK, the blower should run at 80%.
Originally Posted by cpeek
With the switch on, or there is 24v to BK, the blower should run at 100%.
You can verify CFM by counting the blinks of the CFM light on the control board. It is a green LED near the low voltage terminal block.
I did some testing with the switch both ON and OFF. As a reminder, the system is a 5 ton with settings at 5 ton, 400 CFM/ton, and Comfort R enabled.
Originally Posted by mark beiser
With the S5-2 switch set to OFF and Comfort-R mode on, this is the pattern I got:
1st minute - 8 flashes - calculated CFM = 800 (400 CFM/ton * 5 ton * 80% for 1st stage cooling, and the result * 50% for the 50% first minute of Comfort R mode)
Next 7.5 minutes - 13 flashes - calculated CFM = 1280 (400 CFM/ton * 5 ton * 80% for 1st stage cooling, then the result * 80% for the 80% cooling level of Comfort R mode)
After 7.5 minutes - 16 flashes - calculated CFM = 1600 (400 CFM/ton * 5 ton * 80% for 1st stage cooling, and then 100% cooling level for Comfort R at this stage)
Thermostat called for 2nd stage - 20 flashes - calculated CFM = 2000 (400 CFM/ton * 5 ton * 100% for 2nd stage, and 100% cooling mode for Comfort R at this stage)
With the S5-2 switch set to ON and Comfort-R mode on, this is the pattern I got:
1st minute 10 flashes CFM = 1000
Next 7.5 minutes 16 flashes CFM = 1600
After 7.5 minutes 20 flashes CFM = 2000
Thermostat called for 2nd stage 20 flashes CFM = 2000
Mark - you were correct with everything. In summary, it appears that the S5-2 switch set to ON causes the furnace blower to run as a 1 stage/speed but the condenser continues to operate as a 2 stage/speed. The only reason my blower runs at different speeds is due to the Comfort R mode being turned on. By turning the S5-2 switch to OFF (as stated in the manual for the XL16i and XV80), then the blower operates as two stages as well as the condenser.
Thanks for all of your assistance.