Hi folks, i had originally posted a question in the thread single stage or 2 stage thermostat with XV80 But in order to keep from hijacking his thread completely I'll post here with my specifics and hopefully some folks will be able to send me in the right direction.
I"ve been in this house almost 2 years now. It has 3 trane XV80 systems. And each is wired or setup a little differently so I hope you don't mind the length of this question and the amount of info in it
Over a year ago I asked the HVAC guy doing my regular maintenance if these were 2 stage systems and can I get a 2 stage stat for them. He told me in no uncertain terms that no, they were not. But I now think he may be wrong.
Smaller system for the bedrooms upstairs has never worked well enough to make me happy, either with heat or AC as the thermostat calls for either, and it comes on LOW and nothing happens perception wise for a while, and then after the timer kicks it into HIGH (since there is no 2 stage stat) the temp quickly overshoots the setpoint and stops. So the temperature swings up there are really out of control. I've done a lot to improve it from what it was by adding an extra layer of attic insulation, moving the thermostat from the shared hallway into one of the bedrooms, and adding a return air vent to the most uncomfortable of the bedrooms. But it's still not "fixed" and all these little things are starting to add up in cost, though the HVAC company likes me as I keep paying them money! They have been very helpful and friendly and always come in right at their estimates for the little jobs, but don't seem to be very good at suggesting something to fix my problem, only happy to do whatever I ask them to do.
Upstairs air handler/gas heater unit has a model number of "TUD080R9U3H5" and they all have the same White Rogers controller in them with a model number of "50A51-507" The W1 and W2 connections are bridged together which as I understand it is what you do when you have a 2 stage furnace connected to a single stage stat. Would there be a W2 and a Ylo connection on the board if it wasn't a 2 stage furnace?
Then there is the question of the outdoor unit, for 2 stage cooling the outdoor unit needs to be 2 stage too correct? The outdoor unit on that system is a trane XL1200 model number "TTX024C100A2" At this moment there is a 3 conductor cable running to it for controlling it, but there are only 2 wires connected inside the furnace (I haven't opened up the outdoor unit to look to see what connections are available in there yet) I would need to connect the 3rd wire to the Ylo to make that work?
I have a problem with this though. If the outdoor unit isn't connected up to be 2 stage, then how can the indoor unit run the fan at a lower than normal speed for a while and then switch to a high speed? Wouldn't it have to also adjust the output of the outdoor unit? If you just run the fan at a lower speed and keep the outside unit at the same output then wouldn't it freeze up the coil or cause other problems?
So that makes me think that either it is single stage and just runs the fan at 2 different speeds, or it wasn't hooked up properly in the first place, which is quite possible.
My downstairs unit is larger, the mode number on the XV80 airhandler is "TUD080R9U3H6" and the outdoor unit is a XL1200 "TTX036C100A1" the white rogers controller inside is the same, and also the 3rd wire to the outdoor unit is not connected and the W1 and W2 are bridged together with no connection to the Ylo at all. Is this also a 2 stage system wired for single stage?
Lastly the third system is for the added on family room, it's the same models as the downstairs system but is wired a little differently. To my mind it's actually wried wrong... These are all gas fired systems and so don't use the "O" connection at all which is my understanding for the reversing valve for a heatpump system? But on that system the Y and O connections are bridged, NOT the W1 and W2, the W2 is not connected to anything. Also the R and the BK connections are bridged which I've not seen on any of the others. Again the 3rd wire to the outdoor unit is not connected. Makes me think almost that someone meant to bridge W1 and W2 but didn't look carefully at the board?
Sorry for 3 different systems and lots of questions But I hope i've supplied enough info for you to know what I've got and if it can be improved with some 2 stage thermostats!