Gas and Oil Home Heating Furnaces - Trane XV80 - what do connection terminals mean?

I recently had a Trane XV80 2 stage variable speed gas furnace installed...actually dual fuel with 2 stage heat pump as well...fossil fuel kit. Just my nature...but I like to know how things work so I've been looking at the current wiring from the thermostat. The control board in the furnaces has the following terminals and I've been unable to find documentation that explains the meaning of each. They are:

O
Ylo
Y
B/C
G
R
W1
W2
BK

Can anyone just tell me the purpose of each?

I think I've figured out the following:

Y - compressor (but is it 1st or 2nd stage?)
B/C - common
G - Fan
R - 24 volt
W1 - 1st stage heat
W2 - 2nd stage heat

The ones I'm lost on are the O, Ylo, and BK....and well confirmation if the ones I "think" I figured out are correct.

Thanks

Ok, What kit is used? You have two stage t-stat?

O = for the fan profile in Comfort-R (Should have jumper from this to Y)

Ylo = first stage in two stage cooling

Y = 2nd stage on two stage, otherwised use on a single stage system (wire from t-stat must go on here for fan profile from t-stat) then out to the outdoor unit.

B/C = common

G = fan

R = power from transformer

W1 = first stage heating (jumper maybe used to W2 if you don't do two stage t-stat)

W2 = second stage heat

BK = is used of you use a humidstat to control humidity in cooling mode.

The dealer should have the dip switch set up right to match your A/C tonnage on the blower, and CFM per ton.

Comfort-R must be turned on if you want the better humidity control.

Thanks Jay for the info. In looking at the furnance, they actually have the wiring set up as:

O: jump to R
Ylo: no connection
Y: yellow
B/C: Blue
G: Green
R: Red
W1: white
W2: jump to W1
Bk: Black

I have a 3 stage heat / 2 stage cool Honeywell TH8000 series thermostat. Most wire connections make sense except the black white is connected to the emergency heat terminal a brown wire connected to the compressor 2 terminal and an orange to the changeover value terminal. Now in between the thermostat and the furnance is the Trane fossil fuel kit. DIP switches were set correctly except I had to set the switches for comfort-R mode when I started using the A/C and realized it wasn't set.

Overall I am very pleased with the system but am curious as to if one change could be made in the configuration.

Sequence of events as it happens today:

Heat pump operates until temp outside drops below 30, then it changes over to the gas furnance. When thermostat calls for heat, gas furnance runs in stage 1 for 10 minutes then bumps to stage 2. Stage 2 ends up being a bit of overkill and blast you with heat. If it would just run a bit longer in stage 1 it would satisfy the heat requirement. I know why it is doing this...i.e. W1 / W2 jump together. My question is couldn't it be configured where when the temp drops below 30 and it cuts over to the gas furnace, stage 1 request from the thermostat triggers stage 1 of furnance and stage 2 of thermostat request would trigger stage 2 of furnance, rather than having it automatically happen after 10 minutes?

Also, I have the XL16I 2 stage heat pump / cool unit but to me, I've never noticed any difference in the unit outside when running in stage 1 or stage 2...as in noise level or the fan speed of the unit outside. Should I? I mentioned it to the installer who came back a few days after installation to tweak it and he said there isn't much difference and it hard to detect. Does that make sense?

Hiccup. :D

The t-stat is it the Honywell Vision Pro TH8320?

if so, you really don't need the fossel fuel kit.

What is the kit name and model?

From what I see, your A/C is NOT even wired up to run two stage! Unlesss Y2 from T-stat is going to the kit?

What is wired up on the t-stat? You got 4 stages of heat. (2 on heat pump, and 2 on gas.) How many BTU is the furnace and A/C?