Aprilaire 8346 Installation Manual page 6

Set the O/B reversing valve jumper in the proper position
(Models 8346 and 8365 only)
The thermostat comes with an O/B terminal which can be configured to be
an 'O' terminal (for most heat pumps) or to be a 'B' terminal. Configure as an
'O' terminal if the heat pump reversing valve has heating as the default
position, configure as a 'B' terminal if the reversing valve has cooling as the
default position.
CONSULT WITH THE HEAT PUMP MANUFACTURER TO DETERMINE WHICH
CONFIGURATION IS NEEDED.
O/B Reversing Valve Pin Jumper Position
Remove the slide switch caps
for easier access.
5
To configure as an "O" Terminal,
keep the pin jumper in this position.
To configure as an "B" Terminal,
move the pin jumper to this position.