Robertshaw 9520 - Manual (Page 6)

6
TERMINAL LEGEND - 9520
TERM EQUIPMENT TO CONNECT REQ? TERMINAL FUNCTION
C 24VAC common connection Yes For input of 24VAC common
side of transformer
L System fault indicator connection No For connection of system
fault indicator (if present)
R 24VAC hot connection Yes For input of 24VAC hot side
of transformer
Y2 Second stage cooling connection No Energizes on a call for
second stage cooling
Y1 First stage compressor connection Yes Energizes on a call for first
stage heating or cooling
E Emergency heat connection No* Energizes on a call for heat
in the EM mode only
G Indoor fan connection Yes Energizes with E, Y1, Y2 and
W2 terminals or with FAN
option switched to the ON
position
W2 Second stage heat connection No* Energizes on a call for
second stage of heat
(auxiliary heat)
O Cool active reversing Yes** Energizes when in the in
valve connection COOL mode
B Heat active reversing Yes** Energizes when in the
valve connection HEAT or EM modes
* For systems using a backup heat source. If separate E terminal connection is not available,
jumper E and W2.
** Most heat pump systems will have a cool active OR a heat active reversing valve. Use the
appropriate terminal.