Raypak D-2 POWER VENT 206A - Manual (Page 14)

14
SEQUENCE OF OPERATION
On call for heat, the PC board will go through its safety chain (water pressure switch, high limit 1 & 2, roll-out,
etc.). When the safety chain is closed, the IID pilot will begin to spark and the pilot gas valve will open. A flame
will be lit at the pilot assembly. When an acceptable signal is sent back to the PC board, proving the rectifica-
tion, the D-2 Power Vent blower will start. When the blower comes up to speed, a draft proving switch will close
to allow the main gas valve on the heater to open. Note: On Low NOx units, the main gas valve & combustion
blower will turn on simultaneously. A heater with a D-2 Power Vent will continue to operate until call for heat is
satisfied.
DRAFT-PROVING SWITCH
The draft-proving switch ensures that the blower is operating. Once the D-2 Power Vent is wired to the heater,
the switch does not allow the PC board to open the main gas valve, unless it is closed.
WIRING
The D-2 Power Vent includes a wire harness which provides quick connections with the respective controls in
the appliance control box. The harness is of sufficient length to fit the unit for which it is sized.
Reference the connection diagrams on pages 15 & 16 or the wiring diagrams on pages 17 & 18 for actual con-
nections.
RELAY
AIR
PRESSURE
SWITCH
GAS VALVE
Y/BK
Y/BK Y/BK
V/BK
V/BK
V/W
V/BK V/W