Raypak 503-2003 - Manual (Page 37)

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VAC signal is sent to pin P4-9 of the UDB board to
indicate an insufficient flow condition.
19. When 24 VAC is received at TH on the ignition
module, the contacts between pins F1 and F2
close and send 120 VAC to pin 1 of the blower
relay.
20. The coil of the blower relay energizes closing the
NO contacts sending 120 VAC to energize the
combustion air blower motor.
21. Once sufficient air flow is proven the air pressure
switch closes the NO contacts, 24 VAC is sent to
the heater interlock connection at terminal 9 of the
rear j-box low voltage terminal block. If air pres-
sure is insufficient or lost during heater operation a
24VAC signal is sent from the NC contacts of the
air pressure switch to pin P4-10 of the UDB board
to indicate insufficient air pressure.
22. When 24VAC is returned to terminal 10 of the rear
j-box low voltage terminal block, power then trav-
els to the P Switch terminal of the ignition module.
The ignition module employs a 15 second pre-
purge before the next sequence.
23. After 15 seconds of combustion chamber pre-
purge, pin S1 sends 120 VAC to the Hot Surface
Igniter.
24. The Hot Surface Igniter will be energized for
approximately 30 seconds and must exceed 3.1
amp draw during heat up.
25. Once the ignition module determines the proper
operation of the Hot Surface Igniter, a 24 VAC sig-
nal is output from the Valve pin on the module to
energize the gas valve.
26. The gas valve is energized and the blue “Burner
On” LED on the front of the heater energizes.
27. The remote sensor is now trying to rectify the
flame. If the flame is not rectified within 4 seconds,
the ignition module will shut down the gas valve
and lock out.
28. When burner flame is rectified, the heater will
operate based on the electronic operating control.
In the event of an ignition lockout, the ignition
module sends a signal to pin P4-12 (ignition lock-
out) of the UDB board.
29. When the CFH is satisfied, the heater will return to
a standby condition awaiting the next CFH.
Heater Sequence of Operation
Models 1753–2003
1. The black (hot) wire lead, located at the right-mid-
dle front inside the control compartment, goes
directly to the main power switch.
2. When the main power switch is placed in the “ON”
position, the 120 VAC terminal block in the control
compartment, the N.O. contacts of pump relay, the
N.O. contacts of blower relay, the 120/24 VAC
transformer, and terminals L1 and F1 of the igni-
tion module are powered.
3. The 120/24 VAC transformer sends a 24 VAC hot
power signal to the 24V Terminal Block.
4. 24 VAC is sent from the 24V Terminal Block to the
NO pump contacts on the modulating temperature
control (pin #13), to pin TP2 of the optional alarm
relay, to terminal R of the alarm circuit on the mod-
ulating temperature control (pin #24) and the
green “Power On” LED on the front of the heater
will illuminate.
5. 24 VAC power is sent from 24V Terminal Block to
Pin P1-1 of the UDB board, the 24 VAC terminal of
the ignition control module, the common contact of
the manual high limit, pin P3-1 of the UDB board
and L1 of the Low Water Cut Off (if equipped).
6. A 24 VAC signal is sent from the NC contact of the
manual high limit to the common terminal of the
Blocked Vent Switch and to Pin P1-1 of the UDB
board. During a blocked vent condition a 24 VAC
signal is sent from the NO open contacts of the
Blocked Vent Switch to pin P3-5 of the UDB board
to indicate a safety fault.
7. During normal operation of the heater the 24 VAC
signal exits the NC contacts of the Blocked Vent
Switch and is sent to the common terminal of the
Low Gas Pressure Switch (if equipped). During a
low gas pressure condition 24 VAC is sent from
the NC contacts of the Low Gas Pressure Switch
to pin P3-6 of the UDB board to indicate a safety
fault.
8. 24 VAC is sent from the NO contacts of the Low
Gas Pressure Switch to the common terminal of
the High Gas Pressure Switch (if equipped).
During a high gas pressure condition 24 VAC is
sent from the NO contacts of the High Gas
Pressure Switch to pin P3-7 of the UDB board to
indicate a safety fault.