Raypak MVB 5042004 - Manual (Page 37)

The optional single-try ignition module will lock out
after failing to light one time. To reset it, press and
release the small, recessed black push button located
inside of the cut-out on the lower right-hand corner of
the ignition module case. Turning off the power to
the heater WILL NOT reset the ignition module.
High Limit—Manual Reset
This heater is equipped with a fixed setting manual re-
set high limit temperature device as standard or it may
have an optional adjustable setting manual reset high
temperature device.
The fixed setting manual reset high limit is located on
the In/Out header of the heat exchanger on the right
side of the heater (accessible through the front door
for reset as necessary).
The optional adjustable manual reset high limit is lo-
cated inside the heater junction box. Push the reset
button and adjust the setting to approx. 40°F (20°C)
above desired outlet temperature.
37
Heater Sequence of Operation
If all limits are satisfied and there is a call for heat:
1. The heater pump is powered and begins circulat-
ing water through the heat exchanger.
2. The blower is powered and goes through a 15 sec-
ond prepurge beginning when air flow is proven by
closure of the blower suction air pressure switch.
3. The igniter is powered, and once proven, heats up
for 20 seconds.
4. The gas valve is then energized for a 4 second
trial for ignition period. Trial for ignition is fixed at
50% input. The heater is allowed to modulate once
flame is proven and the firing rate will adjust to
match the load based on the configuration and set-
tings of the temperature control or external input.
5. Once the heat demand is satisfied the gas valve
will close and the blower will run a 30 second post
purge. The heater pump will continue to circulate
water for 0 to 10 minutes depending on the pump
delay setting on the Raypak modulating tempera-
ture control.
Ignition Module
When additional heat is needed, the combustion air
blower starts to purge air from the combustion cham-
ber for 15 seconds. On proof-of-air flow, the
air-proving switch closes and the igniter is energized.
To ensure safe operation, the gas valve cannot open
until the igniter is verified. The main burner is automat-
ically lit when the device is powered and pre-purged.
The heater performs its own safety check and opens
the main valve only after the igniter is proven to be
capable of ignition. The standard ignition module will
attempt to light three times before locking out. To reset
it, turn off power to the heater, wait 30 seconds and re-
apply power.
Fig. 38: Ignition Module
Table U: Ignition Module
Diagnostic LED Flash Codes
Code Condition
On System OK; No faults present
Off Possible control fault; Check power
1 Flash Low air
2 Flashes
Flame in combustion chamber;
No call for heat
3 Flashes Ignition lockout
4 Flashes Low HSI current
5 Flashes Low 24 VAC
6 Flashes Internal fault; Replace control
Fig. 39: High Limit (Manual Reset)