Paloma PH2-20R OFN Engineering Handbook page 111

OPERATIONAL PRINCIPLE
WHEN SUPPLYING HOT WATER
1) By opening the Hot Water Top (1), the water fl ows through the Water Flow Sensor (3) to the Primary
Heat Exchanger (20).
2) The frequency signal is given from the Water Flow Sensor (3) and when the PC Board (7) senses the signal
that reached a certain frequency, the Fan (22) starts to turn round.
3) After the Fan (22) turned round and pre-purged, the Gas Inlet Solenoid Valve (9), Solenoid Valve 1 (10),
Solenoid Valve 2 (11), Solenoid Valve 3 (12) and Solenoid Valve 4 (13) open at the same time. Then, the
Proportional Gas Control Valve (14) becomes an ignition motion and allows the gas to fl ow to the Main
Burner (19).
4) At the same time, the Igniter (16) continuously makes sparks and ignites the Main Burner (19).
After ignited, when the Flame Rod (18) senses the fl ame and make sure the combustion, the Proportional
Gas Control Valve (14) fi nishes the ignition motion.
5) After fi nished the ignition motion, the proportional gas control is started. When there is a temperature
difference between the hot water temperature that is sensed by the Hot Water Outlet Thermistor (6) and
the set temperature on the Remote Control, the PC Board (7) judges it and open or close the Solenoid
Valve 1 (10), Solenoid Valve 2 (11), Solenoid Valve 3 (12) and Solenoid Valve 4 (13), and also the
Proportional Gas Control Valve (14) continuously adjusts the gas volume in order to maintain the outlet
temperature.
The Water Flow Servo (2) also adjusts the proper amount of water fl ow to supply a stable hot water
temperature at all times.
6) According to the adjustment of the gas volume by the Proportional Gas Control Valve (14), a signal
from the PC Board (7) is also sent to the Fan Motor (23) in order to maintain the relation between
the gas volume and air volume at all times.
7) (For Direct Vent Models only) When the air intake or venting is blocked, or the oxygen of the air
intake is not suffi cient, the Flame Rod 2 (29) senses the change. When the PC Board (7) senses
this change, it shuts off the Gas Inlet Solenoid Valve (9), Solenoid Valve 1 (10), Solenoid Valve 2 (11),
Solenoid Valve 3 (12), Solenoid Valve 4 (13) and Proportional Gas Control Valve (14) in order to
stop the operation.
8) When the Hot Water Tap (1) is closed, the frequency signal from the Water Flow Sensor (3) is stopped and
the Gas Inlet Solenoid Valve (9), Solenoid Valve 1 (10), Solenoid Valve 2 (11), Solenoid Valve 3 (12),
Solenoid Valve 4 (13) and Proportional Gas Control Valve (14) turn off and becomes a post-purge motion.
9) When the time of the post-purge is up, the Fan (22) stops.
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