Fulton Pulse DWH (PDWH) Domestic Water Heater - Manual (Page 36)

Linkage
Adjustment for
Pulse Modulated
Water Heaters
This instruction covers the adjustment of
the linkage arms and rods between the
modulation (mod) motor and gas
butterfly valve and also between the
mod motor and exhaust butterfly valve.
Prior to Start-Up
- With the water heater off, both the gas
and exhaust butterfly valves will be in
the closed position.
Setting High Fire
- When the water heater is energized
the mod motor will be driven to High
Fire driving the gas and exhaust
butterfly valves to the open position.
- At High Fire the slot in the shaft of the
mod motor should be horizontal in
orientation.
- At this point it is important to note that
the mod motor and gas butterfly valve
linkage arms are as close to parallel as
possible. Also note that the mod motor
and exhaust butterfly valve linkage arms
should be parallel.
- Location of the lock nuts on the linkage
rods is not important.
Linkage Relationships
The location of the linkage rods and the
speed at which the butterfly gas valve
and butterfly exhaust valve opens or
closes will determine whether the unit
operates smoothly or not.
Gas Butterfly Valve Side
- The longer the radius on the mod
motor pivot arm, the quicker the gas
butterfly valve shuts off. Conversely,
the shorter the radius the slower the gas
butterfly valve shuts off.
- The longer the radius on the gas valve
pivot arm, the slower the gas butterfly
valve shuts off. Conversely, the shorter
the radius the quicker the gas butterfly
valve shuts off.
Exhaust Butterfly Valve
Side
- The longer the radius on the mod
motor pivot arm, the quicker the exhaust
butterfly valve shuts off. Conversely,
the shorter the radius the slower the
exhaust butterfly valve shuts off.
- The longer the radius on the exhaust
valve pivot arm, the slower the exhaust
butterfly valve shuts off. Conversely,
the shorter the radius the quicker the
exhaust butterfly valve shuts off.
- At High Fire the linkage arms should
NOT begin or finish travel in the vertical
position. If this occurs there is a
possibility that the gears will bind and
cause damage to the mod motor.
- The gas pressure regulator is the only
means for adjusting High Fire input to
the factory test fire values.
After the water heater is operated at
High Fire to the desired settings,
proceed to operate at Low Fire.
Low Fire Settings
- Manually adjust the temperature
controller on the front of the water
heater to read 50% input. At 50% check
to see if the unit is within test fire values.
Proceed to step the water heater down
to 40%, 30%, 20% 10% and 0% each
time checking to see if the unit is within
test fire values. 0% represents low fire
and 100% represents high fire.
- If you are unable to reach 0%, you will
need to make adjustments on the gas
valve to either increase or decrease fuel
input. The exhaust butterfly valve may
also need adjustment. Start by
adjusting one valve at a time.
- The gas butterfly valve should be used
to adjust Low Fire input. The exhaust
butterfly valve should be adjusted to set
proper combustion. Closing the exhaust
butterfly valve will also decrease input
slightly.
- At Low Fire the linkage arms should
NOT begin or finish travel in the vertical
position. If this occurs there is a
possibility that the gears will bind and
cause damage to the mod motor.
Procedure to Zero
and Span the
Modulation Motor
The following procedure is done on
each modulation (mod) motor at the
factory. It may be necessary to do in
the field in the event the mod motor
requires replacement or the mod motor
linkage is moving up or down the range
when there is no change in the
operating or setpoint temperature
difference.
1) Turn water heater OFF.
2) Put the temperature control in manual
mode (press the A/M key once – the SP
display will show a value between 0 and
100).
3) Follow the electrical drawing and
remove the connection between (F) and
(-) on the mod motor. Disconnect relay
CR3 for safety.
4) Contact point 16(+) on the
temperature control is wired through
CR1 normally closed to contact point (+)
on the mod motor.
Contact point 17(-) on the temperature
control must be disconnected. Install a
jumper from 17(-) to contact point (-) on
the mod motor.
This will provide a direct connection
between (+) and (-) on the temperature
control to (+) and (-) on the mod motor.
5) Refer to the zero and span
adjustment information for the mod
motor (Pages 5 and 10). Follow steps 1
through 8 on page 10 of the mod motor
brochure included in the Pulse
Operation and Maintenance manual.
6) Be sure the linkage does not bend or
catch in any position during travel.
7) When zero and span are complete,
scroll the input rate to 100% - this will
drive the burner to high fire and purge
any left over combustibles- and adjust
the blue cam, if necessary, until the high
edge of the cam pushes against the end
switch.
8) Remove the jumper and install the
wire on contact point 17(+) of the
temperature control. Connect relay
CR3.
9) Test the mod motor signal by
manually setting the output signal from
zero (low fire – 4 mA) to 100 (high fire –
20 mA). At high fire, the slot in the shaft
of the mod motor should be horizontal in
orientation.
NOTE
The unit will still shut off at setpoint plus
5
o F (standard settings). Also, being in
manual mode, the temperature control
ignores any PID or auto tune settings.
10) Set the temperature back to the
Auto setting by pressing the A/M key –
the operating and setpoint temperatures
will be displayed in the PV and SP
displays, respectively.
Operation
33-PDWH