Takagi 100 Series, Service Handbook

Page: 51 / 80

MAINTENANCE
On-Demand Water Heater Service Handbook for 240, 340 & 540 Condensing Models • 51
Flow Sensor/
Control Valve
Removal and
Installation
Tools:
#2 Phillips Screw Driver
See also
“Checking the Flow Sensor,”
page 36.
Removal
1. Shut off power by disconnecting
the power cord or shutting off the
power disconnect.
2. Shut off the gas supply to the
water heater.
3. Drain the water from the water
heater.
3.1 Close the shutoff valves on
the hot and cold side of the
heater.
3.2 If isolation valves are
installed, open the drain
ports.
3.3 If isolation valves are not
installed, remove the filter
(item 406, p. 74) and open
the pressure relief valve.
4. FOR INDOOR MODEL ONLY:
Remove the Temperature
Controller (item 722, p. 71)
by disconnecting it at the
white connectors that go to the
computer board (PCB).
5. Disconnect the flow sensor/
control valve’s wires from the
computer board as described
below. See Figure 41 (p. 49) or
Figure 42 (p. 50).
•
There are two plugs to remove
from the computer board: one
with three wires (red, white,
black) and one with two wires
(red, black).
•
If necessary, refer to the
appropriate schematic on page
30 or 31.
6. Remove the flow sensor/control
valve (item 402, p. 74) as follows:
6.1 Remove fasteners 16A and
14-22 (items 460 & 461,
page 74).
6.2 Pull the cold connection
tube (item 466, page 74)
from the outlet of the flow
sensor/control valve, then
lift the valve off the inlet
connection. You may have
to twist the valve off inlet
connection.
7. Inspect the o-rings on the inlet
water connection and the cold
connection tube for cuts or wear.
Replace as needed.
•
O-ring on inlet water connection:
part no. 100076308.
•
O-ring on cold connection tube:
part no. 100076306.
•
These O-rings are shown as items
456 and 458 on page 74.
Installation
1. Install the flow sensor/control
valve (item 402, p. 74) onto the
inlet water connection.
2. Connect the cold water connection
tube (item 466, p. 74) to the
outlet of the flow sensor/control
valve.
3. Reinstall both fasteners.
4. Plug the flow sensor/control
valve’s wires into the computer
board.
Install both plugs as shown in the
appropriate schematic (page 30
or 31).
5. Turn on the water and verify
that there are no leaks at the
connections. If there are leaks,
shut off the water, drain the water
heater, and fix the leak.
6. Restore power to the water
heater.
7. Open the gas valve.
8. Turn on water to the heater and
test for proper operation.
9. Verify that there are no leaks.
Correct any leaks that are found.
10. Reinstall the front cover. (If yours
is an indoor model, install the
front cover after inserting the
temperature controller into its
opening first.)
If you have any questions, please
contact technical support.
See also “Component Diagrams/Item Numbers” which starts on page 71.