SER
VICE PR
OCEDURE
S
SER
VICE PR
OCEDURE
S
On-Demand Water Heater Service Handbook for 240, 340 & 540 Condensing Models • 35
match up with those listed on the
rating plate, adjust the manifold
pressure. To do so, refer to the
following procedures.
Adjusting Maximum Manifold
Pressure
WARNING!
Complete the following
procedure ONLY if you have been
instructed to do so by the Technical
Service Department. See WARNING
text at the beginning of this section.
1. Ensure that the water heater is not
in operation.
2. Remove the screw from the
3. Connect a manometer to the
manifold port using a tube. Ensure
that this connection is secure
enough to prevent gas leak.
4. Run water through the water
heater to activate its operation. If
presence of a gas leak is detected,
immediately shut off the water
heater and inspect the tube/
manifold connection. Otherwise,
proceed to the next step.
During this step, DO NOT press the
“Increase” or “Decrease” button for
more than two seconds at a time.
Press and hold down the “MAX”
button on the computer board.
(Figure 20 or Figure 21, page 33.)
While holding down the “MAX”
button, press either the “Increase”
or “Decrease” button to increase
or decrease the manifold gas
pressure, respectively. (See Figure
20 or Figure 21 on page 33.) Use
the manometer to verify that
pressure has been set to the
desired value.
5. After the gas pressure has been
set, deactivate the water heater,
remove the manometer tube, and
replace the port screw.
6. Verify proper operation.
Adjusting Minimum Manifold
Pressure
WARNING!
Complete the following
procedure ONLY if you have been
instructed to do so by the Technical
Service Department. See WARNING
text at the beginning of this section.
1. Ensure that the water heater is not
in operation.
2. Remove the screw from the
manifold test port (Figure 22, page
3. Connect a manometer to the
manifold port using a tube. Ensure
that this connection is secure
enough to prevent gas leak.
4. Run water through the water
heater to activate its operation. If
presence of a gas leak is detected,
immediately shut off the water
heater and inspect the tube/
manifold connection. Otherwise,
proceed to the next step.
During the next step, DO NOT press
the “Increase” or “Decrease” button
for more than two seconds at a time.
5. Press and hold down the “MIN”
button on the computer board.
While holding down the “MIN”
button, press either the “Increase”
or “Decrease” button to increase
or decrease the manifold gas
pressure, respectively. (See Figure
20 or Figure 21 on page 33.).
Refer to the manometer to verify
that pressure has been set to the
desired value.
6. After the gas pressure has been
set, deactivate the water heater,
remove the manometer tube, and
replace the port screw.
7. Verify proper operation.
Checking the
Overheat Cutoff
Fuse (OHCF)
1.
WARNING
Disconnect electrical power from
the water heater before servicing.
Failure to do so can result in
electrical shock.
2. Locate the white OHCF which
wraps around the heat exchanger
(Figure 23). See also Figure 41, p.
Overheat Cutoff Fuse
(OHCF)
Blue
Braided
Wires
White
Connector
Left Side of Interior
Figure 23.
