22
2. Turn adjustment knob counter-clockwise 1/4 turn.
3. Turn pump off and on several times. Heater should
shut off immediately. If it does not, repeat the
above steps.
Two-Speed Pumps
In some cases, the flow on the low-speed is insuffi-
cient to operate the heater. This is apparent when the
water pressure switch cannot be further adjusted or if
the heater makes banging noises or shuts off on high
limit. In these cases, the pump must be run at high
speed when heating the water.
Flame Roll-Out Safety Switch
Heaters are equipped with a thermal cutoff device to
prevent flame roll-out in the event the heat exchanger
becomes blocked. This is a "single-use" type fusible
link or thermal fuse, that must be replaced when dis-
abled by an over-temperature condition, caused by
excessive restriction in the heat exchanger flue pas-
sage, roll-out, high winds, etc.
NOTE:
If heater is installed outside of the limits
shown, a higher pressure rated (11 psi) switch may
be used. A flow switch, mounted and wired adjacent
to the heater, may be used in place of the factory
mounted pressure switch. See Illustrated Parts List
for 11 psi water pressure switch.
CAUTION:
Do not operate the heater without the
function of a properly adjusted water pressure switch
or flow switch.
Fig. 27: Flame Roll-Out Safety Switch
High Limits
The heater is equipped with two automatic high limits.
Both are located in the In/Out header. Both are set to
open at 135°F.
High Limit Removal
1. Shut off main electrical power switch to heater.
2. Remove In/Out inspection panel.
3. Remove defective high limit and replace with a
new high limit.
4. Replace inspection panel.
Pilot Safety—Millivolt Models
Heaters equipped with the standing pilot (Millivolt sys-
tem) have pilot generators which act as a safety
device to shut off the flow of gas to the main burners
and the pilot burner in case the pilot flame is extin-
guished. The pilot burner must be manually re-lighted
to place the heater in operation again. Refer to the
lighting instructions provided on the heater label.
Burner Tray Removal
1. Shut off main electrical power switch to heater.
2. Shut off gas upstream of heater.
3. Remove front door.
NOTE:
An erratic high limit is often characteristic of
an internal heat exchanger problem, e.g. scale build-
up, defective bypass. Refer to Troubleshooting
section.
Fig. 28: High Limit Switch
