LXi
™
Pool/Spa Heater Installation and Operation Manual Page 47
10.5.3.4 Fusible Link
To check the fusible link/air louver/fi eld interlock
circuit, place the red lead at test point 6. If there is not
20-28 Volts AC nominal, either the controller or the
two-pin wire harness is faulty, or the water pressure
switch is open.
If 20-28 Volts AC nominal is detected at test
point 6, then move the red lead of the meter to test
point 7. If 28 Volts AC nominal is detected, the circuit
is closed and working correctly.
If the proper voltage is not detected, either the
fusible link or fi eld interlock has opened, or the wire
harness is faulty. Failure of the fusible link must be
investigated further to identify the cause of the failure.
10.5.3.5 Temperature Limit Switches
Circuit
Since the limit switches are not easily accessible,
the voltage can be checked at the two legs of the cir-
cuit at the controller. See test points 8 and 9 in
Figure 37.
Check the voltage at test point 8. If there is not
20-28 Volts AC nominal at this point, either the con-
troller or the two-pin wire harness is faulty, or one of
the two safeties (water pressure or fuselink) before it is
open.
If 20-28 Volts AC nominal is detected at this
point, then move the red lead of the meter to test point
9, where the black wire from the 130° limit enters
the two-pin connector. If 20-28 Volts AC nominal is
detected at this point, the devices in this circuit are
closed and the circuit is working properly.
If there is no voltage, one of the limit switches is
open. This is normally due to excessive water tempera-
ture, which should be thoroughly investigated before
replacement of limit switches. Excessive water tem-
perature may be caused by low water fl ow. Water fl ow
defi ciency may be due to obvious problems such as a
defective pump or blocked water fi lter.
Alternatively, excessive water temperature may
be due to over-fi ring, or to a problem with the water
piping or the heater's internal bypass control. Over-
fi ring might be a result of an incorrect gas orifi ce or
supply of propane gas to a heater intended for natural
gas.
If there are no such fundamental problems, iden-
tify which of the switches is open. Limit switch access
is through the limit switch plugs on the side of the
heater to which water pipes are connected. Remove the
limit switch plugs from the bottom of the header and
gently remove the switches from the wells.
Note that the limit switches have different trip
points, and it is important that replacements are cor-
rect. The 150°F switch has a red dot on the top of the
switch, and must be installed in the lower well in the
header. The 130°F switch has no dot and must be in-
stalled in the upper well in the outlet of the header.
Move the red meter lead to the terminal connec-
tion on the 150° switch that is connected back to the
controller. The voltmeter should read 20-28 Volts AC
nominal. No voltage here means that the two-pin wire
harness is bad and should be replaced.
If voltage is detected at this point, move the lead
to the other terminal of the switch. If the voltmeter
does not show voltage, then the 150° limit is bad and
should be replaced.
If the meter reads 20-28 Volts AC nominal, move
the lead to the terminal of the 130° limit that is con-
nected to the wire that jumps between the two limit
switches. No voltage here means that the wire assem-
bly is bad and needs to be replaced. 20-28 Volts AC
nominal shows that the wire between the two limits is
making a good connection.
Now move the lead to the other connection
terminal on the 130° limit. No voltage at this point
indicates that the limit switch has failed and needs to
be replaced. Voltage here would show that the limit is
good and that the two-pin wire harness may have a bad
connection. Replace the wire harness if necessary.
10.5.3.6 Blower Pressure Switch Circuit
The blower must be operating during the test pro-
cedure for the blower pressure switch. Start by check-
ing the voltage between test point 1 and the common
and normally open contacts of the air fl ow switch.
Leaving the black lead of the meter on test point
1, check the voltage at test point 11. If there is not
20-28 Volts AC at this point, the eight-pin wire harness
is faulty and must be replaced. If 20-28 Volts AC is de-
tected at this point, then move the red lead of the meter
to the Air Flow Switch NO contact. If 20-28 Volts AC
is detected at this point, the device in this circuit is
closed and the circuit is working properly.
If there is not 20-28 Volts AC at the Air Flow
Switch NO contact, the pressure switch contacts are
open. This is usually due to a blower speed problem
or a problem with the air pressure tube connection
between the blower housing and the switch.
Be sure that the blower is on and that it is work-
ing properly. Check that the gray fl exible tube between
the blower pressure switch and the blower housing is
connected at both ends and has no holes or splits. Re-
place the tube if necessary. If there is no problem with
the blower or the tube, check for blockages in the vent,
fl ue or heat exchanger that would prevent air fl ow. If
no blockages are found, replace the pressure switch.
If the Air Flow Switch NO contact shows 20-28
Volts AC and the ignition control shows an air fl ow
fault, then there is a bad connection between the
blower pressure switch and the ignition control, or the
ignition control is faulty.
Check for voltage at test point 12 on the ignition
control. If no voltage is present, then the connection
is bad, replace the wire harness. If 20-28 Volts AC is
present, replace the ignition control.
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