33
MB Pool & spa heater
VOLTAGE OUTSIDE RANGE 21.5-28.5 V.
Check transformer, 230 V supply, correct as necessary.If
230 V side of transformer is open circuit, check combus-
tion chamber for heat leaks
Check 3 Amp fuse.
TEMPERATURE 40°C-40.5° C.
Control ok.
RESISTANCE 0 OHMS (SHORT CIRCUIT)
Check system for shorted wires or open circuits.
Replace sensor if necessary.
MEASURED AND ESTIMATED RESISTANCE
DON'T MATCH.
Replace sensor. Reconnect all leads and check
out system.
Check voltage at 24 V terminals.
VOLTAGE BETWEEN 21.5-28.5 V.
Set control to max. temperature. After 2-3
cycles, check water temperature.
TEMPERATURE ABOVE 42°C
Disconnect sensor leads from circuit board.
Measure sensor resistance with ohmmeter.
RESISTANCE 1-14k OHMS.
Check water temperature; estimate expected
sensor resistance from chart below.
MEASURED AND ESTIMATED RESISTANCE
MATCH WITHIN 20 PERCENT.
Disconnect potentiometer leads from circuit board.
Measure resistance with ohmmeter. If resistance
is:
0-100 ohms at minimum setting:
9k to 11k at maximum setting,
replace circuit board.
Above 11k ohms, replace potentiometer.
0 ohms (short circuit), replace potentiometer.
Reconnect all leads and check out system.
VOLTAGE OUTSIDE RANGE 21.5-28.5 V.
Check transformer, 230 V supply, correct as necessary.
If 230 V side of transformer is open circuit, check combus-
tion chamber for heat leaks
Check 3 Amp fuse.
TEMPERATURE 40°C-40.5° C
Control ok.
RESISTANCE ABOVE 15k OHMS (OPEN
CIRCUIT) OR SHORT CIRCUIT.
Fix loose or broken wires. Replace sensor if
necessary.
MEASURED AND ESTIMATED RESISTANCE
DON'T MATCH.
Replace sensor. Reconnect all leads and check
out system.
Check voltage at 24 V terminals.
VOLTAGE BETWEEN 21.5-28.5 V.
Set control to max. temperature. After 2-3
cycles, check water temperature.
TEMPERATURE BELOW 40°C
Disconnect sensor leads from circuit board.
Measure sensor resistance with ohmmeter.
RESISTANCE 1-14k OHMS.
Check water temperature; estimate expected sensor
resistance from chart below.
MEASURED AND ESTIMATED RESISTANCE
MATCH WITHIN 20 PERCENT.
Disconnect potentiometer leads from circuit board.
Measure resistance with ohmmeter. If resistance is:
0-100 ohms at minimum setting;
9k to 11k at maximum setting, replace circuit
board.
Above 11k ohms but less than
15 k ohms, replace potentiometer.
Above 15k ohms, fi x loose or broken wires;
replace potentiometer if necessary.
Reconnect
all leads and check out system.
ELECTRICAL TROUBLESHOOTING
055, 105 & 155 Models
If the pool/spa water is too cold, troubleshoot the system as follows:
SENSOR RESISTANCE AT VARIOUS TEMPERATURES
Temperature (deg C)
16°C 20°C 21°C 25°C 30°C 31°C 35°C 40°C 41°C
(deg. F)
61 68 70 77 86 88 95
104
106
Resistance (k ohms)
14.9 12.5 11.9 10.0 8.1 7.7 6.5 5.3 5.1
If the pool/spa is too hot, troubleshoot the system as follows:
