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Table 3 continued
SYMPTOM
POSSIBLE CAUSE
CHECK
CORRECTIVE ACTION
System overheats
in mild weather.
Faulty outdoor sensor.
Check outdoor sensor resistance
(see page 3, Fig. 3).
Replace if necessary.
Parallel shift set too high;
e.g., at +35 F.
Check operation with lower shift
setting ''setting reset ratio and
parallel shift" (page 10).
Lower parallel shift
setting if necessary. Do
not alter ratio setting.
Outdoor sensor improperly
located.
Check outdoor sensor for ice or
snow buildup or other reason for
cooling.
Relocate sensor if
necessary.
Too little heat in
very cold weather.
Ratio setting or parallel shift
setting too low; e.g,-35 F
parallel shift.
Check setting of reset ratio and
parallel shift (page 10).
Change ratio schedule
or parallel shift to
increase hot water
temperature in very cold
weather.
Outdoor sensor faulty.
Check outdoor sensor resistance.
Replace outdoor sensor
if necessary.
System undersized.
Check for 100% boiler operation.
Increase heating
capacity if necessary.
Outdoor sensor not located
properly.
Check to see that sensor can
detect average outdoor air
temperature.
Relocate sensor if
necessary.
No reduction in
flow water
temperature
during night
setback (NSB).
Incorrect function switch
setting.
Check function switch is at position
4 (automatic) and clock is set for
night setback period.
Change function switch
to position 4 if
necessary.
Faulty clock.
Visually inspect for:
( i) incorrect time settings
(ii) no clock movement
(iii) correct positioning of program
override switch (page 9) could
be in (1) position
( i) reset time
(ii) replace clock
(iii) manually adjust
override switch to
(0) position and
check program pins
Component failure.
Adjusting NSB control to 76 F has
no effect on flow water
temperature during NSB period.
Replace panel.
Motor closes and
will not open (no
heat).
Function switch set to
position 1
(valve permanently closed).
Check function switch setting.
Change function switch
setting to other position,
if necessary.
Sensors are incorrectly
wired.
Visual inspection, check wiring
diagram.
Correct sensor wiring or
replace if necessary.
Either sensor is shorted out.
Measure sensor resistance.
Correct sensor wiring or
replace if necessary.
continued on next page
13
63
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2036—4
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