Unit will heat up at all
Indicated chamber temperature
unstable
Will not maintain set point
Display and actual reference
thermometer don't match
Can't adjust set points or calibration
Calibrated at one temperature, but not
at another
Door not sealing
1/ verify that controller is asking for heat by looking for controller
light – if controller light is not on, there is a problem with the
controller
2/check amperage – amperage should be virtually at maximum rated
(data plate) amperage
3/ do all controller functions work?
4/ is the High Limit set high enough? – for diagnostics, should be
fully clockwise with the pilot light never on
5/ has the fuse/circuit breaker blown?
1/ ±0.1 may be normal
2/ is blower motor working? – remove top panel and verify
movement of blower motor in shadow box
3/ is ambient room temperature radically changing – either door
opening or room airflow from heaters or air conditioning ? – stabilize
ambient conditions
4/ it may happen if exhaust stack is 100% open or if power exhaust is
cycling – adjust stack to at least ¼ closed
5/ sensor miss-located, damaged or wires may be damaged - check
mounts for control and High Limit sensors, then trace wires between
sensors and controls
6/ calibration sensitivity – call Customer Service
7 / high limit set too low – be sure that High Limit is more than 5
degrees over desired set point; check if High Limit pilot is on
continuously; turn controller knob completely clockwise to see if
problem solved then follow instructions in Section 7.5 for correct
setting
8/ electrical noise – remove nearby sources of RFI including motors,
arcing relays or radio transmitters
9/ bad connection on temperature sensor or faulty sensor – check
connectors for continuity and mechanical soundness while watching
display for erratic behavior; check sensor and wiring for mechanical
damage
1 0 / bad connections or faulty solid state relay – check connectors
for mechanical soundness and look for corrosion around terminals
or signs of arcing or other visible deterioration
1 / assure that set point is at least 5 degrees over ambient room
temperature
2/ see if ambient is fluctuating
1/ calibration error – see Watlow users manual
2/ temperature sensor failure – call Customer Service
3/ controller failure – call Customer Service
4/ allow at least two hours to stabilize
5/ verify that reference thermometer is certified
See above
1/ turn entire unit off and on to reset
2/ if repeatedly happens, call Customer Service
This can be a normal condition when operating temperature varies
widely. For maximum accuracy, calibration should be done at or as
close to the set point temperature.
MECHANICAL
1/ check physical condition of gasket
2/ assure that gasket is in original location
14
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