Thermo NESLAB HX 150 - Troubleshooting Guide; Troubleshooting Runaway Cold

7
START
Is
Setpoint
< actual
?
Calibration
error
NO
YES
Replace
valve
Valve is
mechanically OK
Test
STOP
Refer to
ELECTRICAL & CONTROL
section
Remove coil
from valve
Drawing 67.cfl
Rick Mills
13 March 1995
YES
YES
NO
Valve is
stuck open
Not a
Refrigeration
Problem
Problem is in
Controller or
sensor
See VALVE
REPLACEMENT
Does
unit
warm up?
YES
NO
UNSURE
YES NO
NO
Can you
get cool
lamp off? *
Is
cool lamp
on?
* by manipulating setpoint
Is
coil
on?
Normal
Response
Troubleshooting Chart: Runaway cold