GUSMER FF-2500, Operating Manual

Operating Manual 

Troubleshooting 

2/12/04 

25 

S

OLUTIONS

1.  THERMAL LIMIT SWITCH- The Thermal Limit Switch provided consists of a 

bimetallic switch bonded to the end of the Primary Heater.  When the surface 
temperature of this section exceeds 198° F, the switch trips the Primary Heater 
Circuit Breaker, and removes power from the heater.  Once the heater has cooled 
down to within limits, reset the limit switch.  DO NOT attempt to reset this switch 
more than once.  You must determine the cause of the problem and correct it. 

WARNING:

W

HEN MOVING THE 

P

ROPORTIONING 

U

NIT

, 

IT IS PROBABLE THAT THE 

T

HERMAL 

L

IMIT 

S

WITCH WILL TRIP IN TRANSIT

.  N

EVERTHELESS

, 

IF THE HEATER FUNCTIONS PROPERLY 

AFTER THE LIMIT SWITCH HAS BEEN RESET

, 

IT IS IMPERATIVE THAT THE OPERATION OF THE 

HEATER BE CLOSELY MONITORED TO ENSURE THE SWITCH HAS NOT TRIPPED AS A RESULT OF A 

HEATER MALFUNCTION

. 

To reset the thermal limit switch, proceed as follows: 

a)  Switch OFF the main switch and primary heater circuit breaker. 

b)  Turn OFF and lock out incoming power at the source. 

c)  Remove the cover box by removing the acorn nut and sliding the cover box 

away from the heater. 

d)  Check to ensure all electrical power is OFF. 

e)  Reset the thermal limit switch by pushing in the red button on the switch. 

f)  If the thermal limit switch does not feel as though it reset, then disconnect one 

lead from the thermal limit switch and read continuity across the switch.  If no 
continuity, the switch is defective and must be replaced. 

g)  If this does not solve the problem, replace the thermostat. 

h)  Slide the cover box back into place and tighten the acorn nut. 

i) 

Switch on the electrical power and monitor the operation of the primary heater 
to ensure it is functioning properly. 

2.  CHECK CONTROLLER SET POINT- If the set point is incorrectly set below the 

ambient temperature, the primary heater will not cycle on and off. 

3.  REVERSED THERMOCOUPLE CONNECTION- With the main switch and 

primary heater circuit breaker OFF, check the sensor leads on terminal numbers 1 
and 2.  The red wire must be on Terminal 1.  If it isn’t, reverse the sensor leads. 

4.  SENSOR TYPE MISMATCHED- The preprogrammed controller operates with a 

type “E” thermocouple only.  Ensure that only an SPI or Gusmer supplied primary 
heater thermocouple is used. 

5.  OPEN THERMOCOUPLE- With the main switch and primary heater circuit breaker 

OFF, check all wiring for damage or faulty connections and make sure the primary 
heater thermocouple plug is in place in the rear of the console.