Carbolite BLF 18/21 - Manual (Page 11)

BLF
MF23 – 3.11
11
6.0 F AULT A NALYSIS
7.0
A. Furnace Does Not Heat Up
1. The HEAT light
is ON
 An ohm meter applied to
the element circuit shows
an open circuit
 A heating element has failed
2. The HEAT light
is OFF
 The controller shows a
very high temperature
or a code such as S.br
 The thermocouple has broken
or has a wiring fault
 The controller shows a
low temperature
 The door switch may be faulty
or need adjustment
 The thyristor fuse may have
blown
 The power thyristor could be
failing to switch on due to
internal failure, faulty wiring
from the controller, or faulty
controller
 There are no lights
glowing on the controller
 Check the supply fuses and any
fuses in the furnace control
compartment
 The controller may be faulty or
not receiving a supply due to a
faulty switch or a wiring fault
B. Furnace Overheats
1. The HEAT light
goes OFF with the
instrument switch
 The controller shows a
very high temperature
 The controller is faulty
 The controller shows a
low temperature
 The thermocouple may have
been shorted out or may have
been moved out of the furnace
 The thermocouple may be
mounted the wrong way round
 The controller may be faulty
2. The HEAT light
does not go off with
the instrument
switch and the fault
persists when a 2A
control fuse is
removed from its
fuse-holder
 The power thyristor has
failed “ON”
 Check for an accidental wiring
fault which could have
overloaded the thyristor.
Isolate the furnace if this fault
persists.