Carbolite HTF 18 User Manual download pdf (Page 15)

MF47-3.05 15

6.0 FAULT ANALYSIS

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



The fault light on the

control panel is on



The thermal cutout on the case

or in the transformer has

activated



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.

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