Carbolite HRF (MF05) - Manual (Page 5)

HRF
MF05 – 3.25
5
3.0 O PERATION
The instructions for operating the temperature controller are given in a separate manual. If the
furnace is fitted with a time switch, see also the supplementary manual MS03.
3.1 Operating Cycle
The furnace is fitted with an instrument switch. The switch cuts off power to the control circuit.
HRF 7/22 before late 2003. In these furnaces the Instrument switch does not cut power to the fan.
The fan is on whenever furnace is connected to the supply. See section 7.1.
Connect the furnace to the electrical supply.
Operate the instrument switch to activate the temperature controller. The controller becomes
illuminated and goes through a short test cycle.
Adjust the temperature – see the controller manual.
Industrial Models. Press the Fan Start button. The fan starts, and allows the furnace to heat up. If
at any time the Fan Stop button is pressed, the fan stops and power is no longer be supplied to the
elements. Note that opening the door also cuts power to the fan and the elements.
Overtemperature option only. If the overtemperature controller has not yet been set as required, set
it and activate it according to the instructions in the appropriate manual.
Unless a time switch is fitted and is off, the furnace starts to heat up. The Heat light glows steadily
at first and then flashes as the furnace approaches the desired temperature or a program setpoint.
Overtemperature option only. If the overtemperature trip operates then an indicator in the
overtemperature controller flashes, and the heating elements are isolated. Find and correct the
cause before resetting the overtemperature controller according the instructions supplied.
To turn the furnace off, set the Instrument switch to it’s off position; the controller display will go
blank. If the furnace is to be left off unattended, isolate it the electrical supply.
HRF 7/22: In models from late 2003 where the fan is subject to the Instrument switch, do not
switch off unless the furnace temperature is below 400°C (to initiate cooling, lower the controller
setpoint). Failure to observe this may reduce fan motor life.
3.2 General Operating Advice
Heating element life is shortened by use at temperatures close to maximum. Do not leave the
furnace at high temperature when not required. The maximum temperature is shown on the furnace
rating label and on the back page of this manual.
When heating materials which produce smoke or fumes, the chimney must be correctly fitted and
unobstructed to avoid accumulation of soot in the chamber and possible electrical breakdown of
the heating element. If the furnace is used to heat materials which emit smoke or fumes, regularly
heat it up to maximum temperature for one hour without load to burn away the soot.
Light weight ceramic fibre insulation can easily be marked by accidental contact. Some fine cracks
may be visible on the surface of the insulation, or may develop in the surface of the chamber due
to the progressive shrinkage of the insulation materials. Cracks are not usually detrimental to the
functioning or the safety of the furnace.
3.3 Atmospheres
When an optional gas inlet is fitted there is a label near the inlet saying "INERT GAS ONLY". In
practice inert or oxidising gases may be used, but not combustible or toxic gases. Chamber
furnaces are not gas tight, so it should be understood that gas usage may be high, and that the
chamber is likely always to contain some air. Residual oxygen levels of 1% are to be expected.