Carbolite VST Series - Manual (Page 5)

HST, VST
MF13 – 3.40
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.
If cascade control is fitted, see the supplementary manual MS07.
3.1 Operating Cycle
The furnace is fitted with an instrument switch. The switch cuts off power to the control circuit.
There is also a heater switch which can be used to disconnect power to the elements.
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.
Set the temperature controller to the desired setpoint or program - see the controller manual.
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.
Switch on the Heater switch, located on the instrument panel. Unless a time switch is fitted and is
off, the furnace starts to heat up. The Heat light(s) glow steadily at first and then flash as the
furnace approaches the desired temperature or a program setpoint.
Overtemperature option only. If the overtemperature trip operates then an indicator in the over-
temperature controller flashes, and the heating elements are isolated. Find and correct the cause
before resetting the overtemperature controller according the instructions supplied.
To switch off power to the heating elements, use the Heater Switch. To switch the furnace off, use
both the Heater switch and the Instrument switch. If the furnace is to be left off unattended, isolate
it from the electrical supply.
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.
Lightweight 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 Operator Safety
The ceramic materials used in furnace manufacture become electrically conductive to some extent
at high temperatures. In these models there are partially exposed heating coils in the chamber and
there is danger of contact even with the furnace closed. DO NOT use any conductive tools within
the work tube without isolating it. If a metal work tube is used, it must be earthed (grounded).
The furnace incorporates a safety switch which interrupts the heating element circuit when it is
opened. This prevents the user touching a live heating element, but also prevents the furnace from
heating up when open. The operation of this switch should be checked periodically – see section
4.1.2.
There is also a “Heater switch” which may be used to interrupt power to the elements. Switch off
the Heater switch whenever loading or unloading the furnace. The elements are isolated when the
Heater switch is OFF.
Avoid burns: furnace surfaces can be hot. Before you remove a hot object from the furnace make
sure you have a safe place to put it down.