ELF (B)
O
PERATION
3.1 Operating Cycle
The furnace is fitted with a combined Supply light and Instrument switch. The light is on
whenever the furnace is connected to the supply. The switch cuts off power to the controller.
Connect the furnace to the electrical supply. The Supply light should glow.
Operate the instrument switch, located on the front panel, to activate the temperature controller;
the
O
position is
off
, the
I
position
on
. The controller becomes illuminated and goes through a
short test cycle.
Close the furnace door and adjust the temperature controller – see section 4.0.
As the furnace heats up the Heat light glows steadily at first and then flashes as the furnace
approaches the desired temperature. For further information on temperature control see section
4.0.
To switch off, set the instrument switch to
O
. If the furnace is to be left off, isolate it from the
electrical supply.
3.2 General Operating Notes
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 for ELF models is
1100°C (2012°2F).
When heating large objects, in particular poor conductors, avoid shielding the thermocouple from
the heating elements. The thermocouple is intended to sense the temperature near the heating
element, but if a large cold object is placed in the chamber it may record the average temperature
of the object and the element, which can lead to overheating of the element. Allow large objects to
gain heat at a lower temperature and then adjust the controller setpoint to a temperature close to
the desired maximum.
Materials such as case hardening compounds and other reactive salts may attack the wire
elements, causing premature failure. The insulation chamber includes a ceramic hearth that helps
to protect the insulated floor.
Note that if the door vents are open then the entry of cold air through the vents can give rise to a
cool area in the chamber.
The moulded light weight ceramic fibre insulation can easily be marked by accidental contact with
tongs etc.. Some fine cracks may be visible at the front of the insulation, or may develop in the
surface of the chamber due to the progressive shrinkage of the ceramic fibres. Cracks are not
usually detrimental to the functioning of the furnace.
When heating materials that produce smoke or fumes, the chimney must be correctly fitted and
unobstructed. Otherwise, soot may accumulate in the chamber and could possibly cause an
electrical breakdown of the heating element. To prevent this, regularly heat the furnace up to
maximum temperature for one hour without load to burn away the soot.
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.
3.4
Operator Safety
The furnace incorporates a pair of switches that safely interrupt the heating element circuit when
the door is opened. This prevents the user touching a live heating element, but also prevents the
furnace from heating up if the door is left open.
MF01
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