Carbolite TZF Series - Manual (Page 6)

6 MF12 3.12
the retransmitted set temperature. In level 2 of the end zone controller (see controller operating
instruction), scroll to
LOC.T (local trim) and use the  up  down enter the desired positive or
negative difference to be added to the end zone set temperature. There is no need to alter the
centre controller.
C. Independent Control
In this case the three controllers are completely independent. Note that it is not possible to
maintain very different zone temperatures because of heat transfer within the work tube.
3.2 Operating Cycle
The furnace is fitted with an instrument switch. The switch cuts off power to the controller(s) and
contactor (when fitted). 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.
Control methods A & B: Set the slave (end zone) controllers to the desired offset temperature,
usually zero. Set the main (central) temperature controller to the desired setpoint or program. See
section 3.1 and/or the separate manual(s) for the controller(s).
Control method C: Set the three controllers to the desired temperatures. See the separate
manual(s) for the controller(s).
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.
3.3 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.
3.4 Operator Safety
The ceramic materials used in furnace manufacture become electrically conductive to some extent
at high temperatures. 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).
Switch off the Heater switch whenever loading or unloading the furnace. The elements are isolated
when the Heater switch is OFF. This switch cuts both sides of the circuit directly or via a contactor
(a contactor is used in models where the rated current exceeds 16 Amps).