Carbolite GVC User Manual
CONTENTS
Section page
Installation, Operation &
Maintenance Instructions
1200°C G-range Tube furnaces
Models GHA, GVA, GHC, GVC
This manual is for the guidance of operators of the above Carbolite products
and should be read before the furnace is connected to the electricity supply.
Manuals are supplied separately for the furnace controller
(and overtemperature controller when fitted).
Please read the controller manuals before operating the furnace.
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DANGER of electrical shock– read any warning printed by this symbol.
DANGER – hot surface. Read any warning printed by this symbol.
WARNING: all surfaces of a furnace may be hot.
DANGER – read any warning printed by this symbol.
Instrument switch: when the instrument switch is operated the temperature
control circuit is energised.
Heat Light: the adjacent light glows or flashes to indicate that power is
being supplied to the elements
Heat Switch: the switch disconnects power to the heating elements; unless
this switch is off there is a danger of electric shock when inserting objects
into the furnace
1.0 INTRODUCTION
1.1 Products Covered
This manual contains installation and operating instructions for the single-zone tube furnaces of
model types GHA and GVA, and the three-zone models GHC and GVC.
The single-zone models use one controller or programmer operating on all elements. The threezone models use three controllers, usually linked to achieve and extended uniform temperature
region, but independent controls and extended end zones are available as options.
The horizontal tube furnaces GHA and GHC are supplied with the controls in an integral base (or,
to order, with the base control panel blanked off, and the controls in a separate box). A horizontal
tube support kit, comprising some parts of the versatile stand, is also available.
The “versatile” models GVA and GVC models are supplied with a stand kit for horizontal, vertical
or wall-mounting use, and have the controls in a separate box on a length of flexible conduit.
Optionally the stand foot can be omitted, or the complete stand can be omitted.
All G-range tube furnaces have “modular” heating elements in which resistance wire is partially
embedded in vacuum formed light-weight refractory fibre. The modules are 150mm long. In all
standard models the two end elements (one at each end) are rated at 1170W maximum, while the
other (centre) elements are rated at 780W.
All models are supplied with a pair of “tube adaptors”, which can be made to suit any work tube
size up to 170mm outside diameter. Spare or replacement adaptors can be ordered.
This manual may also be issued with custom versions of the above; for example, with elements of
non-standard wattage, with 2-zone or 5-zone models, or other possibilities based on the underlying
design concept.
1.2 Switches and Lights
1.3 Warning Symbols
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2.0 INSTALLATION
2.1 Unpacking & Handling
When unpacking or moving the furnace always lift it by its base or by both ends of the main body.
Never lift it by the end insulation or by a work tube. It will take 2 or 3 people to lift the furnace,
depending on size and configuration.
Remove any packing material from inside the furnace before use.
NOTE: This product contains Refractory Ceramic Fibre (better described as Alumino Silicate
Wool) for precautions and advice in handling this material see the ‘Repairs and Replacements’
section.
2.2 Siting
Place the furnace in a well ventilated room, away from other sources of heat, and on a surface
which is resistant to accidental spillage of hot materials. Do not mount the furnace on an
inflammable surface.
Ensure that there is free space around the furnace. Do not obstruct any of the vents in the control
section: they are needed to keep the controls cool.
Ensure that the furnace is placed in such a way that it can be quickly switched off or disconnected
from the electrical supply - see below.
2.3 Setting Up – Horizontal Models
The horizontal models generally require no special setting up. Observe the above paragraph on
siting. See section 0 for work tube and end adaptor considerations.
If the optional horizontal tube support kit is supplied, the rails can be fixed to the base, and the
tube supports positioned at a choice of positions.
2.4 Setting Up – Versatile Models
The full stand kit may be used in several combinations.
- vertical use, bench or floor mounted: assemble the two long rails to the foot
- vertical/horizontal: as above, then add one wall bracket; the combination of foot and bracket
makes the furnace body level in the horizontal position
- horizontal use only: the foot is not
required; instead, a second bracket is
fitted
- wall mounting: exactly as horizontal
only: two rails and two brackets
- no stand: mounting of the furnace is
entirely at the customer’s discretion,
but if the furnace is to be used at
1100°C or more in a horizontal
position, then the face of the cylinder
opposite to the terminal cover should
be uppermost. Failure to position
this face uppermost can lead to high
case temperatures, and the customer
may need to provide additional
operator protection from hot
surfaces.
- horizontal with heavy tubes: the rails
fix to the base and the horizontal
tube supports to the rails
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Heated Length
Type C
Type D
End Adaptor
Work Tube
Guards
Work Tubes and Fittings
Tubes of various diameters and lengths
may be fitted.
Type C: minimum length for the furnace
Type D: 300mm longer than C, to allow
for the fitting of end seals.
A pair of removable “tube adaptors” (or
“end adaptors”) form part of the end
insulation. These may be blank (no hole) or may have a hole to suit a work tube, depending on the
customer order. Additional adaptors may be ordered to suit different work tube sizes. Check that
the end adaptors are correct for the tube: if not, seek advice from Carbolite. Small alterations to the
hole in the adaptors may be made with a file, but first read the section on ceramic fibre safety
(5.2).
To insert a work tube it is often convenient to use a long pole (such as a broom handle) to guide it
into the far end of the furnace.
For optimum temperature uniformity, insulating plugs should be placed in the tube ends as shown
in fig.1. With an extended work tube (type D), the stem of the plug assembly should line up with
the end of the tube as in fig.2. Alignment of radiation shields is similar to that of plugs.
If stainless steel seals with gas inlets are supplied they are to be fitted as shown in fig.3; the stem
of any insulating plug should touch the seal. For vertical use a hook and eye arrangement holds the
upper insulating plug assembly (in some cases a gland nut may alternatively be used).
Horizontal use: if heavy fittings are to be clamped to the end of an extended work tube they can
increase the bending stress at the centre of the tube. Support such fittings in such a way that
expansion of the tube is allowed. A horizontal tube support kit can be supplied for this purpose (in
the versatile models the kit includes supports).
If a metal work tube is being used in the furnace, ensure that it is earthed. See the safety warning in
section 3.4.
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CONNECTION DETAILS
supply type
Supply
Terminal label
Cable colour
Live-Neutral
Reversible or Live-Live
1-phase
L
Brown
To live
to either power conductor
N
Blue
To neutral
to the other power conductor
PE
Green/Yellow
To earth (ground)
to earth (ground)
supply
Terminal label
Cable colour
2- or 3-phase
L1
Black
to phase 1
L2
Black
to phase 2
L3
Black
to phase 3 except 2-phase
N
Light Blue
to neutral except delta
PE
Green/Yellow
to earth (ground)
2.5 Electrical Connections
Connection by a qualified electrician is recommended.
All furnaces covered by this manual may be ordered for single phase A.C. supply, which may be
Live to Neutral non-reversible, Live to Neutral reversible or Live to Live. The 2-element models
(-/300) can be supplied for use on two phases of a 3-phase+N supply, and the 3-element models
(-/450) for three phases of a 3-phase+N supply or a delta supply up to 240V. From -/600 upwards
all the G-range are made with “universal” wiring, such that they may be reconfigured between
1phase, 3-phase+N and 3-phase delta. They are, however, factory set to the ordered supply.
Check the furnace rating label before connection. If the supply voltage and phase does not agree
with the rating label, then read section 2.6 – it may be possible to reconfigure the furnace and/or
adjust the power.
The supply should be fused at the next standard size equal to or higher than the design amperage.
See section 8.1. Where a supply cable is present there are internal supply fuses, in which case
customer fusing is preferred but not essential.
If a supply cable is fitted it may be connected to an isolator or fitted with a line plug. Where no
supply cable is fitted a permanent connection to a fused and isolated supply should be made to the
internal terminals after temporary removal of the furnace back panel. A line plug should be within
reach of the operator, and should be quickly removable. An isolating switch should operate on
both conductors (single phase) or on all live conductors (three phase), and should be within reach
of the operator.
The supply MUST incorporate an earth (ground).
2.6 Reconfiguring and Adjusting for Voltage.
In the instructions below, “controllers” means the single element controller in the single zone
modes, or the three element controllers in the 3-zone models. The overtemperature controller
(where fitted) is not affected.
Models –/300
The standard single-phase models can operate over the voltage range 200V-240V. The 2-phase
models can operate over the range 380/220V to 415/240V. The furnace is wired according to the
original order and conversion from 1-phase to 2-phase is not possible. To check for voltage setting
within the appropriate range, or to change to another setting, follow the instructions in section 8.2.
Models –/450 (1-phase)
The standard single-phase models can operate over the voltage range 200V-240V. The 3-phase
models can operate over the range 380/220V to 415/240V. The furnace is wired according to the
original order and conversion from 1-phase to 3-phase is not possible. To check for voltage setting
within the appropriate range, or to change to another setting, follow the instructions in section 8.2.
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Models -/600 to -/1200 (and -/450 3-phase)
These models are all made to a “universal” wiring scheme, whereby the customer may, if
necessary, convert between single- and 3-phase supplies of the following types:
- 200 to 240V single-phase
- 200 to 240V 3-phase without neutral (delta)
- 380/220 to 415/240V 3-phase with neutral
To reconfigure the wiring to change between types of supply, see section 7.7.
To check the setting for the voltage within the range, or to alter it, follow the instructions in
section 8.2.
Special Voltages
The furnaces can be specially made to suit certain special voltages, such as 440/254 or 480/277.
Because of unbalanced phases the furnaces cannot be made to suit 3-phase without neutral of
380V or above.
At the time or writing, 110-120V models are not available.
Furnaces made for special voltages are generally not convertible between configurations and
voltages.
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3.0 OPERATION
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 MS0. 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 that 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.
Single zone models, GHA and GVA: Set the temperature controller to the desired setpoint or
program - see the controller manual.
3-zone models, GHC and GVC, with 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 3.2 and/or the separate manual(s) for the controller(s).
3-zone models, GHC and GVC, with 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 controller 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 overtemperature 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 3-zone Control Methods – models GHC and GVC
These models are typically designed to achieve an extended uniform temperature zone by the use
of three control zones. The control zones are typically linked so that the end controllers follow the
central controller in a master-slave approach, in one of two ways. Alternatively independent
control zones may be ordered. There are thus three control methods (A, B & C).
Zone lengths: The normal end-zone length for all the 3-zone models is 1 element (150mm). The
“equal zone” models (with suffix E after the model name) have longer end-zones of 2 elements
(300mm); only the models 12/450 and 12/900E have truly equal zone lengths. Any of the control
methods can apply to equal zone models, just as they can to the standard models.
Achieving temperature differences across the zones: a small temperature difference may be
achievable, but this is limited by the effect of radiated heat inside the furnace body, and in the
work tube, and depends also upon the furnace contents.
A. Back-to-Back Thermocouples
This is the most commonly supplied option.
The central zone of the work tube is controlled directly by the central temperature controller. Each
end zone thermocouple is wired in opposition to a central reference thermocouple, and the small
voltage resulting when the zones are at different temperatures is used by the end zone controller.
There are thus four thermocouples. The circuit diagram in section 7.6 (A) shows the thermocouple
arrangement.
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Home
List
Access
List
°C/F/k
ACCS
°C/F/k
codE
0.0
Zone temperature
difference; use / to
access offset “setpoint”
home list
for factory access to lists
and parameters not
available to the operator
OP.Hi
Output
List
oP
power limit
setting, if
present
Set the “setpoint” of the end zone controllers to zero. Alternatively, a small temperature difference
(offset) can be created by setting a non-zero value, but the sum of the main controller set-point and
the slave controller offset MUST NOT exceed the furnace maximum temperature. The “measured
temperature” display shows the actual offset.
To alter the setpoint (with the display at “home”), press Down or Up once to display the
setpoint; press again or hold down to adjust it. The display returns to the measured temperature
offset when no key is pressed for 0.5 seconds.
Sometimes a furnace using this type of control does not cool down: the end controllers try to
remain at the current central temperature. Should this occur, contact Carbolite’s technical
department.
2132 Slave Controller Navigation Diagram
B. Retransmission of Setpoint Using Broadcast Comms
When this is ordered there are three independent thermocouples connected to the three controllers.
The controllers are linked together, the central controller communicating the desired setpoint to the
end controllers.
Additional communication modules are fitted in the controllers, rather than an additional
thermocouple as in A. The communication between the controllers of the Eurotherm 3000 series is
known as Broadcast comms. The wiring connections between the controllers are shown in section
7.8
It is possible to switch off the linked control and allow the controllers to work independently. In
level 2 of the end zone controller (see controller operating instruction), scroll to L-r and use the
up down and select NO. The is no need to alter the centre controller.
It is possible to use local trim in the end zone controllers to enter a positive or negative adjustment
from the centre zone temperature. Once entered this trim will always be added or subtracted from
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. Remember that it is not possible to
maintain very different zone temperatures because of heat transfer within the furnace body and
work tube.
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 rating
label and on the back page of this manual.
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
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