Carbolite CFM MODELS Guide

Installation, Operation &
Maintenance Instructions
Combustion Tube Furnaces
CFM models
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.
CONTENTS
Section page
1.0 Symbols & Warnings 1
2.0 Installation 3
3.0 Operation 4
4.0 Maintenance 6
5.0 Repairs & Replacements 8
6.0 Fault Analysis 12
7.0 Circuit Diagrams 13
8.0 Fuses & Power Settings 13
9.0 Specifications 16
Manuals are supplied separately for the furnace controller
(and overtemperature controller when fitted).
Please read the controller manuals before operating the furnace.
1.0
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SYMBOLS & WARNINGS
1.1 Switches and Lights
Supply Light: when the furnace is connected to the electrical supply the
light in the adjacent switch glows
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
Heat Light: the adjacent light glows or flashes to indicate that power is
being supplied to the elements
1.2 Warning Symbols
DANGER of electrical shoc
k
– 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.
2.0
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INSTALLATION
2.1 Unpacking & Handling
When unpacking or moving the furnace always lift it by its base. Do not lift it by the end panels or
by the internal insulation. Use two people to carry the furnace where possible. Remove any
packing material from inside the furnace before use.
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
The furnace is typically used for sulphur and chlorine test in accordance with BS1016 parts 6 & 7,
ASTM D 3177-75; ISO 351 & 609. Please refer to the appropriate documentation. This manual
only gives general guidance common to tube furnaces.
Fit any work tube(s) ordered into place.
If a metal work tube is being used in the furnace, ensure that it is earthed, and that it is mounted so
as not to touch the furnace ceramic tube or insulation. See the safety warning in section 3.5.
2.4 Heating Elements (1400°C Models)
The Silicon Carbide elements are VERY FRAGILE and are packed separately. Fit them according to
the instructions in section 5.7.
2.5
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Electrical Connections
Connection by a qualified electrician is recommended.
The furnaces covered by this manual require a single-phase A.C. supply with earth (ground). The
supply may be Live to Neutral non-reversible, Live to Neutral with reversible plug, or Live to
Live.
Check the furnace rating label before connection. The supply voltage should agree with the
voltage on the label, and the supply capacity should be sufficient for the amperage on the label.
The supply should be fused at the next size equal to or higher than the amperage on the label. A
table of the most common fuse ratings is also given in section 8.1 of this manual. Where a supply
cable is present there are internal supply fuses; customer fusing is preferred but not essential.
Furnace with supply cable: either wire directly to an isolator or fit with a line plug.
Furnace without supply cable: a permanent connection to a fused and isolated supply should be
made to the internal terminals after temporary removal of the furnace back panel.
Connection by line plug: the plug should be within reach of the operator, and should be quickly
removable. Connection to isolating switch: this should operate on both conductors (single phase)
or on all live conductors (three phase), and should be within reach of the operator.
Single phase: connect the supply as follows:
supply type
Cable colour Terminal
label Live-Neutral Reversible or Live-Live
Brown L to live to either power conductor
Blue N to neutral to the other power
conductor
Green/Yellow PE to earth (ground) to earth (ground)
The supply MUST incorporate an earth (ground).
Technical Note (1400°C Models)
The 1400°C models have an electronically controlled power limit. Do not attempt to calculate the
Amps from the Wattage. High break capacity fuses should be used. Avoid fast-blow fuses and
magnetic trip circuit breakers - consult Carbolite if in doubt.
3.0
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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 MS03.
3.1 Operating Cycle
If the furnace has an auxiliary heater, see also section 3.2.
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 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. The Supply light should glow.
Operate the instrument switch to activate the temperature controller; the Oposition is off, the
Iposition on. The controller becomes illuminated and goes through a short test cycle. Adjust the
temperature controller (see 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.
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, set the Instrument switch to off. If the furnace is to be left off, isolate it
the electrical supply.
3.2 Auxiliary heater (if fitted)
The auxiliary heater is controlled by an independent temperature controller, which is affected by
the same instrument switch as the main controller. Note that a time switch (if fitted) may not
switch off the auxiliary heater, depending on other options ordered.
Set the auxiliary heater's temperature controller after setting the main controller, as given in
section.
Auxiliary heater controller navigation diagram:
Home
List Access List
3.3
20.0 ACCS
4
OP codE
4

*C
f
or factory access to
lists and parameters
not available to the
operator
output power,
read only

*C
measured temperature;
use
T / S to access
s
et
p
oin
t

4
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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.
Switch off the Heater switch whenever loading or unloading the furnace - see the safety warning
below.
3.4 Tube Life
A work tube may be cracked if workpieces are inserted too
quickly or at temperatures below 900°C (when the tube is
more brittle). Large pieces should also be heated slowly to
ensure that large temperature differences do not arise.
Poor thermal contact should be encouraged between the
workpiece and the tube; crucibles or boats should be of low
thermal mass and should have feet to reduce the contact
with the tube.
Avoid metal directly touching the work tube - see the safety warning below.
3.5 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.
The work tube is isolated when the Heater switch is OFF. This switch cuts both sides of the circuit
directly or, where the rated current exceeds 16 Amps, via a contactor.
3.6 Pressure
Work tubes are not able to accept high internal pressure. When gas seals or similar fittings are in
use, the gas pressure should be restricted to a maximum of 0.2 bar (3 psi). A pressure of about half
of that should normally be sufficient to achieve the desired flow rate. The customer must ensure
that the exhaust path from the tube is not blocked, so that excess pressure does not occur.
4.0
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MAINTENANCE
4.1 General Maintenance
No routine maintenance is required other than the occasional replacement of consumable items.
The furnace outer surface may be cleaned with a damp cloth. Do not allow water to enter the
interior of the case or chamber. Do not clean with organic solvents.
4.2 Calibration
After prolonged use the controller and/or thermocouple could require recalibration. This would be
important for processes which require accurate temperature readings or which use the furnace
close to its maximum temperature. A quick check using an independent thermocouple and
temperature indicator should be made from time to time to determine whether full calibration is
required. Carbolite can supply these items.
Depending on the controller, the controller manual may contain calibration instructions.
4.3 After Sales Service
Carbolite’s service division (Thermal Engineering Services) has a team of Service Engineers
capable of repair, calibration and preventive maintenance of furnace and oven products at our
customers’ premises throughout the world. We also sell spares by mail order. A telephone call or
fax often enables a fault to be diagnosed and the necessary spare part despatched.
Each furnace has its own record card at Carbolite. In all correspondence please quote the serial
number, model type and voltage given on the rating label of the furnace. The serial number and
model type are also given on the front of this booklet when supplied with a furnace.
To contact Thermal Engineering Services or Carbolite see the back page of this manual.
4.4 Recommended Spares Kits
Carbolite can supply individual spares, or a kit of the items most likely to be required. Ordering a
kit in advance can save time in the event of a breakdown. Each kit comprises one thermocouple,
one solid state relay, one heating element or set of elements. For 1400°C models the kits also
include element clips and braids. Individual spares are also available.
When ordering spares please quote the model details as requested above.
4.5 Power Limit
In the 1400°C models the furnace control system incorporates electronic power limiting. Power is
supplied to the elements in bursts of about 1/3rd second duration. This prevents overheating of the
elements. The power limit is programmed into the furnace controller and may be calculated as a
percentage as follows:
powerlimit = (100 x targetpower x ohms) / volts2
where targetpower is the wattage given on the furnace rating label
ohms is the overall resistance of the combined element circuits (see example)
volts is the voltage across each element circuit (e.g. 240 for a 415/240V supply)
example:
1-phase furnace with 4 elements of 3.6 ohms each in series, running on
220V, with a target power of 2250W:
ohms = 3.6 x 4 = 14.4
powerlimit = (100 x 2250 x 14.4) / (220 x 220) = 67%
A table of power limit settings is given in section 8.2. These are the settings for the furnace with
new elements as supplied.
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All models. Occasionally the power limit is set to zero to permit demonstration of the controls
without the heating elements taking power. The operator may reset it to its standard value or the
value that it had before setting to zero.
4.6 Element Aging
Applicable to 1400°C models.
Silicon carbide elements gradually increase in resistance with use: a process known as aging.
Their heating power reduces correspondingly. To ensure sufficient power to the furnace it may be
necessary to adjust the power limit, and, ultimately, to replace the elements - taking care to
readjust the power limit.
If the furnace does not reach temperature, or is slow, measure the element resistances and
calculate the required power limit using the method given above. If it exceeds 100%, the elements
have too high a resistance and need replacing: check your data and calculations with Carbolite.
See the separate manual supplied for how to adjust the controller. Always record the setting when
first making an adjustment. If new elements are fitted, return the adjustments to the original value,
or remeasure and recalculate. A table of standard power limits in given is section 8.2.
CFM 14/4: This model has only a small margin for power limit adjustment on 240V. Power limit
adjustment should not be necessary.
5.0
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REPAIRS & REPLACEMENTS
5.1 Safety Warning – Disconnection from Supply
Always ensure that the furnace is disconnected from the supply before repair work
is carried out.
5.2 Safety Note - Refractory Fibrous Insulation
This furnace contains refractory fibres in its thermal insulation. These materials may
be in the form of fibre blanket or felt, vacuum formed board or shapes, mineral wool
slab or loose fill fibre.
Normal use of the furnace does not result in any significant level of airborne dust from these
materials, but much higher levels may be encountered during maintenance or repair.
Whilst there is no evidence of any long term health hazards, we strongly recommend that safety
precautions are taken whenever the materials are handled.
Exposure to dust from fibre which has been used at high temperatures may cause
respiratory disease.
When handling fibre always use an approved mask, eye protection, gloves and long
sleeved clothing.
Avoid breaking up waste material. Dispose of waste fibre in sealed containers.
After handling rinse exposed skin with water before washing gently with soap (not
detergent). Wash work clothing separately.
Before commencing any major repairs we recommend reference to the European Ceramic Fibre
Industry Association Bulletin No. 11 and the UK Health and Safety Executive Guidance Note
EH46.
We can provide further information on request. Alternatively our service division can quote for
any repairs to be carried out at your premises or ours.
5.3 Temperature Controller Replacement
201. This controller is fitted to the back of the control panel; in many models this can be separated
from the base by removal of two screws.
Before handling the controller: wear an anti-static wrist strap or otherwise avoid any possibility
of damage to the unit by static electricity.
Refer to the detailed instructions supplied with the replacement controller.
2132, 2416, 2408 etc. Ease apart the two lugs at the side; grip the instrument and withdraw it from
its sleeve; push in the replacement.
5.4 Solid-state Relay Replacement
Disconnect the furnace from the supply and remove the end panel at the supply cable end.
Make a note how the wires are connected to the solid state relay, and disconnect them.
Remove the solid state relay from the base panel or aluminium plate.
Replace and reconnect the solid state relay ensuring that the heat-conducting thermal pad is
sandwiched between the relay and the base panel or aluminium plate. Alternatively a thin layer of
white, heat-conducting silicon paste may be applied between the new relay and the plate.
The new solid state relay contains a built-in MOV which protects it from short periods of excess
voltage. If the old relay had a separate disc-shaped "MOV" connected between the high voltage
terminals of the old relay, discard the old MOV.
Replace the removed panel.
5.5 Thermocouple Replacement
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Disconnect the furnace from the supply, and remove the end panel at the thermocouple end.
Make a note of the thermocouple connections. The negative leg of the thermocouple is marked
blue. Compensating cable colour codings are:
negative positive (type R)
white orange
Disconnect the thermocouple from its terminal block; retain any porcelain spacers.
Withdraw the thermocouple from its sheath and remove any broken bits of thermocouple.
Re-assemble with a new thermocouple observing the colour coding.
5.6 Element Replacement - 1200°C models
Please see safety note 5.2- wearing a face mask is recommended.
The chamber of this type of furnace contains a tubular refractory muffle around which is wound
resistance heating wire. In the event of failure, the whole "wound muffle" assembly must be
replaced.
Disconnect the furnace from the electrical supply and remove both furnace end panels.
Make a note of all the wiring connections; see the section above which refers to the thermocouple
colour coding.
Unfasten the electrical connections to the inner chamber (brick-box) and remove the thermocouple
(see thermocouple replacement instructions). If the connections are secured by hexagonal nuts,
two spanners should be used to avoid cracking the porcelain mounting.
Undo any screws, bolts or hook bolts necessary to release the brick-box.
Support the brick box as you withdraw it from the case so it does not fall onto the electrical
connections below.
Remove the brick box lid and all insulation, noting how it is assembled and observing the position
of the heating element wires (or "tails").
Pull the element tails out of the terminal blocks and remove sufficient insulation to allow access to
the heating element. Check and replace damaged insulation.
Fit the new heating element, ensuring that the tails are separated from the element by at least 25
mm of insulation.
Feed the heating element tails through the terminal blocks and tighten the clamping screws using
two spanners as before. Cut off excess element tails.
Refit the insulation and refit the lid. Do not use any cement unless supplied by Carbolite, as other
types may chemically attack the heating element.
Replace and fasten the brick-box into the furnace case.
Replace the thermocouple and remake the electrical connections. In porcelain and brass terminal
blocks the brass connector should be slightly loose in its porcelain support block to allow for
expansion.
Replace the panels and reconnect the electrical supply.
Switch the furnace ON and heat to 900°C without interruption, and then soak for 1 hour. Some
smoke may be observed during this process, which should be carried out in a well ventilated area.
Check that the furnace is controlling properly to rule out the possibility that previous element
failed because of a fault in the control circuit.
If you have any problems with this procedure, please contact our service division.
5.7 Element Fitting and Replacement - 1400°C models
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CFM
Replacements: read the section on element aging (0). If at any time the power limit has been
increased, measure the new element resistances and recalculate the limit.
Disconnect the furnace from the electrical supply.
Remove the furnace end panels to gain access to the element connections.
The elements are expensive and fragile, and can be damaged by contamination: handle them with
care and keep them clean.
Replacements only: make a note of the actual braid and cable connections to the elements.
Disconnect the clips with the special tool provided (or with finger pressure, depending on the type
of clips supplied), lift off the braids and carefully withdraw each element. See fig. 5.
Carefully insert the new elements into the furnace.
Attach the connection braids according to the note made above or to the appropriate diagram,
fig. 6. Use the special tool (or finger pressure) to fit the clips. Take care that adjacent clips do not
touch each other.
Replace the furnace end guards and connect the furnace to the supply.
If aged elements have been replaced, reset the furnace power limit.
CFM 14/4: this model has 6 elements in series on 220-240V. On 110-120V these are connected as
two sets of 3 elements in series, in which case the L and N connections are at opposite ends of the
furnace.
5.8 Fuse Replacement
Fuses are marked on the circuit diagram (section 7.0) with type codes, e.g. F1, F2. A list of the
correct fuses is given in section 8.1. Depending on model and voltage, the different fuse types may
or may not be fitted.
If any fuse has failed, it is advisable for an electrician to check the internal circuits.
Replace any failed fuses with the correct type. For safety reasons do not fit larger capacity fuses
without first consulting Carbolite.
The fuses are near the cable entry point, and access is by removal of a panel.
6.0
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FAULT ANALYSIS
A. Furnace Does Not Heat Up
1. The HEAT light
is ON ÆThe heating
element has failed ÆCheck also that the SSR is working
correctly
2. The HEAT light
is OFF The controller
shows a very high
temperature or a
code such as S.br
ÆThe thermocouple has broken or has a
wiring fault
The controller
shows a low
temperature
ÆThe door switch(es) (if fitted) may be
faulty or need adjustment
ÆThe contactor (if fitted) may be faulty
ÆThe SSR could be failing to switch on due
to internal failure, faulty logic wiring from
the controller, or faulty controller
There are no
lights glowing
on the
controller
ÆThe SUPPLY
light is ON ÆThe controller may be
faulty or not receiving a
supply due to a faulty
switch or a wiring fault
ÆThe SUPPLY
light is OFF ÆCheck the supply fuses and
any fuses in the furnace
control compartment
B. Furnace Overheats
1. The HEAT light
goes OFF with
the instrument
switch
ÆThe controller
shows a very high
temperature
ÆThe controller is faulty
ÆThe controller
shows a low
temperature
ÆThe thermocouple may have been shorted
out or may have been moved out of the
heating chamber
ÆThe thermocouple may be mounted the
wrong way round
ÆThe controller may be faulty
2. The HEAT light
does not go off
with the
instrument
switch
ÆThe SSR has failed
“ON” ÆCheck for an accidental wiring fault which
could have overloaded the SSR
7.0
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CIRCUIT DIAGRAMS
Safety switches: where the furnace rating is over 16A, there is a single switch in the contactor coil
circuit, and the double switch shown is not present.
7.1 Single Phase
Supply ligh
t
Instrument Switch
coil
temperature
controller
overtemp.
controller
SSR
e
l
e
m
e
n
t
(s)
hea
t
on
safety
switch
F3
F1
F2
F3
N
L
PE
Filter (if fitted) contacto
r
i
f
o/tem
p
f
itted
thermocou
p
le
thermocou
p
le
Supply ligh
t
Instrument Switch
coil
temperature
controller
overtemp.
controller
thermocou
p
le
PE
L
N
SSR
e
l
e
m
e
n
t
(s)
F3
F3
F1
F2
contacto
r
i
f
o/tem
p
f
itted
thermocou
p
le
hea
t
on
7.2 1400°C Model with Auxiliary Heater
Supply ligh
t
Instrument Switch
coil
temperature
controller
overtemp.
controller
PE
L
N
SSR
e
l
e
m
e
n
t
(s)
hea
t
on
F3
F1
F2
F3
contacto
r
i
f
o/tem
p
f
itted
thermocou
p
le
thermocou
p
le
safety
switch
Filter (if fitted)
auxiliary
controller SSR
thermocou
p
le
a
u
x
contacto
r
(o/temp)
F2
transforme
r
F2
7.3 Higher Voltages
For 254V (or above) an isolating transformer is fitted in the
control circuit after the F2 fuses.
Supply light &
Instrument Switch
8.0 FUSES & POWER SETTINGS
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8.1 Fuses
F1-F3: Refer to the circuit diagrams.
F1 Internal
supply
fuses
Fitted if supply cable fitted.
Fitted on board to some types of EMC filter. on-board and up to 16 Amps:
32mm x 6mm type F
other: GEC Safeclip
F2 Auxiliary
circuit
fuses
Fitted on board to some types of EMC filter.
May be omitted up to 25Amp/phase supply
rating.
2 Amps glass type F
On board: 20mm x 5mm
Other: 32mm x 6mm
F3 Heat Light
fuses May be omitted up to 25 Amp/phase supply rating. 2 Amps glass type F
32mm x 6mm
Customer
fuses Required if no supply cable fitted.
Recommended if cable fitted. See rating label for amperage;
see table below for fuse rating.
Model phases Volts Supply Fuse
Rating Volts Supply Fuse Rating (type)
CFM 12/1, 12/2 1-phase 220-240 5A 110-120 10A
CFM 14/1, 14/2 1-phase 220-240 15A or 16A 110-120 30A or 32A
CFM 14/1, 14/2 + Aux 1-phase 220-240 20A 110-120 40A
CFM 14/4 1-phase 220-240 20A 110-120 40A
8.2 Power Settings
The power limit settings (parameter OP.Hi) for the 1200°C CFM models are all 100%, with the
exception of any units supplied for 254V operation where the limit is 89%.
The power limit settings for the 1400°C models are as follows. The figures represent the
maximum percentage of time that controlled power is supplied to the elements. Do not attempt to
“improve performance” by setting a value higher than the correct one from the table.
Model Volts: 110V 120V 208V 220V 230V 240V 254V
CFM 14/1 67 56 89 67 61 56 50
CFM 14/2 67 56 89 67 61 56 50
CFM 14/4 100 100 92 82
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9.0
MF10 15

Thank you for reading this data sheet.
For pricing or for further information, please contact us at our UK Office, using the details
below.
UK Office
Keison Products,
P.O. Box 2124, Chelmsford, Essex, CM1 3UP, Engl nd.
Tel: [phone]
F x: [phone]
Em il: s [email protected]
Please note - Product designs and specifications are sub ect to change without notice. The user is responsible for determining the
suitability of this product.