Carbolite VCF User Manual

CONTENTS

Section page

Installation, Operation &

Maintenance Instructions

1200°C Vertical Chamber Furnaces

VCF 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.

Manuals are supplied separately for the furnace controller

(and overtemperature controller when fitted).

Please read the controller manuals before operating the furnace.

MF25 – 3.09

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

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.

VCF

1.0 SYMBOLS & WARNINGS

1.1 Switches and Lights

1.2 Warning Symbols

2 MF25 – 3.09

VCF

note: throughout this

manual the furnace lid is

referred to as a “door”.

2.0 INSTALLATION

2.1 Unpacking & Handling

When unpacking or moving the furnace always lift it by its

base. Never lift it by the door or by any inset or protruding
parts. Use two people to carry the furnace where possible.
Remove any packing material from the door gear and furnace chamber 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 & Setting Up

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.

If the chimney is supplied unfitted, then fit it into the hole in the top of the furnace door. If the

furnace is to be used to heat substances which emit fumes, then a fume extraction duct of about
150mm inlet diameter may be placed directly above the chimney outlet; the duct would have to be
removable or flexible. Do not make a sealed connection to the furnace chimney as this causes
excessive airflow through the chamber and results in poor temperature uniformity.

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)

VCF

2.3 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 23 litre models can
also be supplied for two or three phase use, and the 100 litre is normally supplied for three phase.
Three phase supplies may be with or without neutral: the furnace must only be connected to the
correct type of supply.

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.
The supply MUST incorporate an earth (ground).

4 MF25 – 3.09

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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 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 controller(s) (and

contactor when fitted).
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.
Close the furnace door and adjust the temperature controller – 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.
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 to the instructions supplied.
To turn the furnace off, set the Instrument switch to it’s off position; the controller display will go

blank. If the furnace is to be left off unattended, isolate it 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 is shown on the furnace

rating label and on the back page of this manual.
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 object is placed in the chamber it may record the average temperature of the

object and the elements, which can lead to overheating of the elements. Allow large objects to gain

heat at a lower temperature and then reset the controller to a temperature close to the desired

maximum.
When heating materials which produce smoke or fumes, the chimney must be correctly fitted and

unobstructed. Otherwise, soot accumulates in the chamber and could possibly cause an electrical

breakdown of the heating element.
If the furnace is used to heat materials which emit smoke or fumes, regularly heat it up to

maximum temperature for one hour without load to burn away the soot.
Materials such as case hardening compounds and other reactive salts may penetrate the furnace

chamber lining and attack the wire elements, causing premature failure. Use of a hearth tile may be

advisable: please consult our technical department.
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 progressive shrinkage of the insulation materials. Cracks are not usually detrimental to the

functioning or the safety of the furnace.