MF07 – 3.05 

Installation, Operation & 

Maintenance Instructions

1400°C - 1600°C Chamber Furnaces 

RHF models: 3 litre - 35 litre 

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. 

CONTENTS

Section page 

1.0 Symbols & Warnings 2 

2.0 Installation 2 

3.0 Operation 4 

4.0 Maintenance 6 

5.0 Repairs & Replacements 8 

6.0 Fault Analysis 11 

7.0 Circuit Diagrams 12 

8.0 Fuses & Power Settings 14 

9.0 Specifications 16 
RHF 

 

2 MF07 

1.0 SYMBOLS & WARNINGS

1.1 Switches and Lights

1.2 Warning Symbols

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. Use two 

or more people to carry the furnace where possible. Remove any packing material from the door 

gear and furnace chamber before use. 

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 case. 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. Do not make a sealed 

connection to the furnace chimney as this causes excessive airflow through the chamber and 

results in poor temperature uniformity. 

Supply Light: when the furnace is connected to the electrical supply the 

light in the adjacent switch glows 

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.
 

RHF 

 

MF07 3 

2.3 Heating Elements 

The Silicon Carbide elements are VERY FRAGILE and are packed separately. Fit them according to 

the instructions in section 5.7. 

2.4 Electrical Connections

Connection by a qualified electrician is recommended. 

Models RHF 14/3, 15/3, 16/3 and 14/8 may be ordered for single phase use or for two phases out 

of a three phase supply with neutral. All other models may be ordered for single phase use or for 

three phase with or without neutral. The furnace must be connected only to the type and voltage of 

the supply for which it was ordered. 

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; in this case 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). 

ELECTRICAL 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) 

Technical Notes 

The furnaces covered by this manual have electronically controlled power limits. 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. 

Two-phase models use two phases out of a 3-phase+neutral supply. One phase is unused. The 

neutral current is equal to the current in one of the used phases. 

Model RHF 16/35 has unequal phases: L1 and L2 have 4 heating elements and L3 has 2 elements. 

In 4-wire configuration, one phase takes half the current of the other two, and the neutral also takes 

this half-amount (see also section 8.1). 
RHF 

 

4 MF07 

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 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. 

Connect the furnace to the electrical supply. The Supply light should glow. 

Operate the instrument switch 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 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 the instructions supplied. 

To switch the furnace off, set the Instrument switch to O. If the furnace is to be left off, isolate it 

the electrical supply. 

3.2 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. 

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 can accumulate 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 insulation, or the elements, causing premature failure. Use of a 

hearth tile may be advisable: please consult our technical department. 
 

RHF 

 

MF07 5 

3.3 Use of Probes

Any metal object used to probe into the furnace chamber while the furnace is 

connected to the supply must be earthed (grounded). This applies in particular to 

metal sheathed thermocouples, where the sheaths must be earthed. The refractory 

material of the chamber lining becomes partly conducting at high temperatures, and 

the electric potential inside the chamber can be at any value between zero and the 

supply voltage. Unearthed probes can cause serious electric shock. 

3.4 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. 

3.5 Operator Safety

The furnace incorporates a safety switch which interrupts 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. The operation of this switch should be checked 

periodically – see section 4.1.2. 

Avoid burns: furnace surfaces can be hot. Before you remove a hot object from the furnace make 

sure you have a safe place to put it down. 
RHF 

 

6 MF07 

4.0 MAINTENANCE 

4.1 General Maintenance

Preventive rather than reactive maintenance is to be preferred. The type and frequency depends on 

furnace use: the following are recommended. 

4.1.1 Cleaning 

Soot deposits may form inside the furnace, depending on the process. At appropriate intervals 

remove these by heating as indicated in section 3.2. 

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. 

4.1.2 Safety Switch 

The door switch operation mentioned in 3.5 should be checked periodically to ensure that heating 

elements are isolated when the door is opened. In normal conditions the safety arrangement should 

outlast the furnace, but it could be affected by rough handling, a corrosive environment or work 

materials, or exceptional frequency of use. 

A qualified electrician should check that the supply to the heating elements is cut, with and 

without power being on, when the door is open partially and fully; it is important that isolation is 

not just marginally achieved. The check is best made on the element terminals after removal of the 

furnace back: probing the element surface inside the furnace could be inconclusive because of 

surface oxidation. Note that all live supply wires of a 3-phase supply, and both live and neutral of a 

1-phase supply, should be isolated when the door is opened. 

4.1.3 Element Ageing and Power Adjustment 

See sections 4.5 and 4.6. 

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. This can 

save time in the event of a breakdown. Each kit comprises one thermocouple, one sheath, one solid 

state relay, one door insulation piece, a set of elements, and a set of braids. Individual spares are 

also available. 

When ordering spares please quote the model details as requested above. 
 

RHF 

 

MF07 7 

4.5 Element Ageing

Silicon carbide elements gradually increase in resistance with use: a process known as ageing. 

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. 

4.6 Power Adjustment

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: 

3-phase furnace with 2 elements of 6.7 ohms each in series per phase, running on 

380/220V, with a target power of 8000W: 

ohms = 6.7 x 2/3 = 4.467 

powerlimit = (100 x 8000 x 4.467) / (220 x 220) = 74% 

A table of standard power limits as supplied with new furnaces is given in section 8.2. 

Occasionally the power limit is set to zero to permit demonstration of the controls without the 

heating elements taking power. In this case the power limit is accessible to the operator and may 

be reset to its standard value or the value that it had before setting to zero.
RHF 

 

8 MF07 

5.0 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. These controllers are fitted to the back of the control panel, which 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 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 furnace back panel. 

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. 
 

RHF 

 

MF07 9 

5.5 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 the back panel. 

5.6 Thermocouple Replacement

Disconnect the furnace from the supply, and remove the furnace back panel. 

Make a note of the thermocouple connections. The negative leg of the thermocouple is marked 

blue. Compensating cable colour codings are: 

negative: white positive (type R): orange

Disconnect the thermocouple from its terminal block. 

Bend the metal tag, or release the screw, to release the thermocouple sheath; withdraw the sheath, 

and shake out any fragments of thermocouple. 

Re-assemble with a new thermocouple observing the colour coding, ensuring that the 

thermocouple is not twisted as it is being inserted and that sheath is refastened. 

5.7 Element Fitting and Replacement

Replacements: read the section on element ageing (4.5). If at any time the power limit has been 

increased, reset it to its original value (section 8.2), or measure the resistances and recalculate 

the limit.

Disconnect the furnace from the electrical supply and remove the furnace back panel to gain access 

to the element connections. 

Remember that the elements are fragile and expensive, and that they can be damaged by 

contamination: handle them with care and keep them clean. 

Replacements: make a note of the actual braid and cable connections to the elements. Disconnect 

the braids or cables and carefully withdraw each element. 

New furnace: the diagrams indicate the connections, but the number and positions of terminal 

blocks may differ from those shown. For example, there may be 3 x N on a 3-phase furnace. If you 

have any problems with this procedure, please contact our service division. A common feature of 

all the RHF models is that elements are always 2 in series between 200-240 volts (for 110V, 2 in 

parallel). 

Carefully insert the new elements into the furnace. Position elements so that the split along the 

length is vertical. 

Attach the braids according to the notes made, or according to the appropriate diagram below 

Replace the furnace back panel and connect the furnace to the supply. 

If aged elements have been replaced, reset the furnace power limit. 
RHF 

 

10 MF07 

 
 

RHF 

 

MF07 11 

6.0 FAULT ANALYSIS

A. Furnace Does Not Heat Up 

1. The HEAT light

is ON

‡ The heating 

element has failed 

‡ Check 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 

‡ The thermocouple has broken or has a 

wiring fault 

The controller 

shows a low 

temperature

‡ The door switch(es) (if fitted) may be 

faulty or need adjustment 

 ‡ The contactor (if fitted) may be faulty 

 ‡ The 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 

‡ The SUPPLY

light is ON

‡ The controller may be 

faulty or not receiving a 

supply due to a faulty 

switch or a wiring fault 

 ‡ The SUPPLY

light is OFF

‡ Check the supply fuses and 

any fuses in the furnace 

control compartment 

B. Furnace Overheats 

1. The HEAT light 

goes OFF with 

the instrument 

switch 

‡ The controller 

shows a very high 

temperature 

‡ The controller is faulty 

 ‡ The controller 

shows a low 

temperature 

‡ The thermocouple may have been shorted 

out or may have been moved out of the 

heating chamber 

 ‡ The thermocouple may be mounted the 

wrong way round 

 ‡ The controller may be faulty 

2. The HEAT light 

does not go off

with the 

instrument 

switch 

‡ The SSR has failed 

“ON” 

‡ Check for an accidental wiring fault which 

could have overloaded the SSR 
RHF 

 

12 MF07 

7.0 CIRCUIT DIAGRAMS

In all RHF models the safety switch in the diagram is a positive-break door switch. 

EMC Filters (if fitted): dependent on the model there may be one filter, or more than one fitted in 

parallel. The circuit diagram examples do not show multiple filter arrangements. 

7.1 Single Phase

7.2 2-phase with neutral

As the following 3-phase diagram, except that one phase is not present. 

In some models, before mid-2002, direct safety switches were fitted in the element circuit, rather 

than the switch in the coil circuit as shown. 

7.3 3-phase with neutral

e

l 

e

m

e

n

t 

(s)

e

l 

e

m

e

n

t 

(s)

F1

N

L2

L3

F2

L1

PE

e

l 

e

m

e

n

t 

(s)

Supply light &

Instrument Switch

coil

temperature

controller 

thermocouple

overtemp.

controller 

thermocouple

safety

switch 

SSR

heat

on 

F3

SSR

SSR

heat

on 

F3

heat

on 

F3

Filter (if fitted)

if fitted

contactor

note on (2- and) 3-phase: depending on filter(s) fitted, there may be (2 

or) 3 separate neutral wires from the elements to the neutral supply. 

e

l 

e

m

e

n

t 

(s)

e

l 

e

m

e

n

t 

(s)

F3 F1

N

F2

L

PE

e

l 

e

m

e

n

t 

(s)

Supply light &

Instrument Switch

coil

temperature

controller 

thermocouple

overtemp.

controller 

thermocouple

safety

switch 

SSR

heat

on 

F3

SSR

SSR

heat

on 

F3

heat

on 

F3

Filter (if fitted)

if fitted

contactor

if fitted: 2- or 3- circuit 

models 
 

RHF 

 

MF07 13 

7.4 3-phase without neutral (delta – 208 to 240V)

7.5 3-phase without neutral (star – e.g. 380 to 415V)

7.6 Higher Voltages (e.g. 440V, 480V 3-phase)

The diagram above (7.5) normally applies, with neutral (if present) not being used. 

For single phase models of 254V or above, diagram 7.1 applies except that a control circuit 

transformer is included as in diagram 7.5. 

e

l 

e

m

e

n

t 

(s)

e

l 

e

m

e

n

t 

(s)

Supply light &

Instrument Switch

coil

temperature

controller

thermocouple

overtemp.

controller

thermocouple

safety

switch

SSR

heat

on

F3

F1

F2

F3

L2

L3

L1

PE

SSR

SSR

F3

heat

on

F3

e

l 

e

m

e

n

t 

(s)

heat

on

F3

F3

if fitted

contactor

Filter (if fitted)

e

l 

e

m

e

n

t 

(s)

e

l 

e

m

e

n

t 

(s)

F1

L2

L3

F2

L1

PE

e

l 

e

m

e

n

t 

(s)

transformer

coil

temperature

controller 

thermocouple

overtemp.

controller 

thermocouple SSR

heat

on 

F3

SSR

heat

on 

F3

heat

on 

F3

Filter (if fitted)

contactor

47k 47k 47k

F2

Note: in this configuration the fuses F2 on the supply side of the transformer may 

be GEC Safeclip, not 32 x 6mm glass as stated in section 8.1. 

if overtemperature 

fitted

Supply light &

Instrument Switch

safety switch
RHF 

 

14 MF07 

8.0 FUSES & POWER SETTINGS

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 10 Amp/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 

RHF 14/3 1-phase 200-240 32A (or 30A) 

RHF 14/3 2-phase + N 380/220 - 415/240 16A/ph (or 15A) 

RHF 15/3,16/3 1-phase 200-240 40A 

RHF 15/3,16/3 2-phase + N 380/220 - 415/240 20A/ph 

RHF 14/8 1-phase 200-240 63A 

RHF 14/8 2-phase + N 380/220 - 415/240 32A/ph (or 30A) 

RHF 15/8,16/8 1-phase 200-240 63A 

RHF 15/8,16/8 3-phase + N 380/220 - 415/240 20A/ph 

RHF 15/8,16/8 3-phase delta 220-240 32A/ph 

RHF 15/8,16/8 3-phase delta 208 40A/ph 

RHF 14/15 3-phase + N 380/220 - 415/240 25A 

RHF 14/15 3-phase delta 220-240, 208 40A/ph 

RHF 15/15,16/15 3-phase + N 380/220 - 415/240 25A/ph 

RHF 15/15,16/15 3-phase delta 220-240, 208 50A/ph 

RHF 15/15,16/15 3-phase + N 380/220 - 415/240 25A/ph 

RHF 15/15,16/15 3-phase delta 220-240, 208 50A/ph 

RHF 14/35, 15/35 3-phase + N 380/220 - 415/240 40A/ph 

RHF 14/35, 15/35 3-phase delta 220-240, 208 63A/ph 

RHF 16/35 3-phase + N 380/220 – 415/240 40A/ph (see note)

RHF 16/35 3-phase delta 220-240, 208 63A/ph (see note)

 380-415V 3-wire: same ratings as 3-phase+N 

RHF 16/35 – technical note.

All phases should be fused as indicated: the same wire size is used in all three internal circuits. For the 

delta configuration the furnace power is set lower to bring the rated current below 63 Amps. The current 

ratings for the three phases are: 

380/220 – 415/240 208-240 delta 

Furnace Power 16000W 15000W 

Phase 1 40 Amps 63 Amps 

Phase 2 40 Amps 48 Amps 

Phase 3 20 Amps 48 Amps 
 

RHF 

 

MF07 15 

8.2 Power Settings

The power limit settings (parameter OP.Hi) for the RHF models on various supply voltages 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: 200V 208V 220V 230V 240V 380V 400V 415V 

RHF 14/3 90 83 74 68 63 74 68 63 

RHF 15/3 62 57 51 47 43 51 47 43 

RHF 16/3 62 57 51 47 43 51 47 43 

RHF 14/8 90 83 74 68 63 74 68 63 

RHF 15/8 60* 56* 76 69 63 76 69 63 

RHF 16/8 73* 68* 74 68 62 74 68 62 

RHF 14/15 92 85 76 69 64 76 69 64 

RHF 15/15 71 66 59 54 49 59 54 49 

RHF 16/15 73 68 61 55 51 61 55 51 

RHF 14/35 93 86 77 71 65 77 71 65 

RHF 15/35 93 86 77 71 65 77 71 65 

RHF 16/35 (star) - - - - - 85 78 71 

RHF 16/35 (delta) - 89 79 73 67 - - - 

 

 * these models use different elements in 200-208V versions 
Copyright © 2004 Bibby Sterilin Limited trading as Carbolite 

For preventive maintenance, repair and calibration of all Furnace 

and Oven products, please contact: 

Thermal Engineering Services 

Telephone: UK: 0845 3308035 Int: +44 1433 623335 

Fax: UK: 0845 3308036 Int: +44 1433 623336 

Email: service@thermalserve.com

The products covered in this manual are only a small part of the wide range of 

ovens, chamber furnaces and tube furnaces manufactured by Carbolite for 

laboratory and industrial use. For further details of our standard or custom built 

products please contact us at the address below, or ask your nearest stockist. 

Carbolite, Parsons Lane, Hope,

Hope Valley, S33 6RB, England.

Telephone: (01433) 620011

Int: +44 1433 620011

Facsimile: (01433) 621198

Int: +44 1433 621198 MF07-3.05 30/3/04 RHF E-mail: info@carbolite.com

 

9.0 SPECIFICATIONS

Carbolite reserves the right to change specifications without notice. 

9.1 Models Covered by this Manual

MODEL Max. 

Temp. 

Max. 

Power 

Chamber Size (mm) 

 

Approx.

Capacity 

Net 

Weight 

(°C) (kW) H W D (l) (kg)

Chamber Furnaces heated by Silicon Carbide elements.

RHF 14/3 1400°C 4.5 120 120 200 2.9 40 

RHF 14/8 1400°C 8.0 170 170 270 7.8 80 

RHF 14/15 1400°C 10.0 220 220 305 14.8 125 

RHF 14/35 1400°C 16.0 250 300 465 35 180 

RHF 15/3 1500°C 4.5 120 120 200 2.9 40 

RHF 15/8 1500°C 8.0 170 170 270 7.8 80 

RHF 15/15 1500°C 10.0 220 220 305 14.8 125 

RHF 15/35 1500°C 16.0 250 300 465 35 180 

RHF 16/3 1600°C 4.5 120 120 200 2.9 40 

RHF 16/8 1600°C 8.0 170 170 270 7.8 80 

RHF 16/15 1600°C 10.0 220 220 305 14.8 125 

RHF 16/35 1600°C 16.0 250 300 465 35 270 

9.2 Environment

The furnaces contain electrical parts and should be stored and used in indoor conditions as 

follows: 

temperature: 5°C - 40°C 

relative humidity: maximum 80% up to 31°C decreasing linearly to 50% at 40°C