Merrychef MC- Service Manual

Page 1 MC Series Ovens 32Z3329 Issue 4

CAUTION MICROWAVE EMISSIONS

DO NOT BECOME EXPOSED TO EMISSIONS FROM THE MICROWAVE

GENERATOR OR PARTS CONDUCTING MICROWAVE ENERGY

SERVICE MANUAL

MC-SERIES

SERVICE MANUAL

For all MC-Series models manufactured from January 2001

Part No. 32Z3329e Issue No. 5

Page 2 MC Series Ovens 32Z3329 Issue 4

Table of Contents

Safety Code ...........................................................................3

Product Specifications MC Series ......................................... 4

Installation Instructions .......................................................... 5

Error Codes and Diagnostics ................................................ 6

A - Power Output Testing to BS EN 60335-2-25:1996 .......... 7

B - Power Output Testing ......................................................8

C - Power Transformer Test ..................................................8

D - High Voltage Capacitor Test ............................................9

E - High Voltage Rectifier Test .............................................. 9

F - Interlock Operation .........................................................10

Exploded View MC Series ................................................... 11

Door Assembly ....................................................................12

Door Replacement and Adjustment .................................... 13

Door Servicing ..................................................................... 14

Interlock Details ................................................................... 15

Membrane Panel Circuit ...................................................... 16

Input Wiring Details .............................................................17

Part Number Identification List .......................................18-19

Wiring Diagram MC-series .................................................. 20

Manual Corrections and Modifications ................................21

Merrychef Limited,
Station Road West,
Ash Vale, Aldershot,
Hampshire, GU12 5XA
United Kingdom
Tel: [phone] Fax: [phone]
Internet address: http://www.merrychef.co.uk
E-mail: [e-mail]

or

[e-mail]

Page 3 MC Series Ovens 32Z3329 Issue 4

This manual is designed to assist engineers who have been on a recognised product familiarisation
and training course run by Merrychef Limited. It has been prepared to off er tec hnical guidance f or the
Merrychef MC Series Commercial Microwave Ovens.

Please remember that it is wiser

not

to attempt a service task if you are unsure of being able to

complete it competently, quickly, and above all

safely

.

To avoid injury to yourself, and to protect the appliance from possible damage, please follow this
Safety Code when servicing these ovens.

Before attempting to repair the oven, check it for microwave leakage.

Check that the oven is not emitting microwaves, even when supposedly not in operation.

Check that the oven is not operating continuously, whether the display indicates cooking or

not.

Always discharge the HT capacitors before working on the oven using a suitably insulated 10

MΩ Resistor

Before removing the rear cover from the oven, do all of the following:

•

Switch off the mains supply and remove the plug from the wall socket.

or

•

If the oven is hard wired, ensure that the power is turned off at the isolator switch.

Note:

the oven does NOT have an On/Off switch.

Upon completion of a service on an MC Series oven, or before reconnecting the appliance to the
mains supply for testing, check all of the following points:

•

All internal electrical connections are correct.

•

All wiring insulation is correct and is not touching a sharp edge.

•

All Earth connections are electrically and mechanically secure.

•

All four door safety interlocks are secure and mechanically sound.

•

The door operation is smooth.

•

The door activates all four of the door interlock switches

in the correct order

.

•

All fuse-holder safety covers are correctly fitted.

Before finishing the service call, recheck the following points:

•

All of the electronics are functioning correctly, and all of the touch pads are working.

•

The power output of the oven is correct (see pages 7 & 8 ).

•

Microwave emission is below permissible limit - 5 mW/cm² (see BS EN 60335-2-90:1998).

•

Oven has correct 50 mm air gap all round. Air flow should not be restricted.

SAFETY CODE

Page 4 MC Series Ovens 32Z3329 Issue 4

PRODUCT SPECIFICATIONS

Model No. MC-Seies

Power Requirements MC1000C45UK

MC1000C25EX
MC1400C45UK
MC1400C25EX
MC1800C45UK
MC1800C25EX

230-240V ac 50 Hz 13.0A Single Phase 2 Wire + Earth
220-230V ac 50 Hz 14.2A Single Phase 2 Wire + Earth
230-240V ac 50 Hz 13.0A Single Phase 2 Wire + Earth
220-230V ac 50 Hz 14.2A Single Phase 2 Wire + Earth
230-240V ac 50 Hz 13.0A Single Phase 2 Wire + Earth
220-230V ac 50 Hz 14.2A Single Phase 2 Wire + Earth

Power Output
Microwave 100%

MC1000
MC1400
MC1800

1000W ( IEC 705 )
1400W ( IEC 705 )
1800W ( IEC 705 )

External Dimensions Height

Width
Depth

335 mm ( Plus 50 mm minimum clearance above )
510 mm ( Plus 50 mm minimum clearance each side )
415 mm ( Plus 50 mm clearance behind )

Internal Dimensions Height

Width
Depth
Capacity

210 mm
330 mm
330 mm
23 litres (0.81 ft³)

Weight Nett

Gross packed

30 kg
35 kg

Construction Cavity & Case- 304 Stainless Steel
Settings Microwave

Timer

100%, 75%, 50%, progressive Defrost
Up to 9 minutes 59 seconds
Up to 3 cooking stages of up to 9 minutes 59 seconds
each (Programmed)

Control System Wipe-clean touch pad operating microprocessor based control system.

Direct readout of time and power set.
10 Pre-programmed cooking sequences accessed by just two key
presses.

Safety Features Four door interlock switches.

Cavity Overheat Sensor.
Magnetron Overheat Sensor.

Additional Features

•

Easy-to-use multistage programming.

•

Manual and Pre-programmed mode always available

•

Magnetron soft-start circuit for increased life and faster activation.

•

Multiple product facility.

Model Number Specification:

Voltage 2 = 220-230V a.c. 4 = 230-240V a.c.

Frequency 5 = 50 Hz 6 = 60 Hz

Country UK = United Kingdom EX = Export

Model No. + Voltage + Frequency + Country

Page 5 MC Series Ovens 32Z3329 Issue 4

INSTALLATION INSTRUCTIONS

MC Series Ovens

Power Supply Requirements

The MC–Series oven should be connected to a suitable elec tricity supply, which can cope with the
switching-on surge that occurs with certain types of catering equipment, such as microwaves.
Because of this requirement, we strongly recommend that a separate, suitably rated supply is
installed for the oven.

The supply for the oven should be fitted with a

Type "C"

circuit breaker, rated at 16A.

In order to maintain adequate ventilation for air intake and exhaust, and to allow access for
cleaning filters, you must allow a minimum of 50 m m clearance all around the oven. Air intake
temperature should not exceed 35°C - ex cessive temper ature can lead to reduced operating duty
cycle or premature ageing of internal components.

Positioning the Oven

maximum

3 ovens

In a stack

ALWAYS

Place containers in the cavity carefully - impact damage may chip the oven shelf

NEVER

Install an oven above fryers, grills, griddles or any other major heat source

NEVER

Stack machines on top of each other without using the stacking adapter provided.

Stacking Adapter

Page 6 MC Series Ovens 32Z3329 Issue 4

Error Codes and Diagnostics

The MC–Series oven will identify some of the m ost com mon problems by flashing an err or m essage
code in the time display window.

These are the error messages, and suggestions for repairing them.

1
2

Door not fully shut.
Possible electrical fault

Close door fully.
Door switch inoperative.

1

2
3

No time has been set.
Invalid time has been set.
Invalid program has been

set.

Set a time.
Set a valid time.
Use call-back to check

program.

Page 7 MC Series Ovens 32Z3329 Issue 4

Procedure A - Power Output Test in accordance with

BS EN 60335-2-25:1996 Annex AA

This test is given in the BSI test standard for microwave ovens. It is repr oduced below - not so that
you can follow it, but to show you why it is impractical in norm al conditions. A sim plified procedure,
which gives a good approximation to the BSI power output, is given in Procedure B which follows.

Note:

This test can only be carried out on a

COLD

oven. If the oven has been operating, even for
only a few seconds, the power given will be lower than the oven rating. This test must also be
carried out at a stable voltage - the voltage in most kitchens varies considerably even within the
period of the test. If the oven has been operating, go to

Procedure B.

You will need:

A thermometer capable of reading to ±0.1°C.
A cylindrical borosilicate glass container, 190 mm diameter, with a wall thickness of
3 mm or less.
A calculator.
A set of scales capable of reading 1 kg to an accuracy of ± 1 g.
A glass or plastic stirrer.
A jug capable of holding over 1 litre of water.
Drinkable water which is at a temperature of 10°C ± 1°C.
A “Variac” or similar variable transformer capable of supplying the oven to ensure a
stable voltage.

WARNING:

The Borosilicate Glass container has thin walls and is therefore fragile

- take care not to break it during use.

Method

A cylindrical container of borosilicate glass is used for the test. It has a maximum thickness of
3 mm, an external diam eter of approxim ately 190 mm and a height of approxim ately 90 mm. The
mass of the container is determined.

At the start of the test, the oven and the empty container are at ambient temperature. Potable water
having an initial temperature of 10°C ± 1°C is used for the test. The tem perature of the water is
measured immediately before it is poured into the container.

A quantity of 1000 g ± 5g of water is added to the container and its actual mass obtained. The
container is then imm ediately placed in the middle of the oven shelf which is in its lowest normal
position. The appliance is supplied at rated voltage and operated at the maximum power s etting.
The time for the water temper ature to attain 20°C ± 2°C is measured. T he oven is then switched off
and the final water temperature is measured within 60’s.

NOTES:

1 The water is stirred before its temperature is measured.
2 Stirring and measuring devices are to have a low heat capacity.

The microwave power output is calculated from the formula:

where

P is the microwave power output, in

watts;

M

W

is the mass of the water, in grams;

M

C

is the mass of the container, in grams;

T

0

is the ambient temperature, in °C;

T

1

is the initial temperature of the water, in °C;

T

2

is the final temperature of the water, in °C;

t is the heating time in seconds, excluding the magnetron filament heat-up time.

4.187 MW (T2-T1) + 0.55 MC (T2-T0)
t

P =