Market Forge 2500HEC Service Manual

SERVICE & PARTS MANUAL

Models:

Form No.

17-0400 2/81

Printed in u S A

35 Garvey Street Everet

t,

ADDENDUM

High Efficiency Gas Convection Oven

2500 HEC
2700 HEC
2592 HEC
2792 HEC

Addendum to S-2207, for ovens
equipped with Carborundum

Ignition Systems.

MA 02149

Tel. [phone], Telex 94-9414, Cable MAFORCO

Facsimiled 617-387-4456

TABLE OF CONTENTS

Paragraph Page Paragraph Page

SECTION 1 INTRODUCTION SECTION 3 MAINTENANCE & PARTS LIST

1.1 Description 1-1 3.1 General 3-1

1.2 Basic Functioning 1-1 3.2 Repair and Replacement 3-1

1.3 Service 1-1 3.3 Direct Spark to Igniter System

SECTION 2 TROUBLE-SHOOTING

2.1 General 2-1

2.2 Electrical Fault Isolation 2-1

Conversion 3-1

3.4 Illustrated Parts List 3-2

17-0400 ii

SECTION 1 INTRODUCTION

1-1

17 0400

This service and parts addendum to High Efficiency Gas Convection Oven Service & Parts Manual contains descriptive

information, trouble shooting and maintenance information, and parts identification for ovens equipped with igniter ignition

systems Only information pertinent to the igniter system is contained in this addendum For details of the direct spark ignition

1.1 DESCRIPTION
High Efficiency Gas Convection Ovens having model suffix

' —HEC' are equipped with Silicon Carbide gas igniter
ignition systems manufactured by the Carborundum
Company in lieu of the standard direct spark ignition
system (model suffix '—HE') Igniter systems are in­corporated in ovens used with LP or butane gas (Direct
spark systems are used primarily with natural gas )

1.2 BASIC FUNCTIONING
The oven with igniter ignition system operates in the same

manner as other Market Forge High Efficiency Gas Ovens
except for the method of initiating combustion of gas at the
burners With the power switch in the ON position, doors
closed and thermostat set, the circuit is completed to the
fan motor (which operates continuously) and the
igniter/thermal delay relay (T D R ) circuit is energized As
current begins to flow, the igniter starts to heat, causing its
resistance to decrease At an igniter temperature of
approximately 1,800°F, the resistance has decreased to
the point that current flowing through the T D R heater
raises the relay temperature to the operating level At the
operating level normally open contacts of the T D R are
closed, energizing the coil of the gas solenoid valve,
allowing gas to flow and ignition to occur

The entire ignition sequence is completed in 10 to 20
seconds, with combustion occurnng after a normal short
delay On initial combustion the igniter temperature
continues to rise until it reaches approximately 2,300°F , at
which its

system and all other oven assemblies, see Service & Parts Manual S 2207

resistance increases, effectively holding the circuit current
at the operating level of the T D R The igniter TDR and
gas valve circuits remain energized with TDR contacts
closed throughout the combustion cycle Only when the
oven temperature reaches the thermostat setting, causing
thermostat contacts to open, are the circuits interrupted
The complete ignition/combustion duty cycle is completed
repeatedly as required by the thermostat control
All other oven operation is as described in the Service &
Parts Manual for the High Efficiency Gas Convection
Oven

1.3 SERVICE
Should repairs be required, a network of authorized
service agencies is available to assist with prompt service
A current Directory of Authorized Service Agencies and
service assistance may be obtained by contacting

Product Service Department
Market Forge
35 Garvey Street
Everett, Massachusetts 02149
Tel [phone]
Product Service Department Market Forge Canada, Ltd
1375 Aimco Boulevard, Unit 5 Mississauga, Ontario,

Canada L4W 1 B5 Tel [phone]
The model and serial numbers must be referenced when
corresponding with Market Forge

SECTION 3 MAINTENANCE & PARTS LIST

3.1 GENERAL

This section contains corrective maintenance
and parts identification information for the igniter
ignition system included in all "HEC" suffix gas
convection ovens For details of other subassemblies
and maintenance procedures, see Service & Parts
Manual, form number S-2207

3.2 REPAIR AND REPLACEMENT

Figures 3-1 and 3-2 include igniter system
assemblies together with a listing of replaceable parts.
Reference is made to these as well as illustrations in
form S-2207, Section 7 in the following procedures.

3.2.1. REPAIR AND REPLACEMENT

3.2.1. Igniter Removal

1. Remove bottom front louvered trim by sliding
forward off frame

2. Remove #8-32 x 1/2 screws securing control panel
to oven front and carefully pull panel forward to the
extent of free-play in connecting wiring.

WARNING

Avoid electrical shock by shutting off incoming

electrical service to the oven Exposed

terminals carry 120 volts.

3. Remove the two phillips head screws (figure

3-1, 16) which fasten the combustion box
manifold shield to the burner pan and lift

shield out.

4. Disconnect igniter leads #44 and #47 by twisting
off wire nuts. (See figure 2-1, 2-2, or 2-3).

5. Remove two #8 x 3/8 screws (41) from igniter
mounting flange and take igniter (40) out

6. Inspect and replace igniter as required and
reassemble in reverse of above.

3.2.2 Thermal Delay Relay Removal
The relay is a pin-mounted vacuum tube

located behind the control panel To access for
replacement and testing remove the control panel
as described in paragraph 321, step 2 The relay is
mounted in a socket base attached to support
bracket (figure 3-2, 5) By sliding shield (4) up off
the socket, the relay (3) is exposed for removal

3.3 Direct Spark to Igniter
System Conversion

Ovens equipped with Fenwal direct spark

ignition systems may be converted to the
Carborundum system when required A conversion
kit (part number 99-4698) containing all required
parts is available for this purpose

3.4 Illustrated Parts List
A complete listing of all replaceable parts of

the Carborundum ignition system for the High
Efficiency Gas Convection Oven is included in
Tables 2-1 and 2-2. Each parts list contains the
figure index number, the Market Forge part
number and an abbreviated description.

Orders for repair parts should be directed to the
nearest authorized parts distributor and should
include the part number, description as well as the
serial number and model number of the oven.

3-1