Bosch Evolution 500 Series

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Models: 715ES, C800ES, 2400ES, 2700ES, Evolution 500, Integra 500

Replacing the control unit

Service Bulletin G3-24

Introduction

Tools needed:

 Phillips head screw driver

 Small flat head screw driver

 Needle-nosed pliers

Note: Avoid touching printed circuit board (PCB) as static discharge

may damage circuitry.

Preparation

 Push power button to “OFF” and unplug power cord.

 Loosen two Phillips head screws on bottom rear of front cover.

Pull cover bottom outwards then lift cover upwards to remove.

Removing control unit

 Remove three Phillips screws on front of control unit. (Fig. 2,

pos. 1)

 Turn control unit to expose the rear. (Fig. 2, pos. 2).

 Locate and remove 6 Phillips head screws on back of control

unit (Fig. 2, pos. 3).

control unit front

Figure 2

 Remove rear cover from control unit to expose circuit board

electrical connections. Slide wire restraints out of control unit.

(Fig. 3, pos. 1).

 Remove two large electrical strip connectors by pulling them

away from board. (Fig. 3, pos. 2).

 Remove medium sized electrical strip connector by pulling it

outwards. (Fig. 3, pos. 3).

 Remove small electrical strip connector by pulling it outwards.

(Fig. 3, pos. 4).

 Remove two large ignition wires by pulling them outwards.

(Fig. 3, pos. 5).

 Remove yellow/green striped ground wire spade connection by

depressing tab on connector and pulling it gently off the board.

(Fig. 3, pos. 6).

 Loosen two small flat head screws on terminal block for power

cord. Pull black and white wires free from terminal block and

control unit. (Fig. 3, pos. 7).

 Loosen Phillips head screw and remove green ground wire con-

nection for power cord. (Fig. 3, pos. 8).

Figure 3

 Remove control unit from the water heater.

Appliance evaluation for PCB jumper location

Please evaluate the following prior to installation of the replacement

PCB:

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Summary

Introduction and Preparation

Tools and Safety Notes

Lists necessary tools and advises on avoiding static discharge damage to the PCB.

Appliance Preparation

Steps to power off the appliance and remove the front cover for access.

Removing the Control Unit

Disconnecting Electrical Components

Details on disconnecting various electrical strip connectors, ignition wires, and power cord.

Physical Control Unit Removal

Steps to physically detach the control unit from the water heater.

PCB Jumper Installation and Evaluation

Model and Gas Type Identification

Locate rating plate to determine model number and gas type for jumper settings.

Jumper Configuration

Install jumpers on the PCB according to model and gas type arrangements.

Reinstalling the Control Unit

Connecting Components

Reconnect all electrical connectors, wires, and power cord to the new control unit.

Securing the Unit and Power Up

Replace rear cover, secure control unit, and power up the appliance.

Summary

Introduction and Preparation

Tools and Safety Notes

Lists necessary tools and advises on avoiding static discharge damage to the PCB.

Appliance Preparation

Steps to power off the appliance and remove the front cover for access.

Removing the Control Unit

Disconnecting Electrical Components

Details on disconnecting various electrical strip connectors, ignition wires, and power cord.

Physical Control Unit Removal

Steps to physically detach the control unit from the water heater.

PCB Jumper Installation and Evaluation

Model and Gas Type Identification

Locate rating plate to determine model number and gas type for jumper settings.

Jumper Configuration

Install jumpers on the PCB according to model and gas type arrangements.

Reinstalling the Control Unit

Connecting Components

Reconnect all electrical connectors, wires, and power cord to the new control unit.

Securing the Unit and Power Up

Replace rear cover, secure control unit, and power up the appliance.

Overview

Function Description
Important Technical Specifications (Implied and Explicit)
Usage Features (Related to the Control Unit's Role)
Maintenance Features (Related to the Replacement Process)

This document is a service bulletin (G3-24) from Bosch, detailing the procedure for replacing the control unit in several models of water heaters: 715ES, C800ES, 2400ES, 2700ES, Evolution 500, and Integra 500. It serves as a comprehensive guide for technicians, covering preparation, removal of the old unit, installation of the new unit, and post-installation checks.

Function Description:

The primary function of this service bulletin is to provide step-by-step instructions for replacing the control unit (Printed Circuit Board or PCB) in specific Bosch water heater models. The control unit is the "brain" of the water heater, responsible for managing its operations, including ignition, temperature regulation, safety features, and communication with other components. A faulty control unit can lead to various operational issues, making its replacement a critical maintenance task. The document ensures that the replacement process is performed correctly, maintaining the appliance's functionality and safety.

Important Technical Specifications (Implied and Explicit):

Models Covered: 715ES, C800ES, 2400ES, 2700ES, Evolution 500, Integra 500.
Replacement Part: Control unit (PCB).
Tools Required: Phillips head screwdriver, small flat head screwdriver, needle-nosed pliers. These are standard tools, indicating that specialized equipment is not needed for this procedure.
Electrical Connections: The control unit involves numerous electrical connections, including large and medium electrical strip connectors, small electrical strip connectors, large ignition wires, yellow/green striped ground wires (spade connection), and power cord wires (black and white) connected to a terminal block. This highlights the complexity of the electrical interface.
Grounding: Specific instructions for connecting green ground wires (both for the power cord and the unit itself) emphasize the importance of proper grounding for safety.
Jumper Settings: The document explicitly details the necessity of installing "jumpers" on the replacement PCB based on the specific model and gas type (Natural Gas or Liquid Propane). This is a critical configuration step, as incorrect jumper settings will prevent the appliance from working correctly. Figures 5 and 7 illustrate the specific jumper configurations for various models (e.g., 2400 ES, C 1050 ES, 940 ES/ESO, 2700 ES, C 800 ES, 715 ES, Evolution 500 (WTD 27), or Integra 500 (WTD 30)).
Static Discharge Precaution: A crucial note warns against touching the PCB directly to avoid damage from static discharge, indicating the sensitivity of the electronic components.
Power Disconnection: The first step in preparation is to push the power button to "OFF" and unplug the power cord, underscoring the importance of electrical safety before any service work.

Usage Features (Related to the Control Unit's Role):

While the document focuses on replacement, the control unit itself enables several usage features of the water heater:

On/Off Functionality: The final step involves plugging the power cord back in and pushing the On/Off button to "ON," confirming the control unit's role in power management.
Gas Type Configuration: The jumper settings for Natural Gas or Liquid Propane allow the same control unit to be adapted to different fuel sources, providing flexibility in appliance usage and installation.
Model-Specific Operation: The need for model-specific jumper configurations ensures that the control unit operates optimally for each water heater model, accounting for variations in design and performance.
Safety Interlocks: The various electrical connections and grounding procedures imply that the control unit integrates with safety interlocks and sensors within the water heater, ensuring safe operation.

Maintenance Features (Related to the Replacement Process):

Modular Design: The ability to replace the control unit as a distinct module simplifies maintenance. Instead of troubleshooting individual components on the PCB, the entire unit can be swapped out, reducing repair time and complexity.
Clear Disassembly/Reassembly Instructions: The bulletin provides detailed instructions for disassembling the water heater to access the control unit (e.g., removing the front cover, loosening screws) and reassembling it. This clarity aids technicians in performing the task efficiently.
Visual Aids: Figures 1, 2, 3, 4, 5, and 7 are integral to the instructions, providing visual guidance for locating screws, connectors, and jumper positions. This significantly enhances the clarity and accuracy of the maintenance procedure.
Pre-installation Evaluation: The "Appliance evaluation for PCB jumper location" section emphasizes the importance of checking the rating plate sticker for model number and gas type before installing the replacement PCB. This proactive step prevents incorrect configuration and potential operational issues.
Post-installation Check: The final step of plugging in and turning on the water heater serves as a functional check to confirm the successful replacement and proper operation of the new control unit.
Wire Management: Instructions to "slide wire restraints out of control unit" and "reseat rubber wire restraints" highlight the importance of proper wire management for safety and longevity of the connections.
Documentation: The service bulletin itself is a key maintenance feature, providing standardized, manufacturer-approved instructions for a common repair, ensuring consistency and quality in service.

In summary, this service bulletin is a critical document for maintaining Bosch water heaters, ensuring that control unit replacements are performed accurately, safely, and efficiently, thereby extending the lifespan and reliable operation of the appliances.