Bosch C 1210 ESC Reference manual

Technical Service Bulletin:

Replacing The Gas Valve

Models: C1210ESC, C1210ES, C1050ES, C950ES, 940ES, 940ESO, 830ES

Introduction

This procedure must be performed by a licensed gas technician

with a calibrated combustion gas analyzer.

The gas valve is not gas type speciﬁc but requires different CO₂

values when calibrating for different gas types.

Tools needed:

Phillips head screwdriver

Small ﬂat head screwdriver

#40 Torx driver

Combustion gas analyzer

30mm open end wrench or large adjustable wrench

4mm allen wrench

Preparation

1. Unplug water heater and turn off gas to heater using installer

supplied manual shut off valve.

2. Loosen two Phillips head screws located at bottom rear of cover.

(Fig. 1, step 1, pos. 1).

3. Lift front cover upward and remove. (Fig. 1, step 1, pos. 2 & 3)

Step 1 Step 2

tep

Figure 1

4. Remove combustion cover by unclipping two upper and two

lower clips securing cover. (Fig. 1, step 2)

5. Remove 3 Phillips screws on control unit (Fig. 2, step 1). Place

control unit into the service postion by engaging its tabs with

the holes in the horizontal sheet metal on bottom of the heater

chassis . (Fig. 2, step 2).

Step 2

Step 1

Ste

Figure 2

Gas

Valve

Removing the gas valve

1. Unplug wire connection from gas valve. (Fig. 3, pos. 1).

2. Disconnect clear silicone pressure balance tube from right side

of gas valve. (Fig. 3, pos. 2)

3. Loosen and disconnect large 30mm hex nut on the left side of

gas valve. (Fig. 3, pos. 3).

4. Unscrew the three 4mm allen screws from the top of the gas

valve. (Fig. 3, pos. 4).

5. Remove gas valve from the water heater.

Data subject to change without notice | Printed in the USA | BTC 740002320 B | 06.2011 Bosch Thermotechnology Corp.

Technical Service Bulletin

18 | Replacing The Gas Valve

Bosch Thermotechnology Corp.

50 Wentworth Avenue

Londonderry, NH 03053

Tel: 1-800-283-3787

Fax: 1-603-584-1687

www.bosch-climate.us

Figure 3

Installing gas valve

1. Replace both the grey ﬁber washer on the left side of the gas

valve and the rubber gasket on the top of the gas valve.

2. Hold replacement gas valve in place and reinstall the three allen

screws into the top of the gas valve. (Fig. 3, pos. 4).

3. Reinstall 30mm hex nut on the left side of gas valve.

(Fig. 3, pos. 3)

4. Open manual gas shutoff valve and check for leaks at all connec-

tions.

5. Reinstall silicone pressure balance tube to right side of gas

valve. (Fig. 3, pos. 2).

6. Reconnect wire connection to gas valve. (Fig. 3, pos. 1).

Calibrating gas valve

1. Reinstall combustion cover. (Fig. 1, step 2).

2. Return control unit to normal position and secure with 3 Phillips

head screws. (Fig. 2)

3. Plug in water heater & push power button to the "ON" position.

4. Open a hot water tap. If heater ﬁres, adjust CO₂using Technical

Service Bulletin: Measuring and adjusting CO₂.

5. If the heater does not fire, allow the unit to display the EA error

code and shut off hot water tap. The fan will continue to run to

purge the heater of gasses. Continue to the next section for a

rough gas valve adjustment.

Rough gas valve adjustment

Note: Do not forcefully tighten adjustment screws past bottom out

point. Stop bottoming out screw when resistance is felt.

Failure to do so will damage the gas valve.

1. Locate adjustment screw on gas valve. Loosen Phillips head

screw so retaining cover can be rotated to expose brass slotted

screw. (Fig. 4, pos. 1 & 2).

2. Turn brass slotted screw clockwise gently until it bottoms out

and/or screw resistance increases. (Fig. 4, pos. 3).

Figure 4

3. Once the slotted screw is bottomed out, make the following

adjustment to the slotted screw depending on your model and

gas type. (Fig. 4, pos. 3)

For models 830ES, 940ES, 940ESO, C950ES:

Natural Gas: 2.5 turns counter-clockwise on brass slotted screw

Liquid Propane: .75 turns counter-clockwise on brass slotted screw

For model C1050ES:

Natural Gas: 3 turns counter-clockwise on brass slotted screw

Liquid Propane: 1 turn counter-clockwise on brass slotted screw

For models C1210ES/C1210ESC:

Natural Gas: 2.5 turns counter-clockwise on brass slotted screw

Liquid Propane: Leave brass slotted screw bottomed out

4. Open a hot water tap. If heater ﬁres, adjust CO₂using Technical

Service Bulletin: Measuring and adjusting CO₂.If heater still

does not ﬁre, contact Bosch Thermotechnology Corp.

5. Reinstall brass slotted screw cover and secure with Phillips

screw. (Fig. 4, pos. 1 & 2).

!WARNING

FAILURE TO PROPERLY CALIBRATE THE

HEATER’S CO₂ LEVEL MAY RESULT IN A

HAZARDOUS CONDITION CAUSING

SEVERE PERSONAL INJURY OR DEATH.

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