Bosch 125B LP Specifications download pdf (Page 25)

6 720 644 951 (2014/11)330 PN

Troubleshooting | 25

Fig. 25

7 Troubleshooting

7.1 Introduction

Many of the questions customers ask regarding operation of

this unit can be answered by following the troubleshooting

steps as outlined below. Visit our web site at www.bosch-

climate.us for more detailed troubleshooting. For best results,

perform each step before proceeding to the next. The

suggested solutions may require that the cover be taken off.

(See chapter 4.4).

7.2 Pilot does not light

1. Verify gas supply is on at Natural Gas meter or Propane Tank.

Make sure all manual gas shut off valves are in the open

position. Have licensed gas technician confirm adequate gas

pressure at the inlet tap (chapter 4.9). If gas is not present,

verify manufacturer supplied Maxitrol regulator is in the upright

position. The arrow on the back of the regulator should point in

the same direction as gas flow.

2. If the unit was just installed or the gas lines have been

worked on, there may be air in the gas line. Centered in the

sparking position, hold down the gas control slide button while

hitting the pilot igniter button every few seconds. It may take

several minutes to bleed air out of the gas line.

3. Verify a spark is being thrown at pilot area while gas control

slide button, centered in the single flame position, is being

firmly depressed. Repeatedly push in pilot igniter button to

light the pilot. If no spark is present, verify proper wire

connection to the electrode.

4. Pilot assembly may be blocked. Clean or replace the pilot

orifice (chapter 6.3).

7.3 Pilot lights, but goes out when button is

released

1. When lighting pilot ensure the gas control slide button is fully

depressed and held down for at least 20 seconds after pilot is

lit.

2. Verify gas type indicated in rating sticker located on right

hand side of cover, coincides with the gas type you are using.

NG is a natural gas unit and LP is for liquid propane.

3. Check all connections of the pilot safety circuit. The pilot

safety circuit consists of a thermocouple, overheat sensor

(ECO), flue gas sensor, safety spillage switch(models with

Powervents only) and the electromagnet (See parts diagram

for locations). Clean sensor connections with light sandpaper if

corrosion is evident. The electromagnet connection is 5mm nut

from the thermocouple which screws into a larger 17mm nut.

Tighten both nuts snugly but do not over tighten.

4. Pilot flame should be blue in color and completely engulfing

the tip of the thermocouple. If not, have a licensed gas

technician verify gas pressure is in accordance with

manufacturer's specifications (chapter 4.9) and clean or

replace the pilot orifice (chapter 6.3).

5. Have a licensed gas technician verify the proper operation of

the thermocouple by measuring the millivoltage from the

thermocouple lead to ground. The proper reading should be

24mVDC or greater. If the reading is lower, the thermocouple

may be defective. Call Bosch Water Heating for further

instructions.

7.4 Pilot goes out during or after hot water use

1. Pilot outage during use typically results from the unit's safety

overheat/high limit sensors interrupting the pilot circuit. The

330 PN does not have a thermostat. If inlet water is preheated,

the unit will overheat, stopping the flow of gas. Plumb inlet with

a cold water line only.

2. Failure to vent properly by reducing pipe diameter, improper

use of elbows or not meeting required vent length are common

causes that deactivate the pilot safety circuit. Confirm venting

is in accordance with manufacturer's specifications (see

chapter 4.7).

3. Confirm the combustion air requirements are being met in

accordance with manufacturer's specifications (see

chapter 4.6). Proper venting and combustion air will ensure a

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Bosch 125B LP Specifications Page 25

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