Bosch 520-HN-N Specifications download pdf (Page 19)

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Troubleshooting

6 Troubleshooting

6.1 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.boschhotwater.com 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

3.4).

6.2 No spark at pilot with water flow

• 1. Verify the ON/OFF button, located behind the flip

down cover plate, is completely depressed in the ON

position (Position ). See chapter chapter 4.2,

Fig. 17.

• 2. Verify the cold water supply is connected to the

right side rear of the water valve.

• 3. Close installer supplied cold water shut off valve (if

none installed, install before proceeding). Open all

hot water taps supplied by the heater. Wait 5

minutes and check all taps. Any water running is a

sign of a plumbing crossover. Consult a local

plumber or service person for help in correcting a

plumbing crossover.

• 4. Confirm that there is an adequate flow rate. With

the temperature adjustment knob on the unit

positioned all the way clockwise, a 1/2 gallon per

minute (GPM) flow rate is required for heater

activation. Fully open a hot water faucet and fill a

quart container. If the container fills in 30 seconds or

less, the flow rate (1/2 GPM) is sufficient to activate

the water heater.

NOTE: When the dial is turned all the way

counterclockwise, a flow rate of 1.1 GPM is required

for heater activation.

• 5. Inspect the water path for obstructions. Make sure

all outlets (i.e. showerheads, faucet aerators and

whole house filters) are clear of debris. Inspect and

clean the water heater's inlet filter screen. See

chapter 5.2.

• 6. Verify all wire connections are secure, paying

close attention to the wire connection between the

piezzo electrode and the electronic control box.

• 7. Check for voltage at the hydro-generator.

Disconnect plug connector on wires leading from

hydro-generator (approximately 3" from hydro-

generator). Verify voltage on hydro-generator side of

plug connector with hot water running. The voltage

reading should be 1.6VAC or greater. If voltage is

lower, then remove and flush the hydro-generator.

Reinstall hydro-generator and take another voltage

reading. If voltage is at least 1.6VAC, proceed to next

step. If voltage is still low, hydro-generator may be

damaged/defective. Visit www.boschhotwater.com

to purchase replacement part, or call Bosch Water

Heating at 800-642-3111 for replacement part if still

under warranty.

• 8. If using a power vent, check the safety spillage

switch reset button (the safety spillage is wired

through the water heater's thermocouple circuit).

The safety spillage switch should be located at the

top of the water heater close to the draft diverter.

Consult power vent manual for more detailed

instructions.

• 9. Verify the spade connectors on the two overheat

sensors (ECO) & the flue gas sensor are plugged in

securely and their terminals are free of corrosion. The

terminals can be cleaned with a pencil eraser. The

ECO's are located on the lower left hot water outlet

pipe and the upper right side of heat exchanger. The

flue gas sensor is located on the upper right side of

draft diverter.

• 10. Verify the microswitch located on bottom of gas

valve is firmly mounted and wire clip connector is

secure.

• 11. Electronic control box may be damaged or

defective. Visit www.boschhotwater.com to

purchase replacement part, or call Bosch Water

Heating at 800-642-3111 for replacement part if still

under warranty.

6.3 Spark appears when hot water is

turned on, but pilot and burners

will not ignite

• 1. Verify gas type indicated in the rating sticker

located on the cover's right hand side, coincides with

the gas type you are using. NG is a natural gas unit

and LP is for liquid propane (see chapter 2.2).

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

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

Bleed out the air trapped in the gas line by turning the

hot water faucet on and off until the pilot flame/

burners ignite. (Please note: depending on how

much air is in the line this could take numerous cycles

of turning the faucet on and off).

• 3. Verify gas supply is on at Natural Gas meter or

Propane tank. Make sure all manual gas shut off

valves are open.

• 4. Have a licensed gas technician confirm adequate

gas pressure at the inlet tap (See gas requirements

in chapter 2.1). 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.

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Bosch 520-HN-N Specifications Page 19

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