Bosch 125B LP Specifications download pdf (Page 24)

6 720 644 951 (2014/11) 330 PN

24 | Maintenance and service

Cleaning pilot assembly

Shut off gas supply to the heater using installer supplied

manual gas shutoff. Locate pilot gas tubing mounted in the

center of the burner assembly. At the base of the pilot gas

tubing there is a retaining clip. Release pilot gas tubing from

this clip. Push upwards on other end of pilot gas tubing to

release it from burner mount. Remove brass hex headed pilot

orifice from gas valve (located near base of pilot gas tubing).

Soak orifice and pilot gas tubing in carburetor cleaner for 30

minutes. Dry off and reinsert orifice in gas valve. If heater is an

LP unit, replace orifice. Reinstall the pilot gas tubing following

removal instructions in reverse. Open gas supply and return

heater to service.

6.4 Main burners

The main burner flames should be blue, with a more intense

blue cone in the center core. Yellow flames could be a sign of

wrong size gas orifices or dirty burners, a blockage on the heat

exchangers fins. If some burners have yellow flames while

others have blue flames, it is likely that dust, lint or spider webs

have partially clogged the burner venturis. To clean the

burners, contact a gas service person.

6.5 Vent assembly / heat exchanger

Inspect the draft hood and heat exchanger fins for signs of soot

build-up or any other foreign material such as spider webs.

Clean out any debris found in the vent hood and/or heat

exchanger fins. Signs of soot indicate insufficient combustion

air or exhaust draft. Check for vent assembly blockage or

combustion air blockage on the underside of the unit.

6.6 Mineral scale build-up

The 330 PN, when operated at lower temperatures settings,

does not accumulate mineral build-up. If however, the heater is

used at the higher temperature settings and the water has a

high mineral content, periodic descaling may be necessary.

The heating coils should be flushed with a descaling solution.

6.6.1 Descaling heat exchanger

1. Disconnect electrical supply from the water heater.

2. Shut off the water supply to the water heater using (installer

supplied) isolation valve.

3. Open hot water taps to drain and relieve pressure from the

plumbing system.

4. Drain water from the unit's heat exchanger by disconnecting

inlet and outlet water connections

5. Connect the line (A) from the outlet of the circulating pump

(installer supplied) to the inlet water fitting on the water heater.

6. Using another line (B), connect to the water outlet fitting on

the water heater. Route the other end of this line into a

descaling reservoir.

7. Using a 3rd line (C) from the descaling reservoir, connect to

the inlet side of circulating pump. Verify there is a filter on the

end of the line in the descaling reservoir.

8. Make sure all connections are "hand tight"

9. Fill tank with descaling solution so lines inside are

submersed. We recommend a straight white vinegar solution. If

using a commercial descalant, refer to manufacturer's

instructions on dilution with water.

10. Operate the circulating pump.

11. Make sure there are no leaks and the solution is flowing

from the descaling reservoir through the heat exchanger and

returning to the reservoir.

12. Run solution through the heat exchanger until the solution

returning to the descaling reservoir comes out clear. (Changing

to a fresh solution may be necessary during this process).

13. Disconnect all lines and drain all solution from heat

exchanger. Properly discard of solution.

14. Position a container below the hot water outlet and connect

cold water supply. Open cold water supply isolation valve and

flush heat exchanger with clean water.

15. Shut cold water isolation valve and reconnect hot water

supply to the water heater.

16. Reconnect electrical supply to unit, open water isolation

valves, and return the unit to service.

CAUTION:

▶ Do not ream or poke orifice as it will

enlarge orifice opening.

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Bosch 125B LP Specifications Page 24

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