Bosch GWH 260 PN Service Bulletin Booklet page 8

DESCALING
MODELS: 1000P, 1600P, 1600H
260PN, 425PN, 425HN
Instructions for removing scale from 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 r elieve pressure
from the plumbing system.
4. Drain water from the unit's heat exchanger b y
disconnecting inlet and outle t water connections.
5. Connect the line (A) from the outlet of the circulat-
ing pump (installer supplied) to the inlet water
fitting on the water heater.
6. Using another line (B), connect to the water outle t
fitting on the water heater. Route the other end of
this line into a descaling reservoir.
7. Using a 3 r d line (C) from the descaling reservoir,
connect to the inle t side of circulating pump. Verify
there is a filter on the end of the line in the
descaling reser voir.
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, ref er to
manufacturer's instructions on dilution with water.
11. Operate the circulating pump.
12. Make sure there are no leaks and the solution is
flowing from the descaling reser voir through the
heat exchanger and returning t o the reservoir.
13. 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)
14. Disconnect all lines and drain all solution from heat
exchanger. Proper ly discard solution.
15. Position a container below the hot water outlet and
reconnect cold water suppl y. Open cold water
supply isolation valve and flush heat exchanger with
clean water.
16. Shut cold water isolation valve and reconnect hot
water supply to the water heater.
17. Reconnect electrical supply to unit, open water
isolation val ves, and retur n the unit to service.
©BBT NORTH AMERICA CORPORATION
Bosch Group
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RESERVOIR
340 Mad River Park, Waitsfield, VT 05673
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Bosch Water Heating
CT-08
page 1 of 1
rev 10/06