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Setting The Water Temperature; Draining Water From Heater - Bosch Model GWH 425 User Manual

Indoor model flow modulated with standing pilot suitable for heating potable water only -
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Operation instructions

Setting the water temperature

The GWH 425 PN has a gas control that modulates
burner input in response to flow. Its purpose is to
ensure that the hot water temperature will remain
steady, although the water flow demand might vary. The
output temperature can be adjusted with either the
temperature adjustment knob or the gas control slide.
Temperature adjustment knob
The temperature adjustment knob on the front bottom of
the heater (see Fig. 23) adjusts temperature by
adjusting flow capacity. See table 4 for details.
Fig. 23
Degree rise
Activation rate
0.5 GPM
Max flow rate
2.0 GPM
Table 4 Temperature rise (slide control to the right)
As the temperature adjustment knob is turned counter-
clockwise, the output temperature will lower and the
activation rate will be raised. Turning the knob
clockwise will raise the temperature and lower the
activation rate.
Gas control slide button
The gas control slide button adjusts temperature by
adjusting how much gas is allowed to flow to the
As the slide is adjusted to the left, the output
temperature will lower, with the lowest setting being the
small flame position.
Fig. 24
1.1 GPM
3.7 GPM
The hottest position is the highest flame position all the
way to the right.
Fig. 25

Draining water from heater

If there is a risk of freezing, proceed as follows:
B Remove the retaining clip from threaded bushing
(pos. 1).
B Remove threaded bushing (pos. 2) from water valve.
B Empty the appliance of all water.
Fig. 26 Drain plug and filter location
Retaining clip
Threaded bushing
6 720 608 034



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This manual is also suitable for:

Protankless gwh-425-pn-nProtankless gwh-425-pn-l