Function - Bosch US3 Installation Manual And Operating Instructions

US
2.7

Function

How the water heater works:
• Water comes in through the cold water inlet.
The heater is designed for cold water supply
only. Do not supply with pre-heated water.
• The flow switch senses how much water is passing
through the unit. If it detects more than the preset
level, the unit's heating elements switch on. This is
shown by the neon light glowing.
• The water is heated instantly as it passes through the
copper heat exchanger tube.
The temperature of the water coming out of the unit
depends on:
• The voltage of the electrical supply,
• The temperature of the incoming water supply,
• The setting of the power selector,
• The flow rate,
• The power rating of the unit.
• Depending on the region of the country, the
temperature of the water supply can vary between
Model Volts Amps
US9 240 40
US9 240 20
US9 208 35
US9 208 18
US6 277 22
US6 277 11
US3 120-110 27
US7 240-220 30
US7 240-220 15
Table 4
Manual reset thermal cut-out
The unit has a thermal cut-out (Fig. 1) which is mounted
on the heat exchanger tube. This will switch off the
heater elements if the water temperature goes above
194 °F.
If the cut-out trips it will need to be reset manually inside
the unit. This cut-out will only operate in exceptional
Element High
Resistance Setting
2x12 Ω 9,5kW
1x12 Ω -
2x12 Ω 7,1kW
1x12 Ω -
2x25 Ω 6,0kW
1x25 Ω -
2x8 Ω 3,4-3,0kW
2x16 Ω 7,2-6,1kW
1x16 Ω -
40 °F in winter to 70 °F in summer, with an average of
50 °F.
Fig. 3
A Manual reset thermal cut out
The table below shows the rise in water temperature you
can expect from the unit:
Low Setting Temperature Rise (deg F) at Flow Rate (GPM)
0,5 0,75
GPM GPM
- NA 84F
4,75kW NA 42F
- NA 64F
3,5kW NA 32F
- 81F 55F
3,0kW 41F 28F
- 41F 28F
- NA 63F
3,6- 3,05kW NA 32F
circumstances (Fig. 3). Call your service person or Bosch
Water Heating if this happens frequently.
Information about the heater | 7
1,0 1,5 2,0
GPM GPM GPM
64F 42F 32F
32F 21F 16F
48F 32F 24F
24F 16F 12F
42F 27F NA
21F 14F NA
20F NA NA
48F 32F 24F
24F 16F 12F
6 720 647 005 (2011/09)
2,5
GPM
NA
NA
NA
NA
NA
NA
NA
NA
NA