andrews R18 Series Technical Documentation Manual page 32

5.2.3.1 Water system
5.2.3.2 Pump information
24
The following notes are of particular importance to these water
heaters.
A drain tap is fitted to the header at the connection end of the
water heater to drain the content of the heat exchanger.
The water connections are normally on het right hand side of
the water heater but can be supplied on the left hand side by
special order, i.e. standard or alternative handing.
To prevent temperature lag time at the tappoint and to keep the
water temperature uniform a suitable sized recirculation pump
must be fitted.
Water treatment and suitable filtration is recommended for
these water heaters and advice should be obtained from a
reputable source.
The primary circulating pump is sized to prevent the depositing
of limescale in the water heater under the following conditions:
Water hardness in ppm
0 - 80
80 - 250
250 - 350
350 - 500
Table 4 Maximum temperature
Fig. 20 TP 50 - 30
18IP22B
Maximum temperature in °C
90
85
80
60