Individual Settings; Mechanical Settings; Checking The Size Of The Expansion Vessel; Setting The Central Heating Flow Temperature - Worcester benchmark ZWB 7-25 R 25 HE Design, Installation And Servicing Instructions

6

Individual settings

6.1

Mechanical settings

6.1.1

Checking the size of the expansion vessel

Maximum pressure at maximum CH flow temperature is
2.5 bar. If the pressure is greater than this then fit an
extra expansion vessel. Refer to table 12.
System Capacity – BS7074:1
Expansion Vessel Pressure and System Capacity
Expansion Vessel
Expansion Vessel
Charge Pressure
System 1 bar
pressure
and
1.5 bar
capacity
Table 12
6.1.2 Setting the central heating flow tempera-
ture
The central heating flow temperature can be set to
between 35°C and 88°C.
With underfloor heating systems, observe
i
the maximum permissible flow tempera-
tures.
Limited maximum setting for low-temperature
operation
The temperature control is factory limited to setting E,
giving a maximum flow temperature of 75°C.
Adjustment of the heating output to the calculated heat
demand is not required by the heating systems regula-
tions.
Removing the maximum setting limit
For heating systems which require higher flow tempera-
tures, the maximum setting limit can be removed.
B Lift off the yellow button on the temperature control
with a screwdriver.
6 720 610 332-27.1O
Fig. 35
6 720 611 441 GB (03.11)
litres 10
bar 0.75
litres 82
litres 46
B Rotate yellow button through 180° and replace (dot
facing inwards).
The CH flow temperature is no longer limited.
Control setting CH flow temperature
1 approx. 35°C
2 approx. 43°C
3 approx. 51°C
4 approx. 59°C
5 approx. 67°C
E approx. 75°C
max approx. 88°C
Table 13
6.1.3

Changing the heating pump characteristic

The speed of the central heating pump can be altered
on the pump terminal box.
At switch position 1, maximum output is
i
not delivered if hot water mode is active.
Position 1 must not be used on combi ap-
pliances.
0,7
H
(bar)
0,6
0,5
3
0,4
2
0,3
0,2
1
0,1
0
0 200 400 600
Fig. 36
1 Pump characteristic for switch position 1
Pump characteristic for switch position 2
2
3 Pump characteristic for switch position 3
H Residual delivery pressure
Water circulation rate
Q
Individual settings
800 1000 1200 1400 1600
Q (l/h)
6 720 610 576-23.2O
27