19
SETTINGS
Gas valve setting
All boilers are tested and factory set during manu-
facture. Should it be necessary to reset a gas valve,
for example, after replacement, proceed as fol-
lows:
l
Shut down boiler.
Minimum setting
l
Remove one electrical connector from the
modulating gas valve coil, see diagram 23.
l
Connect a suitable pressure gauge.
l
Turn the OFF/Summer/Winter switch to the ‘Sum-
mer’ position.
l
Turn the domestic hot water temperature adjuster
to maximum setting.
l
Remove the protective cover from the gas valve
adjuster.
l
Turn nut ‘A’, see diagram 23:
CLOCKWISE: To increase the pressure.
ANTICLOCKWISE: To decrease the pressure.
Maximum setting
l
Reconnect the electrical connector removed
from the modulating gas valve coil.
l
Remove the protective cover from the gas valve
adjuster.
l
Turn nut ‘B’, see diagram 23:
CLOCKWISE: To increase the pressure.
ANTICLOCKWISE: To decrease the pressure.
After adjustment, refit the cover to the gas valve
adjuster.
Bypass
The
ISOFAST
has a built-in bypass. This must be ad-
justed according to the requirements of the system,
refer to the flow rate pressure curve (diagram 4).
The boiler is supplied with the built-in bypass open
a half a turn. It is adjusted by turning the bypass
screw (a), see diagram 24. Turn the screw clock-
wise to close the bypass.When using thermostatic
radiator valves (TRV’s) on all of the radiators, it is
essential that a separate, adjustable bypass of 15
mm minimum diameter is fitted between the flow
and return of the heating circuit, see diagram 8.
Any bypass must be fitted before system controls.
MODULATING COIL
Diagram 23
Reg 020
a
Diagram 24
Reg 054
Summary of Contents for ISOFAST F 28 E
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