Vaillant TURBOmax VUW 242/1 E Instructions For Installation And Servicing page 21

4.8.3 Thermostatic radiator valves
The boiler has a built-in automatic
bypass valve making it ideal for use in
systems with thermostatic radiator
valves (no separate system bypass is
required).
For optimum fuel economy it is
recommended that where TRVs are
used they are used in conjunction with
a programmable roomstat or separate
timer and room thermostat to ensure
complete boiler shutdown when the
heating demand is satisfied. (The
radiator in the room containing the
room thermostat should not be fitted
with a TRV).
4.8.4 Circulating pump
The boiler incorporates a built-in
circulating pump that is fully
pre-wired. (No additional wiring is
necessary). The pump incorporates an
automatic overrun period after the
boiler switches off.
4.8.5 Anti-cycling 'economiser' control
The boiler incorporates a built in
anti-cycling control to ensure that
energy wasteful short cycling of the
boiler cannot occur. This control
prevents the boiler from re-igniting for
a pre-set period of 5 minutes after
central heating operation. (The hot
water operation is unaffected by this
control and hot water can be drawn
at any time).
Note: To temporarily override the
anti-cycling control, turn the main
on/off control to the "off" position
(0), and then back to the "on"
position (I) after a few seconds.
4.8.6 Frost protection
The boiler has an internal frost
thermostat which is designed for
protection of the boiler.
To protect remote or exposed parts of
the heating system or property
additional frost protection measures
must be taken such as the installation
of an external frost thermostat. This
frost thermostat should be connected
across the boiler terminals 3 and 4, in
parallel with any external heating
controls.
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