Potterton Performa 28i Installation And Servicing Instructions page 5

1.0 Introduction
1.3 Instant Domestic Hot Water
(Expansion Vessel & Pre-Heat Store)
1. The boiler expansion vessel incorporates a
small volume of stored primary hot water.
2. When the boiler has been off and there is then
a demand for domestic hot water the stored
primary hot water ensures that domestic hot water
is supplied instantly at temperature.
3. The stored hot water is part of the primary
circuit. This is not supplied as domestic hot water,
which is fresh mains water heated by a heat
exchanger within the boiler.
4. The stored primary hot water temperature is
maintained whilst the boiler is in operation. During
a period when there is no demand for heating or
hot water the temperature of the stored primary
hot water will eventually fall. The boiler will
operate occasionally in order to maintain the
temperature. This is indicated by the domestic hot
water mode neon flashing.
1.4 Optional Extras
1. Various flue extensions, bends, vertical flue
kits, control accessories etc. are available as
optional extras. These are detailed in a separate
publication.
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