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4-2.3 Accumulator
The accumulator must be installed in any convenient location within the dwelling. If the accumulator is to be sited
in an outhouse or garage, adequate frost protection must be provided; this should include an overriding frost stat
so that the system is heated in the event of low temperature.
The accumulator must be installed vertically. Legs and self-tapping screws are supplied for floor fixing.
100mm minimum access is required at the top of the accumulator for adjusting the air charge above or below the
pre-set charge.
Do not fit a non-return valve between the accumulator and the unvented cylinder.
IMPORTANT: The Accumulator must be set between 1 and 1.5 bar below the pressure reducing valve
setting. Minimum accumulator pressure is 0.5 bar (7PSI). If there is an incoming pressure of 3.5 bar or
over DO NOT adjust the accumulator pressure. You should only take air out of the accumulator and not
pump it up on installation
Note: As OSO Dualstream is a sealed system the pressure at the
taps is not affected by the height of the cold water storage.
4-2.4 Tundish
The Tundish must be installed so that it is clearly visible to the householder.
A typical arrangement for the Tundish discharge is shown in fig. 4-2a. Refer to the applicable Building Regulations
for specific details of Tundish installation.
4-2.5 Discharge Pipe
WARNING: Scalding water and steam can be blown out of the discharge pipe. Position the discharge so that
it is not a hazard to property or people (especially children). Refer to Building Regulations G3.
Downward discharges at low level, i.e. up to 100mm above external surfaces such as car parks, hard standings,
grassed areas etc, are acceptable providing that where children may play or otherwise come into contact with
Fig. 4-2a Typical Tundish Arrangement
As the OSO Dualstream Accumulator acts as the system expansion vessel, an independent expansion vessel
system is not normally required.
However if an independent expansion vessel is specified it should be fitted to the domestic hot water system. It
may be installed in any position within the dwelling. The vessel must always be open to the system with no shut
off valve in the line. The expansion vessel should be connected between the cold inlet and the pressure reducing
valve.
discharges, a wire cage or similar guard is positioned to
prevent contact, whilst maintaining visibility.
Discharge at high level, i.e. into a metal hopper and metal
down pipe with the end of the discharge pipe clearly visible
(tundish visible or not) or onto a roof capable of withstanding
high temperature discharges of water and 3m from any
plastics guttering system that would collect such discharges
(tundish visible).
Where a single pipe serves a number of discharges, such as
in blocks of flats, the number served should be limited to not
more than 6 systems so that any installation discharging can
be traced reasonably at least one pipe size larger than the
largest individual discharge pipe to be connected. For further
information contact your Building Control Office. Maximum
permitted length of 22mm pipework is 9m. Each bend or
elbow is equivalent to 0.8m of pipework.
13
INSTALLATION 4
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