Technical data
EXPANSION VESSEL
The expansion vessel accommodates expansion that results from heating the water inside the unit. The expansion vessel is
pre-charged at 3.5 bar. The expansion vessel must be connected between the expansion valve (see Fig. 2, page 5) and the
PremierPlus cylinder (see Fig. 6, page 11). The location of the expansion vessel should allow access to recharge the pressure
as and when necessary, this can be done using a normal car foot pump. It is recommended that the expansion vessel is
adequately supported. An expansion vessel wall mounting bracket is supplied for this purpose and should be tted.
SECONDARY CIRCULATION
If secondary circulation is required it is recommended that it be connected to the PremierPlus cylinder as shown in Fig. 3,
page 6 via a swept tee joint into the cold feed to the unit. A swept tee joint is available as an accessory (order code no. 94
970 033).
The secondary return pipe should be in 15mm pipe and incorporate a check valve to prevent backow. A suitable WRAS
approved bronze circulation pump will be required. On large systems, due to the increase in system water content, it may be
necessary to t an additional expansion vessel to the secondary circuit. This should be done if the capacity of the secondary
circuit exceeds 10 litres.
In direct electric installations where a secondary circulation is required particular attention should be paid by the installer to
maintain the return water temperature (guidelines state that a minimum of 55°C return temperature is advisable) . Factors
such as, but not limited to, secondary circulation ow rates, minimising heat loss of all secondary circuit pipework and timed
operation during periods of high demand are critical to the correct operation and longevity of the heating element(s) and
thermostats.
Secondary circulation is not recommended for direct electric units using off-peak tariffs where the secondary circulation is
not controlled in conjunction with the heat source as performance can be affected.
Pipe capacity (copper):
15mm O.D. = 0.13 l/m (10 litres = 77m)
22mm O.D. = 0.38 l/m (10 litres = 26m)
28mm O.D. = 0.55 l/m (10 litres = 18m)
Fig 3: Secondary circulation connection
HOT WATER OUTLET
The hot water outlet is a 22mm compression tting located at the top of the cylinder. Hot water distribution pipework
should be 22mm pipe with short runs of 15mm pipe to terminal ttings such as sinks and basins. Pipe sizes may vary due
to system design.
Cold inlet
connection
Check
valve
Secondary
circulation
pump
Swept
tee
Cold
supply
Secondary
return
6