Heatrae Sadia Megaflo solar Installation Manua page 10

3.5 DRAIN TAP
A draining tap is supplied and should be installed in the cold water supply to the Megaflo Solar
unit between the Cold Water Combination Valve (or Expansion Core Unit if being used) and the
heater at as low a level as possible (see Diagram 1). It is recommended that the outlet point of
the drain pipe work be at least 1 metre below the level of the heater (this can be achieved by
attaching a hose pipe to the drain tap outlet spigot). The drain tap supplied provides very good
water flow control and blanking cap for extra security.
3.6 OUTLET PIPEWORK
Ideally the pipework from the Megaflo Solar to the outlet fittings should be in 22mm pipe with
short runs of 15mm pipe to showers and basin taps. Small bore pipe can also be used to suit
some taps, but runs should be of minimum length. Pipe sizes may vary due to system design.
3.7 EXPANSION VESSEL
The Expansion Vessel accommodates expansion that results from heating the water inside the unit.
The unit is pre-charged at 0.35 MPa (3.5 bar). The Expansion Vessel must be connected between
the Cold Water Combination Valve and the Megaflo Solar (see Diagram 1). 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.
NOTE: DO NOT USE THE POTABLE WATER EXPANSION VESSEL SUPPLIED WITH THE
MEGAFLO SOLAR FOR ANY OTHER PURPOSE. IT MUST NOT BE USED IN PLACE OF THE
SOLAR PRIMARY SYSTEM EXPANSION VESSEL.
3.8 SECONDARY CIRCULATION
If a secondary circulation system is required it should be connected to the Megaflo Solar as
shown in Diagram 6 via the connection provided. The secondary return pipe should be in 15mm
pipe and incorporate a check valve to prevent backflow. A suitable WRAS approved bronze
circulation pump will be required. On large systems, due to the increase in system water con-
tent, it may be necessary to fit additional expansion volume to the system by fitting an external
expansion vessel to the secondary circuit. This should be done if the capacity of the secondary
circuit exceeds 10 litres.
Pipe capacities (copper)
15mm o/d = 0.13 litres per metre run (10 litres = 77m)
22mm o/d = 0.38 litres per metre run (10 litres = 26m)
28mm o/d = 0.55 litres per metre run (10 litres = 18m)
Secondary circulation is NOT recommended for direct electric units being used on Off Peak
electricity tariffs. The secondary circulation return must not be connected to the inlet as this
would lead to indirect heating of the dedicated solar buffer volume.
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