Megalife Product Guide
8
5: Installation - Auxillary Coil (Indirect Units)
5.1 Boiler Selection
The Auxillary coil on the Megalife solar indirect models are suitable for use with most gas, oil or electric boilers. The
boiler used can either be a sealed system or open vented type. The maximum primary circuit pressure is 3.5 bar. If
an open vented type boiler is used it must be fed from a separate boiler feed and expansion cistern, it MUST NOT
be fed from the Megalife solar cold water feed cistern.
The auxilary primary flow from the boiler
MUST
be pumped. Gravity circulation will not work due to the special design
of the primary heat exchanger. It is recommended that an air bleed point or automatic air vent is incorporated in the
primary return pipework close to the Megalife solar unit to aid in bleeding air from the primary heating coil.
The boiler should be fitted with adequate thermal control. This will normally include a primary flow thermostat and a
safety over temperature cut-out. The boiler flow temperature should usually be set to 82
o
C (maximum flow temperature
to primary heat exchanger 90
o
C).
The boiler cannot be vented through the Megalife solar unit.
5.2 Indirect Thermal Controls
Control of the storage temperature when indirectly heated is provided by the fitted cylinder thermostat. The control is
located under the white plastic cover located to the right of the indirect coil connections. If necessary the temperature
can be adjusted by inserting a flat bladed screwdriver in the adjustment knob and rotating. The minimum thermostat
setting is 10°C. Adjustment represents a temperature range of 10°C to 72°C (See Fig. 05, page 9). If in any doubt
contact a competent electrician.
5.3 Wiring
All electrical wiring should be carried out by a competent electrician and be in accordance with the latest I.E.E.
Wiring Regulations.
The Megalife solar indirect thermostat and thermal cut-out are factory pre-wired. It is recommended that these controls
are wired in series with a suitable 2 or 3 port motorised valve to control the primary flow through the heater coil. Wiring
to external controls is made via the terminal block fitted. The cable should be routed through the aperture in the
terminal cover and secured using the cable grip provided. The indirect thermal cut-out
MUST NOT
be bypassed.
5.4 Heating System Controls
The controls provided with the Megalife solar will ensure the safe operation of the Megalife solar when heated
by an auxillary heat source. Additional controls will be required for the control of the solar primary heating circuit.
Other controls will be necessary to control the space heating requirements and times that the system is required to
function. Depending on the auxillary boiler selected, heating circuit design and controls used it may be beneficial
to incorporate a system by-pass in the auxillary heating system pipework.
The Megalife solar is compatible with most heating controls, examples of electrical circuits are given in Fig’s 06 and
07, page 10. However, other systems may be suitable, refer to the controls manufacturers’ instructions, supplied with
the controls selected, for alternative system wiring schemes.
5.5 Immersion Heater
The Megalife solar indirect units are supplied with an immersion heater which can be used as an alternative heat
source should the boiler supply need to be isolated from the Megalife solar unit. Refer to Fig. 05 page 9 for details
of the wiring and operation of the immersion heater.
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