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6
Installation - Auxiliary coil
(Indirect units)
6.1 BOILER SELECTION
The Megaflo Solar Indirect (CL) models are supplied with an auxiliary heating coil suitable for
use with most gas or oil fired boilers compatible with unvented systems i.e. fitted with a tempera-
ture control thermostat and thermal cut-out.
If in doubt consult the boiler manufacturer.
Solid fuel boilers or any other boiler in which the energy input is not under effective thermostatic
control, unless additional and appropriate safety measures are installed, should NOT be used.
The boiler used can either be a sealed system or open vented type, maximum primary circuit
pressure 0.3 MPa (3 bar).
The 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 auto-
matic air vent is incorporated in the primary return pipework close to the Megaflo Solar unit.
The boiler flow temperature should usually be set to 82
primary heat exchanger 90
The boiler cannot be vented through the Megaflo Solar unit.
6.2 INDIRECT THERMAL CUT-OUT AND 2-PORT MOTORISED VALVE
To comply with Building Regulations and to prevent the Megaflo Solar from overheating the
2-port motorised valve supplied MUST be fitted to the primary flow to the auxiliary heating coil
(see Diagram 12).
6.3 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 Megaflo Solar Indirect Thermostat and Thermal Cut-out are factory pre-wired. The 2-port
motorised valve supplied MUST be wired in series with the Indirect controls such that the power
supply to the valve is interrupted should either the Thermostat or Thermal Cut-out operate. The
Wiring Diagrams 14 or 15 detail the wiring required between these controls and the motorised
valve. 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 clamp provided.
The Indirect Thermal Cut-out MUST NOT be bypassed.
6.4 HEATING SYSTEM CONTROLS
The controls provided with the Megaflo Solar will ensure the safe operation of the Megaflo Solar
within a central heating system. Other controls will be necessary to control the space heating re-
quirements and times that the system is required to function. Depending on the boiler selected,
heating circuit design and controls used it may be beneficial to incorporate a system bypass in
the heating system pipework.
18
18
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C (maximum flow temperature to
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