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5
Installation - Indirect units
5.1 BOILER SELECTION
The Megaflo Indirect (CL) models are suitable for use with most gas or oil fired boilers compat-
ible with unvented systems i.e. fitted with a temperature 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 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 unit.
The boiler flow temperature should usually be set to 82
primary heat exchanger 90
The boiler cannot be vented through the Megaflo unit.
5.2 INDIRECT THERMAL CUT-OUT AND 2-PORT MOTORISED VALVE
To comply with Building Regulations and to prevent the Megaflo from overheating the 2-port
motorised valve supplied MUST be fitted to the primary flow to the indirect coil (see Figure 11).
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 Megaflo 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
Figures 13 or 14 detail the wiring required between these controls and the motorised valve. Wir-
ing 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 Megaflo will ensure the safe operation of the Megaflo within
a central heating system. Other controls will be necessary to control the space heating
requirements 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.
The Megaflo is compatible with most heating controls, examples of electrical circuits are
given in Diagrams 13 and 14. However, other systems may be suitable, refer to the controls
manufacturers' instructions, supplied with the controls selected, for alternative system wiring
schemes.
18
18
C).
o
C (maximum flow temperature to
o
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