Heatrae Sadia Megaflo solar Instruction Manual

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36 00 5823 Issue 4
Fitting and using the Megaflo Solar unvented
mains pressure water heater
Solar
36005942 issue 5

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Contents
SECTION PAGE
1 INTRODUCTION ............................................................................ 3
2 GENERAL REQUIREMENTS......................................................... 4
3 INSTALLATION - GENERAL........................................................... 6
4 INSTALLATION - SOLAR PRIMARY .............................................. 15
5 INSTALLATION - DIRECT UNITS................................................... 16
6 INSTALLATION - AUXILLARY COIL (INDIRECT UNITS)............... 18
7 COMMISSIONING.......................................................................... 23
8 USER INSTRUCTIONS .................................................................. 25
9 MAINTENANCE.............................................................................. 27
10 FAULT FINDING & SERVICING ..................................................... 29
11 DIMENSIONS & SPECIFICATIONS ............................................... 32
12 GUARANTEE.................................................................................. 35
13 CONTACTS .................................................................................... 36
.......................................................................
Contents
Please read and understand these instructions before starting work.
The information contained in these instructions details how to connect the
Megao Solar water heater to a solar primary circuit. Other controls will be
necessary to provide control over the primary circuit, refer to the instructions
supplied with the solar controls and ancillary equipment for details of how to
integrate them with the Megao Solar unit.
Please leave this leaet with the user following installation

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Congratulations on your purchase of a Heatrae Sadia Megao Solar unvented water
heater. The Megao Solar is manufactured in the UK from top quality materials and
meets all the latest relevant safety and constructional standards. The high grade
Duplex stainless steel cylinder offers exceptional strength and corrosion resistance
which is backed by a 25 year guarantee. Its performance and insulation levels exceed
the latest requirements of Building Regulation Part L.
The Megao Solar unvented water heater can be fed directly from the cold water
mains supply to the property without the need for separate feed cisterns or vent pipes.
It is supplied complete with all the necessary inlet and safety controls, electric immer-
sion heater(s) and, for units tted with an auxiliary heating coil, a cylinder thermostat,
thermal cut-out, 2-port motorised valve and wiring centre.
Generally its pressure and owrate performance will far exceed that from a compara-
ble vented system, thermal store, multipoint instantaneous gas heater or combination
boiler.
Introduction
Introduction
Diagram 1 - Schematic installation details

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IMPORTANT : PLEASE READ AND UNDERSTAND THESE INSTRUCTIONS BEFORE INSTALLING THE
MEGAFLO SOLAR WATER HEATER. INCORRECT INSTALLATION MAY INVALIDATE GUARANTEE.
THIS APPLIANCE IS NOT INTENDED FOR USE BY PERSONS (INCLUDING CHILDREN) WITH REDUCED
PHYSICAL, SENSORY OR MENTAL CAPABILITIES, OR LACK OF KNOWLEDGE AND EXPERIENCE, UNLESS
THEY HAVE BEEN GIVEN SUPERVISION OR INSTRUCTION CONCERNING THE USE OF THE APPLIANCE
BY A PERSON RESPONSIBLE FOR THEIR SAFETY.
THE MEGAFLO SOLAR MUST BE INSTALLED (SECTIONS 2 - 6), COMMISSIONED (SECTION 7) AND MAIN-
TAINED (SECTIONS 9 - 10) BY A COMPETENT INSTALLER IN ACCORDANCE WITH BUILDING REGULATION
G3 (ENGLAND AND WALES), TECHNICAL STANDARD P3 (SCOTLAND) OR BUILDING REGULATION P5
(NORTHERN IRELAND) AND THE WATER FITTING REGULATIONS (ENGLAND AND WALES) OR WATER
BYELAWS (SCOTLAND). FOLLOWING INSTALLATION AND COMMISSIONING, THE OPERATION OF THE
HEATER SHOULD BE EXPLAINED TO THE USER (SECTION 8) AND THESE INSTRUCTIONS LEFT WITH
THEM FOR FUTURE REFERENCE.
2.1 COMPONENT CHECK LIST
Before commencing installation check that all the components for your Megao Solar unit are contained in
the package. The following components are supplied as standard with your Megao Solar unit:
• Factory tted immersion heater (s) and thermal controls
• Cold Water Combination Valve (comprises Isolating Valve, Pressure Reducing Valve,
Strainer, and Check Valve).
• Expansion Core Unit (comprises Check Valve and Expansion Valve)
• Expansion Vessel (including wall mounting bracket)
• Factory tted Temperature/Pressure Relief Valve (set at 90oC/10bar)
• T&P Relief Valve Insulation Set
• Drain Valve
• Wiring Centre (CL units only)
• Tundish (included in the Cold Water Combination Valve pack)
• Factory tted Auxiliary heating coil Thermostat and Thermal Cut-out (CL units only)
• 2-port Motorised Valve (Indirect units only)
• Lifting handle
2.2 SITING THE MEGAFLO SOLAR (see Diagram 1)
The Megao Solar unit must be vertically oor mounted. It can be placed anywhere convenient provided
the discharge pipe(s) from its safety valves can be correctly installed. Areas that are subject to freezing
must be avoided. Ensure that the oor is of sufcient strength to support the “full” weight of the unit (refer
to Tables 4 and 5 on page 33 for unit weights). Pipe runs should be kept as short as possible for maximum
economy. Access to associated controls, immersion heaters and controls housings should be possible for
servicing and maintenance of the system (Note: controls housings hinge open to the left hand side).
Please do not install valves or pipework (except discharge pipe) within 50mm (2”) of the T&P relief valve to
allow your insulation set to be tted. The insulation set is important to ensure heat and energy conserva-
tion. See section 3.9 for more information.
To aid installation the Megao Solar is provided with lifting points located in the base moulding and a lifting
handle. The lifting handle should be fully threaded onto the outlet boss before use. Once the Megao Solar
is suitably positioned the lifting handle should be removed to allow connection of the outlet pipework. The
weights of the units are noted on the tables on page 33.
2General Requirements
General Requirements

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2.3 WATER SUPPLY
Bear in mind that the mains water supply to the property will be supplying both the hot and cold water
requirements simultaneously. It is recommended that the maximum water demand be assessed and
the water supply checked to ensure this demand can be met.
NOTE: A high mains water pressure will not always guarantee high ow rates.
Wherever possible the main supply pipe should be in 22mm. We suggest that the minimum supply
requirements should be 0.15 MPa (1.5 bar) working pressure and 20 litres per minute owrate. At
these values outlet owrates may be poor if several outlets are used simultaneously, the higher the
available pressure and owrate the better the system performance will be.
The Megao Solar has an operating pressure of 0.3 MPa (3 bar) which is controlled by the Cold Wa-
ter Combination Valve. The Cold Water Combination Valve can be connected to a maximum mains
supply pressure of 1.6 MPa (16 bar). The water supply must be of wholesome water quality (Fluid
Category 1 as dened by the Water Supply Regulations 1999).
2.4 OUTLET/TERMINAL FITTINGS (TAPS, ETC.)
The Megao Solar can be used in conjunction with most types of terminal ttings. It is advantageous
in many mixer showers to have balanced hot and cold water supplies. In these instances the bal-
anced cold water supply should be teed off the supply to the Megao Solar immediately after the Cold
Water Combination Valve (see Diagrams 4 and 5). Branches to cold drinking outlets should be taken
before the valve.
Outlets situated higher than the Megao Solar unit will give outlet pressures lower than that at the
heater, a 10m height difference will result in a 0.1 MPa (1 bar) pressure reduction at the outlet tting.
NOTE: Accessories should have a rated operating pressure of at least 0.8 MPa (8 bar).
2.5 LIMITATIONS
The Megao Solar unvented water heater should not be used in any of the following instances:
• 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.
• Gravity circulation primaries.
• Steam heating plant unless additional and appropriate safety devices are installed.
• Ascending spray type bidets or any other Class 5 back syphonage risk requiring that a
Type AA, AB, AD or AG air gap be employed.
• Water supplies that have inadequate pressure or where the supply may be intermittent.
• Situations where it is not possible to safely pipe away any discharge from the safety
valves.
• Areas where the water consistently contains a high proportion of solids, eg. suspended matter
that could block the strainer, unless adequate ltration can be ensured.
• The installation must be carried out in accordance with the relevant requirements of:
• The appropriate Building Regulations: either The Building Regulations (England), The
Building Regulations (Scotland) or Building Regulations (Northern Ireland).
• The Water Fittings Regulations (England and Wales) or Water Byelaws (Scotland).

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3.1 PIPE FITTINGS
All pipe connections to the Megao Solar are made via 22mm compression ttings directly to
the unit (nuts and olives supplied). The ttings are also threaded 3/4” BSP male parallel should
threaded pipe connections be required.
3.2 COLD WATER SUPPLY
A 22mm cold water supply is recommended, however, if a 15mm (1/2”) supply exists which pro-
vides sufcient ow (see section 2.3) this may be used. More ow noise may be experienced
from small bore pipes due to the increased water velocity through them.
The Cold Water Combination Valve supplied with the Megao Solar incorporates a full ow
isolating valve which will enable the Megao Solar to be isolated from the mains supply for
maintenance or servicing. To close the valve the black handle should be turned so that it lies at
90o to the direction of ow. To open turn the handle so that it lies parallel to the direction of ow.
3.3 COLD WATER COMBINATION VALVE (see Diagram 2)
The Cold Water Combination Valve can be connected anywhere on the cold water mains sup-
ply prior to the Megao Solar unit. There is no requirement to site it close to the unit, it can be
located at a point where the mains supply enters the premises if this is more convenient. The
Expansion Valve connection must not be used for any other purpose.
The Cold Water Combination Valve can be installed as a complete one-piece unit. The valve
incorporates a factory set, non-adjustable Pressure Reducer/Strainer, an Expansion Valve
connection and a single Check Valve. The valve can be tted in any orientation to suit the in-
stallation, however, ensure that the Valve is installed with the direction of ow arrows (stamped
on the side of the brass body) pointing towards the Megao Solar heater. Should you wish to
site the Expansion Valve on the Cold Water Combination Valve this can be done by unscrewing
the connection nut beneath the Expansion Valve on the Expansion Core Unit and removing the
Expansion Valve. The connecting nut and blanking plug should then be unscrewed from the
Cold Water Combination Valve and replaced with the Expansion Valve. NOTE: IF THE EXPAN-
SION VALVE IS FITTED TO THE COLD WATER COMBINATION VALVE THE EXPANSION
CORE UNIT SHOULD NOT BE USED AS THE CHECK VALVE WITHIN IT WILL PREVENT
FREE PASSAGE OF EXPANDED WATER TO THE EXPANSION VALVE. Ensure the discharge
from the Expansion Valve can be correctly installed.
If a balanced pressure cold water supply is required to a thermostatic shower mixer valve this
may be teed off the supply to the Megao Solar immediately after the Cold Water Combination
Valve (see Diagram 5). Branches to drinking water outlets should be taken before the valve to
avoid the possibility of warm expanded water being drawn from the tap.
3.4 EXPANSION CORE UNIT (see Diagram 3)
Should a balanced pressure cold water supply be required for other cold water outlets the
Expansion Core Unit supplied should be used. The Core Unit should be tted into the pipework
Installation - General
Installation - General

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between the Cold Water Combination Valve and the Megao Solar (Note direction of ow
arrows). The cold water balanced draw off connection should be taken from between the
Cold Water Combination Valve and the Expansion Core Unit (see Diagram 4). The Expan-
sion Valve connection on the Cold Water Combination Valve should remain blanked off
using the blanking nut and seal provided. Ensure the discharge from the Expansion Valve
can be correctly installed.
Diagram 2 - Cold Water Combination Valve
Diagram 3 - Expansion Core Unit

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Diagram 4 - Schematic installation diagram using Cold Water Combination Valve in conjunction with Expansion Core Unit
Installation - General
Tundish
Megatech
Solar
Discharge pipe to atmosphere (See Section 3.9 “Discharge Pipework“)
KEY MCWS Mains cold water supply HWS Hot water service SC Stop Cock DOC Drain O Cock
Temperature/Pressure Relief Valve
Balanced cold water draw o
Balanced HWS and MCWS to bathrooms, showers,cloakrooms, etc.
Isolating/Regulating Valves as required
HWS supply
Expansion Core Unit (combined Expansion Relief Valve/Check Valve)
SC
SC
DOC
EXPANSION VESSEL
Incoming Cold Water Main
MCWS to Kitchen (unbalanced cold mains supply) Cold Water Combination Valve incorporating Pressure Reducing Valve, Isolating Valve, Strainer and Check Valve NB Expansion Valve tapping must be blanked o
CODCOD DOC

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Diagram 5 - Schematic installation diagram using Cold Water Combination Valve
Tundish
Megatech
Solar
Discharge pipe to atmosphere (See Section 3.8 “Discharge Pipework“)
KEY
MCWS Mains cold water supply HWS Hot water service SC Stop Cock DOC Drain O Cock
Temperature/Pressure Relief Valve
Balanced cold water draw o to shower mixer valves (Note: tapping must be min. 3m from Megao inlet connection)
Balanced HWS and MCWS to each shower.
Isolating/Regulating Valves as required
HWS supply
SC
SC
DOC
Incoming Cold
Water Main
Incoming Cold Water Main
MCWS to Kitchen and drinking water outlets (unbalanced cold mains supply)
Cold Water Combination Valve incorporating Pressure Reducing Valve, Isolating Valve, Strainer and Check Valve and Expansion Relief Valve
CODCOD DOC
EXPANSION VESSEL

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3.5 DRAIN TAP
A draining tap is supplied and should be installed in the cold water supply to the Megao 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 ow control and blanking cap for extra security.
3.6 OUTLET PIPEWORK
Ideally the pipework from the Megao Solar to the outlet ttings 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 Megao 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 Megao 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 backow. 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 t additional expansion volume to the system by tting 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.
Installation - General

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Diagram 6 - Secondary circulation connection
3.9 T&P RELIEF VALVE INSULATION
A set of insulating components is supplied with the Megao water heater and should be
installed to gain maximum heat and energy saving benets. See Diagram 7 for installation
instructions.
3.10 WARNINGS
i) Under no circumstances should the factory tted Temperature/Pressure Relief Valve be
removed other than by Authorised Heatrae Sadia personnel. To do so will invalidate any
guarantee or claim.
ii) The Cold Water Combination Valve must be tted to the mains water supply to the
Megao Solar unit.
iii) No control or safety valves should be tampered with.
iv) Water may drip from the discharge pipe of the pressure relief device (Expansion
Valve) and this pipe must be left open to atmosphere. The discharge pipe should not be
blocked or used for any other purpose.
Diagram 7 - Installation of T&P Insulating set

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3.11 DISCHARGE PIPEWORK
It is a requirement of Building Regulations that any discharge from an unvented system is conveyed
to where it is visible, but will not cause danger to persons in or about the building. The tundish
and discharge pipes should be tted in accordance with the requirements and guidance notes
of Building Regulations. Building Regulation G3 Requirements and Guidance section 3.9 are
reproduced in the following sections.
Information Sheet No. 33 available from the British Board of Agrément gives further advice on
discharge pipe installation. For discharge pipe arrangements not covered by G3 Guidance or BBA
Info Sheet No.33 advice should be sought from your local Building Control Ofcer.
Any discharge pipe connected to the pressure relief devices (Expansion Valve and Temperature/
Pressure Relief Valve) must be installed in a continuously downward direction and in a frost free
environment.
G3 REQUIREMENT
“...there shall be precautions...to ensure that the hot water discharged from safety devices is
safely conveyed to where it is visible but will not cause danger to persons in or about the build-
ing.”
G3 GUIDANCE SECTION 3.9
The discharge pipe (D1) from the vessel up to and including the tundish is generally supplied by
the manufacturer of the hot water storage system. Where otherwise, the installation should include
the discharge pipe(s) (D1) from the safety device(s). In either case the tundish should be vertical,
located in the same space as the unvented hot water storage system and be tted as close as
possible and within 500mm of the safety device e.g. the temperature relief valve.
The discharge pipe (D2) from the tundish should terminate in a safe place where there is no risk
to persons in the vicinity of the discharge, preferably be of metal and:
a. be at least one pipe size larger than the nominal outlet size of the safety device unless its
total equivalent hydraulic resistance exceeds that of a straight pipe 9m long i.e. discharge pipes
between 9m and 18m equivalent resistance length should be at least two sizes larger than the
nominal outlet size of the safety device, between 18 and 27m at least 3 sizes larger , and so on.
Bends must be taken into account in calculating the ow resistance. Refer to Diagram 8, Table 1
and the worked example.
An alternative approach for sizing discharge pipes would be to follow BS 6700:1987 Specication
for design, installation, testing and maintenance of services supplying water for domestic use within
buildings and their curtilages, Appendix E, section E2 and table 21.
b. have a vertical section of pipe at least 300mm long below the tundish before any elbows or
bends in the pipework.
c. be installed with a continuous fall.
d. have discharges visible at both the tundish and the nal point of discharge, but where this is not
possible or is practically difcult there should be clear visibility at one or other of these locations.
Installation - General

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Examples of acceptable discharge arrangements are:
i. ideally below a xed grating and above the water seal in a trapped gully.
ii. downward discharges at low level; i.e. up to 100mm above external surfaces such as car
parks, hard standings, grassed areas etc. are acceptable providing that where children may
play or otherwise come into contact with discharges a wire cage or similar guard is positioned
to prevent contact, whilst maintaining visibility.
iii. discharges at high level; e.g. into a metal hopper and metal down pipe with the end of the
discharge pipe clearly visible (tundish visible or not) or onto a roof capable of withstanding
high temperature discharges of water and 3m from any plastics guttering system that would
collect such discharges (tundish visible).
iv. where a single pipe serves a number of discharges, such as in blocks of ats, the number
served should be limited to not more than 6 systems so that any instalation discharging can be
traced reasonably easily. The single common discharge pipe should be at least one pipe size
larger than the largest individual discharge pipe (D2) to be connected. If unvented hot water
storage systems are installed where discharges from safety devices may not be apparent i.e.
in dwellings occupied by blind, inrm or disabled people, consideration should be given to the
installation of an electronically operated device to warn when discharge takes place.
Note: The discharge will consist of scalding water and steam. Asphalt, roong felt and non-
metallic rainwater goods may be damaged by such discharges.
Worked example of discharge pipe sizing
The example below is for a G1/2 temperature relief valve with a discharge pipe (D2) having
4 No. elbows and length of 7m from the tundish to the point of discharge.
From Table 1:
Maximum resistance allowed for a straight length of 22mm copper discharge pipe (D2)
from a G1/2 temperature relief valve is 9.0m.
Subtract the resistance for 4 No. 22mm elbows at 0.8m each = 3.2m
Therefore the permitted length equates to: 5.8m
5.8m is less than the actual length of 7m therefore calculate the next largest size.
Maximum resistance allowed for a straight length of 28mm pipe (D2) from a G1/2 tempera-
ture relief valve equates to 18m.
Subtract the resistance of 4 No. 28mm elbows at 1.0m each = 4.0m
Therefore the maximum permitted length equates to: 14m
As the actual length is 7m, a 28mm (D2) copper pipe will be satisfactory.

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Installation - General
Table 1 - Sizing of copper discharge pipe (D2) for common T&P relief valve sizes
Diagram 8 - Schematic discharge pipe arrangement
Valve outlet size Minimum size of
discharge pipe
D1
Minimum size of
discharge pipe
D2 from tundish
Ma x im um
resistance
allow ed,
e x pre ssed a s a
le ngth of stra ight
pipe (i.e . no
e lbow s or be nds)
Re sista nce
cre a te d by e a ch
e lbow or be nd
G1/2 15mm
22mm
28mm
35mm
up to 9m
up to 18m
up to 27m
0.8m
1.0m
1.4m
G3/4 22mm
28mm
35mm
42mm
up to 9m
up to 18m
up to 27m
1.0m
1.4m
1.7m
G1 28mm
35mm
42mm
54mm
up to 9m
up to 18m
up to 27m
1.4m
1.7m
2.3m
Fixed grating
Discharge below
fixed grating
(Building Regulation
G3 section 3.9d gives
alternative points
of discharge)
Trapped
gully
Discharge pipe (D2) from tundish,
with continuous fall. See Building
Regulation G3 section 3.9d i-iv,
Table 4 and worked example
300mm
minimum
500mm maximum
Metal discharge pipe (D1) from
Temperature relief valve to tundish
Tundish
Safety device
(e.g. Temperature
relief valve)

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Installation - Solar Primary
Installation - Solar Primary
4.1 CONNECTION TO SOLAR PRIMARY CIRCUIT
The lower (solar) coil of the Megao Solar must be connected to a fully pumped solar primary
circuit. The connections are suitable for 22mm copper pipe direct to the compression ttings
provided. The connections are also threaded 3/4” BSP male parallel should BSP connections
be required.
The solar primary circuit must have its own dedicated circulating pump, thermal and safety
controls which must be installed as per the manufacturer’s instructions.
4.2 CONTROL OF SOLAR PRIMARY CIRCUIT
Temperature control of the Megao Solar must be carried out using a suitable proprietary solar
differential temperature controller. The cylinder temperature sensing probe (usually supplied
with the solar differential temperature controller) should be inserted into the pocket provided on
the Megao Solar (see diagram 9) and its cable secured using the cable clamp supplied.
The solar controller and solar primary circulation pump must be wired via the over-temperature
cut-out mounted in the lower solar controls housing (see diagram 9). This will ensure that the
heat input to the solar coil is interrupted in the event of the cylinder over-heating. There must
also be suitable Check (non-return) valves installed in the solar primary ow and return to
prevent the possibility of any thermo-syphoning if the solar circulation is stopped.
Connection to the solar differential temperature controller should be in accordance with the
manufacturer’s instructions. The controller should be set to give a recommended cylinder tem-
perature of approx. 60oC. The maximum setting should not exceed 70oC otherwise nuisance
operation of the thermal cut-outs may occur.
Diagram 9 - Solar Coil Control Connections
Cylinder Temperature
Control Probe Pocket
Cable Clamp
Solar Cylinder
Controls Housing
Over Temperature
cut out
Note: wires removed from diagram for clarity

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Installation - Direct units
5.1 IMMERSION HEATER(S)
The Megao Solar Direct is supplied with two factory tted immersion heaters. Each immersion
heater is rated 3kW at 240V.
To remove the immersion heater:
Ensure the cylinder is drained of water rst. Open the cover to the upper immersion heater.
Unplug the thermostat from the element by gently pulling the thermostat outwards. Unscrew the
brass backnut using the key spanner provided. Remove the immersion heater assembly and
sealing gasket from the boss.
Replacement:
Insert the immersion heater and sealing gasket into the required boss. Ensure that the sealing
gasket is not displaced when inserting. It may be helpful to support the immersion heater using
a round bladed screwdriver inserted into one of the thermostat pockets. Hand tighten the brass
backnut. Secure the immersion heater in position by tightening with the key spanner provided.
Insert the blanking plate into the remaining boss ensuring the sealing gasket is not displaced
when inserting. Hand tighten the brass backnut. Secure in position by tightening with the key
spanner provided.
If an additional immersion heater is required order Part No. 95 606 964.
5.2 WIRING (see Diagram 10)
All electrical wiring should be carried out by a competent electrician and be in accordance
with the latest I.E.E. Wiring Regulations. Each circuit must be protected by a suitable fuse and
double pole isolating switch with a contact separation of at least 3mm in both poles.
The immersion heater(s) should be wired in accordance with Diagram 10. The immersion heat-
ers MUST be earthed. The supply cable should be 1.5mm2 3 core HOFR sheathed and must
be routed through the cable gland provided with the outer sheath of the cable rmly secured by
tightening the screw on the cable gland. Replace the immersion heater cover(s) before operat-
ing ensuring that the threaded edge clip is in position to provide a suitable thread for the cover
screw.
DO NOT OPERATE THE IMMERSION HEATER(S) UNTIL THE MEGAFLO SOLAR HAS
BEEN FILLED WITH WATER.
5.3 OPERATION
It is recommended that the immersion heater thermostats are set to between position 4 and 5
(60o- 65oC), however they can be set between 1 and 5 (10o and 70oC). The thermostat incor-
porates a thermal cut-out that will switch off the immersion heater in the event of a thermostat
5Installation - Direct units

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failure. The thermal cut-out reset button position is indicated on Diagram 11, DO NOT
bypass the thermal cut-out in any circumstances.
5.4 SAFETY
DO NOT BYPASS THE THERMAL CUT-OUT(S) IN ANY CIRCUMSTANCES.
DISCONNECT FROM THE MAINS SUPPLY BEFORE REMOVING ANY COVERS.
NEVER ATTEMPT TO REPLACE AN IMMERSION HEATER OTHER THAN WITH THE
RECOMMENDED HEATRAE SADIA MEGAFLO SOLAR SPARE PART.
Diagram 10 -
Schematic wiring
diagram - Direct
immersion
heaters
THERMOSTAT
FUSED (13A) DOUBLE
POLE ISOLATING
SWITCH
Diagram 11 - Immersion heater details
1.5mm23 CORE
HOFR SHEATHED
CABLE
EARTH
CONNECTION

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Installation - Auxiliary coil
6.1 BOILER SELECTION
The Megao Solar Indirect (CL) models are supplied with an auxiliary heating coil suitable for
use with most gas or oil red boilers compatible with unvented systems i.e. tted 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 ow 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 Megao Solar unit.
The boiler ow temperature should usually be set to 82oC (maximum ow temperature to
primary heat exchanger 90oC).
The boiler cannot be vented through the Megao Solar unit.
6.2 INDIRECT THERMAL CUT-OUT AND 2-PORT MOTORISED VALVE
To comply with Building Regulations and to prevent the Megao Solar from overheating the
2-port motorised valve supplied MUST be tted to the primary ow 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 Megao 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 tted. 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 Megao Solar will ensure the safe operation of the Megao 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 benecial to incorporate a system bypass in
the heating system pipework.
6Installation - Auxiliary coil
(Indirect units)

Megaflo He
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The Megao Solar is compatible with most heating controls, examples of electrical circuits
are given in Diagrams 14 and 15. However, other systems may be suitable, refer to the
controls manufacturer’s instructions, supplied with the controls selected, for alternative
system wiring schemes.
6.5 IMMERSION HEATER
The Megao Solar indirect units (CL models) 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 Megao Solar unit. The immersion heater is located within the controls housing.
Refer to Sections 5.2 and 5.3 and Diagram 10 and 11 for details of wiring and operation of
the immersion heater.
Diagram 12 - Primary connections to indirect (CL) units
TO HOT
OUTLETS
PRIMARY
RETURN
PRIMARY
FLOW
AIR
VENT
2 PORT MOTORISED
VALVE (SUPPLIED) INLET
AUXILLARY
HEAT SOURCE
PRIMARY
RETURN
PRIMARY
FLOW
SOLAR
PRIMARY
CIRCUIT

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CABLE CLAMPS TERMINAL BLOCK
INDIRECT
THERMOSTAT
THERMOSTAT
ADJUSTMENT
INDIRECT
THERMAL
CUT-OUT
INDIRECT THERMAL
CUT-OUT RESET
BUTTON
NOTE:
THE HOUSING COVER AND ELEMENT ASSEMBLY HAVE BEEN REMOVED FROM
THIS VIEW FOR CLARITY
Diagram 13 - Indirect controls housing details
Installation - Indirect units