Technical data

16
2000225294A
3 Heating System Design
BOILER
DOMESTIC
WATER
HOT OUT
COLD SUPPLY IN
DRAIN
POINT
'A'
CONTROL
VALVE
HEATING
CIRCUIT
RETURN
ADDITIONAL
EXPANSION
VESSEL (if required)

Filling device
BYPASS 
(if required)
Diagram 3.2
12254
- The EnviroPlus F24e, F28e and F28e SB are for use with
sealed central heating systems.
- The safety valves are an integral part of the boiler and cannot
be adjusted.
- The circulation pump is integral with the boiler.
- Pipe sectional areas shall be determined in accordance with
normal practices, using the output/pressure curve, see diagram
3.1. The distribution system shall be calculated in accordance
with the output requirements of the actual system, not the
maximum output of the boiler. However, provision shall be
made to ensure sufficient flow so that the temperature difference
between the flow and return pipes be less than or equal to 20°C.
The minimum flow is 1249 l/h this equates to a system
temperature differential of 20°C.
The system can be fitted with a lockable balancing valve if
necessary in the main flow or return pipes shown as valve 'A'
in (F24e & F28e ONLY diagram 3.2) or (F28e SB ONLY
diagram 3.2a).
- The piping system shall be routed so as to avoid any air
pockets and facilitate permanent venting of the installation.
Bleed fittings must be provided at every high point of the system
and on all radiators.
- The total volume of water permitted for the heating system
depends, amongst other things, on the static head in the cold
condition. The expansion vessel on the boiler is pressurised at
0.5 bar and allows a maximum system volume of 110 litres for
an average temperature of 75°C and a maximum service
pressure of 3 bar. This pressure setting can be modified at
commissioning stage if the static head differs. An additional
expansion vessel can be fitted to the system if required, see
diagram 3.2.
- Provision shall be made for a drain valve at the lowest point of
the system. A drain for the appliance is provided as an integral
part of the boiler positioned at the rear bottom of the boiler, see
diagram 9.2.
The installation of the boiler must comply with the requirements
of the current issue of BS6798, in Ireland, refer also to the
current edition of I.S.813 "Domestic Gas Installations".
In GB it is necessary to comply with the Water Supply (Water
Fittings) Regulations 1999 (for Scotland, the Water Byelaws
2000, Scotland).
To comply with the Water regulations your attention is drawn to:
The Water Regulations guide published by the Water Regulations
Advisory Service (WRAS) gives full details of the requirements.
In IE the requirements given in the current edition of I.S.813
"Domestic Gas Installations" and the current Building Regulations
must be followed.
3.1 Bypass
NOTE: All systems must have at least one radiator not fitted with
a thermostatic valve.
The boiler is fitted with a fixed bypass. Ensure that the flow rate
does not drop below the figure specified, see diagram 3.1.
A bypass is not required on the central heating circuit unless the
system controls could allow the boiler to operate when there is
no flow.
Where an additional bypass is fitted, it must be placed at least
1.5 metres from the appliance, see diagram 3.2.
3.2 Filling the Sealed System
NOTE: The water pressure at the boiler must be at least 1.2bar
to enable filling the boiler to a minimum pressure. If not
pressurisation must be carried out by an alternative filling loop.
The boiler has a built in filling device, see diagram 3.3. A push-
on extension is supplied in the loose items pack to ease access
to the filling device tap.
This filling device is designed to enable the re-pressurisation of
the system in the event of loss of pressure. It is not intended to
be used to completely fill the system. If so used, it may take a
long time to fill the system.
Refer to diagram 3.3. Using the tap extensions connected to
tap (a) and tap (b) open tap (b) and then slowly open tap (a). Re-
pressurise the system to a pressure of 1.0 bar indicated on the
digital display with no demand. When the system is pressurised
you must close tap (b) and then tap (a).
To fill the system quickly provision should be made to include a
proprietry filling loop external to the boiler.
Suitable external filling systems are shown diagramatically, see
diagram 3.4. The system should be pressurized to 1 bar,
indicated on the digital display with no heating demand.
3.3 Water Treatment
In the case of an existing installation, it is ESSENTIAL that prior
to installing the new boiler the system is thoroughly flushed. For
optimum performance after installation of a new system, the
boiler and its associated central heating system should also be
flushed. Flushing should be carried out in accordance with
BS7593: 1992 using a cleanser such as Sentinel X300 or X400,
or Fernox Superfloc.
For long-term corrosion protection, after flushing, an inhibitor
suitable for cast aluminium exchangers should be used, refer to
the current issue of BS 5449 and BS 7593 on the use of
inhibitors in central heating systems.