GENERAL
Mini
--- Installation & Servicing
10
3
ELECTRICAL SUPPLY
Warning
. This appliance must be efficiently earthed.
Wiring external to the appliance MUST be in accordance with
the current I.E.E. (BS.7671) Wiring Regulations and any local
regulations which apply. For Ireland reference should be
made to the current ETCI rules for electrical installations.
The point of connection to the mains should be readily
accessible and adjacent to the boiler, except for bathroom
installations where the point of connection to the mains MUST
be situated outside of the bathroom.
Note
. Where a room sealed appliance is installed in a room
containing a bath or shower then the appliance and any
electrical switch or appliance control utilising mains
electricity should be so situated that it cannot be touched by
a person using the bath or shower.
4
SEALED SYSTEM REQUIREMENTS
Central Heating
Note.
Mini
boilers are suitable for fully pumped pressurised
sealed systems only.
REQUIREMENTS
1 General
The installation must comply with the requirements of
BS. 6798 and BS. 5449.
2 Flow Temperature
The installation should be designed to work with flow
temperatures of up to 90
˚
C.
3 Working Pressure
All components of the system must be suitable for a working
pressure of 3 bar (45 lb/in
2
) and temperature of 110
˚
C. Extra
care should be taken in making all connections so that the
risk of leakage is minimised.
The following components are incorporated within the
appliance:
a. Circulating pump.
b. Safety valve; with a non---adjustable pre---set lift pressure of
3 bar (45lb/in
2
).
c
. Pressure gauge; covering a range of 0---4 bar.
d1. 6 litre expansion vessel; with an initial charge pressure of
0.7 bar (10.5 lb/in
2
) for
Mini C24
,
Mini C28
,
Mini S24
and
Mini S28
.
d2. 7 litre expansion vessel; with an initial charge pressure of
1.0 bar (15.0 lb/in
2
) for
Mini C32
.
For further details refer to BS.5449:1 and the British Gas
Corporation publication ’Specifications for Domestic Central
Heating and Hot Water’.
4 Filling the system
Fill the system through a temporary hose connection from a
draw---off tap supplied from a service pipe under mains
pressure. Where the mains pressure is excessive a pressure
reducing valve shall be used to facilitate filling.
When installing the filling connection provided with the boiler
an additional WRAS approved valve must be fitted to the
mains water supply upstream of the double check valve to
fully comply the Water Regulations
C
H
ret
urn
Hose unions
Mains
Water
Supply
Temporary hose
(disconnect
after filling)
Stop valve
Additional stop valve
Double check valve
assembly
Note direction of flow
System filling and make---up
Proceed with the following:
F
Thoroughly flush out the whole of the system with cold
water before fitting the boiler.
F
Fill and vent the system until the pressure gauge registers
1.5 bar (22 lb/in
2
). Examine for leaks.
F
Release water from the system until a pressure of 1 bar
(15 lb/in
2
) is reached.
To avoid getting debris on the valve seat, do not use
the safety valve to do this.
F
Light the boiler and heat the system to the maximum
working temperature. Examine for leaks.
F
Turn off the boiler and drain the system while still hot.
F
Refill and vent the system.
F
Re---pressurise the system to the desired charge pressure
(see Table 5).
Table 5 Mini C24, Mini S24, Mini C28, Mini S28
System charge pressure
(bar)
0.5
0.7
1.0
Safety valve setting
3.0
Vessel pre---charge pressure
(bar)
0.7
System volume (litres)
Volume of expansion vessel
in addition to 6 litre unit
fitted to boiler
75
---
---
---
100
0.3
0.8
1.4
125
1.8
2.5
3.2
150
3.4
4.2
5.0
175
5.0
6.0
7.0
200
6.5
7.6
8.7
225
8.1
9.3
10.6
250
9.6
11.1
12.4
275
11.2
12.8
14.3
300
12.8
14.5
16.1
Multiply this factor by
system volume and deduct
6 litres to obtain size of
additional vessel for other
system volumes.
0.063
0.069
0.074
5 Size of expansion vessel
For the system water expansion to be contained by the
6
litre
expansion vessel fitted to the following models:
Mini C24
,
Mini S24
,
Mini C28
,
Mini S28
the cold system volume must not exceed:
96 litres when pressurised to 0.5 bar (cold)
88 litres when pressurised to 0.7 bar (cold)
81 litres when pressurised to 1.0 bar (cold)
If the pressure exceeds 2.65 bar when the boiler is up to
temperature with all radiators in use then an additional
expansion vessel MUST be installed on the return pipework.
