11
6.0
SYSTEM DETAILS
Publication No. 5106451
6.3
Pipework
1. The sizes of flow and return pipes from the boiler
should be determined by normal methods, according
to the requirements of the system. The connection to
the boiler is 28mm (compression).
2. Due to space requirements within the boiler
outercase, pipework should comprise of solder
fittings.
3.
A 20 °C (36°F) drop in temperature across the
system is recommended for condensing boilers.
Existing radiators may be oversized and so allow
this, but where radiator sizing is marginal it may be
advisable to retain a system temperature drop of
11°C (20°F).
4. In systems using non-metallic pipework it is
necessary to use copper pipe for the boiler Flow and
Return. The copper must extend at least 1 metre
from the boiler and include any branches (Fig. 7a).
6.4
System Controls
1. For optimum operating conditions, the heating
system into which the boiler is installed should
include a control system.
2. Such a system will comprise of a timer control and
separate room or cylinder thermostats as
appropriate.
3. The boiler should be controlled so that it operates
on demand only.
4. Operation of the system under control of the
preset boiler thermostat & TRV’s only does not
produce the best results.
6.5
Low Head Installation
1. Using a close couple arrangement the minimum
head is as shown in the diagrams (Figs. 8 & 9)
subject to the following conditions:
a) The pump being adjusted to give an 20
o
C
drop across the boiler.
b) The pump must be fitted on the flow.
c) The pump must be fitted in accordance with
the pump manufacturer's instructions.
d) The open vent pipe must be taken up from a
tee in a horizontal section of the flow pipe.
An alternative Low Head Installation
(Fig. 10)
2. For heads below 400mm then a combined vent
and feed pipe may be connected. This must be a
minimum of 22mm diameter. It is recommended that
an air separator is fitted when using a combined feed
and vent pipe.
6.6
Thermal Stores
1. The Promax 15 & 24 HE is suitable for fitting with
a Thermal Store, for details please contact Technical
Enquires (08706 049 049).
Typical Low Head Installation
If Conditions Require,
This System Possible
Alternative Low Head Installation
Boiler
500mm
45°
22mm
Open Vent
1000mm
Min
150mm
Max
15mm
Cold
Feed
400mm
Min Head
Return
Pump
Flow
Boiler
500mm
45°
22mm
Open Vent
400mm
Min Head
1000mm
Min
Automatic
Air Vent
15mm
Cold
Feed
150mm
Max
Return
Pump
Flow
Return
Pump
Flow
Boiler
200mm
Min
Air
Separator
22mm
Feed & Vent
Pipe
Fig. 8
Fig. 9
Fig. 10
Boiler
Flow
Return
Copper
0.5m
Copper
1m
Copper
0.5m
Fig. 7a
