9
xtra
-
Installation & Servicing
GENERAL
Rated output
Minimum bore
Nominal Size (DN)
kW
m m
in
61 to 150
32
1
1
/
4
151 to 300
38
1
1
/
2
'Steel pipe sizes complying with medium or heavy quality or BS 1387.
Detail reference should be made to the appropriate standards listed on
page 4.
The information and guidance given below is not intended to override any
requirements of the above publications or the requirements of the local
authority, gas or water undertakings.
The vertical distance between the pump and feed/expansion cistern MUST
comply with the pump manufacturer's minimum requirements, to avoid
cavitation. Should these conditions not apply either lower the pump
position or raise the cistern above the minimum requirement specified by
Ideal Stelrad Group
. The isolation valves should be fitted as close to the
pump as possible.
The information provided is based on the following assumptions:
1.
An independent open vent/safety pipe connection is made immediately
after the system flow pipe connection.
2.
An independent cold feed/expansion pipe connection is made
immediately after the open vent/safety pipe connection.
3.
The maximum flow rate through the boiler is based on a temperature
difference of 11
o
C at full boiler output.
4.
The boiler is at the highest point of circulation in the system. Systems
designed to rise above the boiler flow tappings will automatically
require a minimum static head higher than that shown.
5.
The position of the open vent/safety pipe above the expansion cistern
water level is given as a guide only. The final position will depend upon
the particular characteristics of the system. Pumping over of water into
the expansion cistern must be avoided.
6.
Both open vent/safety pipe and cold feed/expansion pipes must be of
adequate diameter to suit the output of the boiler. Refer to Tables
below.
4
OPEN VENTED SYSTEM REQUIREMENTS
Note.
•
With a cold feed head of <8m, the pump
must be fitted on the return to the boiler.
•
This diagram does not show safety valves,
water flow switches, etc. necessary for the
safe operation of the system.
5
SEALED SYSTEM REQUIREMENTS
Open Vent Pipe Sizes
Rated output
Minimum bore
Nominal Size (DN)
kW
m m
in
60 to 150
25
1
151 to 300
32
1
1
/
4
'Steel pipe sizes complying with medium or heavy quality or BS 1387.
Cold Feed Pipe Sizes
Note.
Refer to Frame 22 for typical system arrangements.
Feed/expansion
cistern
Open vent
safety pipe
3 m
minimum
see notes
System
flow
Shunt Pump
(if required)
Inverted
cold feed
entry
Cold
Feed
Water
level
(cold)
Open vent
System
return
im8250
Connections
to boiler
Working pressure 6 bar maximum.
Particular reference should be made to BS. 6644 and
Guidance note PM5 "Automatically controlled steam and hot
water boilers" published by the Health and Safety Executive.
The information and guidance given below is not intended to
override any requirements of either of the above publications or
the requirements of the local authority, gas or water
undertakings.
In general commercial closed pressurised systems are
provided with either manual or automatic water make up.
In both instances it will be necessary to fit automatic controls
intended to protect the boiler, circulating system and ancillary
equipment by shutting down the boiler plant if a potentially
hazardous situation should arise.
Examples of such situations are low water level and operating
pressure or excessive pressure within the system. Depending
on circumstances, controls will need to be either manual or
automatic reset. In the event of a shutdown both visual and
audible alarms may be necessary.
Expansion vessels used must comply with BS. 4814 and must
be sized on the basis of the total system volume and initial
charge pressure.
Initial minimum charge pressure should not be less than 0.5
bar (7.2psi) and must take account of the static head and
specification of the pressurising equipment. The maximum
water temperatures permissible at the point of minimum
pressure in the system are specified in Guidance Note PM5.
When make up water is not provided automatically it will be
necessary to fit controls which shut down the plant in the event
of the maximum system pressure approaching to within
0.35bar (5psi) of the safety valve setting.
Other British Standards applicable to commercial sealed
systems are:
BS. 6880: Part 2
BS. 1212
BS. 6281: Part 1
BS. 6282: Part 1
BS. 6283: Part 4
