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7.2.3
UN-VENTED
Figure No 5.2. to 5.6. Any un-vented installation
must follow the essential safety requirements of the
Buildings Regulations part G3 Section 2. This
document further states that the system should be
designed by appropriately qualified engineers and
fitted by approved installers.
The cold feed un-vented kit(s) offered by
Hamworthy
Heating
assembly incorporating expansion relief valve, non-
return valve, strainer and pressure reducing valve
plus a suitably sized expansion vessel compatible
with potable water and sized for the unit and local
pipework. A temperature/pressure relief valve is also
supplied which follows the sizing recommendations
from the valve supplier. This ensures adequate
protection even with low incoming water mains
pressures.
Refer to Figure No 7.3: Cold Water Supply Valve
Train.
For
comprehensive
design, installation and testing of water supply
services, attention is drawn to the appropriate
sections of BS 6700.
The maximum hot working head of the Powerstock
Storage Tank is 10 bar g. (102 metres).
Dead legs to water draw off points should be as
short as possible and in no case should they exceed
the lengths laid down in the water regulations guide.
For example:
(i)
Pipes < 19mm I/D
(ii) Pipes 19-24mm I/D
(iii) Pipes > 25mm I/D
7.2.3.1. UNVENTED CONTROLS.
7.2.3.1.1 The pressure temperature relief valve must
be fitted into the vessel at the location indicated in
Figure No's 2.4 to 2.7.
Remove the ABS top cover from the vessel
exposing the top connection point. Remove the
1" (ST300 & ST500) or 1 1/4" (ST750 & ST1000)
BSP brass plug and screw the P & T, relief valve kit
supplied into this position using a suitable WRAS
approved jointing compound.
Cut a 130mm-diameter hole in the centre of the ABS
top cover to clear the P & T, relief valve then refit
the cover to the vessel. The installation of pipework
from the P & T, relief valve outlet should conform to
the recommendations given in BS6700 and any
other relevant codes of practice.
The following P & T discharge pipework kits are
available . See pages 9,10,11 & 12:-
563605525- Discharge Piping Kit ST300
563605526- Discharge Piping Kit ST500
563605527- Discharge Piping Kit ST750
563605528- Discharge Piping Kit ST1000
HAMWORTHY HEATING LTD
APPLICATIONS
Refer to
comprise
a
valve
recommendations
on
Maximum dead leg = 12m
Maximum dead leg = 7.6m
Maximum dead leg = 3m
7.2.3.1.2 COLD WATER FEED. The Hamworthy
Heating cold water feed valve train (see figure 7.3 :
Cold Water Supply Valve Train) is sized to provide
flow rates of approximately 4800 l/h under the
assumed conditions of 2 bar incoming mains water
pressure and 1 bar static back pressure resulting
from the highest distribution lines above the vessel
and flow resistances of the system.
train
Potential flows will increase with higher mains pressures
up to the 3.5 bar preset regulator pressure. However due
to the many variables involved it is recommended that the
flow rate of 4800 l/h is considered the maximum.
An expansion vessel that is pre-charged at 3.5 bar and
sized to accept the water expansion volume from the
storage tank and its local associated pipework is supplied
with each un-vented tank.
If the water train is serving a large distribution system
additional expansion vessels maybe required and the
acceptance volume V2 can be calculated as follows:
the
V2 =
Where e
is the expansion factor which for a 65°C rise
t
= 0.02.
V1 is the volume of the entire system including the
heater.
Pc is the absolute expansion vessel cushion pressure
normally preset to 4.5 bar. Absolute = (3.5 bar gauge
+ 1 bar.)
Pw is the absolute working pressure and is the same
value as that of the expansion relief valve setting 6
bar. Absolute = (5 bar gauge + 1 bar.)
V2 is the volume of the required expansion vessel.
3
POWERSTOCK
e
x V1
t
Pc
(
)
1 –
Pw
500001177/I
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