Hep20 Technical Handbook

Hep 2
O ® Design Considerations
Systems Planning
Temperatures and
Pressures
This section covers the maximum
temperatures and pressures
associated with hot, cold and central
heating systems.
Table 10 relates to plumbing and
heating systems generally and shows
the type of service, the temperature
at which it operates and the
pressure usually assoiciated with
these.
Cold water systems
The normal working pressure for
cold water systems is 3 to 4 bar
although in some areas this may rise
to 7 bar during the night.
Hot water systems
These are usually tank fed with a
maximum of 1 bar. Unvented
systems operate at about 2 to 2.5
bar. A safety device prevents the
system operating over 3 bar or
100ºC. The maximum safe
temperature is 60ºC.
Combination boilers operate
between 1 and 1.5 bar only: a safety
device prevents the boiler operating
above 3 bar.
Note that 1 bar = 14.5 pounds per
square inch = 100,000 Pascals = 10
metres of static head.
Recommended service
temperatures and pressures for
Hep 2 O ® pipework
Hep 2 O ® has a minimum design life
expectancy of 50 years provided the
system is installed in accordance with
the manufacturer’s recommendations.
These recommendations include
service temperatures and pressures.
Service temperatures are defined as
the maximum temperature that can
occur during normal operation.
The malfunction temperature is
defined as the maximum
temperature applied to the system
in the event of control thermostat
failure or malfunction. The system
could remain intact at this
temperature and pressure for 3 to 4
months.
Table 11 shows the recommended
service temperatures and pressures.
Table 10 Maximum Temperatures and Pressures
Flow rates
Although the bore of Hep 2 O ® pipe
is less than its copper equivalent
actual system flow rates are not
significantly lower. This is due to
four reasons:
•
the system requires fewer fittings,
i.e. elbows - a 15mm copper
elbow reduces the flow of a
system by being equivalent to
adding 0.5m to the pipe run.
•
the smooth bore does not allow
corrosion or scale to build up
and reduce the flow of a system.
•
the method of cutting and
jointing ensures there are no
burrs or protrusions of solder to
impede the rate of flow.
•
by using the flexibility of the pipe
the course of the water takes
fewer sharp bends and the flow is
impeded less.
Service Temperature Pressure
Cold water 10ºC to 20ºC up to 7 bar
Hot water up to 60ºC 1 bar for vented systems
3 bar for unvented systems
Central heating 82ºC 1 bar for vented systems
3 bar for pressurised and combination
systems
Table 11 Recommended Service Temperatures and Pressures
Temperature (ºC) 20 30 40 50 60 70 80 90 114
Pressure (Bar) 12.0 11.5 11.0 10.5 9.0 8.0 7.0 6.0 3.0
Note that 114ºC = malfunction
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