© Intatec Ltd 2017
3
Unvented Mains Pressure System
The drawing shows a typical installation of a
shower mixing valve in conjunction with an
unvented hot water system. This type of
installation must be carried out in accordance
with Part G of the Building Regulations.
Whilst pressures are theoretically equal
(balanced) most unvented hot systems have a
pressure reducing valve on the incoming cold
water prior to the hot water storage vessel.
This means that the hot and cold pressures can
be significantly different.
Most unvented systems use an inlet manifold
located directly after the pressure reducing
valve.
It is recommended that the cold supply be taken
from one of the outlets of the manifold directly to the shower as an independent supply.
For systems without a manifold unit after the pressure reducing valve and where the cold water
supply pressure is significantly higher than the hot supply we recommend that a separate
pressure reducing valve is fitted to the cold supply, as close as possible to the shower valve
and with no draw off points between it and the shower valve.
Flow regulators are required for installations where a PRV is not fitted to ensure simultaneous
demand is accounted for.
Modulating Combi Boiler / Instantaneous Gas Water Heater
The drawing shows a typical installation of a shower valve in conjunction with a combination
boiler.
Combi boilers will produce a constant flow of water at a
temperature within its operating range.
The hot water flow rates are dependant upon the type of
boiler / heater used and the temperature rise required
to heat the cold water to the required temperature.
The cold water flow rates may be much greater as
they are generally unrestricted from the mains cold
water supply. To ensure relatively balanced flow
rates, we recommend that a pressure reducing valve
or 6 l/min flow regulator is fitted in the cold water
supply pipe.
Manifold
PRV
PRV if
manifold is
not used
Cold Supply direct
from mains
Summary of Contents for Nulo CB10031CP
Page 19: ...Intatec Ltd 2017 18 Notes...
