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DESIGN
SY
STEM DET
AILS
Hot and Cold Water System
General
A schematic layout of the hot and cold water services in a typical small dwelling is
shown below. BoilerMate A-Class OV SOL will operate at mains pressures as low as 1
bar and as high as 5 bar although the recommended range is 2-3 bar. These pressures
are the minimum dynamic pressures at the cold connection to the BoilerMate A-
Class at the time of the maximum calculated simultaneous demand. If the manifolds
(available as an optional extra) are being used the inlet pressure to the manifold must
be a minimum of 2 bar. Particular consideration should also be given to available
pressures in the case of 3 storey properties. It is also important to check that all other
equipment and components in the hot and cold water system are capable of accepting
the mains pressure available to the property. If the mains pressure can rise above 5
bar (or the maximum working pressure of any item of equipment or component to be
fitted in the system) a pressure limiting (reducing) valve set to 3 bar will be required
(or the pressure rating of the piece of equipment or component).
If you encounter a situation where the water pressure is adequate but flow rates are
poor please contact our technical helpline for details of an effective solution.
Note: Each BoilerMate A-Class OV SOL is fitted with a strainer and flow regulator on
the cold mains supply connection. If the supply pressure is less than 2 bar or if the
manifolds (available as an optional extra) are being used or if all taps are provided
with flow regulators the flow regulator on the cold inlet should be removed.
No check valve or similar device should be fitted on the cold water supply branch to
the BoilerMate A-Class OV SOL.
The Building Regulations L1A: New dwellings/L1B: Existing dwellings and the
requirements set out in the Domestic Heating Compliance Guide specify that “where
the mains water hardness exceeds 200ppm provision should be made to treat the
feed water to water heaters and the hot water circuit of combination boilers to reduce
the rate of accumulation of lime scale”.
To comply with this requirement the hardness
of the mains water should be checked by the
installer and if necessary the optional factory
fitted in-line scale inhibitor should be specified
at the time of order for hardness levels between
200 and 300 ppm (mg/l).
Where the water is very hard ie 300ppm (mg/l)
and above the optional polyphosphate type,
inhibitor should be specified at the time of
order. However, this will need to be fitted by
the installer at a suitable point in the cold water
supply to the appliance.
If scale should ever become a problem the plate
heat exchanger is easily isolated and quickly
replaced with a service exchange unit which can
be obtained at a nominal cost from Gledhill.
The hot water flow rate from the BoilerMate A-
Class OV SOL is directly related to the adequacy
of the mains cold water supply to the dwelling.
This must be capable of providing for those
services, which could be required to be supplied
simultaneously, and this maximum demand
should be calculated using procedures defined
in BS 6700.
If a water meter is fitted in the service pipe,
it should have a nominal rating to match the
maximum hot and cold water peak demands
calculated in accordance with BS 6700. This
could be up to 80ltr/min in some properties.
Warning/
overflow
pipe
MCWS
Safety/open vent
Shower
Expansion/
cold feed
Second
dwelling
Pressure limiting valve
NOT REQUIRED at
pressures below 5 bar
unless any components
have a lower
maximum working
pressure
Double check valve
NOT REQUIRED unless
chemical water
treatment unit is fitted
‘a’ - flow regulator recommended for
better balance of hot and cold
water supplies
MCWS
supply
pipe
Sink
H C
a a
SV
a a
a a
Bath
H C
Hand basin
H C
WC - fitted
with BS1212
ballvalve
C
Figure 1.9
Typical hot and cold water distribution (to a smaller property)
Check valve
NOT REQUIRED unless
chemical water
treatment unit is fitted
Optional polyphosphate scale inhibitor
NOT REQUIRED unless the hardness
level exceeds 300ppm (mg/l)
a
F&E cistern
BMA OV SOL
225 model
