Page 4
Remote
F&E tank
Full bore automatic bypass valve NOT REQUIRED
unless the heating system incorporates
mechanical thermostatic control valves e.g.
T.R.V's to all radiators or 2 port zone valves.
Primary flow
Primary
return
BM
A-Class
OVR
Boiler
Warning/overflow
pipe
Cold feed
Mains cold
water
Open Vent
DESIGN
INTRODUCTION
Description
The BoilerMate A-Class OVR shown schematically above is designed to provide
improved space heating and mains pressure hot water when coupled to any remotely
sited condensing boiler.
The principle of a BoilerMate A-Class is to separate the heat generator e.g. a boiler
from heat emitters (radiators) by a thermal store, which evens out the uctuating
demands for heating and hot water.
Because this product does not require a safety discharge from a temperature and
pressure relief valve, any installations will be easy to incorporate into the building
and will not suer from the problems associated with using PVCu soil stacks to take
the discharge from unvented cylinders.
An important feature of this concept is that hot water can be supplied directly from
the mains at conventional ow rates without the need for temperature and pressure
relief safety valves or expansion vessels. This is achieved by passing the mains water
through a plate heat exchanger. The outlet temperature of the domestic hot water
is maintained by a printed circuit board (A.C.B.), which controls the speed of the
pump circulating the primary water from the store through the plate heat exchanger.
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 tted electronic in-line scale
inhibitor should be specied 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 specied at the time of order. However, this will need to
be tted 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 A.C.B. also incorporates the facility to
operate the heating pump for a few seconds
every few days when the heating is not being
used (to reduce the likelihood of the pumps
sticking) as well as providing a boiler pump
overrun facility.
Any automatic boiler designed to operate on an
82°C ow and a 71°C return up to a maximum
of 35kW can be linked to any suitable model of
BoilerMate A-Class and the deciding factor is the
space heating and the hot water requirements
of a dwelling. See the Technical Data section
for further details.
The heat losses from thermal stores should not
be directly compared with heat losses from
unvented or vented cylinders because they are
treated dierently in SAP. The SAP calculator
takes account of the type of store and various
correction factors are included to reect the
dierent ways that the hot water and heating
operates.
Gledhill are part of the ‘Benchmark’ scheme and
a separate commissioning/service log book is
included with the product.
A 13mm connection is required on the primary
return on all units to allow for the provision
of a pumped summer use towel rail circuit if
required (see page 16 for further details)
Note: The BoilerMate OVR is a SYSTEM
appliance and only requires a basic boiler. If a
system boiler is chosen this will present wiring/
operational difficulties as well as incurring
extra costs.
