Benchmark mCHP BoilerMate Design, Installation And Servicing Instructions page 7

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SYSTEM DESCRIPTION 2.0
2.1 INTRODUCTION
The 'N' models shown schematically in figures
2.1 and 2.3 are primarily designed for the new
build market. In these models the thermal store
completely isolates the mCHP unit from the space
heating and hot water demands and functions.
The 'R' models shown schematically in figures
2.2 and 2.4 are primarily designed to replace
the conventional hot water cylinder in an airing
cupboard for example in the retrofit market and
the system controls are arranged as a 'Y' plan in a
traditional heating system to minimise pipe work
changes during installation.
To comply with the Benchmark Guidance Note for
Water Treatment in heating and hot water systems
the installer should check the hardness levels of
the water supply and if necessary fit an in-line
scale inhibitor/reducer to provide protection to
the whole of the domestic water system.
This can be specified for inclusion within the case
as an extra which therefore does not require the
provision of a fused spur in the cupboard.
If scale does become a problem, the plate heat
exchanger is easily isolated and replaced with a
service exchange unit.
The mCHP BoilerMate
the following main functions:-
• It senses the demand for space heating and hot
water from external user controls and switches
on the appropriate system components to
satisfy these demands.
• The space heating and plate heat exchanger
pumps operate for a few seconds every 36 hours
when there is no demand for space heating and
domestic hot water to reduce the likelihood of
the pumps and diverter valves sticking.
• It provides the mCHP pump overrun facility
when necessary.
• Depending upon the store temperature and
the energy demands, it provides switch on and
off control signals for running the mCHP unit in
normal and boost modes.
• Depending upon the store temperature and the
energy demands,it also provides switch on and
off control signals for the built in electric boost
heater (if this option is selected) to satisfy short
term peak space heating loads greater than the
thermal rating of the mCHP unit.
• In the event of failure of the mCHP unit it
provides a 6kW electric backup facility by a
'switch' electric boiler for hot water and central
heating.
Page 7
A-CLASS controller incorporates