Automatic Bypass - Mitsubishi Electric Ecodan HUS210FTC4ST Installation Manual

Automatic Bypass Valve
18
The Mitsubishi Electric pre-plumbed cylinder
has a spring differential automatic bypass valve
fitted as standard.
This serves two purposes; it allows for the
minimum flow rate of the Ecodan unit to be
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maintained and hence eliminates the possibility
of high pressure or temperature faults due to
insufficient flow rate. It will also ensure that in
the event of a pump overrun occurring when
the demand for heating or hot water has been
satisfied that the primary circulation pump
(heat pump flow) is able to bypass the zone
valves and hence no pump damage will occur.
The diagram to the left shows the position
which the field supplied pipework must exit the
bypass valve and join onto the space heating
return. It is important that this diagram is
adhered to; any deviation could cause the
bypass valve not to operate correctly. The
bypass should be connected to the space
heating return at least 300mm away from
the suction side of the circulation pump
where possible.
As the valve works on differential pressure and
two circulation pumps are being utilised for an
adequate pressure difference to exist the
pipework routing shown ensures that on the
inlet side of the bypass valve there is greater
pressure than on the outlet side which is
connected behind the space heating
circulation pump.
The automatic bypass valve should be set so
as to open at the minimum flow rate achieved
for the Ecodan unit in question.
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In situations where an adequate bypass has
been provided elsewhere on the system it is
important to cap the factory fitted auto bypass
valve. Installation of a suitable flow setter (0-10
L/min) on the bypass pipework may help with
commissioning. If you have any questions
about the fitting and commissioning of this
component please contact Mitsubishi Electric
Presales Technical Support on 01707 278666
FTC4 Installation Manual
26