STIEBEL ELTRON Heat pumps, Technical Manual

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IntEgratIon Into tHE HEatIng SyStEm
Buffer cylinder
For a perfect operation, heat pumps
require a minimum flow rate of
heating water. A buffer cylinder is
recommended to ensure a trouble-
free heat pump operation. buffer
cylinders (cylinder sbP) provide
hydraulic separation between the flow
rate in heat pumps and that in the
heating circuits. the flow in the heat
pump circuit remains constant if, for
example, the flow rate in the heating
circuit is reduced by thermostatic
valves.
Convector heating systems are
generally filled with a small amount
of water. For such systems, a buffer
cylinder of appropriate size should be
installed, to prevent frequent cycling
(start and stop) of heat pumps.
A buffer cylinder is also required for
the defrost operation of air | water
heat pumps.
subject to tariff, heat pumps can be
switched off by some electricity supply
companies during peak periods.
therefore, size the volume of the
buffer cylinder so that with a heating
system that cools down quickly (i.e.
radiators), the stored heat will be
adequate to cover the heat demand
during the above-mentioned power-
oFF periods to prevent a rapid cooling
down of the building.
Benefits of buffer cylinders:
 no modification of the sizing of
existing system pipework
 no flow noise in the heat
distribution system
 no replacement of the circulation
pump of existing heating systems

constant water flow rate through
the heat pump

no loss of comfort during the
power-oFF period
Benefits of applications without buffer
cylinder:
(in conjunction with underfloor heating)
 less space requirement
 lower investment outlay
 higher annual performance factor
Heat pump with overflow facility
Heat pump with separating cylinder (low loss header)
1 Heat pump
2 Control unit
2a temperature sensor
3 Circuit pump
4 overflow valve
5 Heating circuit
1 Heat pump
2 Control unit
2a temperature sensor
3 Circuit pump
4 overflow valve
5 Heating circuit
6 buffer cylinder