Benefits
■ Hydraulic separation of the heat pump from the heating circuits
ensures a constant flow rate through the heat pump.
For example, if the heating circuit flow rate is reduced via thermo-
static valves, the flow rate through the heat pump remains con-
stant.
■ Due to the low pressure drop to the heating water buffer cylinder,
the secondary pump can be made smaller.
■ Heating circuits with mixer can be supplied with a different flow
temperature to a heating circuit without mixer.
■ Additional heat generators can be integrated into the system, e.g.
solar central heating backup.
■ Bridging power-OFF periods:
Subject to the electricity tariff, heat pumps can be switched off at
peak times by the power supply utility. The buffer cylinder supplies
the heating circuits including during this power-OFF time.
■ The large buffer volume is used to extend the runtime of the heat
pump. This avoids frequently switching the heat pump on and off
(cycles).
■ Due to the high energy content, a heating water buffer cylinder
always provides the required defrost energy for the heat pump.
Implementation instructions
■ When sizing the heating water buffer cylinder, note whether under-
floor heating circuits and/or radiator heating circuits are connected.
■ Due to the large volume of water and possible separate shut-off
equipment for the heat generator, allow for a second or a larger
expansion vessel.
■ Set up the safety equipment for the system according to
EN 12828.
■ The volumetric flow rate of the secondary pump must be greater
than that of the heating circuit pumps.
■ In conjunction with an underfloor heating circuit, a temperature lim-
iter must be installed to limit the maximum temperature of under-
floor heating (part no. 7151728 or 7151729).
Sizing for underfloor heating on the ground floor and radiators
in the attic
A heating water buffer cylinder of at least 200 l is required to prevent
the heating circuits cooling down completely.
Connect the heating water buffer cylinder to the secondary circuit
flow, in parallel with the heat pump (do not connect to the return).
Sizing for radiators (100 %)
A heating water buffer cylinder with a capacity of 200 l is required.
Systems with heating water buffer cylinder connected in series
In systems with a heating water buffer cylinder connected in series
the required minimum system volume can be ensured. This type of
heating water buffer cylinder is integrated into the secondary circuit
return.
Benefits
■ The large buffer volume is used to extend the runtime of the heat
pump. This avoids frequently switching the heat pump on and off
(cycles).
■ Due to the high energy content, a heating water buffer cylinder
always provides the required defrost energy for the heat pump.
Implementation instructions
■ An overflow valve
must
be integrated in the heating circuit to
ensure that the additional system volume is always available even
in sealed unvented heating circuits.
The flow rate of the overflow valve must be selected to ensure the
minimum flow rate of the heat pump.
■ Set up the safety equipment for the system according to
EN 12828.
■ In conjunction with an underfloor heating circuit, a temperature lim-
iter must be installed to limit the maximum temperature of under-
floor heating (part no. 7151728 or 7151729).
Systems without heating water buffer cylinder
In systems without a heating water buffer cylinder, trouble-free oper-
ation of the heat pump is only ensured if the following conditions are
met:
■ The minimum flow rate and the minimum system volume of the
heat pump are ensured at all times.
■ To avoid any loss of comfort caused by blocking periods, set up
the heat pump power supply without power-OFF.
Implementation instructions
Take the following measures to ensure that the minimum flow rate of
the heat pump is always available even in sealed unvented heating
circuits:
■ Fit an overflow valve in the heating circuit.
The flow rate of the overflow valve must be selected to ensure the
minimum flow rate of the heat pump.
■ Keep parts of the heat distribution system open:
Observe the relevant national regulations and/or Energy Savings
Ordinance. The consent of the system user is required.
■ In conjunction with an underfloor heating circuit, a temperature lim-
iter must be installed to limit the maximum temperature of under-
floor heating (part no. 7151728 or 7151729).
7.9 Planning aids for the secondary circuit
The required minimum flow rate and the minimum system volume
must always be guaranteed. The following tables give an overview of
which components can be used to achieve this:
■ Secondary circuit pipework
■ Heating water buffer cylinder connected in parallel to the heat
pump
■ Heating water buffer cylinder connected in series to the secondary
circuit return
Design information
(cont.)
120
VIESMANN
VITOCAL
7
5831388
