Technical data

62 | Project planning manual for heat pumps for heating and domestic hot water preparation | 01.2012 www.dimplex.de
6.1.2 Domestic hot water preparation with heat pumps
Cleaning and maintenance
The mandatory cleaning intervals vary according to the water
quality and the temperatures of the heating medium and the cyl-
inder. We recommended having the tank cleaned and the system
checked once a year. The glass-like surface prevents extensive
build-up of lime scale and enables rapid cleaning using a power-
ful water jet. Large pieces of lime scale may only be broken up
using a piece of wood before being rinsed away. Sharp-edged
metal objects must on no account be used for cleaning.
The operational reliability of the safety valve must be checked at
regular intervals. We recommend having an annual service in-
spection carried out by a qualified specialist company.
Thermal insulation and covering
For cylinders with up to 500 litres nominal capacity, the thermal
insulation is made up of high-quality PU (polyurethane) rigid
foam, which is applied directly on the cylinder walls.
For cylinders larger than 500 litres, the thermal insulation is re-
movable and consists of PE (polyethylene) or PS (polystyrene)
foam with foil cladding for minimal stand-by losses.
Controller
The cylinders are equipped as standard with a sensor with an ap-
prox. 5 m long connecting lead, which is connected directly to the
heat pump manager. The characteristic curve of the sensor com-
plies with DIN 44574. The heat pump manager regulates the
temperature settings and the time-controlled charging and re-
heating with the flange heater. Attention should be paid to the
hysteresis when setting the domestic hot water temperature. It
should also be noted that the measured temperature will rise
slightly because the thermal processes in the cylinder still require
some time to equalize after the domestic water has been heated.
Regulation can also be carried out using a thermostat. The hys-
teresis should not exceed 2 K.
Operating conditions:
Table 6.1: Permissible operating conditions
Installation
Assembly is limited to connecting the hydraulic components of
the system along with its respective safety devices and to con-
necting the sensor.
Accessories
Flange heaters with bleeder resistor, designed for enamelled do-
mestic hot water cylinders for thermal disinfection!
Electrical installations should only be connected by authorised
electricians according to the corresponding circuit diagram. The
relevant regulations according to the Technical Specifications for
Electrical Installations (TAB) and the guidelines of the Associa-
tion of German Engineers (VDI) should be observed.
Fig. 6.1: Structure of a flange heater
Table 6.2: Legend flange heater
Installation location
The cylinder should only be installed in a room protected from
frost. Installation and commissioning must be carried out by an
authorised specialist.
Water pipe connections
The cold water pipes are connected according to DIN 1988 and
DIN 4573 Part 1 (see Fig. 6.2 on page 63). All connecting pipes
should be joined using pipe unions.
A circulation pipe should only be connected if the domestic water
supply system is extensive because it causes high stand-by
losses. If a circulation system is required, it should be fitted with
an automatic device to interrupt the circulation.
All connecting pipes including fittings (with the exception of the
cold water connection) must be protected against heat losses ac-
cording to the German Federal Energy Efficiency Ordinance
(EnEV). Poorly insulated or uninsulated connecting pipes will
lead to a loss of energy which is many times greater than the en-
ergy loss of the cylinder.
A check valve should always be fitted to the heating water con-
nection to prevent the cylinder from heating up or cooling down
uncontrollably.
The air outlet pipe of the safety valve connected to the cold water
pipe must always remain unblocked. The operational readiness
of the safety valve should be checked at regular intervals by
venting it.
Drainage
A means of draining the cylinder should be provided in the cold
water connecting pipe during construction.
Pressure reducing valve
It is essential to equip the connecting pipe with a pressure reduc-
ing valve if the max. supply pressure could exceed the permissi-
ble operating overpressure of 10 bar. However, according to
DIN 4709, the pipe pressure should be lowered inside buildings
to a level which still permits technical operability to reduce the
generation of noise. Depending on the type of building, it may
then be worthwhile to install a pressure reducing valve in the cyl-
inder inlet.
Permissible operating overpressure
Heating water max. 3 bar
Domestic water 10 bar
Permissible operating temperature
Heating water 110 °C
Domestic water 95 °C
1 Protective cap
2 Heating flange
3Seal
4 Electrical connection