Glandless Pumps - THERMO-ECO-ENGINEERING úvod

Switchgears and Control Devices
Planning Guide
Pump performance control
Need for control
Three main criteria, in line with the steady development of mechanical
equipment for building services and the growing sensibility
towards energy consumption, have led to the increased consideration
of controls for utilisation in conjunction with heating pumps.
1. Function optimisation
Adjusting the pump capacity/heat flow to actual load demand, particularly
to stabilise hydraulic conditions and to reduce circulating
losses.
Pump performance control through speed variation
Of the many procedures developed and tried in the past to automatically
control pump performance to actual load demands, among them
mechanical/hydraulic processes (bypass/throttling control), the
method of variable speed control has proved to be the most lasting.
Particularly the high efficiency and the easy handling have ensured its
dominance as the vital performance parameters – volumetric flow,
head and input power – directly relate to changes of speed.
n 1 /n 2 = Q 1 /Q 2 (n 1 /n 2 ) 2 = H 1 /H 2 (n 1 /n 2 ) 3 = P 1 /P 2
Heating, Air-conditioning,
Cooling
2. Economic efficiency
Reducing power consumption and operating costs, particularly in
partial- or low-load operation (i.e. in over 80 % of the overall
operating time).
3. Comfort and convenience
Avoiding system noise, in particular flow noise and noise in the thermostatic
valves that are due to excessive flow and thermostatic
radiator valves (TRV’s).
Power savings in relation to reducing CO 2 emissions are in conjunction
with environmental-protection considerations playing an ever
more important role. It is widely known that generating power from
fossil fuels produces significant levels of CO 2 emissions. In Germany
engineers use the calculation principle that one kWh of current
generated in a power station produces about 0.56 kg of CO 2 in the
form of emissions.
The decisive factor for concentrating studies on pumps in particular is
their proportionally high share of power consumption within the
energy balance of buildings.
The causes for this are the high levels of operating hours as well as
the familiar phenomenon of over-dimensioning heating pumps
at the planning stage, factors which considerably add to the energy
balance. Over-dimensioning by a factor of 2 to 5 times is the usual
standard.
Thus, for example, when motor speed is doubled, the flow volume is
increased by a factor of two and the delivery head by a factor of
4 while the power input must be about 7 to 8 times greater.
H (%)
P (%)
Q [m 3 /h]
Potable water circulation
Solar thermal
Single-family house
Pumps account for 10 – 15 % of the overall
power consumption, because...
- Two to four pumps are available (heating/
potable water circulation/accumulator
charging, etc.) each pump with about
1500 h to 5000 h operating time per year
(depending on application), i.e. with three
pumps on average:
- 3 x 65 W x ca. 3500 h/a = ca. 700 kWh/a
- In comparison: Mean statistically verified
total power consumption of a detached
family house:
- about 5000 to 8000 kWh/a
Large buildings
Pumps account for
5-8% of the overall
power consumption
Fig.:
Q [m 3 /h]
Pump curves of a pump during operation at different speeds
Service/Accessories, Systems
Switchgears and Control Devices
Pump Management Systems
Wilo Catalogue A1 - Circulating pumps in glandless design
355