Glanded Pumps - THERMO-ECO-ENGINEERING úvod

Switching 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.
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.
Single-family house Large buildings
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 singlefamily
house:
- about 5000 to 8000 kWh / a
Pumps account for
5 –8 % of the overall
power consumption
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
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.
Q [m 3/h]
Q [m
Fig.: Pump curves of a pump during operation at different speeds
3/h] Q [m3/h] 170 Subject to change without prior notice 09/2006 WILO AG
H (%)
P (%)