FAQs

Here you will find answers to the most important questions about Baelz-hydrodynamic® ejector technology for industry and building services.

1. Is there only one provider for ejectors in the European market?

There are at least 7 providers. But Baelz was the first to bring the water jet pump to marketability.

2. Can ejectors be used in combination with conventional systems?

Systems can be run with a combination of ejectors and conventional components, i.e. circulation pumps and control valves.

3. Are ejectors more sensitive to dirt than control valves?

No, but we generally recommend placing a dirt trap before each ejector. Control valves also requre the use of dirt traps; ejectors are no more dirt-sensitive. A central dirt trap before the distributor is also sufficient. A dirt trap in the return flow is not necessary when using ejectors.

4. Is there a higher risk of ejectors freezing during frost?

The risk of freezing during frost is not increased with ejectors. Approx. 60 – 75 % water volume is utilized in partial load operation (approx. 0 °C outside temperature). As for conventional systems, the usual start-up mode should also be used for ejectors. We recommend providing a water-end return flow cooler directly after the register for this.

5. Does more noise occur with thermostat valves?

Quite the opposite, thanks to one of the strengths of ejector technology: the volume-variable control in partial load operation. The ejector switches more quietly than a comparable conventional system with speed-regulated pumps. With ejectors in conjunction with thermostat valves, the potential for noise at the thermostat valves is virtually eliminated.

6. Does the use of ejectors entail increased expense for commissioning in comparison to conventional circuits?

There is no increased expense. Commissioning is conducted completely normally at full load. The system water volume is the same as with a conventional setup. However, we wish to point out that proper commissioning by a Baelz Customer Service technician is an indispensable basis for functional guarantee and warranty.

7. Does the ejector actuation only work with three-point step output?

No, all control companies are familiar with the use of ejectors. The following actuation is possible: - continuous (0 – 10 V oder 0/4 - 20 mA) or - three-point step output...

8. Can ejectors only be operated in certain installation positions?

No, ejectors can be installed in all directions - from a hydraulic viewpoint – i.e. diffusor upwards, sideways or downwards (here: protect actuator from any water drips).

9. Do ejectors generate more noise?

Noises do not occur in ejectors, even at very high differential pressures.

10. Does the use of ejectors mean that consumers in a lower location cannot be supplied with enough heat?

If this situation actually occurs it is not a problem for the ejector. Corresponding throttle valves must be provided in the riser if consumers are located in both lower and higher positions. Alternatively, the radiators located lower down can also be started up with a siphon.

11. Is control accuracy better than with valves?

Yes, the ejector allows much more accurate control (e.g. of temperature). This also applies in the lower setting range: from 0 up to approx. 5 % stroke, a control valve only executes OPEN / CLOSED – but the ejector adjusts. The ejector has a much higher valve authority, as the pressure drop is extended with the secondary circuit and does not have to be fully dissipated in the control element.

12. Are ejectors very sensitive to primary pressure?

No, this is one of the major advantages of ejectors. The pressure ratios can essentially deviate further from the design, as the partial load control is much more precise. Irrespective of primary pressure, so-called differential pressure controllers must be provided when using valves in larger systems with fluctuating primary / differential pressure. The ejector does not entail any additional requirements here.

13. Is a high admixture up to 10 °C necessary when the ejector is fully open?

Baelz ejectors also work with small admixture. Depending on customer wishes and design, the reduction can remain less than 1K below the flow temperature in the fully open position (e.g. 90 °C into the ejector, 89 °C out from the ejector into the system; at 30 °C temperature difference, 59 °C system return).

14. Is there a risk of cavitation in the ejector?

There is no negative pressure! Baelz ejectors are not designed as vacuum ejectors and are therefore far from exposed to cavitation range, unless the network-end return pressure is disproportionately low and lower than the intake level of the ejector. With ejectors, cavitation is not usually a problem.

15. Is it only possible to use ejector technology in ventilation systems, or only in heating systems?

Ejectors can be used anywhere, in district heating as well as in heating / ventilation air-conditioning systems; but also in refrigerating systems. All fluid and vaporous media can be controlled.

16. Does an uneven distribution to the individual consumers occur in the full load range as lower volumes of water are circulated?

In well balanced systems, an even distribution of water volume is ensured. The same also applies when using control valves and speed-regulated circulating pumps. The ejector does not entail any special requirements here.

17. Does the motive jet in the ejector stall in partial load operation and does that mean its use is limited (e.g. only up to 30% minimum delivery rate)?

The motive jet cannot stall as a rule – an intake is ensured from 0 – 100 % stroke. Baelz will also be pleased to advise use for special application issues in the partial load range.

18. Is a careful design of the ejectors necessary and hence increased planning expense?

Systems are normally designed for maximum heating load. The technical operating data must be known in both cases (ejector or conventional), e.g. output, pressure losses, temperature spread. We even believe that the design of the ejector is simpler and safer: 2 assembles (valve and circulating pump) need to be dimensioned for conventional systems. That means the ejector does not have to be chosen more carefully, but with just the same conscientiousness.

19. Are ejectors damaging to turnover and fees?

Ejectors represent a transparent saving potential for investment and operating costs. The project-relevant share of fees might be reduced with this, but satisfied customers are the best advertisement for your business. Especially serious planners should therefore point out to customers that money can be saved with ejectors. This can be incorporated into planning for new projects, leading to valuable follow-up orders. Together, clients, planners and manufacturers can also gain significant advantages for greater operational reliability, less downtime for maintenance as well as improved control quality by using ejector technology – so as to gain more satisfied customers for this technology.