Application guide
Cascade control of heat exchangers
District heating distribution station
Distribution station
Application
A district heating utility wants to build a distribution station between the power plant and a residential area.
The distribution station should be able to supply approx. 100 residentials ~ 1 MW capacity and be future-prepared to expand the supply capacity when the residential area grows.
The district heating utility wants to establish the distribution station with 2 heat exchangers (or more) instead of one big one to achieve maximum efficiency and to control the heat temperatures by means of electronic controllers.
ECL Comfort 310 controller with key
We recommend
•A362 application key
•ECL Comfort 310 controller
•ECL Portal
•Heat exchangers, XB71, brazed type
•AMV + AME actuators
•Motorized control valves (VS, VM, VB, VFM...)
•Pressure independent control valves (AVQM, AFQM)
For this application Danfoss has developed the A362 application key.
Together with the ECL Comfort 310 controller it offers weather compensated control of the flow temperature in a heating circuit (residential area) based on advanced cascade control of 2 heat exchangers (HEX).
Up to 6 heat exchangers can be cascade controlled by 1, 2 or 3 ECL Comfort 310 controllers, each equipped with the application key A362.
The ECL controllers are interconnected by means of the ECL 485 Bus.
Control valve characteristics are taken into consideration, and flow in unused heat exchangers circuit can be stopped.
Optional sliding return temperature limitation. Scheduled shift for inversed cascade (HEX-1 - HEX-2 and HEX-2 - HEX-1) can be set.
Override inputs for start of HEX-1 and HEX-2 are available. M-Bus based signal can be used for flow / energy limitation.
Alarm functions are related to flow and flow temperatures.
The ECL Comfort 310 controller can be connected to the ECL Portal for remote monitoring and control of the distribution station.
With the ECL Portal it is possible to monitor and control one or more ECL Comfort 310 controllers remotely from a pc or a smartphone app.
The ECL Portal is an effective tool for service personnel of district energy stations to streamline service, commissioning, maintenance and control tasks. Also, alarm messages can be sent directly to users via e-mails.
This internet-based SCADA solution requires no local server and will automatically configure its user interface and functionality to support the application in the controller.
Heat exchangers to be chosen for this application can be gasketed or brazed heat exchangers with 1-pass or 2-pass. They are available with both thread and flange connections.
In a 1-pass exchanger all connections are placed on the same side thus making installation very easy.
A 2-pass exchanger has connections on front and back, and smaller temperature difference between primary and secondary side can be obtained.
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