Hot water boilers are routinely operated in residential/commercial/industrial building heating, in service-water systems and many other areas. Power burners of the boilers are usually delivered with a burner management system which provides:
- Burner purge before ignition
- Control of single, double and modulated burners
- Automatic ignition and combustion maintaining
- Air pressure control before the burner.
This is not the full list of process parameters to be controlled, that’s why there is a necessity to use additional automation equipment which will:
- Control water pressure
- Control fuel pressure
- Interrupt the process in case of an accident.
Such equipment was usually represented by way of relay protections. Herewith we have some difficulties when realizing ON or OFF time delays. And also relay cabinets take much place.
The akYtec GmbH offers a rational solution (Fig. 1) based on the programmable relay PR200. According to this solution, the alarm of water pressure, fuel pressure, vacuum in combustion chamber, burner accident or boiler overheating is realized with a simple algorithm. An output variable is assigned to each input, taking in account the corresponding time delay. On the basis of the output variable value the boiler operation is blocked and an appropriate alarm is sent to the control cabinet.
Fig. 1
Switching program in akYtec ALP
First it has to be created a project and selected PR200 in the suggested list (Fig. 2). Now the Display Manager tab is available. When programming in akYtec ALP, there can used already existing macros – completed functional units which are available in online macro database for free (Fig. 3).
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| Fig. 2 | Fig. 3 |
But also this programming environment allows to create own macros. For this specific task it should be created an individual new macro ‘Boiler accident’ (Fig. 4). When the macro is completed and all connections are set, it’s time for the display configuration. In the Display Manager it is possible to set up any alarm message for each control parameter (Fig. 5). After that it only remains to test the project in simulation mode and the program is ready for use, if there are no mistakes.
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| Fig. 4 | Fig. 5 |
The given example is a little part of PR200 capabilities in boiler plants. With this programmable relay you can create both on/off control algorithms of the heating medium temperature and more complex control algorithms of boiler units. For instance, it can be a PID control of a modulated burner subject to the temperature of outdoor air and also some cascade control (up to four boilers) with automatic switch of the leading boiler in accordance with preset accrued operating time.