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Technical Info
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Proven Technology MK TEC Management Systems access the latest technology. The system incorporates the latest microchip electronic circuiting technology, which is programmed to the changing load on the boiler as well as to regulate the firing pattern accordingly. The MK TEC boiler thermal management controllers supplied by MK Energy, increase the efficiency of existing central heating boiler systems without physically altering any constituent part of that system. To understand how this is achieved consideration must be given to a typical commercial heating installation. What is Boiler Thermal Management and is it Necessary ? At its most simplistic, a system would consist of a boiler thermostat in addition to a hot water and single wall mounted thermostat. This form of control system is termed 'two-step' control with hysteresis. Thermostats have a typical hysteresis of plus and minus 2.5?C, consequently if pre-set at 65?C the minimum temperature differential will cycle between 62.5?C and 67.5?C at the thermostat and, if air circulation is poor, in addition to long thermal time constants, this problem would be compounded to a greater extent at other parts of the property. Climatic changes and the inherent hysteresis within the boiler thermostat further exacerbates this situation. Consider the higher temperature excursion. Under these conditions heat transfer rate from radiators within said environment will be reduced, resulting in the temperature of the water returning to the boiler approaching that of the flow. Nevertheless, the boiler will continue attempting to heat the water at a faster rate than it can be absorbed, the excess heat being vented into the atmosphere. This sequence of events will continue until either the boiler thermostat temporarily inhibits the action or alternatively the wall mounted thermostat senses the upper limit temperature. Residual radiator heat will continue to raise the overall temperature, thereby creating an additional temperature overshoot. Consequently, gas is being wasted by attempting to force heat into the premises at a rate greater than it can be absorbed. A similar scenario will occur with the lower temperature excursion or changing climatic conditions e.g. temperature, wind speed and wind direction. Clearly, Boiler Thermal Management is Necessary. MK TEC's product range approaches thermal management of boilers for hot water and central heating systems in the most innovative manner. MK TEC systems have achieved this by introducing a proportional control element within the existing control loop, thereby minimising temperature over-shooting attributed to two-step thermal controllers. This is attained by employing an Embedded Micro controller with its associated input sensors that measure the flow and return water temperature and variations in external temperature. This data is computed instantaneously, only initiating boiler firing when the differential temperature exceeds the pre-set limit, thereby matching the boiler's thermal output to the average heat transferred by the radiators. Boiler efficiency and comfort of employees is further enhanced by measuring external temperature trends and computing a new boiler firing pattern in anticipation of future demands thus maintaining the premises at the desired temperature by averting large temperature deviations. MK TEChnical Overview When installed, the MK TEC thermal management systems derive their 240 V ac. 50 Hertz mains supply from the existing system's de-activated time clock. This permits the energy management controller to implement and manage the pre-programmed heating patterns and control efficiently boiler firing as and when dictated by either the external temperature sensors or alternatively the hot water thermostats. All models are housed in self extinguishing, commercial grade PVC enclosures conforming to IPP 55 standard and contain two separate printed circuit boards, each being manufactured from FR-4 material, and termed: The Microcontroler Energy Management Module; The Power Supply and Boiler Interface Module. Micro controller Energy Management Hardware This module is constructed around the Intel 80C198,8-bit micro controller with an external 32K electrically programmable read only memory (EPROM), containing the thermal management algorithm. Incoming and outgoing communications between the micro controller and the heating system can be subdivided into the following functions:
Analogue voltage signals proportional to water temperature and external temperature are derived from high responsive semiconductors thermistors, the water temperature sensors being bonded to the flow and return water pipes. These signals enter the micro controller's 10-bit analogue to digital converter via an 8-channel software controlled analogue multiplexer. Communication between the micro controller and the boiler firing solenoids and their associated status mimic display is achieved with the employ of a Programmable Parallel Interface. When the BC 500 is considered, this parallel mode of communication facilitates individual boiler control in addition to lead boiler cycling and consequently enables system efficiency to be maximised. Programming heating requirements into or alternatively retrieving historical data from the controller can be performed remotely or locally. The former permits a PC to communicate with the controller via a full duplex serial port conforming to the RS-232-C interface standard whereas the latter is achieved via the controller's integrated keyboard and liquid crystal display. Programmed operating requirements and historical operating data is stored within a nonvolatile Watchdog Timer, namely the MK48T02. This device is menu driven via the micro controller and consists of a programmable calendar, real time clock and non-volatile random access memory (RAM). In the event of a total mains failure the device's real time clock and calendar circuitry will continue to function whilst the programmed operational instructions and historical operating data will be stored in non-volatile RAM, thereby reintroducing control in synchronism when power is restored. |
Micro controller Energy Management Software The energy management program is written in the PL\M 96 block structured programming language specifically designed by the Intel Corporation for microprocessor programming. The program is best considered when subdivided into three constituent parts:
Programming the product range or alternatively data retrieval can be performed either locally via the integrated keyboard and liquid crystal display or remotely by means of the PC's communication software. Providing the security code entered is correlated to that previously stored, access will be gained . The program then permits the operator to enter any one of seven hierarchically structured menus, the first menu being dedicated to programming the desired operational heating patterns of the complex, whereas the remaining six menus enable historical operating data to be displayed, printed, or stored on magnetic disk. The thermal control algorithm in all models initially samples and linearises temperature equivalent voltage signals derived from the systems temperature sensors. The program then proceeds to maintain both the flow and return temperatures within two pre-programmed limits. In the event of a cold start-up the flow and return temperatures will be below the desired thresholds and the algorithm will demand maximum thermal output until both parameters are correlated, thereby providing a rapid warm-up capability . Having achieved temperature correlation, the program changes its priority to maintaining a thermal equilibrium throughout the property. This is achieved by further interrogating temperature signals and maintaining the flow and return water at a pre-defined differential temperature, ensuring that heat is generated at the optimum rate. Normal central heating controllers only sense internal temperature and do not allow for variation in the external ambient temperature or the thermal time constant of the property, consequently wasting gas and causing discomfort to the occupants. MK Energy's software design circumvents this situation by monitoring and comparing the external temperature to a set-point and if necessary, computing a new differential water temperature, thereby increasing or alternatively decreasing radiated heat output. This data, in conjunction with the return water temperature, is then used to compute a revised look-ahead boiler and water pump firing pattern, minimising temperature overshooting or alternatively undershooting. Frost prioritising software overrides all programmed heating cycles by comparing the external temperature to the pre-programmed value. If frost is deMK TECted the program immediately samples the water temperature, and if necessary, initiates a frost proMK TECtion override signal automatically firing the boiler as ill a rapid warm-up situation. This continues until the return water temperature attains the pre-programmed magnitude. In contrast, the MK TEC encompass all of the above features in addition to multi-boiler operation. Multi-boiler control and optimisation is achieved by rotating the sequence of lead and slave boilers, these are individually controlled via a temperature window deMK TECtor. On the initiation of a plant or heating demand the controller will initiate lead boiler firing, the program will constantly compare the flow temperature to the pre-defined minimum and maximum temperature. If within a pre-defined time, the flow temperature has not attained the designated minimum temperature, the first slave boiler will be fired and the interrogation repeated until the number of active boilers are sufficient to attain the upper temperature threshold. At this juncture the algorithm reverses the process and reduces the number of operational slave boilers, ensuring a thermal capacity sufficient to maintain a constant differential flow and return temperature. Power Supply and Boiler Interface Module Electrically, this module isolates the Micro controller & Energy Management Module from mains borne electrical transients and noise or, alternatively, boiler solenoid failure. The former is achieved by isolating the 250 V a.c. 50 Hertz supply (derived from the existing systems time clock) from the controller via a transformer, with its primary winding fused. The secondary low voltage winding supplies two monolithic integrated circuit voltage regulators, namely the uA7812 and the uA7805. These devices possess internal current limiting and thermal shutdown making them essentially immune to overload. In conjunction with filter capacitors the voltage regulators stop mains borne transients and electrical noise from entering the controller. Electrically isolating the micro controller energy management module from the boiler solenoids in the MK TEC is achieved by energising an electro-mechanical relay or relays as dictated by the thermal algorithm. The relays' associated contacts having a rated life of ten million operations, consequently providing electrically isolated and Volt free contacts. When installed these contacts will derive the necessary electrical mains supply by being connected in series with the existing boiler thermostat and the boiler solenoid, thereby controlling boiler operation. Communications Software 
The Communications Software System allows the user to be in full control of all remotely sited heating systems where a MK TEC 100, 200, 500 Boiler Management System is installed Providing the ability to access all the programs contained within the MK TEC system, view the current settings and change any of the parameters to suit individual requirements, at the touch of a button.
With it's 10-Day Graphical Log displaying an hour by hour analysis of system temperatures together with a daily statistical information log of minimum / maximum flow temperatures, compensated flow temperature, minimum / maximum external temperatures and the number of boilers firing, a complete history can be built of all the important facets of the heating system, it's performance outputs and efficiency. All program changes, holiday settings, extended heating periods, logging of historical information etc, can be accessed and controlled from the convenience of the office via a modem link from a PC, eliminating the need for time consuming and costly site visits. The Communications Software Package if fully upgradeable to cater for future enhancements or additional programs and is available with new systems or as an upgrade to existing MK TEC 100, 200, 500 installations. Telephone Hotline and E-Mail support are provided for advice or assistance if required. |
