Blower and exhaust fan interlock
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Regarding the interlocks related to the blower and exhaust fan of this furnace, firstly, if the blower stops, an interlock will activate to open the quick-opening damper; meanwhile, if the damper is in the open position, an interlock will stop the blower and the exhaust fan. ??So does that mean that when starting the blower, all the dampers need to be set to bypass mode? According to the first logical sequence, when the reset button is pressed and the blower and exhaust fan are stopped, the dampers will not close either, unless the condition for bypass mode is met. Which expert familiar with chain operations can give some guidance?
This drawing style is definitely a LPEC template
This is quite simple, right? The logic diagram is already provided; one just needs to write the program in the DCS. It’s a good idea to add a first-run memory function to make it easier to identify the cause of triggers later on
No, the fans are mainly started according to a interlock logic; does that mean all bypasses have to be activated during startup?
During startup and shutdown, certain interlocks must be disabled; otherwise, startup cannot proceed, and interlocks will be triggered immediately during shutdown.
The problem is that even during normal startup, a bypass is required
This post was last edited by jlshnlhj on 2019-9-11 at 16:08. The file “50-00-LG05.pdf” was downloaded and viewed; the following section seems to contain the driving conditions. Look at the first OR gate: when the feedback indicating that the F7101 quick-opening damper is open is ‘open’, and the feedback indicating that it is closed is not ‘closed’, this OR gate outputs 0. Similarly, if all the feedback signals from the quick-open valves F7101 and F7201 meet the requirements, each OR gate will output 0, and the final NAND gate will then output 1. The RS output is 1; after inversion, it becomes 0. The alarm light goes out; close the two shutters, and reset \"Stop blower\" and \"Stop exhaust fan\". (Notice the small text at the bottom: \"For electrical systems, operation stops when the logic output is 1,\" representing an \"on\" state, while \"0\" indicates a reset state.) "Now the output is 0 for positive values. ) In summary, the responses from the quick-opening dampers of F7101 and F7201 all met the requirements; the alarm lights went out, the two shutters were closed, and the outputs for “Stop blower” and “Stop exhaust fan” were reset. However, there is a problem with the reset button: according to the instructions, it is a \"spring-loaded reset button (normally closed), with a value of 1 when the switch contacts are closed.\" Therefore, there should be an inverter behind it, which would then provide an input for the OR-inverter.
The waste heat recovery system is equipped with interlocks that are activated during startup and shutdown. These interlocks are engaged only when the heating furnace is operating properly; natural ventilation is switched to forced ventilation, and improper operation can trigger these interlocks
Hey, are you from Luoyang too?
The drawings are not clear, but opening the air dampers quickly and turning on the blower should not be equipped with a safety interlock; it may result in slightly more power consumption, but there will be no safety issues. If it is to be installed, it should be triggered by the conditions that cause the quick-opening damper to operate; there is no need to use the damper’s status as a trigger. Moreover, if a two-way valve is used for the quick-opening damper, then any problem with that damper will result in the shutdown of the fan, which is clearly inappropriate; it can lead to the shutdown of the furnace and even the entire installation.