Just looking for some advice here...
We're just about to commission two new boilers. Both are equipped with Rielo burners and Siemens RWF40.001A97 controllers. Regretably, I failed to select controllers with Modbus connectability (RWF40.002B97), so operating pressures must be set directly at the burners.
Of course, I could swap out the controllers, but they're $1800 a pop.
As a cheaper, more versatile alternitive, I'm considering the use of PLC to manipulate the signal from the pressure sensor. By adding or subtracting a bit to the analog value before it reaches the controller, I can effectively control which burner is lead or lag. For instance, let's say 0V = 0PSI and 10V = 100PSI. If both boilers are set to fire between 80 and 90 PSI (8V and 9V), I could send a value of 7.5 volts to the lag boiler and 8.0 volts to the lead boiler at 80 PSI and 8.5 volts to the lag and 9.0 volts to the lead at 90 PSI.
The boilers are equipped with a high-limit switch for safety, and the controllers default to a safe condition if no analog signal is detected, so there shouldn't be any safety concerns.
I'd appreciate any opinions and, would be more than willing to swap controllers with anyone if they happen to have the Modbus models and have no need for the feature.
We're just about to commission two new boilers. Both are equipped with Rielo burners and Siemens RWF40.001A97 controllers. Regretably, I failed to select controllers with Modbus connectability (RWF40.002B97), so operating pressures must be set directly at the burners.
Of course, I could swap out the controllers, but they're $1800 a pop.
As a cheaper, more versatile alternitive, I'm considering the use of PLC to manipulate the signal from the pressure sensor. By adding or subtracting a bit to the analog value before it reaches the controller, I can effectively control which burner is lead or lag. For instance, let's say 0V = 0PSI and 10V = 100PSI. If both boilers are set to fire between 80 and 90 PSI (8V and 9V), I could send a value of 7.5 volts to the lag boiler and 8.0 volts to the lead boiler at 80 PSI and 8.5 volts to the lag and 9.0 volts to the lead at 90 PSI.
The boilers are equipped with a high-limit switch for safety, and the controllers default to a safe condition if no analog signal is detected, so there shouldn't be any safety concerns.
I'd appreciate any opinions and, would be more than willing to swap controllers with anyone if they happen to have the Modbus models and have no need for the feature.