Siemens RS-485 manual Control strategy for, Floating output with, Modulating burner, Operation

Mudulating burner	Modulating controller:
	The management system predefines the value (degree of modulation) for the analog
	output via «RY».
	Setting the «RK2» and «RK3» by the management system has no impact.
	Both relays «K2» and «K3», are deenergized.
	Floating step controller:
	The management system controls the actuator («RK2» and «RK3», relays «K2» /
	«K3»).
	Setting the «RY» by the management system has no impact. In that case, the analog
	output delivers 0 V or 0 / 4 mA.
	The RWF40... always checks to ensure that «RK2» and «RK3» (opening / closing) are
	not activated simultaneously. In such a case, the response is «K2 = K3 = deener-
	gized».
	If both relay contacts change their position during the controller’s sequence time, the
	output is «K2 = K3 = deenergized». This time contact interval («K2 = K3 = off» for one
	scanning time) is also permitted in 2-stage operation.
Control strategy for	The remote relay commands «RK2» and «RK3» (relays «K2» / «K3») control the
floating output with	opening and closing travel of the controlling element. Using parameter «RSTEP», the
modulating burner	management system predefines the required number of control cycles.
operation	Output «K2» (opening) is controlled by a travel command and a positive number.
	Output «K3» (closing) is controlled by a travel command and a negative number.
	The number gives the number of RWF40... scanning cycles (210 ms) with which the
	output is controlled.
	The travel command with number 0 deenergizes immediately «K2» and «K3».
	If a new travel command is given before the control time has elapsed, the RWF40...
	ascertains the direction of rotation requested by the command. If the direction of rota-
	tion does not change, the control time will immediately be replaced by the new value. If
	the direction of rotation must be reversed, the controlled output will be dactivated and,
	for the next scanning cycle, the appropriate control time is used (time contact interval).
	If, simultaneously with the control strategy for the floating output, outputs «K2» and
	«K3» (via «RK2» and «RK3») are directly set by the management system, the relay
	information from the control strategy and output information «K2» and «K3» have a
	logic «OR» connection. «RK2» and «RK3» (opening / closing) must never be energized
	simultaneously. In such a case, the response is «K2 = K3 = denergized».
Supervision of actual	In operating mode «FULLY REMOTE», the management system ensures burner con-
value by setpoint-	trol. The RWF40... monitors the actual value to make certain the switching hystereses
dependent switching	will be observed.
thresholds	If the actual value crosses the upper switch-off threshold, the management system will
	be locked (status flag, «Management system locked» can be read via the interface).
	The management system is released again when the actual value returns to a level
	below the switch-on threshold.
	If supervision of the actual value is not desired, the switching hystereses in the
	RWF40... must be set to the respective maximum value.
	In operating mode «REMOTE SETPOINT», the control algorithm ensures this kind of
	supervision.

	￿2002 Siemens Building Technologies
14/14	Subject to change!
Siemens Building Technologies	CC1A7865.1en
HVAC Products	31.10.2002