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6 720 887 546 “SM FP_ErP LPP-MPP Europe 2018/05 en”
4.4
Fan
The control unit monitories the primary air flow to the burner by varying the fan motor
power supply voltage (DC), ensuring a correct variable speed during the operation
according to the output needed in MPP range while in LPP the fan have a fixed speed due
to the unit be fix power version.
The fan motor provides an additional control signal to enable/disable operation and the
speed of the fan is measured by the feedback signal provided by the fan’s motor. The
signal consists on a square wave with a frequency proportional to the speed of the fan.
Pict. 15 – DC Fan (WTD-3&4 / T5600&T5700)
In order to simplify the after sales stock of parts, the modes share same type of fan according:
Low Power Fan:
MPP1 12/15 shares same fan of MPP2 12
High Power Fan:
MPP1 17 shares same fan of MPP2 15/17
The Fan in the LPP range is AC powered and have fix speed. The safety element that controls
the fan start up / stop and blockage is a pressure switch.
Pict. 16 – AC Fan (W/WD/T2400)
4.5
Gas Valve
Over the control unit it is possible to control the gas flow to the burner by the modulating
gas valve (MV1). This valve controls the thermal load in order to ensure the correct hot
water set temperature, under water flow or temperature variations.
