Laars NeoTherm NTV Service Manual

Contents

Laars NeoTherm NTV Service Manual Manual pdf 62 page image

52 Service Manual - NeoTherm 500Servicing the TransformerFig. B34-1 - Transformer installation (typical)The transformer changes the 120V AC input powerinto 24V AC for use by the controls in the NT unit.The transformer includes an integral 4 Amp circuitbreaker, and is mounted on the machine frame, nearthe top of the unit. A reset switch on the bottom ofthe unit can be used to reset the circuit breaker.The transformer is sized for the appliance load only,and should not be used to supply power to additionalfield devices. Additional loads may cause the circuitbreaker to trip.YesUnit startsrunning?Reconnect the sensor leadIs Outdoor Reset enabled on the controller?Check programming -Example - Low boiler temp. set to 130°, heat setpoint set to 120°, so unit never fires.Example - High and low boiler temps. set the same, so unit never fires.The high temp. setting must always be higher than the low temp. setting.Disconnect one lead fromoutdoor temperature sensorNote -On units with the current interface produced before October 2012 -If the sensor for outdoor reset is disconnected, the unit will operate at the highest setpoint,as if the outdoor reset function was inoperative.On units with the current interface produced after October 2012 -The unit will operate at 140°F.B33 Troubleshooting the Outdoor Reset SystemB34