Quadrafire MT Vernon AE Control Circuit Question

[kortorsmk]

All.... New to the forum.. Purchased a MT Vernon AE back in the spring and enjoying it now going into the winter. Have question for individuals that have a working knowledge on the control circuit for the unit. Looking to grab a DC signal off the board ( 1-15VDC range) that is present when the convection blower is on. Could take directly off the motor drive input that as this is a variable speed motor, voltage goes from 2--> 7-8 volts depending on heat call. Just need a off/on output for dry contacts...

Thanks for any direction in advance......

 

[kappel15]

The drop tube thermocouple operates the convection fan. kap

 

[dhall28]

As kap said the speed of the fan is changed by the control board looking at how how the thermocouple on the drop tube is reading. It is not a straight variable dc voltage sent to the motor, it is a brushless dc motor that uses a pulsed dc voltages, with a hall effect sensor to tell the motor control the initial starting position of the motor and then how fast it is turning. I believe it is all a closed loop information pulsed dc to look like and act like ac to induce voltage/magnetism into the rotor. There are electrical engineers on here that can correct any of this if im wrong but i know its not as simple as a 2-15 dc voltage constantly applied.