Developed Electric Heater Load Shedder Sequencer for Lion Industries

Vansco Electronics was in bay 3 of the Industrial Technology Centre, at Lagimodiere and Fermor.  Lion Industries, a similarly sized mechanical product manufacturer, was next door in bay 2.

With the energy shortage in the recent past, and ongoing issues with the cost of oil, the Canadian government sponsored the “off oil” program which would subsidize homeowners to switch from oil heat to electric heat.  Lion Industries manufactured an electric furnace that would retrofit into the ductwork, leaving the oil furnace intact.

The Load Shedder Sequencer would intercept the thermostat request for heat, and instead of letting the oil furnace start, would turn on the furnace’s blower only, and engage the electric furnace elements, one at a time, in sequence.

The challenge was that the home would not have had its electrical service panel updated, so we put a small current transformer (CT) on the incoming service power, measured the overall current consumption, and would shed, or turn off, elements to keep the total current under the rating for the panel.  We had little plug-in modules that would “program” the system for the capacity of the panel in the house.

The concept was that if power was being used by another device in the home, that would generate heat which would help to heat the home.  For instance, a stove or oven.

If, after a long time (15 minutes), the thermostat was still asking for heat, the electric furnace would shut down and engage the old-fashioned oil furnace.

I developed the entire design, end-to-end, of course with the oversight of the other, more experienced staff.  It was my first encounter with thyristors – in particular, TO-202 triacs.  I had considerable difficulty with them apparently engaging when they weren’t supposed to – and found out that they were overheating and becoming overly sensitive to stray gate currents.  What an experience!