Jacob Foss House

Interesting find in our Victorian. This box was found in our basement. It is ... a mechanical thermostat for an old coal furnace.

I’m holding the key to wind it. If you’ve ever wound a 7-day clock, it feels just like that. In the other picture are some OLD dry cells. Those are connected to a mercury switch that triggers on and off when the temperature gets higher or lower.

Now just above the key, you see a brass arm. That’s a lever. When the electrical part registers a low temperature, it turns on the mechanical part that pulls that lever.

Not shown are two pullies on the ceiling above where our current steam heat furnace is and where the old coal furnace was. A cord was attached to the arm, through the pulley and then to the draft on the coal furnace.

When it got cold, this device would pull the cord and open the draft (let’s more air in) which makes the coal furnace hotter.

There is an identical arm on the other side that operates when it gets warm to close the draft again.

This device could have a range of dates, but appears to be from about 1890.