Tuesday, March 31, 2020

Maiden voyage of the fireplace insert

Today we did the inaugural, shake-down run of the fireplace insert.

It is forty outside. It seemed like a good idea to bake off the manufacturing oils while it was warm enough to open windows and air out the house.

The wood seems to last a long time. I currently have half-rounds of 6" Black Locust going.

The heat is NOT blowing us out of the room. The fireplace is in a 800 square-foot "great room" and doors to basement and the hallway back to the bedrooms are open. Inside temperature is 67 degrees which is three degrees higher than when we started the test three hours ago.

It seemed like a long time before the fan activated. There is a snap-disc thermostat that closes at 110F to energize the fan. There is also a rheostat inline to modulate the fan.  I think a dab of heat-sink grease or adhesive will tighten up the thermostat performance.

I also admit to having a jaunticed view of snap-disc durability and am considering adding a second one in parallel with the factory one which is mounted below the firebox. I understand that the factory location was predicated more on a desire to keep the blower modular and to keep wiring out-of-sight than to optimize performance. From a performance standpoint, I think the fan will kick-on in a more timely manner if a thermostat is mounted on the side of the firebox about two inches above the floor.

I am not sure this is the very best solution if things went totally in the ditch. The fan pulls 140W which is very doable if the sun is shining. If the best it can do is to raise the living space temperature by thirty degrees above ambient (during the sunny hours) then that is thirty degrees better than being outside. Although we drop below -15 F five times a decade, our normal, nightly, winter-time lows tend to be about 20F.

50 degrees Fahrenheit is a much happier temperature than 20 degrees F!

---Just noticed the furnace fan is running. We have had it ON to maximize filtration of our inside air. I turned off the fan to see what the temp rise in the great room is. 

Temperature in the great room rose two degrees an hour with the furnace fan off. I stopped throwing wood into the unit when the temp hit 71.---


  1. Black locust...I'm jealous. I'm currently burning the remains of a cottonwood tree we had cut down a couple years back. Still many years left of wood to burn, but we don't have fires every day, and this past winter was pretty mild.
    Thanks for the information about the snap disk thermostat. I didn't realize how those worked, and mine has been getting more and more laggy, and temperamental. This summer's stove maintenance will now include heat sink paste on the thermostat, if not an outright replacement.
    Inserts are far better than fireplaces, but I still wish my wife would go for moving it out into the room, and building a firebrick enclosure around it for thermal mass.

  2. In my experience, the snap disc units usually take a surprisingly long time to kick on; on my stove the disc is mounted on the bottom, the last part of the stove to warm up.
    I have a 1800 square foot house and heat almost entirely with wood in the winter. My 500 gallon propane tank is down to 50% after 2 winters; the furnace runs primarily when we are not home.
    I find that running my furnace fan doesn't help the house heat up, probably due to poor location of the returns.

  3. Mine, too, takes a long time for the fan to kick on. I always figured it was just the nature of the beast.


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