Chimney fire alarm

[muckamuck]

With my indoor wood stove I sometimes get lazy and open the ash door to get a big draft when lighting the stove with kindling. But I forget and walk away and then I sometimes get an overheated stove and/or a chimney fire.  To avoid this I made a chimney alarm with the following:
1) one of those $10 spiral dial chimney themometers that stick on with a magnet
2) heat resistant plastic tab 2 inch by 1/4 inch by 1/8 inch thick cut from a spatula
3) 2 conductor wire
4) a fire alarm that is set off by heat (like those in garages)

Just attach one end the tab to the thermometer at the center,
Attach one wire to the metal indicator of the thermometer
attach the other wire to the tab in a spot where the indicator will hit it when it moves in that direction.
Attach the other ends of the wire to the alarm on either side of the thermister that sticks out of the alarm.

To use, swing the tab to 500F.

When the chimney gets a fire and heats to 500 the dial indicator moves and touches the wire on the tab making a connection which short circuits the alarm thermister and the alarm goes off very loud.  Put out the fire and reset the tab as needed.
It has saved me a number of times.

[Woodchuck53]

That's a 'continous improvement' a lot of people ought to think about. Thanks for sharing.

[Ironwood]

I think that is a great idea.....I have had the chimney hot enough that the magnet on the thermometer stopped working and it crashes to the stove top. After cooling the magnetism works again. Just a thought when connecting semi flammable things to it (wire insulation and such).


Ironwood

[beenthere]

hot enough that the magnet on the thermometer stopped working and it crashes to the stove top

There is the trigger for the alarm !!   8)

[Ironwood]

Yeah, that is HOT, I dunno at what temp, I will look that up.

Dropped here from eHow.com:


"Temperature, like a strong external magnetic field, can cause a magnet's domains to lose their orientation. When a permanent magnet is heated, the atoms in the magnet vibrate. The more the magnet is heated, the more the atoms vibrate. At some point the vibration of the atoms causes the domains go from an aligned, ordered pattern to a nonaligned disordered pattern. The point where excessive heat reaches a temperature that causes the atoms to vibrate and rearrange a magnet's domains is called the "Curie Point" or "Curie Temperature."

"The temperatures below a Curie Point are referred to as a magnet's magnetic ordering temperature. Below the Curie Point, the dipoles rearrange themselves from a disordered, nonparallel orientation into an ordered aligned orientation. However, if a heated permanent magnet is allowed to cool while oriented parallel with a strong external magnetic field, the permanent magnet is more likely to successfully return to its original or stronger magnetic state."

Read more: The Effects of Temperature on Permanent Magnets | eHow.com http://www.ehow.com/info_8267667_effects-temperature-permanent-magnets.html#ixzz2EEQ7Mdp0


I read elsewhere for every 100* C, you lose 20% effiecency


ironwood