Bimetal thermostat troubleshooting

[jonih]

My homemade incubator has this exact thermostat, but my temps are fluctuating 10 degrees through the heating cycle. Any ideas? My heating source is 2 150 watt bulbs (near top and bottom) in a cabinet that is 4'high x 2' wide x 18" deep. There are several computer fans circulating the air. I selected the bimetal thermostat because of its supposed accuracy and small range of fluctuation, but something isn't right. Ideas?

 

[matlock585]

I use a traditional water heater thermo in my build. In my first one I had it about 3-4 inches away from the light bulb and it fluctuated about 8 degrees. I rebuilt it into a bigger cooler and put the thermostat right above the light bulb and my temp leveled right out after that. No fluctuation at all unless the room temp has a big swing. It's night and day!
I've never seen one like yours. How do you adjust it?
Hope you get it figured out.

 

[ozexpat]

My homemade incubator has this exact thermostat, but my temps are fluctuating 10 degrees through the heating cycle. Any ideas? My heating source is 2 150 watt bulbs (near top and bottom) in a cabinet that is 4'high x 2' wide x 18" deep. There are several computer fans circulating the air. I selected the bimetal thermostat because of its supposed accuracy and small range of fluctuation, but something isn't right. Ideas?

i concur

the thermostat should be near the heat source.

initially it will turn on and off a lot as it comes up to heat. the air in the area of the thermostat will heat fast and shut it off, cool as the warm air spreads and the heat equilibrates.

that thermostat is new to me also

 

[jonih]

There

I use a traditional water heater thermo in my build. In my first one I had it about 3-4 inches away from the light bulb and it fluctuated about 8 degrees. I rebuilt it into a bigger cooler and put the thermostat right above the light bulb and my temp leveled right out after that. No fluctuation at all unless the room temp has a big swing. It's night and day!
I've never seen one like yours. How do you adjust it?
Hope you get it figured out.

There is a knob on the outside of the box to adjust it. In all the reading I've done, I've not found anything on placement for this particular type. Bimetal stats are supposed to last longest and be the most accurate of any of the mechanical thermostats, by the report of anyone who uses them. Any additional comments would be appreciated.

Any Bimetal users out there?

 

[Fred's Hens]

the thermostat should be near the heat source.

Absolutely. Within 3 inches of the heat source (bulb usually) works the best. You'll likely find you want it to cycle very quickly, which it won't do if it is 10" from the heating device.