thermostat question

[John Arnold]

44 year old condo with electric baseboard heat with separate thermostats in each room.
Anyone know what the bottom circular opening is for?

[Billy Stephens]

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Anyone know what the bottom circular opening is for?
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.....:D

[John Kogel]

A round thermometer would be my guess.

If all the rooms have the same unit with the same hole, it would be time to break out the boroscope. :)

[Raymond Wand]

I'm with John on this one, a thermometer which has long ago be taken out.

[H.G. Watson, Sr.]

A mercury-based bimetal spring thermometer display.

[Billy Stephens]

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A mercury-based bimetal spring thermometer display.
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With or Without Air Cooled Suspension ? :rolleyes:
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[John Kogel]

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With or Without Air Cool Suspension ? :rolleyes:
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With.

Mercury with cool suspension