How does this old mercury switch work?

January 14th, 2019, 9:02 pm

As the title says, can someone explain how this one works? I'm trying to figure it out how does the old mercury switch works from ON position to OFF and how'd you know if the bellow is broken.

Thanks

#2: Post by **ira** » January 14th, 2019, 9:40 pm

The bellows tilts the glass capsule. The mercury is conductive and when its on the left side like it is now, it connects the two wires, when it's on the right side, the contacts are not connected.

Ira

#3: Post by **OldNuc** » January 15th, 2019, 12:02 am

If the bellows is cracked steam comes out and the glass tube doen't tilt.

#4: Post by **another_jim** » January 15th, 2019, 12:03 am

Odd, it looks to me like the bellow should contract as the boiler gets to pressure, so that the plunger descends, and the switch tilts down to the right. Lovely piece of steampunk kit.

#5: Post by **Paul_Pratt** » January 15th, 2019, 12:06 am

If the bellows are not leaking steam/hot water then they are ok.

It is obscured by the mercury bulbs in the photo but there should be a knurled screw that you can turn which will adjust the pressure up or down. Tighten the nut should increase the pressure, loosen the nut would decrease the pressure. (When I say pressure I mean indirectly as all you are doing is adjusting when the bulbs tilt to break the circuit).

Of course the only way to play with the setting is when you have the machine on and with boiler pressure. You should always unplug the machine before poking your hand near the mercury switch.

The switch you have is one of the first switches used on Faema machines.