Have a home forced hot water heating system.
Regarding the numerous Thermostats that have been available for it, and similar systems over the years, are all of these simple SPST switch closures, without any voltage/current being provided by the Thermostat itself ?
(irrespective of whether there are "fancy electronics" for the display, etc. these days)
I think that this is the case, but wanted to ask here for all you experts to be sure. At one time we had a Honeywell round Mercury switch Thermostat, so this one absolutely had to be nothing more than a contact closure, obviously.
And, let me also ask this, please:
Have a symbol on a schematic I am not too sure what it means. Unfortunately, I do not think there is any way of showing it here, so let me try to describe it.
The symbol for a Resistor is the triangular up down points, several of them up, several pointing downward.
What is a symbol where it only goes from the baseline up, down below the baseline, then up again to the baseline ? (one triangular point up, one triangular point down)
Is it a switch, or a relay contact, perhaps ?