HVAC problem this morning.

[dadster4]

It was so much simpler with a match light floor furnace...

Heck... even a millivolt furnace with thermostat...

I maintain some very old furnaces going back over a 100 years...

The way things are going they could very well be here in another 100 years...

Old gravity furnaces were great...no power necessary, quiet, mostly reliable. Replace the thermopile every fall and you're good to go, that octopus of 12" round duct eats up a lot of room in the basement though.

 

[gsganzer]

Go back to the days of a Dearborn. We have one at the deer lease. I always make sure the ceramic blocks are properly installed and the smoke and CO detector is working. It works great though.

 

[kenmac]

Think of them as pressure differential switches.
The ignition cycle is interesting... 1- All safety switches are checked for closure. 2-the ignitor, or glow plug, is powered to light a pilot flame. 3- The pilot flame is proven by flame rectification whereby a dc voltage is passed through the flame and produces a microvolt ac voltage which the control board senses. 4- The main gas valve is allowed to open as long as the pilot remains lit or the cycle completes.

I'm well aware of the process/ Sequence of operation. But that switch actually operates on vacuum . not pressure

 

[dadster4]

I'm well aware of the process/ Sequence of operation. But that switch actually operates on vacuum . not pressure

Correct, the switch closes when it senses the pressure difference between the negative (vacuum) pressure of the combustion chamber and atmosphere (14.7 psi)...pressure differential.

 

[gsganzer]

Correct, the switch closes when it senses the pressure difference between the negative (vacuum) pressure of the combustion chamber and atmosphere (14.7 psi)...pressure differential.

Y'all's pedantic discussion on the vacuum vs. pressure switch sounds like a similar one I've always had with new piping designers. In the piping industry, they have concentric and eccentric "reducers" that neck a pipe from one size to another. The new pipers will try calling them "expanders" when going from a small pipe to a larger size. However, they're only referred to as reducers.