For the outcome of my friend's boiler problem, see the next post.
One more questoin about gas boilers. Why on this commercial or semi-commeicial boiler are there two control circuits of different voltages? And since the 24volt circuit controls the mian electric gas valve and thus turns the burners on and off, , what does the 110 volt circuit control?
There is one circuit that has in it a 24 volt transformer output, the pilot swich, which turns off the pilot and interrupts the electric circuit if the pilot goes outt, the therrmostat which interrupts the the same electric circuit and turns off the main electric gas valve (but not the pilot, and that mail electric gas valve, which opens when the thermostat calls for heat (and the pilot is lit.)
There was also the Low-water cutout, which controls 110 volts AC. I read that it is in the same circuit as the High Presssure cutout, the maybe a low pressure cutout and other safety devices.
But how doe sthis turn off the gas when there's a problem. What does it contrrol? How come these 3 sefety devices aren't just in series with the thermostat and the pilot switch?. I know they're not because that circuit is 110volts and this one is 24 volts??
Does the main electric gas controlv valve turn off from both the absences of 24 volts and the absence of 110 volts? How come these 3 sefety devices aren't just in series with the thermostat and the pilot switch?