I have a 1970's era 2 group Pavoni commercial machine with 110 volt and/or propane power. I am having trouble adjusting the temperature and maintaining stability with propane (with 110 volt power only, it works fine with adjusting the pressurestat). I plan to operate it exclusively with propane.
The gas travels first through a valve that has a large knob on the front that you push in to light (over-riding the safety mechanism) and then you rotate the same knob to increase or decrease the flame size. I am assuming that the purpose of this adjustment is to set the minimum heat level.
Then the gas passes through a second valve, which is the one I'm trying to understand. The gas arrives from the first valve on the right and leaves the valve to go to the actual burner on the left. This valve has a knurled adjustment knob on the front and a locked adjustment screw on the top. There is a copper tube on the back (larger in diameter than the safety thermocouple on the first valve).
So I am guessing that the copper tube on the back runs to a fitting on the boiler so that this valve manages the gas flow to maintain a certain pressure in the boiler.
I am also guessing that the front knurled adjustment is the "fine" and that locked screw on the top is the "rough" adjustment.
I need to understand what the valve does, what the two adjustments do, and the proper procedure to adjust them, and test to see if they are working correctly. And if it is not working correctly, how to fix it or where to get a replacement.
I've flailed with the adjustment knobs, making changes each direction, but not seeing a pattern in the temperature I am observing at the group head. As I said, I was able to do this successfully with the electric power and pressurestat adjustment, but no luck figuring out how to adjust with propane.