Thanks. I found a couple of the threads. I think I was/am still confused about the comparison between HP and LP propane.
No problem, we have all been there. In fact most of this stuff is new to me and it takes me a while and a lot of reading and help from all the good people here to understand all these new terms and how all these things work. I have learned so much since I started building my system (and you will to) and I have a long way to go, but is not only challenging, it's also a blast!
Another way to explain high pressure and low pressure propane is that when you use a 20 lb. propane tank like the kind used in gas grills, it comes out of the tank at high pressure. This is good for turkey fryers and some grills. Many solenoid gas valves operate at high pressure allowing them to open and close to let the propane gas flow through to the burners. People using high pressure propane burners with high pressure propane solenoid valves, also use a high pressure regulator that has a built in knob that controls the psi output from lets say 0 to 30 psi, either on the tank, attached to the main gas beam, or pipe manifold if they did not use the stand tubing as a gas beam, to better control the amount of gas going to the burners. They also use a gas ball valve or needle valve attached to the pipes before each burner for further flame control.
Honeywell and other standing pilot furnace valves are used in natural gas and propane gas heating systems in many homes. These valves are also being used in many brewing systems (thanks mostly to Kladue, you rock brother! :rockin: and Sawdustguy
who have posted and shared their knowledge on these valves, how to wire them, etc) and offer an excellent safety feature. The pilot light that is attached to each burner has a thermocouple heat sensor that the pilot light flame touches. If the pilot light goes out (like on a windy day) and your Love, Auber, computer program, (or whatever electronic temperature control switch you used), tells the valve to open to let gas flow to the burner to make the burner fire up, and the thermocouple heat sensor does not detect heat from the pilot light, it will not open up the valves. If you didn't use the valves with the thermocouple heat sensor, then the valves would open when the switch sent a signal to open, and the gas would be pouring into and out of your burner. If the burner next to this one then then fired up when it's switch told it to then the accumulation of gas coming out of the neighboring burner (with it's pilot light out) might ignite, and there is a possibility of a very large explosion. (A home in a city near us, had a 20 lb. propane tank explode in a garage and the whole house was completely leveled. This was not a brewing accident, but the whole house was gone after the explosion. That got my attention when I saw the camera footage on the news. I couldn't believe the destruction and how powerful the explosion must have been, all from one 20 lb. propane tank!)
Because the furnace valves like Honeywell offer this safety feature many people are choosing to incorporate them in their build. Others do not think that the accumulation of gas is large enough to stay around and it dissipates into the air and the explosion risk is minimal. I chose to go the safety route, as I am not an expert on any of this stuff and I would like to be around to keep brewing and not blow my family up! Since I wanted to use these furnace valves for safety, I learned that they only operate at 1/2 psi of pressure (yes you read it right one half, .5, or one half of one psi of pressure). The valves can not handle or operate correctly at higher psi (I think the higher psi pressure blows the seals). This low pressure psi requirement forces you to make the high pressure propane coming out of your propane tank and convert it to low pressure, hence the low pressure regulator. You can still use gas ball valves and needle valves on the gas pipes going to the burners for increased flame control, but these ball valves and needle valves only control the amount of gas going into the burners and flame size, and does not convert high pressure to low pressure.
Here are some links to threads that might help:
https://www.homebrewtalk.com/f51/understanding-high-pressure-versus-low-pressure-propane-157415/
https://www.homebrewtalk.com/f11/low-pressure-ignition-system-wiring-diagram-153752/
https://www.homebrewtalk.com/f51/gas-temperature-control-dummies-116632/
Hopefully this will clear some of this high pressure, low pressure stuff up and you can understand it better. If not just let me know. I am not an expert on this stuff but I can hunt down some more links/threads, or put you in touch with the right members who are experts and know what they are doing. I know what it is like trying to understand some of these concepts that these brewing systems utilize and trying to grasp how some of these technologies, equipment, parts, and engineering all work. After all we are working with propane gas, fire, electricity, and water all together, and combining them so close together goes against everything common sense, the laws of nature, or your teachers ever taught you about safety!!!! The things we do to brew excellent beer
John