No gas to cook top

JBarca wrote:


You are very welcome, thankyou.

There are a few undisputed facts in all this if we stop and think the whole thing through. The atmospheric pressure in the upper chamber of the regulator "does" have an effect on the on the force holding the diaphragm open or closed. The effect may be very small, or not so small, but there is an effect.

The diameter of the diaphragm plays into this as well as the spring force. There is a formula, S=P/A where the units are: psi= lb force/inches squared. The larger the diaphragm, the more force can be exerted for the same pressure applied to the diaphragm. On a larger diameter diaphragm, a very small change in pressure can create a larger change in force exerted. And visa versa with smaller diameters.

Lets think of it this way, take the spring out of the stove regulator and for this example declare the weight of the poppet valve as 0 lb. Inside the regulator is 11"WC gas pressure pushing against the gas side of the regulator. At sea level, the atmospheric pressure in the upper chamber is 0.0 psi. It is undisputed that the poppet valve will close tight shutting off the gas flow as there is no spring, the 11"WC acting on the diaphragm is working against 0.0 psi at sea level.

Now insert the spring. The spring force and the diameter of the diaphragm now come into play along with the atmospheric pressure in the upper chamber. This is where the issues come. If the 11"WC gas pressure acting on the lower part of the diaphragm is stronger then the spring force combined with the force on the diaphragm exposed to pressure from atmosphere the system is at, the poppet valve will close and stay closed.

I do feel we understand the problem, now how to get out of the problem? There needs to be a way to compensate for the lower atmospheric pressure exerted onto the upper part of the diaphragm as this weakens the spring force applied. Granted, there may be a practical max elevation limit where the cost to overcome the issue becomes too much. But 4,500 ft is not much.

My first instinct is, the regulator needs a slightly larger diameter diaphragm, a slightly heavier poppet valve or a slightly less stronger spring in some combo to allow the lower atmospheric pressure to not be overpowered by the 11"WC constant pressure and still work with the 1" WC regulation need of stepping down to 10" WC.

I'm sure this has been solved as home stoves working on LPG I'm sure work at high elevation in the US. Say Denver etc? They should have the same need for a step down stove regulator. Us folks on the east coast never had to worry much about this.

Here is a post for RV.Net in 2014. They got closer to the issue, but they mixed up the low oxygen issue and the main tank regulator and never drilled down into just the stove regulator with it's very sensitive balance of trying to control 1" WC pressure. https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27518594/print/true.cfm

I'm still thinking on this. I was hoping someone would jump in and explain what changes in the spring, poppet or diaphragm that makes the stove regulator work at higher attitudes.

Hope this helps

John

your instincts are corect in that atmospheric pressure plays a part but non of your calculations will work if you us 0 as a atmospheric pressure. it is 14.7psia or 101kPa at sea level and at 4500 feet it is aproximatly 12.5psia or 85.7kPa and 10 to 11" of watter colume is 0.36 to 0.4psi so realy at 4500 feet there should still be plenty of differential for it to work, maybe a slight yellowing at the tips of the flames. the problem with atmospheric relief regulators is they do use atmospheric pressure to act on the diaphram, the intent is to prevent an air lock from forming above it and preventing it from closing and it has a neglagable effect, but it is also much cheeper than using a pressure ballanced regulator set up.

myself I would remove the regulator , make a fitting to bridge the gap and try the stove, if it works put a new regulator in. mind you this might be more than you want to do while camping. the other option is to change it out and see how it works next time your camping.

this thread has me wondering if mine is starting to get week, I changed out my main regulator and everthing got better but I do have a flame that is a little two yellow but I am under 1000 feet and even when I am at 4500-5000 feet it doesnt change realy, hmm something else to updte now I guess... thanks ;)