Pressure Drop

Unfasten the sea level orifice, and in its place install the altitude orifice.

I too agree with you.

Tornado apparently did not read your entire post.

I agree with DRFREON.

My first impulse was to calculate the flow rate & velocity, and check for how close it was to choked flow. However, at 12kBth/hr (low) and 1/2" tube and 3.5" required at the burner, the pressure drop is so great that it seems obvious to agree with you that the orifice could be installed in either location with nearly identical results.

If the orifice is at the burner, the pressure will essentially equalize everywhere in the line before the orifice. If it is at the valve, the flow is so low as to probably have almost no measurable loss around that bend. (I would be very surprised if the expansion loss at the burner is lower than that sweep.) The margin of safety for the valve location is that a system designed for sea level operation is going to be very low loss at altitude. The margin of safety for the burner location is that percent pressure variations at altitude are greater than at sea level and the orifice is probably engineered with the tolerances favoring the small side.

Classic pressure (potential) energy conversion to velocity (kinetic) energy, with high pressure, and low velocity after a radical orifice reduction. I would feel confident enough to try it wherever it would go in.

I doubt we have enough information to do a Colebrook Equation or choked-flow analysis on this problem (the latter of which I suspect wouldn't apply anyway). This is a dirt-simple orifice change-out question. Your obfuscation is not useful.

By the way, "DRFREON" was largely mystified and was asking a question rather than expressing an opinion. What is there to "agree with" in that, pray tell? I wasn't arguing with him, so why do you "pick sides"?

I am not "picking sides." DRFREON said: "I claimed it would make little or no difference." I agree with him. Period. What is YOUR problem??

Whoever clicked "Off Topic" should learn English. Those of us looking for intellectual entertainment or enlightenment are actually seeking a good gentleman's fight. "Forum" means someone might disagree, Bozo.

Uncalled for. Self conflicting argument. Arrogant. 'Hissy fit'.

Please accept additional OT

Now I understand the picture. Cheers.

This is why they have a 1-800 number.

Pressure drop be damned. If you put the orifice back 8" the flame will burn in the tube until it burns through and then who knows where it will burn. Contact the factory and get the right orifice and be sure. TM

I would never advocate not seeking factory help first, but the problem as stated was no help from factory, and that the supplied fitting did not match threads. Given those hypotheticals, if you have ever looked into a gas boiler and seen the flame tubes, the gas is injected into the tubes, mixed with air and the flame is well beyond the tube. It never burns in the tube.

I have not looked into a gas boiler fire box. If it is similar in function to a gas stove, barbecue grill, camp stove etc. the final flow restriction appears to be at the multiple jets in the burner and all seem to have the orifice mounted well back from the burner. I will leave that up to you as you are Accountable (pun intended).

It would be difficult to measure the difference in the pressure. Might call it "practically no damn pressure drop",. TM

I want to thank ALL responders to " Pressure Drop " on the high altitude orifice location- It's a good feeling to have so many Professionals answer back!

DRFREON