"Related Gas Pressure" and/or "Rated Gas Pressure"?

[Leafgreen]

Specs of some tankless heaters show a "Related Gas Pressure" in PSI. Specs of other tankless heaters show a "Related Gas Pressure" in Pa. Can someone explain the difference?

 

[phishfood]

Are you sure that the second isn't kPa (kilopascals)? That is metric form of pressure measurement, I believe.

Any US based plumber working with gas is going to work with inches of water column when it comes to gas pressure.

 

[frodo]

https://en.wikipedia.org/wiki/Pascal_(unit)

http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Phases_of_Matter/Gases/Gas_Pressure

 

[Leafgreen]

Are you sure that the second isn't kPa (kilopascals)? That is metric form of pressure measurement, I believe.

Any US based plumber working with gas is going to work with inches of water column when it comes to gas pressure.

On this page http://gadgetsgo.com/GA16LETL-instantaneous-efficient-hot-lp-liquid-propane.html...

"Related Gas Pressure (PSI)
0.4"
...and
"Rated gas pressure
Natural Gas: 7 inch W.C. (1 740Pa) Propane (LPG): 11 inch W.C. (2 740Pa)"
I just don't understand why one is typically called Related and one is called Rated. I Googled both terms but do not get an answer.

 

[Caduceus]

Related gas pressure could be a reference to the over all gas piping system pressure. 0.4 psi is 11 inches of water column. Tankless water heaters can consume a fair amount of fuel and if other appliances are also in use the demand on the system could starve the water heater if there is not enough system pressure to meet demand and performance would be diminished.
...It could also be a typo and should read Regulated Gas Pressure which would be the maximum pressure for the appliance and if it was too high, it would need an inline regulator.
These are just guesses, but I like my first answer better.