what direction to turn adjustment knob

[hockeymulder]

On the Scubapro G250, what direction do I turn the adjustment knob to adjust the cracking pressure.

Is it counter-clockwise for less breathing effor (easier to free flow)
and clockwise for more breathing effort (harder to free flow)

or vice versa?


Thanks everyone!

 

[scubasean]

hockeymulder once bubbled...
On the Scubapro G250, what direction do I turn the adjustment knob to adjust the cracking pressure.

Is it counter-clockwise for less breathing effor (easier to free flow)
and clockwise for more breathing effort (harder to free flow)

or vice versa?


Thanks everyone!

I'm going to be a wise guy....The answer to the first question is "both", that is, both directions adjust the cracking pressure.

As for the second question, I'm not a certified tech, and my nonscubapro reg operates as you describe.

 

[redacted]

counterclockwise is easier.

But the difference between the two extremes of the adjustment should make it obvious. If yours is not that sensetive, you may want to investigate why.

 

[MechDiver]

With the G250, you should either be inhaling if underwater, or pushing the purge button while adjusting the cracking effort knob. This turns directly against the valve seat and will score it. I don't believe that is necessary with the G250 HP, and not with the 500 or 600.

MD

 

[DA Aquamaster]

MechDiver once bubbled...
With the G250, you should either be inhaling if underwater, or pushing the purge button while adjusting the cracking effort knob. This turns directly against the valve seat and will score it. I don't believe that is necessary with the G250 HP, and not with the 500 or 600.

MD

This is not neccesary with the G250 either. The external adjustment knob presses against a spring and a plastic piece that comprises the balance chamber for the second stage. The lugs on the poppet assembly itself are captured by the demand lever and the poppet assembly is not able to rotate. Consequently the seat on the end of the poppet assembly will not rotate against the orifice when the adjustment knob is turned whether the purge button is depressed or not.

I believe what is referred to as a G250HP uses a lighter weight all plastic single piece poppet design, but this is again captured by the demand lever in the second stage and cannot rotate against the seat. (I have one of these poppet assemblies in an updated Balanced Adjustable and it is a very sweet breathing reg - of course so are the regular Balanced Adjustables with the old style poppet.)

However, when adjusting the orifice (usually housed inside the fitting where the LP hose attaches to the second stage) in any of these regs as well as in any standard downstream non externally adjustable regulator design, you should depress the purge valve before screwing the orifice further in or out as in that situation it will bear against the seat and potentially engrave it.

The same poppet and balance assembly is used in the Balanced Adjustable, G250 and G200B. I have never owned or worked on a G200B so I am not sure how this is adjusted. If the reg is adjusted from the orifice side of the assembly rather than the balance side, then the purge would need to be depressed when adjusting the breathing resistance.

The Balanced Adjustable came with a key to keep the purge button depressed during storage to prevent the seat from taking a set. The G250 and later regs do not have this feature so with them it is very important to back the adjustment knob all the way out to the lightest setting to minimize the pressure on the valve seat.

The average G250 or Balanced Adjustable on E-bay usually has the adjustment knob turned all the way in indicating it leaked badly on the last dive it made, or alternatively has been stored improperly and will freeflow constantly on the next dive.

 

[Genesis]

the balance chamber adjustment is made with a hex wrench on the outside - its the same as a G250, but its not "during the dive" adjustable as there is no knob to turn.

They are otherwise identical internally (I own a couple of both.)

The G250 seat life can be RADICALLY prolonged by snapping off the wire retainer on the adjustement knob (it locks the "outward" position of the knob) and backing it WAY off to the point where it unthreads (but not where it falls out!) This releases almost all the pressure on the seat and crown.

If you're not going to dive the reg for a while this is a good thing to do. Just don't forget to put it back before putting it back on a tank!

BTW, the usual failure mode on the 250s is that they leak and can't be adjusted with the knob not to. The only fix is a new seat. The good news is that the new-style seat is the same poppet that is in the S600, and the seat ALONE (instead of the entire poppet) can now be popped out and replaced - in fact, the S600 seat is identical, so there is a good amount of parts interchangability now.

 

[neil]

Genesis once bubbled...
.
The G250 seat life can be RADICALLY prolonged by snapping off the wire retainer on the adjustement knob (it locks the "outward" position of the knob) and backing it WAY off to the point where it unthreads (but not where it falls out!) This releases almost all the pressure on the seat and crown.

That seems unsafe. Why not just adjust the reg so that when the knob is unscrewed as far as possible, WITH the stop clip, that it freeflows slightly? I can just see someone having that knob fall out while diving. What a surprise!

Neil

 

[Genesis]

The poppet spring pressure is what seats the LP seat in the reg.

The crown setting does not control the poppet spring pressure. All you do by loading the crown is smash the lever up against the diaphram and "preload" it, which makes the reg EXTREMELY sensitive to freeflows.

Pulling the clip is a 30 second job. If you want, take some "painters tape" (the kind I use for my mix marking - doesn't leave sticky gunk on the tanks!) and cover the mouthpiece AND ADJUSTER with a single piece. Now you have to LOOK at the thing before you use it again.

I don't do this for my G250s that are going to sit for a short while (a few days between dives), but I have two "spares" that are in my closet, rebuild, ready for immediate substitution if necessary. I do it with those and my "spare reg" that sits assembled but is rarely used, since this way the seats will be as good as new a couple of years from now if they are unused, and since I put all EPR O-rings in there, with Christolube, the O-rings should be ok even after that storage as well.

For the diver who uses their regs only for "vacation" this will greatly prolong the seat life and likely give them three to five years - or more - between needing parts. Tearing them down to just do a general cleaning doesn't take long, and if the seat is ok, its a "partless" rebuild. ANYONE can rebuild a G250 - I can show anyone how to take one apart and reassemble one in about 10 minutes, and replacing the O-rings and cleaning it gives you the effect of a "rebuild" without needing anything more than 25 cents worth of parts.

 

[Sean326]

I've got a 250hp and I have dove with it for 3 years, I love it.
For the most part I dive 1 to 3 tanks every other weekend, a little less in the winter but more on vacation..

I have played with the adjustment knob on dry land. on the surface and at every depth and never noticed any diff. at any adjustment point.

Of course I never was able to taste the diff. between expensive wine and cheap wine..

Seriosly should I feel a big difference?

 

[Genesis]

is basically a S600 in a different case (the G250 case)

There is a somewhat-significant difference in inhalation resistance between full-in and full-out on the knob - perhaps 1" of water or so in terms of inhalation resistance.

Normally you would dive that reg with the knob all the way out, but in heavy surge or current you may get some leakage in that position, which you can control with the knob.