MK5/109 and Conshelf 14 breathing

[ozziworld]

Have been using mk5/109 set for the past two year and recently reverted back to a Conshelf 14. Noticed the Conshelf breathes a lot harder beyond 60 feet. I never recalled that big a difference in breathing effort between the two.

Is it just tuning or is there an inherent difference in design and performance?

 

[Rich Keller]

It may just be a simple adjustment that needs to be made. I have used and serviced both types and have not seen any measurable difference between them.

 

[scubafanatic]

The 109 can (and may have already been) upgraded to a balanced 2nd stage. I'm not sure the Conshelf is (or even offers) a balanced 2nd-stage. That can make a big difference.

 

[AFdivedoc]

I have both, and dive both. Not a huge difference between them if the Conshelf second stage is tuned properly. I've not found that it breathes any harder below 60'. The Conshelf XIV second stage is a classic downstream design (unbalanced) with a fixed orifice, and lever height is the only adjustment that can be made during maintenance (except maybe changing the spring). The 109, being a barrel poppet design (and with the capability to upgrade to a balanced version), has an adjustable orifice and external adjustment knob. It can be tuned very close to free flow if desired.