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Permalink Reply by Griffin Hagle on March 12, 2014 at 10:04pm

Ted, I see your point now. Thanks for clarifying. The CAZ pressure was recorded independly of the draft. I haven't seen anyone measure both results simultaneously on one manometer, but that is a really good way to illustrate the interaction between the two forces.

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Permalink Reply by tedkidd on March 12, 2014 at 10:08pm

... and one of the things that makes dg700 such a cool tool.

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Permalink Reply by Paul Morin on March 13, 2018 at 8:31am

When testing draft, using the straight probe will be a close approximation of static pressure because the velocity is so low.  You should have the end of the probe close to the center of the vent and at a 90 degree angle to the pipe. 

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Permalink Reply by Jose Macho on March 14, 2018 at 5:20pm

Forget the draft measurement issue,,, just look at that incorrectly applied pipe wrap next to the flue.. Surprised it hasn't melted yet. Anyway,,, many who follow the 1200 standard simply test draft using a smoke pen or some visible indication (yes a mirror does work) of proper draft. The old BPI rule of outside temp and draft pressure failure made no sense at all when we could visibly see it drafting under worst case conditions.. 

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Permalink Reply by Paul Morin on March 15, 2018 at 8:34am

I agree that checking for combustion spillage is more important that checking for draft.  It is possible to have high draft pressures and spillage at the same time.  For example, if a 75,000 BTU water heater is vented with a 3" pipe, you will have high draft pressure and spillage at the same time.

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