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View Full Version : Horbgorbeling testo magnehelic


powerup
02-03-2010, 07:56 AM
Will someone please explain how to use this gadget. Have been using this thing for a few years now and now all of a sudden its all over the place. Is it the air flow changing or me using this incorrectly now. I have readings on a 16 ton airhandler at .80" to 1.50" supply and .25" to .56" on my return. Its been a while since I've used it. Correct me if I'm wrong here. You get up to .50" for a 10 ton unit. Thanks in advance.
Tech Rob
02-03-2010, 08:22 PM
The best thing to do would be to bench test it against a traditional magnehelic or find a way to apply a known pressure to it. Also remember that your "hi" readings depend greatly on your "lo" point of reference. If you measure 3" in an air handler supply plenum, but the mechanical room you're standing in is in a vacuum to the tune of -1.5" and your "lo" port is open to said mechanical room, what you actually have inside that air handler supply plenum is 1.5".

FYI, static pressure has nothing to do with tonnage.
powerup
02-04-2010, 07:07 AM
The best thing to do would be to bench test it against a traditional magnehelic or find a way to apply a known pressure to it. Also remember that your "hi" readings depend greatly on your "lo" point of reference. If you measure 3" in an air handler supply plenum, but the mechanical room you're standing in is in a vacuum to the tune of -1.5" and your "lo" port is open to said mechanical room, what you actually have inside that air handler supply plenum is 1.5".

FYI, static pressure has nothing to do with tonnage.

I believe your response is right on the mark. Thanks, will take my new readings and get back with them. As for the tonnage not having anything to do with my readings. Only the cfm counts?