Jack Baikoff's Page

"Rick Karg has instructions for using a pitot tube to assess airflow in ducts. His website Residential Energy Dynamics includes a calculator to determine duct CFM.  It's fairly accurate, provided you have plenty of straight duct…"

"That duct is an economizer. It's purpose is ventilation, and possibly cooling (rather than using the AC). Night time cooling works great in the western states in many places, where it's dry, and the temperatures drop at night to below…"

"Use a duct blaster as apowered flow hood, look in duct blaster manual. "

"Any chance that duct is configured as some sort of "economizer"? A/C is not common here so I'm not familiar with all the permutations. What I usually see is a 4" or 6" duct from the exterior, with no means of controlling how…"

"Sure John.   Have you ever seen such a huge intake?  And so close to the unit.  LOT of air!  Not worried about shocking the heat exchanger?  Where is this house? "

"Ted, Thanks.  I had to pull the image of and lighten it up to make out the details down there.  It looked like a duct with no bottom in the original."

"John, the huge duct on the right with the blue zone control apparently ducted into a "bottom" return (bottom of the picture)  I don't think anyone was referring to combustion make up air.  I think this is about meeting…"

"Ted, That is a sealed combustion furnace. We don't know what the hot water heater is.  If that is someones idea of mechanical ventilation to meet ES 3.0, I believe they missed a class somewhere. Code compliance for fresh air in this area…"

"Wow, just looked at the picture!   Jack, you sure that's a fresh air intake?  Looks like 16" duct - and it's got a Carrier Infinity Zone Control damper on it.  I guess the Infinity might be managing fresh air, the…"

"Others have given good ideas for roughly measuring the actual airflow. If I had a bit of time to kill, and the freedom to experiment with the house, I would probably seal the exterior inlet of the fresh air duct and then measure any changes in…"

"Set up your blower door and duct pressure testing. Get a duct leakage to the outside, with the vent open. Then repeat with the vent taped off.  That would be the amount of air flow in CFM at 25pa through the duct.  If you are wanting the…"

"HVAC contractor (ideally) drills the 1" hole, then tapes over afterward.  I invested about $250 for 4", 5", 6", 7" and 8" versions of the device. "

"Not inexpensive! Do you install it and leave it, or do you drill a hole, and have to patch?"

"By the way...not sure what climate you're in, but someone should probably should insulate that fresh air duct!"

"There are in-duct measurement techniques that are accurate enough for this purpose. Here's what I use - http://www.kele.com/flow/fxp-series.aspx It's essentially an "averaging" pitot tube to take care of the likely…"

"Why are you wondering how much airflow occurs at this intake?   1) Required for Energy Star 3.0 certification 2) Code compliance 3) Ensure there's enough airflow to help ensure healthy indoor air quality 4) Ensure there's not too…"