Thank you very much!

Great to hear! Let us know if there's a topic you want and we'll make it happen!

Thanks!

Awesome, let us know what you want to see next and we'll make it happen!

Glad to hear that!

Thank you!

You would use head pressure, but if the suction is a positive you need to subtract it from the head, if its a negative pressure, you would need to add it. Watch our pump performance video and let me know if it helps.

You are correct; these videos do not dive into theory; they are folks who need the base information "now"... like when a Technician is on a job site and just needs the answer, not the science behind it. For this test, the pump is moving no water with the discharge valve closed, so the pressure should line up with "0" GPM on the chart. The suction pressure needs to be subtracted so you are only checking the pressure the pump is creating, not the standing pressure of the system.

Thank you for the feedback Levi! Good observation on what is NOT included in our videos! The reason they're short and without theory or concepts included is they're what we call 'Explainer Videos' that are intended to give you what you need to get the job done in the least amount of time possible...like when your on a job site. That's whey we include the tag line - "What you need to know, when you need to know it, in ten minutes or less". We have plans for other video series that will include more background information that the Explainer Videos don't cover. Let us know what you would like to see and we'll make it and give you full credit for the idea! About the pump pressures...it's like when you calculate "Absolute pressure" by subtracting atmospheric pressure (14.69 psi) from "Gauge pressure" . Oh, and you can't be a simpleton when you ask questions like yours!

Jerk. 😆

Great question! Think of it this way; feet of head is like miles or kilometers, its a course measurement. Mercury HG is like millimeters or tenths of an inch. Which would you use to measure the distance between the North-Pole and the South-Pole; kilometers or millimeters?

You're best to shut the pump off when moving the gauge. The other option is install a valve on each gauge port and tee them together, installing the gauge on the tee branch. That allows you to open the valve for the suction, then shut it and open the discharge gauge port valve.

You're right, air would skew your readings, but that isn't the culprit if the system has a standing positive pressure and the pump isn't at the high point of the system (the air typically is at the high point/s in the system) Can you give an example suction / discharge readings and the pump data? Also, if the pump has a VFD on it, be sure it's running at 60 hertz.

Good question! subtract it if its a positive, add it if its a negative.

Good question! We subtract it because we want to see the true discharge pressure. Think of it like this; if you weigh yourself while you're holding a 30# jug of refrigerant, the weight will be off by 30#. It's the same reason we add the suction if it's a negative number. If you weigh yourself while someone is picking you up, the reading will be off. Hope that helps!

For psi (head in feet) pressure x 2.31/specific gravity

I think this only applies to C. P PUMPS.

Keep in mind this check is for centrifugal pumps only, NOT positive displacement. You also do not keep the valve shut for more than a few seconds, just long enough to gather the zero flow pressure.

@@MrQarni1 You are correct! this is for centrifugal pumps only.

Send the questions over to patrickpeterson@zenhvac.com

Good question Max! Most engineers design systems assuming the individual components they select for the system will work as designed. While Engineers typically design systems to work properly, HVAC Technicians troubleshoot systems that once worked properly, but now do not work properly.

Sorry Brian, I should have explained that! The water pressure is measured in Feet of "Head", and when you close the discharge valve the flow is "Dead" so they use the term "Dead-Heading" the pump.

why do we need to know the dead head?