Checking Pump Performance (Dead Head Check)
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- เผยแพร่เมื่อ 18 เม.ย. 2018
- If you work on hydronic chilled or hot water systems you need to know how to troubleshoot pump issues. And one of the most common issues is a pump that's not performing correctly. Considering the water pump is the heart of boiler and chiller water systems, knowing if the pump is working properly is a priority for the HVAC Technician. This video gives a simple step-by-step guide to checking a water pumps. In less than 6 minutes you'll be a master at pump troubleshooting.
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Love your video. Explains a lot on the pump curve.
Thanks for spending the time to create and share this content
Really appreciate the way of explanation , thanks 😊
This is what I was looking for longtime and I found it thanks sir great explanation straight forward.
Please could make video on NPSHr & NPSHa checking and calculation
Great video! Very easy to follow. Your other videos are just as good!
Thank you very much!
Fantastic videos! Instant education I can use in the field tomorrow! Thank you!
Great to hear! Let us know if there's a topic you want and we'll make it happen!
Phenomenal! Thank you.
Just gained additional knowledge.
Excellent
Good video!
Thanks!
I found this video trying to find information about PI and VK , found on the side of fuel trucks. So is this the PI or VK or both?...or neither
i'm learning again. i like it:D
Awesome, let us know what you want to see next and we'll make it happen!
Glad to hear that!
🔥🔥🔥🔥🔥
What would be the inlet pressure if the pump is sitting open water, such as a submersible pump in a sump?
Wonderful
Thank you!
Thank you. If I wanted to see what I’m actually pumping compared to a pump curve do I just take the head pressure?
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.
Could you advise me about what is the max allowable time to perform the dead head time, as you say "I have to use the same pressure gauge " , So it will take around 3 minutes to install the gauge
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.
So, for a simpleton like myself, the general idea idea is to compare the psi of the sucking in side to the pushing out side of the pump? This video reminds me of many math /science class I took where you're given a set of steps to follow with no explanation of the underlying logic,
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!
I got question for you! I am doing pump curves on new pumps most of the time and actual dead head pressure doesn't match with the given performance curve dead head(curve given by manufacturer)! I checked speed, and impeller size and new pump might not have worn seal or impeller. Is it possible to have air trapped in water system and it will give a wrong reading as air has low density!? its happening a lot! I am really confused and looking for solution to how to find if air in water system? or its something else causing problem! Please help me if you can. Thanks!
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.
Sir I have a question, if it is a closed loop like Chilled Water Piping. The system shows a suction and discharge pressure while it is running. If we want to know the pump head(in feet)do we have to subtract Suction from Discharge Pressure(in PSI) and multiply by 2.31, please clarify thanks
Good question! subtract it if its a positive, add it if its a negative.
If you have a negative psi on a CB, that is considered a vacuum and should be measured in inches of mercury HG. This will be more precise in your calculation
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?
Hi Zen team. Do you guys have a Facebook page or email where I can contact you for some questions I have regarding how to test a pump?
Send the questions over to patrickpeterson@zenhvac.com
why do we need to subtract the suction pressure and discharge pressure?
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!
How to check pump running as per pump performance curve..
How to check head flow pressure
Wow and I just change capacitors and switches and leave🤣. Awesome
Jerk.
😆
Does it need to divide the specific gravity?
For psi (head in feet) pressure x 2.31/specific gravity
i feel its danager to start thje pump when the valve is closed
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.
How come none the Engineers I've worked with have mentioned this test.
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.
I still don't know what dead head means.
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?