We're going to be looking at pump calculations and, specifically, we're going to be looking at how to calculate theÂ

- Flow RateÂ
- Pump RPM
- Head Pressure
- Pump Power
- Impeller Diameter

If you already have a pump installed in one of your buildings, then you should have a checklist or a sheet that comes which is the datasheet for that pump.

All too often, parts of this design data are missing and that's frustrating. But if you have some data missing then we're going to look at some formulas of how to calculate and fill in these gaps, and also, we'll look to see what would happen if you were to change some of these parameters.

Also Read:Â *How to Calculate Cooling Capacity of a Chiller in HVAC*

If you haven't got the pump installed yet, you're in a design phase, and then
you can also use these formulas to determine what the performance will be. Remember that these calculations will only give us theoretical values. The
actual performance may vary from these. And, you know, certainly, the old a
pump gets, the larger the discrepancy becomes between the theoretical and the
actual answer. You might need to add on a correction factor to adjust these.

Now we jump into
the calculations

### Flow Rate (Increase/Decrease RPM)

### Flow Rate (Change Impeller Diameter)

Now, I will point
out that this is an older way to do, to trim down the impeller to change its
diameter. It's not the preferred way anymore, and that's because if you, once you
trim it down, you can't, obviously, add that material back on. So you need to
replace the entire impeller. A much better way is to actually use a variable
speed drive or variable frequency drive to change the speed of the pump to meet
your design criteria. But if you are looking to change the impeller or to even
trim the impeller down, then you can use these calculations here.

Also Read:Â *How to Calculate Chiller Efficiency in HVAC*

### Pump RPM (Increase/Decrease Flow Rate)

### Pressure Head (Increase/Decrease RPM)

### Head Pressure (Increase/Decrease Flow Rate)

### Pump Power

So the next one
is the pump power, how to calculate it? What the new pump power would be? Should
you increase or decrease the revolutions per minute of the pump?

### Impeller Diameter

And then, last
one we're going to look at is the impeller diameter. So if you were to adjust
the flow rate and you wanted to achieve this new flow rate, what diameter
impeller would you need? And this is usually used in the case where the
impeller is being trimmed down to meet a new flow rate.

If you have any
questions, please leave them in the comments section below.

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