old pump and estimation of the turnover time

Jump to latest Follow Reply
The MOTOR is consuming 1.3 kw which is the electrical input power required to turn the impeller. And again, the 0.75 kw is an output power RATING not an input power. 0.75 kw is the manufactures recommended maximum load for the motor and not what it is acutally dilvering at any point in time. Think of it this way

Electrical Power --> Mechanical Shaft Power --> Impeller Water Power

At each stage of conversion, energy is loss. The HP and KW label ratings refer to the middle stage but again are simply maximum ratings and not operating conditions.

I copied this out of the Hydraulics 101 sticky which might help you understand the terms better:

Pump and Motor Definitions

Nameplate HP (NPHP) - This is the HP rating on the motor nameplate but is pretty much meaningless without the service factor.

Full Rated HP (FRHP) - Similar to nameplate HP but used when the pump is full rated.

Up Rated HP (URHP) - Similar to nameplate HP but used when the pump is max rated or up rated.

Nameplate KW = NPHP * 0.7457 - This is the KW rating and is similar to the nameplate HP and is generally used outside the US. Note that this is not the input power to the motor only the rating for the output power of the motor.

Energy Horsepower (EHP) = watts / 745.7 = Volts * Amps * Power Factor / 745.7 - Energy input delivered to the motor

Brake Horsepower (BHP) = EHP * Motor Efficiency - Energy delivered by the motor shaft to the load. As will be explained below this is not the same as SFHP nor SF * NPHP in general. BHP is a function of the load on the motor shaft and will change with Head, GPM and RPM.

Hydraulic HP (HHP) = BHP * Pumping Efficiency = Head (ft) * GPM / 3960 - Energy delivered to the water. Sometimes called water HP (WHP) or pumping HP (PHP).

Motor Efficiency = BHP / EHP - I2R, magnetic and mechanical losses in the motor only.

Pumping Efficiency = HHP / BHP - Recirculation and internal friction losses in the wet end only.

Total Pump Efficiency = Motor Efficiency * Pumping Efficiency = HHP / EHP (note this is why total pump efficiency approaches 50%).

Service Factor - This is an overload rating for motors which states that the motor can be safely operated over the NPHP by the service factor for short periods of time. However, for pumps, this overload rating is typically used as the maximum load that a motor would need to deliver to the wet end. Because the load on a pump does not rapidly change over time, the service factor load is often used as the maximum design point for the pump.

Total HP (THP) or Service Factor HP (SFHP) = NPHP * Service Factor – This is the maximum load that can be safely be driven by the motor. This is not the same as BHP although BHP can safely reach THP but not exceed it. BHP is the energy delivered by the motor shaft while THP is the motor rating. A motor can be driven above the THP but will likely fail in a shorter period of time. For pumps, the motor is usually driven at a BHP that is less the THP.

Service Factor Amps - The amp draw when the motor is loaded to the service factor. Also, multipling the SF amps by voltage should also give a good estimate as to the upper limit for power draw. However, sometimes the motor is over dimensioned for the pump so it will not always be an accurate measure of input power.

Full Load Amps - This can mean several things depending on the motor manufacture. It is either the amps at the NHP or it can be the amps at the THP. I have seen it both ways so unfortunately, there is not a good standard for this one.

There are others but I think that the above definitions are the most important.

For further reading on this subject, I strongly recommend a web site put together by Joe Evans, a PHD from Pentair: http://www.pumped101.com.
Click to expand...
 
mas985 said:
You could go to 1" eyeballs but I suspect that you won't see that much of a difference (<1 GPM). Since you have three eyeballs, the flow rate is divided between them so the head loss experienced by any one of the eyeballs is much much less than if you had only one return.
Click to expand...

Mark,

I put down the solar cover today and had to adjust the jets to direct the water lower so it won't bunch up my cover to the middle of the pool. When jest are adjusted to blow towards the skimmer, all the junk would get removed pretty quickly. With the cover on I realized that I don't really need to point towards the skimmer any more. As long as I have a good circulation, I should be ok.

Since i had to adjust the eyeballs, i decided to remove them to see if i get any psi drop at the filter. The pressure dropped from almost 10 psi to steady 8 psi. With the pressure drop that much, do you think that the flow rate would be up more then 1 GPM? 3/4" eyeball is 4 times more restrictive as 1-1/2" pipe. but maybe hydraulics don't work that way.

I expect that the clean filter pressure would be about 7 psi.
 
With a 2 PSI change, you might get closer to 4 GPM change in flow rate but overall that is only about a 6% change and not really something to get too concerned over. But it wouldn't hurt anything either to leave them out for a while and see how things go.
 
Mark,

Thanks a lot for answering all my questions. It bugs me when I don't understand/know something and I'm always trying to find out. You were the victim this time and I hope you didn't mind too much me bugging you.

I really appreciate your help and the time you spent answering! Thank you a lot.

Stan.
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply