Pump Total feet of head

[mr ken]

or just total head............

I read on a thread on this forum from over a year ago where mas 985 was discussing total head..

He went thru the technical calculations and then ( and I'm paraphrasing not quoting), gave a good guesstimate way to figure total feet of head....

He said to multiply the clean filter psi by 3-4 for total head....He said for 1 1/2 inch pipe to lean closer to the 4 ...

So then with my 1 1/2 inch piping and 12 psi clean filter,, 3 x 12 =36 and 4 x 12 = 48....

As I've stated in other posts, I have one 60 foot suction line from the skimmer...I also have one 40 foot suction dedicated line for an automatic cleaner, but I've never opened it or used an auto matic cleaner...

My 2 return jets are 20-25 feet from the pump...
I have a 100 Sq. ft. cartridge filter rated at 100 GPM max flow...

My current Centurion motor has a BHP of 1.2hp....

So is my guess of total head around 45 correct ???

I've done a ton of research and have found that even if 2 or 3 or 4 or 5 pumps have the same BHP, they can have vast different GPM to total head numbers on the curve...


mas 985 says to go with the lowest hp. that will do the job...Easier said than done....You really don't know for sure if a lower bhp
will do the job well until it is installed and then you are stuck with it...

I see that Jason Lion has a 20,000 gal. pool yet only has a 3/4 hp pump...My pool is 9,500 to 10,000 gal...1 1/2 inch piping.

I would love to go 2 speed, but only the whisper flo have the toggle switch on the motor..The other brands you have to install a special timer....Too much hassle and expense for that...The 3/4 hp whisper flo 2 speed has the toggle switch but only 115v.. I now have 230v and again do not want the hassel and expense to change it to 115v..

Every pool store that I call in my area says pipe sizing means nothing and go with a 1 hp to 1 1/2 hp pump.......But on checking all the curves on most of the 1 to 1 1/2 hp pumps, the GPM at 40-50-60 ft of head would be way too many GPM for me.

Taking into account that Jason Lion has a 20,000 gal pool and mas 985 says to go with the lowest yet efficient hp, I have narrowed my choices to the following single speed pumps...Dual speeds are out !!!
CHOICES:::
Whisper flo full rated WFE-2 1/2 hp, .95 BHP,,,

FT. of HEAD GPM

60 FT 40 GPM
50 FT 55 GPM
40 FT 67 GPM
30 FT 73 GPM


Sta- Rite Max E Pro

1/2 hp BHP .95

Ft of Head GPM
60 FT 30 GPM
50 FT 47 GPM
40 FT 55 GPM
30 FT 62 GPM

Sta Rite Max E Pro
3/4 hp BHP 1.23

Ft Head GPM

60 FT 55 GPM
50 FT 62 GPM
40 FT 70 GPM
30 FT 75 GPM

When I originally asked some of these questions, I had thought that I would get more and thorough responses...If I had the knowledge and expertise like most of you I wouldn't ask....
I do know about water chemistry, vitamins and Dog nutrition are my specialties...Not pool pumps and pipe sizing,,,but I am learning every day...
I hope you will have patience and offer your expertise...If not, I can always watch American Idol tomorrow nite....I heard that Paula reads this forum !!

Thank You
Ken

 

[JasonLion]

If I am following things correctly you should look at the WhisperFlo 1 HP two speed pump. The 1 HP works on 230 volts and on low speed uses less electricity than the 1/2 or 3/4 HP single speed pumps use. Then you have high speed available in case you need it. Low speed will move half the number of GPM as high speed does.

 

[mas985]

Mr Ken,

First, it might be helpful if you stick to a single thread on your topic of choosing a pump. Folks that read this thread but have not read the others are at a disadvantage. I don't think having multiple threads on the same topic is helping your cause much.

So on to your decision. I think you may be over analyzing this too much. I am not sure who these other people are who are saying you won't be happy with some of the recommended pumps but I can assure you that this is not the case. Ask these folks to back up there claims with detailed analysis and data and see what happens.

When comparing pumps you really have to look at braking HP (BHP). Your current pump has a BHP of 1.2. The 1/2 HP Whisperflo (full rated) has a BHP of 0.95 and the 3/4 HP Whisperflo has a BHP of 1.25. Your pump falls somewhere in between the two. Since the 3/4 HP Whisperflo is not that much different than your pump, the results will be about the same as what you are getting now. A few hundreths of a BHP really aren't going to matter much.

Also, the estimates I gave for head loss (3-4x) assume a balanced system. So suction head is somewhat less than return head. But in your plumbing , the suction line is much longer than the return line and you have multiple return lines with only one suction line so it is likely that your suction head is higher than your return head. This may be why your filter pressure is only at 12 PSI. This is a unique situation which requires a bit more analysis than 3-4 x filter PSI. Using the pipe lengths you gave plus some margin for fittings, I estimate with a 3/4 HP would have about 58 GPM @ 62' of head. This is probably more flow than what you are currently getting. The 1/2 HP would be close to 53 GPM @ 52' of head maybe slightly less than what you are getting now but it is hard to say. These are estimates based upon only the information you gave me and could vary by as much as +- 10%.

No one can tell you what to do but what we can do is help understand some of the trade offs so you can at least make a well thought out decision. If you want a bit more flow rate than you have now go with the 3/4 HP. If you want to save a little more money and are fine with a little bit less flow rate, go with the 1/2 HP. If you want to save a lot of money, go with a 2 speed. Take a look at the 1 HP uprated Whisperflo WFDS-24 but you need 115v.

What exactly are you trying to accomplish? Answer this first and then choose the pump.

 

[mr ken]

Thanks to both of you.....
I am just trying to have an efficient pump that works well, circulates the water , and no problems.....I guess that I have been spoiled as my pool and pump system were installed in 1995 and the only problem I ever had was a crack in the pump basket lid after a hurricane in 2004...
I read a week ago that too much GPM over 44 GPM for 1 1/2 inch piping may hurt the plumbing..That has stuck with me....

Thanks for all your help....
The whisper flo pumps are better that the Max E Pro ??? Why ??

Thanks
Ken

 

[JasonLion]

The GPM limit based on pipe size isn't a hard limit, nothing actually goes wrong at that flow rate. It is just that as the flow increases you lose more and more energy to flow resistance in the pipes. If you have a two speed pump it would tend to be below the limit and very efficient at low speed and above the limit and just fine but not as energy efficient at high speed.

There aren't any large differences between the pumps, the WhisperFlo is just a little better. The WhisperFlo is slightly more efficient and has fewer complaints/problems than the others.