GPH, PSI, RPM, head pressure - HELP!

What specs of an external chiller in terms of HP and RPM will achieve 10PSI in a 1.5in pipe, with 7ft of head pressure?

Hint: 3/4 HP, High Pressure (3400 RPM), a ball valve in-line cutting the flow in at least half.

Actually, the hint is the answer, but I cannot put GPH, RPM, PSI and head pressure in the same equation.

tangster - im baaaack!

Cheers!

 

I'm confused what you are even asking.

 

I think he wants to know, what size Chiller for his tank
and what size pump to run it with and that the pump will be pushing water 7ft
through the plumbing/pipes to the chiller

If I am correct
what size is the tank Darren ?

Steve

 

sorry to respond so late, got real busy...and now its late so my follow up message will be equally unclear. sigh.

first off, i need a new pump for my protein skimmer, not chiller. my skimmer: etss 2500, which specs a pump with high-speed RPM (3400), 3/4HP 2500GPH@ 10PSI.

What i dont get is the PSI requirment. The rough equation to determine PSI is: feet of head pressure / 2.3. So right now, i have about 3 PSI. To get to 10PSI, i need to SLOW down the rate of flow?? I guess a high rpm pump cant handle a lot of head-prssure, but puts out a lot of water flow, so i will need to throttle the flow with a ball valve which will get me a slow 2500GPH and 10PSI. whew.

Dolphin makes one, and their new abrasive seal can handle nasty water and also has a built in thermal switch which will shut down the pump if water stops flowing.

cheers, darren

 

So.... a pump is rated for flow and pressure. I'm not even sure what the RPM requirement has to do with it. I mean..... sure, if you speed a pump up it will increase pressure, but some pumps can do 2500/10 at 1000rpms and some can do it at 3000 prms. It is determined by the pump specs and how they built it. Slowing down a pump will decrease head pressure, but has nothing to do with throttling a pump.

I'm not exactly sure how you are applying your equation..... unless it is an equation to determine head pressure per foot..... which is not the same as getting your specs. 2500 gph at 10 psi is a "high" pressure pump, capable of sustaining 2500gph at ~23 feet of head. So with 23 feet of water sitting on it, it can deliver 2500 gph. Much more with zero.

If you have 2500 gph now at 3 psi, that does not mean you can throttle it to get 2500 gph at 10 psi..... even though.... restricting a pump will increase pressure... to a point.... but at the expense of flow.

The skimmer needs 2500 gph at 10 psi, because ETSS knows that when you mate such a pump up to the skimmer, you will get a certain pressure drop with a corresponding flow drop yet still meet the requrements for optimal performance from the skimmer.

Does that make sense?

 

ack, just two cup’s o’ joe into my morning and this thread makes my head hurt. You lost me at chiller, what was the question again?

 

Powerman - thanks for the lengthy reply, and while at this point (1030 PST) i cant comment, i promise to re-read your post until i understand!

cheers, Darren

 

yes.

I was told i needed a 3/4HP, 3400 RPM (that pumps 8,000 GPH) and to throttle the flow by a quarter (to get to 2500GPH) with a ball valve. What i dont understand is why i cant just get a pump that pushes 2500 GPH based on my 7 ft of head pressure?? How does RPM effect the flow rate? I have yet to see pressure as a spec with pump curves (head pressure vs GPH)

I guess i am missing something here, and its the 10PSI.

thanks, foggy

 

OK, getting a 8000 gph pump and throttlinhg it down with a ball valve a quarter turn to 2500.....no. That is no exact science by any means.

I looked up your skimmer... what a beast... is your tank that big? Anyway... ya 2500 gph at 10 psi. All you have to do is convert your psi to feet of head since that is what most pump curves for us are given as. Most regular pump curves are flow and pressure, but out pump they seem to like giving us feet of head. That is that ~23 feet I gave earlier. One ATM is 14.7 and 33 feet of water is one ATM or roughly there .... so the formula you had is what that is for. You need to look at a pump curve that will give you 2500 gph at 23 feet of head...

But you don't throttle it..... you may very well wind up with a pump that gives 8000 gph at zero feet.... but you don't throttle it to 2500 gph at zero feet..... the skimmer is the throttle.... you just need to find a pump that will flow 2500 gph at 23 feet of head or at 10 psi and hook it up. That will give the proper curve the skimmer needs.

 

Your right!!

It came to me this morning lying in bed. I get all your math and will post my new pump curve shoretly. Whew. I like Dolphin pumps because they have a strong seal which can literally handle small debris, like sand and shells.

As far as a tank size: 2,800 gallons of chilled seawater!

much thanks, Darren