Pump RPM -Pentair Intelliflo VSF, 3hp

[cacciato2006]

Morning. Yesterday I had a new Intelliflo 3hp pump installed and two IC60's. My question revolves around the pump speed. Since we dumped a 1,000 lbs of salt in the pool yesterday the pool company asked me to run the pump all night before turning on the SWGs and running the rpm faster than needed. After slowing the pump down I noticed that to get the flaps in the skimmer boxes (SB) to lay down with a bit of water over them I had to set the rpm at 2,200 with the main drain/SB valve choked a tad bit towards the SB. I would certainly like to run the pump slower and I could continue to choke the valve to send more water to the SBs but that would certainly reduce the volume turnover in the deep end of the pool. I've read several running their pumps slower in the past and it just seems a little odd that I have to run the pump so high. Maybe not. What do you guys think?
Thanks,

 

[Texas Splash]

Good morning David. If it were me, I would focus more on the skimmers and less on the drain. Ensure adequate water flow to those skimmers which should allow you to lower your rpms yet still provide adequate water circulation.

 

[Jimrahbe]

David,

Your weir doors just need to move and allow water to flow over them, they don't need to lay all the way down.

The speed you need to run the pump depends on what all is in the path of the water flow.

I do not have a heater and have a large cartridge filter, so I can run at 1200 RPM and have plenty of flow with a filter pressure of about 1 or 2 lbs.

If you add a heater, you have to run faster, if you have a small filter, you have to run faster, if you have a DE filter with a multiport valve, you have to run faster.

Even at 2200 RPM, you are still saving a lot of money compared to a single speed pump.

If you are used to seeing your skimmer operating with a single speed pump, it will not look that way when using a VS pump. I get very little water movement when I look down into my skimmers, which make you feel like they are not working. But in fact they are working just fine.

I would set your main drain at 10% open and your skimmers at 100% open.

Thanks,

Jim R.

 

[cacciato2006]

I have one valve to split flow between the main drain and the SB. Right now I guess that the flow is split 40/60 and 60 being the SB. At that split the weir doors are skimming a little bit of water over them. I'll adjust the valve down prioritizing the SB to continue to lower the RPM and see where I end up. I appreciate the input.
Thanks,
David

 

[Jimrahbe]

David,

In my mind the key speed is what you are going to need to turn on the flow switches in your IC60's. If you plumbed them in parallel, then I suspect that will be the lowest speed that you ever want to run.

Thanks,

Jim R.

 

[reggiehammond]

I run my main drain ~95% closed until leaf season. During times of heavy leaves, I open it more.
Otherwise, I run ~1400 rpm almost solely to the skimmers to maximize skimming effect, while keeping RPM's low and SWCG happy.

As mentioned, no issue if the weir door is opening and closing regularly. That'd be normal to what I expect and see on my pool.

 

[ajw22]

The volume turnover in the deep end makes no difference in the quality of your pool water. That should not be a consideration in how you set your valves.

Turnover of Pool Water - Further Reading

www.troublefreepool.com

 

[brucehenson]

First of all, I am by no means an expert or really very knowledgeable.

I run my VSF on flow rather than speed. 40 gpm runs at about 1,400 rpm. My IC40 flow switch makes at about 25 gpm. When my cleaner is running I set flow to 60 gpm (about 2,150 rpm). When I notice that the pump is working harder, meaning it requires higher rpm in order to maintain flow rate, I know that it’s time to do something such as clean the pump strainer basket, dump the skimmer baskets, or even backwash.

Thanks for posting the question, I’m interested to monitor the responses.
Bruce

 

[cacciato2006]

Great information all. Both cells are installed horizontally right out of the heater. I know both cells complain of low flow at 1,500 rpm since that was a preset. Now I'm running the pump 9am to 5pm at 2,200rpms. I'll pinch off the main drain some more and lower the pump speed down and see where the cells say no.

On another note: I'll be bumping the cya up to 70 per pool math. Should my target for Fc be 7 or 10%? Pool math provides a very large range from 3 to 10.

The salinity in the pool was 700 and we put 1,000 lbs of salt in which should be close to 3,000. On the label of the SWG it says Ideal salt is 3,600 ppm and it says acid clean every 3 months. I'll buy the salt and dump it in. I've read here several times discouraging that practice acid cleaning the cells if the water quality is good?

I've also read in the manual that pH higher than 8.0 is discouraged. The makeup water here has a pH of 8.1 or higher and 350ppm of TA. To prolong the life of these cells I can keep the pH lower with acid if necessary. Very expensive equipment.

I tested everything today and the CSI is -0.04.

FC 6.0, pH 8.0, TA 80, CH 250, CYA 50, Salt 3050 (calculated), Temp 66.

 

[reggiehammond]

The Free Chlorine and Cyanuric Acid Relationship

Managing your cyanuric acid and Free Chlorine levels is key to stabilizing your pool. Learn how these two items affect each other.

www.troublefreepool.com

Min 3, Range 5-10 at 70 CYA. Target should be 5 or higher.

You'll fight the TA-induced pH rise when you add water. That's typical and something I deal with on my well water (~250TA.)
Just keep your pH in the 7's and manage the TA to reduce the pH drift. That's really all I do in the summer, add MA to control pH.

Run your pump long enough to make the FC you need, and skim the pool. No need to go more than that if you don't desire. I enjoy running 1400 rpm 24/7 just for peace of mind, constant skimming and constant FC creation.

If you control your CSI, you won't scale and there's no reason for acid cleaning the cell. That's an absolute last-resort - but scale can typically be pushed off with popsicle sticks and a water hose.