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Reasons for low pressure/low flow?

Posted by ukmatt (My Page) on
Tue, Feb 24, 09 at 11:37

I have a newish pool with all Pentair equipment including a 4x160 pump, intellichlor salt cell and a cartridge filter.

The pressure gauge on the filter has 20psi marked as "Start" and 25 or 30psi (don't remember) marked as "Clean".

When I run the pump at 2500rpm in pool mode, the reading is only around 12psi and it has been like that for some time although we believe it was higher when the pool first started up. In addition, even though my Intellichlor is producing chlorine just fine (all green lights), the diagnostics on the EasyTouch say "Check Flow/PCB".

If the pool is clean, the water features working as expected and the chlorine level acceptable, is there any need to worry about the PSI?

UKMatt


Follow-Up Postings:

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RE: Reasons for low pressure/low flow?

How long does the pump run each day. If the on and off times for the cell are matched to the pump, delay the start of the cell for 10 minutes and have it turn off 5 minutes before the pump. I'd bet that ends the flow sensor trips.

12 PSI at your speed seems about right for normal 2 inch plumbed system. A 2 HP Whisper Flow with an FNS 60 usually reads 16 to 18 lbs. which is about 80 to 95 GPM flow. I'd venture to guess that your current mode is pushing about 50 to 60 GPM.

What conditions exist that the pump speed needs so much water?

Scott


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RE: Reasons for low pressure/low flow?

Your filter pressure is going to be dependent on the RPM of the pump. The higher the RPM, the higher the filter pressure.

A typical pool with 2" plumbing, 30' runs and two suction lines, might have a filter pressure around 12 PSI @ 2500 RPM. At full speed, the pressure would rise to about 22 PSI.


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RE: Reasons for low pressure/low flow?

If you are certain about what the pressure used to be then you may have a partially clogged impeller. Also check if any return eyeballs are missing. Also, turn off the pump and see if the guage drops to 0. If not it likley needs replaced. In fact, just replace it anyway to see if there a difference. This is a common wear item. I sold over 200 last year.


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RE: Reasons for low pressure/low flow?

Guys,

Thanks for the replies.

I hate to admit some of this is black magic to me as the pool builder ran with the money and I didn't get to ask too many questions before he ran.

When the system was set up they put speed 2 (for normal pool operation) at 2900 rpm. I backed it off (to save electricity) to the point where the spillover and bubblers work fine and it is still perfectly clean.

Is it ok to run at the lower PSI?

Poolguynj - I don't understand your question about pool conditions... can you re-state?

UKMatt


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RE: Reasons for low pressure/low flow?

Actually, running at lower RPM and lower pressure will save you money. It is a lot more efficient to run at 900 RPM than it is at 2500 RPM.


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RE: Reasons for low pressure/low flow?

Pool size, features like your bubblers, spa, plumbing size, vinyl, fiberglass or concrete.... Filter size, additional equipment...

BTW, The start an clean points n the gauge may be movable.

How much is spilling from the spa.

Since the idea is stretch out the filter cycle to still get a turn of the pool or so per 24hrs, is the current speed what you need.

Are the bubblers on always except in spa mode?? Can they be turned off with a valve
Are there other returns in the pool?
Are the spa jets returning water in pool mode or is there a pool return in the spa?
Is there a pool sweep? Which?
Is there an automation system? Which?

You have 4 presets available. I think the question to ask is what speeds should each preset be for each of the functions you want.


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RE: Reasons for low pressure/low flow?

Poolguynj,

Thanks for the assistance... some answers:

We have a concrete pool w/ pebblesheen, roughly 15k gallons with a raised spa (12") with a stacked stone spillway. There are two bubblers on the sunshelf, two skimmers in the pool and two bottom drains each in the spa and pool.

There is just enough spilling over the spa when I set it to 2250.

I am not 100% clear on the terminology to be honest - there are 6 or so eyes in the pool and 6 jets in the spa. the jets in the spa operate at a slow rate when the pool is in normal mode (i.e. the spa jets appear to be returning water to the spa from the equipment).

The filter is a Pentair cartridge, not sure what size - four filters inside, each about 30 inches tall.

We have a Polaris 280 cleaner.

We have an EasyTouch 4 with wireless remote.

I have no clue how much water is being cycled per day at the moment - it's on for 6 hours at the moment although I expect to push that up as it warms up.

UKMatt


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RE: Reasons for low pressure/low flow?

Can the bubblers be turned off? We could then expect more flow to the pool returns and spa jets. Then we can slow the pump some to save energy. Then slowly decrease the pool returns which will send still ore return to the spa for efficient spill action. It'll probably spill faster than you want. THen we can slow the pump some more, down to about 30 gallons a minute to allow the chlorinator and heater to function with a 5 gpm allowance for the cartridges to get dirty. The slower the pump runs, the more cost effective it is, even when we extend the system's run time.

At 30 GPM (Guessing about 1100 rpm) you'll run the system for for about 8.5 hours for a complete turn of the pool water.

Do you have the IC20 or IC40 cell?

Can you post a picture of your equipment pad? That can help as a picture is worth a thousand words.


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RE: Reasons for low pressure/low flow?

UK-

Agree with the other posters here.....decrease the speed on your 4x160 to start saving energy, which is probably why you bought the 4x160 to begin with.

With the size of your pool, I would recommend at a minimum, decreasing it's speed to less than 1,725 rpm. Any speeds higher than 1,725 rpm will be using more energy than a plain 'ole 2 speed pump operating at low speed.

Decrease the 4x160 speed so you can start earning a return on your investment.....this may be one of the few things these days that can guarantee a return! Of course this return will depend on your utility rate and hours of run time each day.

PSI is important for indicating the healthiness of your filter pump circuit. At constant pump speed, when closely monitored day to day, it can tell you when something has changed in your system and needs attention...such as a dirty filter, air in the filter, new pressure gauge needed, etc.

Hope this helps!


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RE: Reasons for low pressure/low flow?

If it's possible, if the cell is only needed 4 hours a day at 30 GPM, we can slow the pump down after that, spill way permitting.

Trhought. The motor in the 4x160 is a lot more efficient at all speeds. that because the motor is a 3phase motor. Even though it's connected to a standard 220VAC. One of the functions of the drive unit attached is to convert that to a 3 phase current source.

2 Speed pumps are single phased. That makes them only 50% compared with the 4x160 90% plus. Less wasted heat and less current draw. If the motor had a drive that allowed a true 3 Phase power source, the motor is rated to 8 BHP. The drive on the 4x160 won't allow more than 3 BHP. We don't want to push it to that level but you never know when you might need 130 GPM.


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RE: Reasons for low pressure/low flow?

/me whistles and sits off to the side on this one.


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RE: Reasons for low pressure/low flow?

/me assigns Racket the task of setting umatt's valves so we can slow the pump down.

/me updates .profile to reflect he ca give a builder orders and not get fired.

heh


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RE: Reasons for low pressure/low flow?

good one racket!

poolguynj - sorry, didn't mean to confuse the uninitiated. This topic has been hashed out in lots of detail on this forum in the past. There is some good stuff related to this topic if you search for it. Pentair has posted some real world field test data taken over a few weeks time comparing variable speed to 2 speed technologies. The differences are not as great as you suggest and depend largely on the speeds the pumps are used and the length of time at each speed.

Didn't mean to hijack....just thought that UK should know the biggest contributor to power consumption with pool pumps is pump speed. Keep the speed low and the power consumption is reduced exponentially regardless of pump technology.

This is so important but yet I see variable speed owners on this forum who are running their pumps at higher speeds thinking they are saving money because it's a variable speed pump....not entirely true. The true savings come with low pump speed operation which can be achieved with a variable speed or a 2 speed. Obviously the variable speed has more flexibility than the 2 speed. Take advantage of the variable speed and keep the speeds lower than 1725 rpm whenever possible. This is where the variable speed pumps really have an advantage over 2 speeds. The 2 speeds cannot be designed to go much lower than 1725 rpm without efficiency falling off sharply as you suggested.

By the way, I work for a major US company that manufactures variable speed motors and drives as well as standard technology PSC motors with multi-speed capability. I sell these components to the HVAC industry and work with their engineers daily to help meet their performance and efficiency needs.

Hope this helps.


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RE: Reasons for low pressure/low flow?

Hi,

Thanks to all for the continuing advice - it is appreciated.

I played around a bit today and found the valve that controls the flow to the bubblers. I turned them off for the time being as we don't need them at the moment.

I haven't managed to take a photo yet but I can see four manual valves and two automatic valves. Three of the manual valves are close to the automatic valve that is close to the pump. They control flow from the two skimmers and (I assume) the main drains in the pool. The other two valves (one manual and one automatic) are over near the Intellichlor. The manual valve there operates the bubblers.

I am not sure what the automatic valves do - I know one of the two controls the pool/spa return flow so that in spa mode it doesn't spill over and simply heats the spa water in place. The other???

I played around with the pump speeds too - 1700 is a little too slow to push water over the spillway evenly. We always thought the spillway was a little tiny bit higher on one side and this confirms it.

I would have the pool builder come and fix that but did I mention he ran with our money? :-:

I guess if we could direct more of the water to the spa rather than the pool we could run the pump slower but I have no clue what determines that split.

UKMatt


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RE: Reasons for low pressure/low flow?

EDIT: I realize now that both automated valves are used to change from pool mode to spa mode.

Doh! One each for water from and water to the pool/spa.

Sorry for being dumb!

UKMatt


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