Variable Speed Pumps Maximum Speed.

[JamesW]

Variable speed pumps have a maximum speed of 3,450 RPM because the pumps are mostly just the same pumps as the original single speed pumps with a variable speed motor.

These pump designs are decades old and based on system designs that are no longer relevant.

The larger VS pumps can get up to about 90 to 100 feet of head loss, which is completely unnecessary for most system with a good design.

A well designed system should not have a total head loss of more than 50 to 60 feet at the highest flow.

In my opinion, the VS pumps really do not need to have speeds in excess of about 2,450 RPM for most applications.

This would allow the use of a bigger impeller for the same HP pump.

I would suggest that the pumps come in 3 models with maximum speeds of 1,725 RPM, 2,600 RPM and 3,450 RPM.

For example, a 3 HP pump with three models with three top speeds can come with a different impeller for each model and this will give 3 different head loss curves.

This will allow the pump to run slower for the same GPM.

This will allow people to choose which head loss curve best fits their system.

The 3,450 RPM will still be available for the people who want that, but it will give the people a choice to have a quieter pump if a lower top speed will work.

 

[JamesW]

For example a variable speed pump with a top speed of 2,070 RPM could use the same impeller as the Intelliflo VS pump, which is a 3.95 total HP pump and it requires 16 amps or 3,200 watts at full speed.

However, a variable speed pump with a top speed of 2,070 RPM and the same impeller would require a motor with only about a maximum of 920 watts of total power and 4 amps at 230 volts and full speed.

For a simple system with a low head loss this would allow the pump to run at low speed.

If you had a motor with about 1,600 watts total power, you could install a bigger impeller than the one on an Intelliflo and this would allow even slower speeds.

Right now, people are getting an Intelliflo and running at lower speed, which works, but if you never need full speed, then you are buying a much bigger motor than necessary.

In many cases, you could use a motor with half the total HP available and just limit the speed such that it does not exceed to power available.

 

[Texas Splash]

Very interesting.

 

[Toxophilite]

Great idea, but I would imagine inventory costs would dictate over the benefits to pool owners.

 

[JamesW]

Great idea, but I would imagine inventory costs would dictate over the benefits to pool owners.

In my opinion, the pumps would be a better value and they should sell significantly more, which would take market share from the competition.

The biggest hurdle is getting the builders, service people and customers to understand the value.

Pumps are currently sold based on idiotic nonsense like WEF, which has to be the stupidest and most useless metric ever invented.

Even if they sold only two models, a 2,400 to 2,600 RPM model and a 3,450 RPM model, it would be a huge improvement.

They only need to make enough of each based on projected sales.

 

[Toxophilite]

In my opinion, the pumps would be a better value and they should sell significantly more, which would take market share from the competition.

The biggest hurdle is getting the builders, service people and customers to understand the value.

Pumps are currently sold based on idiotic nonsense like WEF, which has to be the stupidest and most useless metric ever invented.

Even if they sold only two models, a 2,400 to 2,600 RPM model and a 3,450 RPM model, it would be a huge improvement.

They only need to make enough of each based on projected sales.

Agree! You were probably around at the time, but what really moved the use of variable speed pumps to what it is now? Was it demand or regulation? Was wondering if consumers were really that interested in energy savings on their pools, other than the few that understood the difference enough to ask their PB's for VS.

 

[Newdude]

Was wondering if consumers were really that interested in energy savings on their pools, other than the few that understood the difference enough to ask their PB's for VS.

I was concerned in 2012 on my first pool. I'd heard dozens of echos from friends that their pools cost $100 in electric a month to run. If they weren't complaining about the always swamps, they were complaining about the energy cost. PB brought me down to the showroom and I saw a running intelliflo on display and the readout on the screen removed that concern.

For the 2nd pool the new intelliflo was in my garage before I even had a PB.

 

[JamesW]

What really moved the use of variable speed pumps to what it is now? Was it demand or regulation?

Mostly regulation.

Most builders and homeowners had no idea that they were using about 5 to 10 times more energy than necessary.

Builders mostly didn't care because it did not cost them anything whether they installed a 3/4 hp pump or a 3 hp pump.

The whole pump sizing situation was ridiculous and based mostly on builders buying whatever felt right with zero knowledge about efficiency.

The mentality was just throw on a big pump with 1.65 to 2.2 total HP with no reason for the choice other than it seemed right.

Customers mostly trusted builders to know how to size a pump and they assumed that if the builder installed a specific pump, then there must be a good reason and that is what they must need.

Without regulation almost certainly nothing would have changed.

The same is true about suction safety.

Until VGB regulation, most pool builders and operators had no clue about how dangerous suction could be.

Kids would sit on main drains and literally get their guts ripped out or get stuck on the main drain and drown.

 

[Toxophilite]

I was concerned in 2012 on my first pool. I'd heard dozens of echos from friends that their pools cost $100 in electric a month to run. If they weren't complaining about the always swamps, they were complaining about the energy cost. PB brought me down to the showroom and I saw a running intelliflo on display and the readout on the screen removed that concern.

For the 2nd pool the new intelliflo was in my garage before I even had a PB.

I will firmly admit that when we bought this pool, it was my wife mostly who dealt with the PB, and I didn't think about these things and on silent revolt. Not that it's not my area of home improvement, but I wasn't that hip on having the pool at the time. Thought it was just going to cost to run what it did 20 years ago, a lot. But, I never once remember the PB discussing pump efficiency with me when discussing equipment. A VS pump basically fell in my lap because that's all they use, and I was happily surprised and move to next line item.

 

[Newdude]

I wasn't that hip on having the pool at the time. Thought it was just going to cost to run what it did 20 years ago, a lot.

I was dead set against the pool and had a list of complaints. The SWG satisfied my expensive/PITA chemical complaint.

But, I never once remember the PB discussing pump efficiency with me when discussing equipment. A VS pump basically fell in my lap because that's all they use, and I was happily surprised and move to next line item.

Sometimes profit margin works in our favor if the PB made the most money on the pump with all the bells and whistles. Mine knew about the power savings and they had a display pumping (tank water?) to show it off. There's probably an even mix these days of PBs 'stuck in their ways' and those who appreciate the benefits of the VS pumps.

We have seen plenty of builds where it appeared that the PB was unloading old equipment, so that can be a thing sometimes too, even if the PB knows better.

 

[Toxophilite]

Mostly regulation.

Most builders and homeowners had no idea that they were using about 5 to 10 times more energy than necessary.

Builders mostly didn't care because it did not cost them anything whether they installed a 3/4 hp pump or a 3 hp pump.

The whole pump sizing situation was ridiculous and based mostly on builders buying whatever felt right with zero knowledge about efficiency.

The mentality was just throw on a big pump with 1.65 to 2.2 total HP with no reason for the choice other than it seemed right.

Customers mostly trusted builders to know how to size a pump and they assumed that if the builder installed a specific pump, then there must be a good reason and that is what they must need.

Without regulation almost certainly nothing would have changed.

The same is true about suction safety.

Until VGB regulation, most pool builders and operators had no clue about how dangerous suction could be.

Kids would sit on main drains and literally get their guts ripped out or get stuck on the main drain and drown.

Agree! I think PB's are in a role not unlike the mortgage business. The consumer is more shopping what the payment is going to be over what is in their best interest. They want the house, will take hit that it might not be the best deal and cost more in the end, but that payment is going to dictate a yes or no if can happen today. So, sell them a nice rendition of a nice pool and the rest will just fall in place.

 

[JoyfulNoise]

Excellent write up as always James.

My IntelliFlo has had the “MAX SPEED” setting at 3000RPM since about Day 1 10 years ago. I have NEVER needed to run my pump at full speed ever. I would definitely see benefit in my pool with a impeller change to trade off more flow for less energy.

With suction cleaners, they often need higher flow rates to operate well. Being able to achieve that without simply just upping the RPMs (and eating up more electrical energy) would be a big benefit. Also water features could use VSPs that can pump more volume at fewer RPMs since many people want their waterfalls and sheers running a lot but hate the extra money it costs to do it. One reason my waterfall runs sparingly is because it’s attached to a 1.5HP single speed WhisperFlo which is a giant energy hog. I don’t like running it because I can see it on my electric bill when it gets used a lot.

 

[ajw22]

Engineering, Marketing, Manufacturing, and Finance all have different objectives.

Engineering proposes to design a low RPM high flow economy value pump.

Marketing asks for the specifications to be as high as possible as bigger is better and they can charge more for higher numbers. Customers always want the biggest stuff. This is America.

Manufacturing wants to know if there is any cost difference in producing a low RPM motor versus a 3450 RPM motor. If not then the price will be the same so where is the value?

And finance wants to know how many will we sell at what profit margin. Which will deliver the most profits?

Many engineering ideas do not make it to market leading to frustrated engineers muttering under their breath about management.

 

[JamesW]

Going to a bigger impeller moves more water at the same speed or the same GPM at a lower speed.

The actual energy savings depend on system design, which still has many ways to improve.

So, it's really about creating a pump head curve that better fits the more efficient system designs, which does lower the total energy use, but the biggest benefits are slower speeds, which are quieter and the ability to use a smaller, less expensive motor without needing to ramp up to high speed to get the same flow.

One big improvement would be to improve heater designs for better hydraulic efficiency, which are pretty bad.

1) Go to a one pass design, which actually improves thermal efficiency contrary to popular belief that more passes is more efficient.

2) Get rid of the thermal regulator and use an automatic bypass like the new MasterTemp that opens the line to the heater on call for heat, which eliminates the need for a restrictive thermal regulator.

3) Limit the flow through the heater to the lowest necessary as shown in the manual, which is 40 GPM for a 400,000 btu/hr heater.

4) Add a flow switch to every heater that can be read by the automation so that the heater does not fire with insufficient flow and the automation can increase the pump speed until the flow switch is closed and then add some speed for margin.

5) Add a heater outlet temperature probe to check temperature rise, which also verifies flow.

6) Use a differential pressure switch that measures the difference between the inlet and outlet pressure, which also verifies flow.

 

[mas985]

Background: Maximum head in a pump is determined by the impeller diameter while maximum flow rate is determined by both impeller diameter and vane width. To increase the flow rate at a given RPM, you can either increase the diameter which also increases maximum head or increase vane width which leaves maximum head the same or do both. Also, the flow rate of an impeller is directly proportional to the impeller diameter so much like changing RPM, one can reduce the diameter of an impeller and get a proportional change in flow rate. The water distribution industry routinely does this to match a wet end to a particular application. This is far cheaper than having an extremely large pump line to match every application. The pool industry took a different approach with multiple sized pumps in a given pump line but this was likely driven by PB demand more than anything else because they are not interested in trimming impellers. Of course VS pumps have changed this approach as well offering a pump design that fits many different applications which benefits both the manufacture as well as the consumer with lower costs.

@JamesW, correct me if I am wrong but I think what you are suggesting is a quasi VS waterfall pump design. For waterfall applications, this could be desirable for adjustment in the look of the waterfall but it comes at a cost.

For other applications;

Doubling the diameter of the impeller and halving the RPM would result in the same flow rate as with the existing impeller. However, the volute would need to double in diameter which would make the pump much much larger and installation would likely quite difficult. Plus, increasing the impeller diameter reduces efficiency because friction losses within the impeller increase.

A better solution is to increase the vane width. This has slightly better efficiency but the volute would likely require redesign since most large VS pump impeller already max out the volume in the volute. The redesign is less impactful for installation in this case but it would still require new injection molding and thus more NRE to recover. If the new design captures more market share, it might be worth it. However, if it simply replaces the other pumps in a manufacture's inventory, there is really no benefit from a business perspective. But all this assumes there will be demand for such a product which I am not convinced of. The only real benefit to the end consumer is a quieter pump and small increase in efficiency but a higher cost so it might end up as a niche product.

 

[JamesW]

Manufacturing wants to know if there is any cost difference in producing a low RPM motor versus a 3,450 RPM motor.

The difference is just the software in the drive.

So, no cost to change the top RPM.

 

[ajw22]

The difference is just the software in the drive.

So, no cost to change the top RPM.

So what is the difference in the sales price of the lower speed pump versus higher speed pump?

 

[JamesW]

For example, you could put the smaller 1.65 hp variable speed motor on the Intelliflo or the IntelliFloXF as long as you limit the top speed (or amps) of the motor such that you don't overload the motor.

For someone who runs only low speeds, this would create a less expensive pump.

For example someone with an IntelliFlo that never exceeds 2,000 RPM can use the Intelliflo with the smaller motor.

Many people use an IntelliFlo or IntelliFloXF for fountains, shears, infinity edges, spa jets etc.

If they need to use full speed to get enough flow, it would be better to use a larger impeller and a lower RPM because it is a quieter pump and it should be more efficient or give better flow because the head curve will be lower and flatter.

 

[JamesW]

So what is the difference in the sales price of the lower speed pump versus higher speed pump?

If you can use a smaller motor, the pump will cost less.

Many people have the IntelliFlo even though they never intend to run it at full speed.

If you are never going to run at more than 500 watts, then the bigger 3,200 watt motor is just a wasted expense.

 

[ajw22]

If you can use a smaller motor, the pump will cost less.

Many people have the IntelliFlo even though they never intend to run it at full speed.

If you are never going to run at more than 500 watts, then the bigger 3,200 watt motor is just a wasted expense.

OK Engineering, now it is not simply a software change.

Manufacturing will check the supply chain on manufacturing costs as soon as marketing provides the numbers they can sell.