Save electricity with a 2 speed pool pump

[ICanHas]

You failed to bring a surplus 2 speed pumps or something originating from freight damaged pool/spa equipment on the table for consideration. A VFD will likely cause line harmonics that maybe non conducive to the "eco" mission of the whole idea.

[NiHaoMike]

That's another option, assuming you manage to find one that fits your application. Even then, it can be helpful to get a VFD first so you can try different speeds and then decide what would be a good permanent solution. (After that, use the VFD for some other motor load, such as HVAC!)

[ICanHas]

do you have the LINE SIDE waveform capture and or the power factor and THD values for a ~1hp range VFD that you might find on the surplus market?

[NiHaoMike]

Those figures are almost completely irrelevant for residential use.

[gtojohn]

Variable speed motors do have some good applications in pools. Keep in mind pools are mostly a luxury item, a lot of pool owners have less concern with operating costs vs having the best. Your average person isn't going to see past the pool guy's sales pitch or knowlege. Laminer flow jets and deck jets can be adjusted more easily with a variable speed. If your spa runs from the same pump as your pool. Swim Lane and endless pool treadmills use huge variable speed motors, I think the Badu Swimjet has a 7hp drive. Some of the early ones used dc motors and battery packs. But I agree, the amount of electronics running these motors make them more likely to fail. I would rather buy the less expensive workhorse that hopefully will last forever. My 3/4 hp single speed is nearly 12 years old, paid maybe $130 for it.

[ICanHas]

Originally Posted by gtojohn

Variable speed motors do have some good applications in pools. Keep in mind pools are mostly a luxury item, a lot of pool owners have less concern with operating costs vs having the best.

Just like the hybrid $100,000 Lexus for feel goodism and personal satisfaction. It's not for money savings. Green washing is a technique used by sales producers with vested interest in selling the perception of self satisfaction rather even if the said activity have higher environmental impact than what it is intended to replace.

Your average person isn't going to see past the pool guy's sales pitch or knowlege.

Practically useless features to use for sales and marketing is what they're looking for and goddamn embedded systems for residential products is one such thing.

Things like vector drive (that some people like to call FOC have no practical essential use around the home.

Embedded systems power electronics are generally pointless in residential equipment. VSDs are very useful regardless of size when high degree of precision is needed for functional needs.

Laminer flow jets and deck jets can be adjusted more easily with a variable speed. If your spa runs from the same pump as your pool. Swim Lane and endless pool treadmills use huge variable speed motors, I think the Badu Swimjet has a 7hp drive. Some of the early ones used dc motors and battery packs. But I agree, the amount of electronics running these motors make them more likely to fail. I would rather buy the less expensive workhorse that hopefully will last forever. My 3/4 hp single speed is nearly 12 years old, paid maybe $130 for it.

One important thing to consider is that special considerations are added or removed as you scale things up or down. You can start a vacuum cleaner across the line many times an hour with no issues, but you can't start a 7,500 hp pump house motor the same way and the benefit of high failure rate associated with power electronics outweighs the demerit in this case.

Cost does not scale down either. You wouldn't get the capability and quality of a $250,000 7,500 hp motor drive controls for $33 on a 1hp vacuum even with China made crap.

Adding slow ramp up, acceleration control, infinite RPM control, etc for a vacuum cleaner by power electronics uber complicated solutions don't add up. Expensive canister vacuums with variable speed control uses light dimmer type control with brushed motor.

Cordless drills, electric trains or endless pools use VSD for controlling purposes.

The failure on that 3/4 hp will likely be mechanical like bearings or corrosion.
Motors are hard to kill without abuse. The running cost of having a 3/4hp motor going all the time is considerable, so the dual speed instantly creates some savings, an existence that complexication advocates wished it didn't exist.

[NiHaoMike]

What's wrong with getting a surplus VFD for the purpose of finding what speed steps are optimum?

You also seem to want PFC in residential applications yet object to the cost and reliability issues. In most residential applications, PFC just adds complexity for little benefit, pushing costs up and encouraging OEMs to cut corners even more.

Where a VFD almost makes too much sense is in a heat pump. During less cold weather, a heat pump properly sized for the more usual cold weather in the area will be way oversized unless a VFD is used to dial it down.

[ICanHas]

You also seem to want PFC in residential applications yet object to the cost and reliability issues. In most residential applications, PFC just adds complexity for little benefit, pushing costs up and encouraging OEMs to cut corners even more.

You complained new two speed pump is not as cheap as used fleabay VFD. Buying a VFD in addition to a used pump is MORE cost than buying just a used pump.

I disagree with your claim. As the number of dirty power loads increases as they go into more common use, the total demand distortion on power transmission equipment increases.

Take a look at Energy Star program requirements for LED lamps. Why do you suppose power factor requirements exist if it was pointless like you claim? Cheap VFDs that have rectifier + big caps combo front end are highly line polluting by having a high TDD which then increases the voltage THD for everyone served from that transformer.

A 2kVA 1hp VFD of the aforementioned cheap design will have a power factor of about 0.5 with a current THD of whopping 180% and depending on transformer's load level, the total demand distortion can be considerable. 2KVA demand is about 100 CFLs operating at one location.



Solution is to not buy China made stuff. Energy Star's quality as well as performance requirements(such as 3 year warranty minimum on LED lamps) designed to avoid minimize the corner cutting in predominantly China made junk.

[NiHaoMike]

The extra cost is well justified since the VFD can be used elsewhere, such as HVAC. Also, it allows you to get things perfect on the first go. For example, if the existing pump is a 1HP single speed, you might find that the speed settings that correspond to a two speed 3/4HP pump are enough. Then you can either swap the pump for a 2 speed 3/4HP or just keep using the existing pump on the VFD until the pump actually needs to be replaced.

Some new Dell servers have an option to disable PFC in the BIOS. Even in a commercial setting, there are places where the power factor improvement is not worth the loss in efficiency, even though new server PSUs are very efficient to begin with.

[ICanHas]

The extra cost is well justified since

Buying a new pump is justified if funds allow, but if not, buying a VFD is not justified.

Some new Dell servers have an option to disable PFC in the BIOS. Even in a commercial setting, there are places where the power factor improvement is not worth the loss in efficiency, even though new server PSUs are very efficient to begin with.

This is an "eco" forum. Where are you looking when you say "efficiency"? For someone with this line of thinking, what you said is correct! You're just indirectly calling power factor requirements bunk. As quantities of harmonic producing loads like CFLs and LEDs increase, the total demand distortion is increased and lowers efficiency.

You therefore, increase "carbon foot print" coefficient by lowering distribution efficiency in addition to wasting capacity of utility infrastructure. The 180% 0.5% 2kVA 1kW input VFDs do a great job of compounding onto this problem.