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Old 08-02-14, 11:03 PM   #11
gtojohn
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Single speed pumps are more efficient in terms of service factor and windings. 2nd speed is kind of an additional thought in their design, thus the windings are less than optimal. However the savings is in resistance to flow and head pressure. 2 speed give us the option of a high speed for running things like spa jets and pool cleaners vs just under sizing the equipment. The ao smith centurion 2 speed series has better service factor on their low speed vs traditional 2 speed. Running a larger filter can dramaticly reduce head pressure. I started with a 84 sqin hayward cartridge with 10-20 psi head. I swapped over to a clearways 320 sqin cartridge and run 3 psi on less than clean filters. The main difference is the jets are twice as powerful and the skimmers have eddys in them while the suction cleaner still has enough gusto to scoot around all for 3/4 hp.
I actually did an energy audit last week, our houses were quite similar in size, pools the same size. his pump 1 1/2 hp timed 10 hrs a day, his hvacs were twice the size of mine and dirty. House was modern construction, decent windows and insulation, his electric bill was $900 last month! For so many people it takes a giant bill to consider if they might be wasting power.

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Old 08-03-14, 10:48 AM   #12
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Don't confuse service factor with efficiency. 2 speed pumps deliver less HP per watt on low speed. Pump laws dictate that double the flow requires a CUBE in HP. The optimum solution would be to have and ECM or 2 seperate pumps. ECM's have a HUGE reduction in power when GPM is reduced, since they aren't based on simply increasing the "slip" of the motor. Same with 2 pumps, the smaller pump only uses a fraction of what the "cleaning pump" would use. It's just a matter of weighing energy costs vs. upfront motor costs.

Another option is switch to time of use power rates if your utility offers it. Run pumps when power costs less. No upfront equipment costs !!
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Old 08-03-14, 02:32 PM   #13
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Although the low speed isn't as efficient in watts per rpm the real gains are in lack of resistance to flow. 1/2 the rpm and flow but 1/4 the power usage. variable speed ecm motors are great but super pricey. Depending on what you pay for power the payback could be way out vs a cheap 2 speed. Though 2 speeds aren't necessarily perfect I'd rather make my money back sooner in case of failure.
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Old 08-03-14, 08:26 PM   #14
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1/4 the HP requirement is very different than 1/4 the power use. Measure the power you will find 1/4 HP requirement requires 3/4 of the wattage of a single speed motor of the same HP. 1HP = 746W, a real world single speed PSC motor will use about 900W at full load. A 2 speed motor will use 950W on high (1HP), 650W on low (1/3HP). ECM will use 850W on high, 275W on low. It's best to measure your actual motor on both speeds since load vs. rated HP varies considerably.
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Old 08-03-14, 09:27 PM   #15
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What about use a VFD?



A centrifugal pump is very similar to a fan as far as load characteristics go. (In fact, you could say that a centrifugal fan is a centrifugal pump for air!) Thus there shouldn't be any difficulty with starting, unlike a compressor load that calls for high starting torque.
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Last edited by Daox; 08-07-14 at 10:13 AM..
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Old 08-03-14, 10:01 PM   #16
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VFD is excellent IF used with a compatible motor. Some motors are happier with VFD than others. All an ECM is a 3 phase motor with a VFD...
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Old 08-07-14, 09:32 AM   #17
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Quote:
Originally Posted by Servicetech View Post
Multispeed PSC motors don't save as much money on "low" and buyign a smaller single speed pump. Currently running a 1/4HP pump on my own pool (uses 250W) for (2) 4hr shifts per day.
The motor the thread starter is talking about doesn't change the speed the same way as low/med/hi tapped PSC HVAC fans or shaded pole table top fan motors.

This motor's the real deal true sped with 2 pole/4 pole windings with industrial motor standard rating. A well made AC motor is quite efficient. The motor runs at constant RPM for each setting.

I'm looking in the catalog and I see these specs. You might find them to be strange specs, but fan law will tell you that cutting the fan to 1/2 the speed drops the GPH to 1/2 and (1/2)^3 =1/8 the horsepower requirements, hence 1:8 split.

0.75hp/3450RPM 230v 6.0A@1.67 SF
0.10hp/1725RPM 230v 1.0A @1.67 SF

Those amps are at maximum allowed overload conditions.

I guessed the PF, but I did it so on the conservative side. These motors are heavy and use copper generously, so they're not cheap.

1/6hp @ ~67% (PF at 0.9)
1 1/4 hp @ ~75% (PF at 0.9)
These are plug-to-shaft efficiencies. Not bad for something this size. It's at the 67% overload given in the specs, and they're more efficient when they're not overloaded, so you'll probably get closer to 80% to the shaft.

AC motors are very reliable, tough and they don't create harmonics. Adding a VFD will just make it much more susceptible to surge damage, reduce efficiency and induce high levels of harmonics into the line. You don't need controlled ramp or a bunch of in between speeds for a pool pump. You'll lose another 10% or so of kW going into it in conversion process in the VFD box.

Why the over load rating on motors? It's so you can size it for continuous use at 3/4hp, but have the ability to handle increased load from cleaning attachments and such without the need to actually oversize the motor. It will handle an overload up to 67% for quite some time without issues.

If you run a 3/4 hp VFD with and you overload to 1 1/4 hp load for more than a few seconds, it will let the smoke out.

Attached picture shows you how a common air handler fan is made multi-speed.
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Old 08-07-14, 11:36 AM   #18
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Didn't realize these were real 2 speed motors. That changes everything.
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Old 08-07-14, 11:47 AM   #19
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I went from adding about $100 a month to my power bill for my pool to adding $2 a month.
we are at a fixed rate .10 KWH
Well worth to change out. I even was able to sell my old pool pump.
Speck Pumps - Badu EcoM3V - Variable Speed

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Old 08-07-14, 10:17 PM   #20
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Quote:
Originally Posted by pinballlooking View Post
I went from adding about $100 a month to my power bill for my pool to adding $2 a month.
Well worth to change out. I even was able to sell my old pool pump.
Here's an objective look. I looked up a few pumps and this is what I was able to dig out. I was wrong on the mechanical efficiency guess on the low speed, but the difference is still de minimis. Pick your game. The more expensive, delicate and fragile or good coil and core both save about 1kW by switching to low speed. The difference in savings between uber expensive electronic motor vs time proven highly reliable coil&core pump in power savings is

reduction of running kilowatts by 1.04 vs 0.97 vs 0.87.

ECM pros:
Savings are roughly 1kW from switching from 3450 to 1725.
Saves 1.04kW while a very good non-electronic circuitry motor saves only 0.97kW
The ultra-low mode that saves an additional 0.14kW by turning down to 1,000RPM.

ECM cons:
Module failure means factory OEM parts required, probably $$$$$.
Susceptible to sudden failure by blowing power electronics.

May have extremely high THD, particularly odd harmonics from 3rd to 11th which is overall detrimental to power transmission and swell "carbon footprint"

Straight motor pros:

1/4 to 1/2 the purchase price of ECM variable speed.
Resilience to power surge and overload.
Gradual failure.
Operates directly on line voltage. Does not require electronic control module to function.
Readily repaired controls with off the shelf components.
Do not produce harmonics that is unfavorable in terms of system wide energy savings.

Cons:
Only saves 0.97kW rather than 1.04kw compared to ECM, so the savings is 6.7% less.

Less bragging rights.

Real comparison on C curve impeller...
Badu Eco M3 V 1.0hp 1 SF
A buncha chips and power electronics in factory OEM only control module does all the speed change and starting.

1.24kW @ 3450 72 gpm
0.20kW @ 1725 38gpm
0.064kW @ 1000 21 gpm

1.0hp 1.0 SF coil and core. Capacitor run, capacitor start by mechanical relay. Relays and coils to change speeds. probably available off the shelf.
Hayward SP15922S
1.1kW @ 3450 64 gpm
0.23kW @ 1725 33 gpm

Hayward SP2607x102S
1hp 1.0 SF. PSC,
mechanical relay speed change. probably available off the shelf.
1.28kW @3450 68 gpm
0.31kW @1725 32 gpm


When we talk about savings, we should always talk in terms of electrical terms and how it is achieved. (kWh, demand reduction, demand shifting(time of use rate etc)

That very expensive Badu M3 V pump has proprietary power electronics stuff that is fragile against power surge, or accidental overload, such as lock-up. It's got some computer chips controlling it, so more than likely that's part of the single module that must be replaced as one unit.

Surges and accidental lock ups can lead to losing the smoke in drive module which can only be replaced with factory parts.

Dollars figures are not useful, because the utility account plans vary as much as cell phone plans depending on poco, rate schedule chosen by customer, customer type, etc. Greenwashing sales tactics that use dollars and cents are designed to produce best figure to close the sale, nothing else.

Let's see for example:

Allocating the kW savings to highest possible tier rate, and possibly reducing demand charge used by very few utilities on residential.

Compared:
Cheap inefficient single speed @ full speed, no timer.

The green touting super expensive pump:
Saving at highest tier rate + demand charge at lowest speed setting compared to above and possibly the time of use savings achieved by using standard feature electronic timer to do demand shifting.


Last edited by ICanHas; 08-07-14 at 10:32 PM..
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