Reducing electricity use with pump mods

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blackPlaster

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Jun 15, 2011
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Hello,
I have a sta rite wet end (from the 70s?). I believe 1hp impleller (not sure. i have not removed the impeller, I attached a picture and serial # on the shrout is C103-137P1)). The wet end was formerly (before i got the house) attached to a 1hp sf 1.65 a.o.smith (8A@230V). now attached to an a.o. smith 3/4hp sf 1.65 motor (7.3A@230V) model SQ 1072. Plumbing is 1.5inch from/to pool and 2inch from/to spa. Cartridge filter says 138GPM / 136sqft. No water features except 3 spa jets, no solar. The pump uses electricity at about 20cents/kWh. I currently run it for 6 hours a day. Vacuum power is plenty now and I feel a bit less would be fine.

I want to reduce electricity use, so I want more efficiency. I would not mind running the new pump setup almost continuously. I plan to install a SWG in the future and not sure how much minimum GPM these need. I'm contemplating several options.

0) drop the impeller HP to 3/4 or 1/2 $50
1) install a two speed a.o. smith ~$350
2) drop to a 1/2hp or 3/4 hp impeller and install a two speed a.o. smith ~400
3) the above with an efficient a.o. smith ~550
4) get a used whisperflow (about $100 here) and hook it up to a two speed. $450 to $ 650
5) intelliflow or another pump with $200 electical utility company rebate

Basically i'm wondering
- do i save electricity if i keep this motor and down-size the impeller? is there any reason why the result would be less _efficient_ at moving water? (i.e. I assume it would move less GPM, draw some less A and I could run for a little longer)
- if a recent whisperflow wet end would significantly enhance efficiency compared to sta rite from the 70s.
- is changing the impeller is all i need to modify the wet-end's HP (i.e. need to change housing?).

I've been quite impressed by some posts in this section. Some serious engineering is going on here. Still a lot to learn so I will appreciate your suggestions.
thanks
 

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Reducing the impeller will reduce your electric usage, but not by anywhere near as much as getting a two speed motor. The main thing is that the motor size (on high speed) needs to be at least as large as what the impeller is designed for.

If I am following correctly, your current motor is undersized for your impeller, which could be causing problems. The smaller motor also has smaller windings, so it has more internal resistance than the larger motor. It is also possible that it is lower efficiency, likely even, though there isn't enough info here for me to say for sure about that either way. Depending on how you are measuring power, it might be a misleading reading, rather than an actual difference. You shouldn't measure with an amp meter, and instead should use a power meter (watts).

The new variable speed pumps can save more electricity than a two speed, but they also cost much more. You get most of the potential savings from using a two speed, so variable speed pumps are only worth it if your electric rates are quite high. In most common situations, a variable speed is worth it if your electric rates are above $0.20/kwh. Rebates can also affect this.
 
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do i save electricity if i keep this motor and down-size the impeller? is there any reason why the result would be less _efficient_ at moving water? (i.e. I assume it would move less GPM, draw some less A and I could run for a little longer)
Click to expand...
Downsizing the impeller will produce less flow rate but because of that, the efficiency is better as meassured by gallons/watt-hr.


-if a recent whisperflow wet end would significantly enhance efficiency compared to sta rite from the 70s.
Click to expand...
It might be a little better but probably not enough to justify the cost. Most of the efficiency of a pump is determined by the size of the pump.


- is changing the impeller is all i need to modify the wet-end's HP (i.e. need to change housing?).
Click to expand...
You may need to change out the diffusor as well. The manual should tell you what is needed for the different sized pumps.


- why is the new motor (3/4 hp) capable of drawing 7.3A while while the old 1HP with same SF was capable of drawing 6A? Does it mean the new motor is of lower efficiency?
Click to expand...
A typical full rated 1 HP should have a much higher rating than 6 amps. Are you positive that the old motor was not uprated?
 
I took the pump apart and discovered
1) a broken diffuser around 2/3 of the perimeter. part#C1-200PA
2) impeller is C105-137P EB

I am a bit confused because the dura-glas manual (http://www.staritepool.com/pdfs/DuraGlasOM.pdf) says this impeller/diffuser are found on 1HP as well as 1.5HP pumps. Most places list it as a 1HP impeller however.

Here is a theory to explain why my electricity usage went up a lot the past two months (in proportion more than the additional run time): Broken diffuser made the water go circles: diffuser, impeller, diffuser, etc. I read somewhere here (I think it was mas985 about someone who had too much water flow) that the motor uses most energy when working least hard. Maybe that explains the high consumption. I did notice reduced water flow.

In spring i had taken the pump apart to change seals and the diffuser was not broken. I guess it could not take the load under normal suction without intake air leak. This pump is old. I wonder what is next.

Thanks for the replies.
JasonLion, the voltage/amps I provided are read on the label. They are not actual measurements. I assume the actual power used is somewhere south of that. I am not geared to measure gallons/hour and kW/h (other than reading the meter periodically) .

I noticed that both JasonLion and Mark use 1/2 HP pumps and have ~20k gallon pools. Seeing experts use what I would have considered too small pumps got me thinking... Do you have two-speed motors on the 1/2hp pumps?

My current plan is to buy a 1HP two speed motor, since it does not hurt to couple it to either 1/2hp, 3/4 hp or 1hp impeller and hardly costs more than lower HP. More reading to decide between basic two speed and efficient two speed (like a.o. smith 2green) is needed.

thanks for this fantastic site
 
Planning to pick up this used 2-speed motor. Came off a no-name SPA pump. Shaft is threaded. Seller says 4 hp. Any reason why it would not attach to a starite wetend?
I had no idea GE makes pool motors. But after all what do they not make?
thanks
 

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blackPlaster said:
Here is a theory to explain why my electricity usage went up a lot the past two months (in proportion more than the additional run time): Broken diffuser made the water go circles: diffuser, impeller, diffuser, etc. I read somewhere here (I think it was mas985 about someone who had too much water flow) that the motor uses most energy when working least hard. Maybe that explains the high consumption. I did notice reduced water flow.
Click to expand...
It is a missconception that pumps under high head loss/pressure "works harder". A pump "works harder" and uses the most energy when it is moving the most water which is on the right side of the head curve. Also, the most efficient part of the head curve is on the right side.


I noticed that both JasonLion and Mark use 1/2 HP pumps and have ~20k gallon pools. Seeing experts use what I would have considered too small pumps got me thinking... Do you have two-speed motors on the 1/2hp pumps?
Click to expand...
Mine is a two speed, but you won't find a 1/2 HP two speeds. You have to make it like I did. It turns out that the Northstar 1/2 HP impeller has the same head curve as the SuperPump uprated 1 HP impeller so they both have the same head curve. I put a SuperPump two speed motor on my Northstar pump and also downsized the impeller to a 1/2 HP. So the performance and energy use is not much different than the SuperPump. Label HP doesn't mean all that much. It is the head curve that primarily determines energy use and pumping efficiency.
 

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mas985 said:
blackPlaster said:
Here is a theory to explain why my electricity usage went up a lot the past two months (in proportion more than the additional run time): Broken diffuser made the water go circles: diffuser, impeller, diffuser, etc. I read somewhere here (I think it was mas985 about someone who had too much water flow) that the motor uses most energy when working least hard. Maybe that explains the high consumption. I did notice reduced water flow.
Click to expand...
It is a missconception that pumps under high head loss/pressure "works harder". A pump "works harder" and uses the most energy when it is moving the most water which is on the right side of the head curve. Also, the most efficient part of the head curve is on the right side.
Click to expand...
I have a smart meter which let me confirm the above :
With the broken diffuser, the average house consumption while pump runs at night is 1.93kWh. With the repaired diffuser, it fell by 65.9W.

I also noticed that while the air vents in the fridge were iced, my fridge was using an extra 127W.

I should have my B2982 motor up and running shortly. Looking forward to test its actual gains.
 
blackPlaster said:
I have a smart meter which let me confirm the above :
With the broken diffuser, the average house consumption while pump runs at night is 1.93kWh. With the repaired diffuser, it fell by 65.9W.
Click to expand...
My statements were based upon a properly working impeller. There is no question that a broken diffusor can put a higher load on a motor. But not because it is moving more water or has higher pressure but because the friction losses are higher.
 
Time to report on pump efficiency. Input is 1h total power consumption, provided by the smart meter, at night while pump runs. The rest of the house also runs, so actual pump power drain of the pool motor is lesser, but the difference is a good approximation of the gain between motors.
The wet end is a 1HP sta-rite. The filter was not cleaned in between, as much as I can tell all other conditions are equal.

With A.O. smith SQ 1072 (3/4 hp SF 1.65, 48Y frame single speed) average power used: 1841W (averaged over 11 1-hour samples)
With A.O. smith B2982 (1hp SF 1.65 56Y frame) on high speed, average power used : 1627W (averaged over 12 1-hour samples)
difference: 21.4%
With A.O. Smith B2982 on low speed, average power used: 397W (averaged over 31 1-hour samples).

I have taken some measurements without the pump and estimate that the house uses about 150W at night (mostly fridge). So on low speed, the pump actually uses ~250W.
5.5h at high speed used to take 9.3 kWh (SQ1072)
5.5h at high speed now takes 8.1 kWh ( B2982)
Assuming that on low speed it pumps half the volume, I need to run the pump double the time.
11h at low speed now takes 2.7 kWh ( B2982 )

gain 66%

A.O. smith New Centurion's claim of energy efficient is verified in the field. Very pleasant! If this motor was only a single speed, it would save already $12/month.

Bye bye electric tier rates 3 and 4 :whoot:
 
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