Is it worth switching out my single speed pump for variable

[bk406]

Sounds like a bunch of engineers. My neighbor is one. Overthinks EVERYTHING!
Great discussion, but over kill I would think. Jason's one to one works. Even if you figured all of it out ot the last decimal place, it would still take a long time to recoup the money.

 

[polyvue]

Perhaps some of this discussion would best be moved to the Deep End, but it's hardly overkill to be interested in identifying the right parameters so one can come to a correct conclusion. That way one doesn't have to be at the mercy of sales literature that boasts pay-back times of a few months for their new "gamma-ray powered variable-supersonic-warp drive." Don't laugh -- this is how some of the specs thrown off by these companies sound to us electrical neophytes.

Usage matters, too. Is there a difference between suggesting a 10 year vs. 20 year pay-back (re: BrentR's pump)?

 

[mas985]

Sounds like a bunch of engineers. My neighbor is one. Overthinks EVERYTHING!

Or perhaps everyone else underthinks everything. :lol:

Anyway the easiest way to do this type of comparison is to use the CEC data (Curve A) for each pump.

The Super Pump efficiency is 2.56 gallons / Watt-hr. So for a 18k pool, that is 7 kwh per turnover.

The Intelliflo at 1000 RPM is 10 gallons / Watt-hr or 1.8 kwh per turnover.

That is a difference of 5.2 kwh per turnover. At $0.10/kwh, that is $0.52 saved per turnover. 30 turnovers in a month, that is about $15 saved per month.

The best two speed (Whisperflo WFDS-24) is close to 6 gallons / Watt-hr or 3 kwh per turnover but still saving 4 kwh per turnover and $12/month.

So the Intelliflo saves only $3 more a month than a two speed. Assuming there is a cost difference of $1000 between the two pumps, it would take 333 months (28 years) of operation to make up the difference in the cost of the pumps.

So I would say, no it is not worth.

 

[polyvue]

Anyway the easiest way to do this type of comparison is to use the CEC data (Curve A) for each pump.

I'll bite. What is CEC data? When I google it, I get:

CEC DataCEC Data is a full service IT support company. We handle onsite home technical support, on site programming, on site business networking and technical ...
http://www.cecdata.com/ - Cached

DASYLab: Icon-based data acquisition, graphics, control, and ...The updated Diagram display module supports multiple y-axes, and outstanding interactive versatility with time-domain data. New Reference Curve Editor for ...
http://www.mccdaq.com/dasylab.aspx - Cached - Similar

INVERTER PERFORMANCE CERTIFICATION: RESULTS FROM THE SANDIA TEST ...by C Whitaker - 2006
reported data points regardless of resulting shape of the overall inverter curve. CONCLUSIONS. The Sandia Inverter Test Protocol and the CEC ...

ieeexplore.ieee.org/iel5/4059527/4059868/04060116.pdf

 

[PaulR]

Anyway the easiest way to do this type of comparison is to use the CEC data (Curve A) for each pump.

I'll bite. What is CEC data?

If you follow the "Pool Pump Efficiency Data" link in Mark's sig, you'll find it's the California Energy Commision. See his link for details. (Mine isn't listed, hmph.)
--paulr

 

[polyvue]

Thanks, Paul. It seems, however, that neither Mark nor other posters felt this data to be very reliable, so don't know if it's worthwhile to try to interpolate these for a particular pump.... back to where we started from.

One disturbing point on this data is that some of the test points do not lie on the published head curves which could mean that either the test data is inaccurate or the published head curves are inaccurate.

 

[mas985]

polyvue,

My primary objection with the data was that the GPM values seem to rounded so they didn't fall exactly on the published head curves. However the gallons per watt-hour metrics seem to be reasonable for each pump's HP and/or RPM values. There a few measurements where I would have expected different results and it would have been nice to have more RPM values for the variable speed pump but stiill, think it is reasonable to use the data to compare pump's.

The CEC is suppose to be publishing a thrid curve (Curve-C) shortly which is a bit more reasonable for a well designed plumbing system. This is the curve that I would use for most pools but even Curve-A is applicable to the older style pools with 1 1/2" plumbing. However, even using Curve-A will help someone make a decision on which pump to go with since all the pumps are compared with the same plumbing curve.

 

[Ohm_Boy]

I'm pretty sure that none of these calculations take into consideration the minute manufacturing differences in the actual geometry of the impellers from one production piece to another...

<ducking and running now>

 

[mas985]

I'm pretty sure that none of these calculations take into consideration the minute manufacturing differences in the actual geometry of the impellers from one production piece to another...

<ducking and running now>

True, but I doubt that the impact is that significant. Injection modling should yield parts less than 8 thousandths of inch in tolerance. For a 4.8" impeller (1 HP), that is only 0.2% change in GPM and 0.6% change in watts.

Plus, in order to capture those effects, every pump would need to be measured which is not very practical.

 

[Ohm_Boy]

..I doubt that the impact is that significant

I think that this has been the point of most of the "rule of thumb" vs. "scientifically precise" debate transpiring hence. My response was, as you obviously realize, tongue-in-cheek (read: Smarta$$).

Besides, 0.6% of a 5.2 kwh savings calculation (pulled from a previous example) could mean some 31-ish watts per hour, and in just over three hours would amount to an entire killowatt, which would account for anywhere from 11 to 31 cents, depending upon the electric rate! In a single day, that alone could feed a hungry child in an emerging nation...

 

[bk406]

Besides, 0.6% of a 5.2 kwh savings calculation (pulled from a previous example) could mean some 31-ish watts per hour, and in just over three hours would amount to an entire killowatt, which would account for anywhere from 11 to 31 cents, depending upon the electric rate! In a single day, that alone could feed a hungry child in an emerging nation...

 

[larryb]

Hello:

A few years ago I replaced my single speed pump with a multi. I had to buy a new pump anyway, and the difference in cost was minimal. The multi-speed was a great investment. Here are my actual measurements:

flow high 41 gpm
flow low 19 gpm

kw high 1.30
kw low 0.26

So I get half the flow for 20% of the power. In my case I went from running the pump 4 hours / day to 24 hours / day at the same cost, but the pool stays much cleaner with the additional filtering.

Larry