I'm trying to find the "list" of pumps that comply with Title 20. I'm reading all these articles that say the pump must be on "the list", but I cannot find this list.
Thanks!
Jennifer
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The energy consumption of a variable speed pump is not linear with speed nor with flow rate. So running a pump at half the flow rate but for twice as long to turnover the same amount of water takes less total energy (i.e. a lower electric bill). That's how a 2-speed or variable speed pump can save a lot of energy even if you run it longer in order to achieve the same number of turnovers per day.
However, as one gets to lower speeds and flow rates, this effect flattens out (becomes more linear). So if you truly want to compare different speeds or flow rates for their true cost, you should do so for their cost for one turnover of water. That is, don't look at just Watts which will always get lower at lower speed or flow rate, but look at kilowatt-hours which is that formula ratio of watts divided by flow rate that I gave in my post (the formula at the end of the post).
The net result is that at some point for variable speed/flow pumps, there is an RPM or GPM setting (for a given plumbing configuration) below which you don't get any more energy savings for the same number of turnovers. At that point, your choice is to use a speed/flow that runs the pump for the length of time you desire or that gives you a high enough flow rate for decent skimming action. It is almost always the case that the lowest 15 GPM setting on an IntelliFlo is not the only lowest energy setting if one is looking at turnovers. In my own pool, I can run at 26 GPM for a shorter time with the same total energy usage/cost.
David Penton said:
In this post, I list actual measurements from my IntelliFlo VF for my pool where you can see that if one looks at the energy (kWh) required for one turnover, that the pump flattens out at lower flow rates. The point where this starts to flatten out depends on the plumbing since my solar on situation has far longer pipe runs. With solar off, you can see that though 15 GPM clearly has the lowest power, it doesn't use less energy than 26 GPM or any flow rate in between since you need to run the pump longer at lower speeds for the same turnover rate. This effect may primarily be due to the fixed energy cost of the pump even with no flow rate. A rough energy formula for the pump based on IntelliFlo's published curves is the following:
Watts = (1310-80)*(RPM/3450)^3 + (300/20)*GPM*(RPM/3450)^2 + 80
This is an approximate formula and isn't as accurate at higher GPM especially with my measured data, but it gives the general characteristics of seeing a very large dependence on RPM (to the 2nd to 3rd power), but also a fixed 80 Watt factor.
On the other hand, I have a high-tension spring check valve in my system that could be causing excessive flow resistance at lower flow rates. Anyway, the main point is that to find the "sweet spot", one should calculate the energy for one turnover via the following:
kWh = Watts * (Pool Size in Gallons) / (GPM * 60 * 1000)
We have been using 4.5fps suction and 6.5fps return @ 6hr. turnover for a few years now...
When the system gets slowed down with VFD pumps (we typically program 18 hr. run times) you end up with a system that has a suction velocity of about 1.5fps...
I'm not sure exactly where the "sweet spot" is, but it seems to me that above 1.5 fps (suction velocity) the resistance seems to come into play more significantly... I'm sure TDH plays a role here as well, but it seems to me like the suction plumbing seems to play a significant role in pump efficiency.
I see this when we use the VF series pumps from Pentair which allow us to see the real time electrical usage. There is a point where as you decrease the pump speed (lower flow) the electrical usage seems to be drop proportionally... for example a 20% drop from 25gpm to 20gpm will yield a similar 20% decrease in electrical usage. There is definitely a "sweet spot" where this seems to take place. I have not done extensive "research" on this, just what I have observed in the field, and it seems to me that when you exceed 1.5 fps on the suction side of the pump, you start to see the electrical usage rise exponentially rather than linearly.
On 2" pipe this comes into play at just abov 15gpm (which is as low as the VF pumps will allow), but on 3" (which is what we use for our suction plumbing) we don't start to see the exponential change in electrical consumption until about 30 - 35 gpm.
This may be a topic which should be moved to its own discussion...
Richard A. Falk said:
The APSP-15 standard requiring a maximum 8 fps velocity on the return side and 6 fps on the suction side translates to the following maximum flow rates for various pipe sizes where I also show the head loss:
.............. Flow Rate (GPM) ..... Head Loss (ft/100ft)
Size ..... Return ..... Suction .... Return .... Suction
1.5" ........ 51 ............. 38 .......... 13.3 ......... 7.8
2.0" ........ 84 ............. 63 ............ 9.8 ......... 5.8
2.5" ...... 119 ............. 90 ............ 7.8 ......... 4.7
3.0" ...... 184 ........... 138 ............ 6.0 ......... 3.6
Since the standard is supposed to be about energy efficiency, I don't know why it isn't based on pipe head loss at normal operating flow rates (or worst-case flow rates) or even better on overall system losses since it is more important to have larger piping on longer runs. I suppose they were just trying to keep things simpler. Note that the above are not particularly aggressive standards and will really just prevent the worst abuses.
Clint Combs said:
APSP is working on new National Standards which will be heavily based on the CA standards. APSP-15
There is a new article in the latest Aqua Magazine on it.
http://aquamagazine.com/articles/article.aspx?articleid=1988&zo...
This will soon be the standard throughout the country, so it's not a bad idea to get up to speed now, so that your prepared.
Don Parish said:
Jennifer,
Is this the list you are looking for? http://www.appliances.energy.ca.gov/
It is a link to the "Appliance Efficiency Database" on the California Energy Commission's website.
Title 20 applies to all pump motors sold in California. It consists of two parts. The first part when into affect in 2006. It eliminated induction motors and mandated energy efficient motors.
The second part went into effect in 2008. It applied only to filtration pumps on residential pools. These filtration pumps must either be less than 1 total hp (rated hp x service factor) or be multi-speed (either two speed or variable speed).
For more information see an old blog post of mine on this topic:
http://technicalpoolrepair.blogspot.com/search?updated-max=2008-05-...
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