Fixed or Variable Speed Pool Pump?

[bdunham7]

because the windings are not optimal for either use case, they aren't very efficient on slow speed.

The one I have is essentially two separate concentric motors sharing the induction armature and the stator poles but using entirely separate windings and capacitors for each speed. 

https://www.inyopools.com/Products/00200017039443.htm

If this type were not available, I'd switch to an ECM variable-speed model like this:

https://intheswim.com/p/ec-342001---superflo-vs-variable-speed-pool-pump-1.5-hp---limited-warranty/387245.html

[Siwastaja]

Mandatory car analogy:
You have two hours to drive 200km.
1) You drive at 200km/h for an hour, then rest for an hour
2) You drive at 100km/h for two hours

In (2), because at high speeds aerodynamic losses dominate, average power is 1/8th of (1), but for double the time, so energy consumed is 1/4. 75% savings right here.

Then you change to a more efficient motor type - say, from 30% efficient internal combustion engine to 80% efficient EV. Now the energy consumed goes from 1/4 to below 1/10th. Large savings are possible when the real physical work done is zero, and everything is unnecessary losses. Things are different if you are moving heavy objects on the top of the hill, and come back with empty cars. Or if you are pumping water from a well to higher grounds. Then you are doing actual work which cannot be made more than 100% efficient, plus those losses.

[HarryDoPECC]

I have thought about this for some time too and had many of the same doubts about just reducing pump speed by some (arbitrary) factor.
Maybe this is a kind of X-Y problem: what we are really looking for is the most energy efficient way to move a required volume of water thru the system. 
The opportunity for speed reduction arises because the pumps are believed to be pretty crudely (over)specified.  Filter resistance also varies significantly.
Those factors led me to think that a much better approach would be to control speed and time using flow as input and daily volume as target.  Implementing the control is easy enough but I never found a flow sensor at price I could bear. But did not look too hard….

Is this a more valid approach,
Anyone got sensor ideas (where I am pool pipe work is typically PVC 40 or 50mm)

[HarryDoPECC]

… and flow rates say 200-800 LLM

[HarryDoPECC]

* LPM. Litre / min

[EEVblog]

I have thought about this for some time too and had many of the same doubts about just reducing pump speed by some (arbitrary) factor.
Maybe this is a kind of X-Y problem: what we are really looking for is the most energy efficient way to move a required volume of water thru the system.

Yes, but when it comes to practice sometimes you just want it done in the fastest time possible rather than in the most energy efficienct manner.
In my case right now I don't how a variable speed pump is going to help when I mostly want to run it during excess sun daylight hours.
That could change if I get a battery solution, in which case it might pay to run it 24/7 at a slower speed at less power.

[vk6zgo]

For dave it looks like the pump is already running quite long, much of the time that solar power is available. So there is not really an option to run longer and thus slower. It would be a thing only if not that much filtering is needed.

4hrs per day. I just lowered that to 3hrs.
Correct, running longer outside of solar periods defeats the purpose unless we had battery storage.

So you have circulation for only 3 hours a day?  When I had a pool that wouldn't be enough to keep all the airborne crud filtered out, or to keep the pool chlorinated properly.  But that was an old pool using trichlor, and with no automatic cleaner for the bottom.  I guess things are a lot different with a modern pool.

That is similar to the point I was just going to make.

Years ago we bought our current house.

When we first looked at it, we were delighted to see a large, quite recently installed saltwater pool, & were surprised that the house was cheaper than others without a pool.
Unbeknownst to us, the previous owner had been "conned" with a saltwater chlorinator which was inadequate for the job, requiring almost constant operation to produce enough Chlorine to be within the safe level.

After battling with the original setup for some years, where most of the time we still had to add additional chlorine, we "bit the bullet" & bought a new, heavier duty pump & chlorinator.
It wasn't the "magic bullet" to fix all my woes, though, & there were still "issues".

Everybody else in the family had become disenchanted with the pool, & I ended up becoming the "pool boy".
Eventually we got it ripped out.

Anyway, the point was that you can play with speeds till you are "blue in the face", but it is the efficiency of the chlorinator in a saltwater pool which is the determining factor.

That said, I don't know if Dave's pool is a saltwater type or something more exotic.

[EEVblog]

For dave it looks like the pump is already running quite long, much of the time that solar power is available. So there is not really an option to run longer and thus slower. It would be a thing only if not that much filtering is needed.

4hrs per day. I just lowered that to 3hrs.
Correct, running longer outside of solar periods defeats the purpose unless we had battery storage.

So you have circulation for only 3 hours a day?  When I had a pool that wouldn't be enough to keep all the airborne crud filtered out, or to keep the pool chlorinated properly.  But that was an old pool using trichlor, and with no automatic cleaner for the bottom.  I guess things are a lot different with a modern pool.

That is similar to the point I was just going to make.

Years ago we bought our current house.

When we first looked at it, we were delighted to see a large, quite recently installed saltwater pool, & were surprised that the house was cheaper than others without a pool.
Unbeknownst to us, the previous owner had been "conned" with a saltwater chlorinator which was inadequate for the job, requiring almost constant operation to produce enough Chlorine to be within the safe level.

After battling with the original setup for some years, where most of the time we still had to add additional chlorine, we "bit the bullet" & bought a new, heavier duty pump & chlorinator.
It wasn't the "magic bullet" to fix all my woes, though, & there were still "issues".

Everybody else in the family had become disenchanted with the pool, & I ended up becoming the "pool boy".
Eventually we got it ripped out.

Anyway, the point was that you can play with speeds till you are "blue in the face", but it is the efficiency of the chlorinator in a saltwater pool which is the determining factor.

That said, I don't know if Dave's pool is a saltwater type or something more exotic.

It's salt water as per my videos.
It's been upped to 4hrs per day on the advice of the pool guy.
4hrs per day at the pump rate is two and a half complete pool exchanges per day.
We just added extra salt yesterday, as I believe we are still in the initial salting phase.
Don't have enough data yet. People we know with a salt water pool have no problems.

[ogdento]

Just saw this post while searching for VFD info...

Dave, did you ever get a variable speed pump?  I don't think you'll be unhappy if you do... six or seven years ago I swapped a 2-speed Pentair pump (similar to what bdunham had) for an Intelliflo VS and while it has saved me money, my favorite thing is it's super quiet.  For me it's worth it just for the peace and quiet.