Advantages of a 2.5 or 3 hp VS pump over 1.5 hp?

[Bean19]

I am going to upgrade my old single-speed 220v pump to a new VS pump, at least 1.5hp but maybe 2.5 or 3. I have a 28k in-ground plaster pool with a 48 square foot Hayward DE filter.
I understand that going with a more powerful 2.5/3 hp pump I can turn over the entire volume of the pool in 2-3 hours, as opposed to 6-8 with a 1.5 hp. What I don’t understand is what the advantages of that are other than being able to spend a longer time running at lower speeds.
Would that save money?
Would it be able to more quickly pull surface debris into the skimmer baskets?
Would it keep the pool cleaner?
The cost difference is considerable, $500 or more for the more powerful pumps.

 

[jblizzle]

Turnovers don't matter. The advantages of the larger pump are that you can move more water if you want, and you can run at a lower RPM to move the same amount of water as the smaller pump which means the motor should be quieter. Also it seems that the larger vs pumps are the only ones that integrate well into automation systems.

But if you do not have high flow needs and do not have automation system, then the smaller one will work just fine for you.

 

[Mayorb]

Consider an old school 2 speed motor. It does not have a computer on its back.
These have been on the market for decades and will essentially do the same thing as what you're looking for in a VS.
Intermatic has electro-mechanical timers that can run 2 speed motors. Stay at the same HP which has been working for you. Maybe less since pool pumps are notoriously over powered.
Keep it simple.

 

[Pool_Medic]

Bigger is definitely better in vs pumps, if they are run at very low speeds they in fact last longer and burn way less energy than a antiquated two speed pump.

 

[ILoveGrits]

Our 2.0HP Jandy recently bit the dust, so we upgraded to a 1.65HP PureLine VSP thinking it would be a good replacement. We have a spillover & small fountain and I'm unhappy with how quickly I need to run the pump to get the look we want at the feature (negating the purpose of the VSP). I ended up ordering a larger 2.7 HP and will try and sell the smaller 1.6 to recoup some of the loss.

I typically buy stuff that's way overbuilt for the job its needed for. This time I didn't, and I regret not doing it the first time.

 

[SDor]

There's some kind of magic with electric motors where when they run slower they use A LOT less energy than when they run fast. It's called the "Pump Affinity Law", and it says that a pump running at 1/2 the speed moves 1/2 the water, but uses only 1/8th of the energy as the full speed pump. Therefore, if you run your pump at 1/2 speed twice as long, you move the same water, but use 1/4 of the energy. Lower speeds are quieter, and, for me at least, the filter works better.

If you buy a bigger VS pump, it allows you to run it at a lower speed and take even more advantage of the pump affinity law. If a big pump can move 2x as much water as a small pump at the same RPM, then you can either run it 1/2 as long (and use 1/2 the energy), or at 1/2 the RPMs twice as long and use 1/4 of the energy of the smaller pump (more or less, the bigger pump will use more energy at the same RPM as the smaller pump, but you get the idea).

A two speed pump also sees similar savings, but since low speed is not adjustable, if it is too slow (i.e. if your heater or SWG need a certain flow), then you can't use it, and you're stuck with running high speed all the time. With a VS, you can tune the desired speeds to get what you need at the lowest RPM (for most energy savings).

You may also be able to get a rebate from your electric company.

 

[Bean19]

Thanks, everyone, for your responses. I think it will be worth it in the long run to get a bigger pump. My electric utility offers a rebate on a VS pump so I think that helps make the case economically, plus the other advantages of working better with a heat pump and SWG (which will be part of the same equipment order).

I’m new to the forum but I must say I think TFP has got to be one of the most helpful communities on the internet—right up there with the home brew forums. I’ve ordered my TF100 test kit!