On Apr 22, 12:51*pm, DD_BobK wrote:
On Apr 22, 9:08*am, wrote:
On Fri, 22 Apr 2011 08:16:36 -0700 (PDT), "
wrote:
In the Polaris pool cleaner thread the subject of variable speed
pool pumps came up. * Which got me thinking about them
again because a friend who has a pool with a single speed
pump is considering options. Doing a bit of research, here's
what I have concluded and I wanted to see if anyone has
addional thoughts.
First, it looks like because of the design of the variable speed
permanent magnet motors, they are inherently more efficient
so you use about 15-20% less energy even at full speed.
Second, the biggest savings in energy come from slowing
the pump down, reducing the flow resistance. *That means
you can run the pump for say 4 times as long, at 1/4 the
flow rate, move the same amount of water, but save 70 to
80% or so in energy.
However, the price of these pumps is very high. *A complete
new pump runs from $900 to $1200 dollars online. *The next
obvious problem is that they typically have only a 1 yr
warranty. * I found an online story where a guy bought
a Pentair Intelliflow one where one of the two small control
boards failed shortly after the warranty ended. *He says
Pentair will not sell the replacement board as a seperate
part or take pumps back for repair. *He would have to buy
a whole new pump. * It looks like Jandy, another major
manufacturer, does sell parts, but the equiv part for their
pump would be $400.
So, this got me to thinking. *It appears to me the biggest
part of the energy savings can be obtained by just going
to a dual speed pump. * And since my friend has a working
pump that is about 5 years old, I'm thinking the most
cost effective solution is to just replace the motor with
a dual speed motor. *We could do that for under $300.
With the variable speed pump, assuming we bought the
lowest cost one, by my calcs, with the energy savings
it would take almost 4 years
to break even. * With the dual speed motor, it would take
less than 2 years. *The pool is seasonal, used 3.5 months
a year. * And it looks to me like the additional savings in
energy going with the true variable speed pump is only
about $50 more a year over the dual speed. *And then
what happens if the fancy electronics on this motor,
which sits outside all year, fails at say year 3, 5 etc?
The only other advantage of the variable is you can fine
tune it to run at exactly the speed you want, but I don't
see a compelling need for that. *Also, there aren't any
utility rebates available here that would alter the
equation. * So, it seems for this app, the variable speed
makes no sense. * If you had a pool running year round,
higher cost electric, rebates, etc, then the results
might be different.
So, swap out the motor for the dual speed for $300? *Any other
thoughts, issues I missed?
This still does not make sense to me and it has become law in a lot of
places.
If you can really keep your pool clean with a 1/4th hp pump, why not
just buy a 1/4th hp pump?
I run my 1HP on a timer that assures one turn over a day and runs
strong enough to vacuum at the same time. I am not sure how a variable
speed pump would save me a dime.
You can probably 95% of the time get by at 25% power (low speed
running)
BUT there might be sometimes when you need full system flow.
In SoCal we have seasonal winds that can super load a pool with dirt,
leaves & other debris.
To clean the pool up quickly, it might take a couple days running
24hrs at full RPM.
At low speed it would take a lot longer. *
But for "typical" / "low dirt load" many hours at low speed could do
the job.
Agree with the advantage to full speed if the pool has some
problem, eg it's startup after winter or it's dirty and you have
a pool party this afternoon, etc.
The higher speed would probably be needed to backwash the
DE filter. Doubt that low speed would do the job. And also
if the pool gets too full from rain and you want to lower it
would be better to get it done in 20 mins instead of an hour.
But overall, I think the backwashing is the one thing I don't
think you can get around. Plus a dual speed motor is only
$100 more than single.
Two speed pumps give you enough flexibility to tailor motor speed to
pool cleaning requirements.
Kinda goes along with the concept of *"side stream" / "kidney loop"
filtering of a hydraulic oil tank as opposed to full flow filtering.
It's all about the total energy used to accomplish the job.
At first glance dual speed pumps might seem silly but they do the job
AND save money.
cheers
Bob- Hide quoted text -
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