On Wed, 21 May 2014 11:37:20 -0700 (PDT), trader_4
wrote:

I replaced a 1 hp full speed pool pump with a dual speed pump
with the goal of hopefully substantially reducing the electric
power used. I was concerned if the pump would startup and work
with the solar heat on low speed. Testing has shown that it
will always startup and work when water is going to the pool
directly, ie non-solar. It will also startup and work OK if
the water is going through the solar heater, but only with
a clean DE filter, or one that is maybe halfway to needing to
be cleaned. Without a clean filter the pressure required is too
great. So, I'm going to put in the time delay relay system
that we discussed in the other recent thread to
have it start out at high, then switch to low. Once it gets
going on high, I can switch it to low in a minute or so and
it then runs solar on low fine.

I also did some power measurements by counting the revolutions
of the power meter for a few mins with the pump off, on high,
and on low. The pump is using 1/4 the power at half speed as
it does at full speed. This means if I run it twice as long
at 1/2 speed to move about the same amount of water, it will cost
about 1/2 as much. That's great news. Even better is that at
1/2 speed the pump is now perfectly matched to the amount of
time it should run for solar. Before for solar heating, it was
running about 9 hours a day at full speed, which is more than
was needed to keep the water clean. Now it will run 9 hours
at half speed, which is enough to keep the water filtered.
So, instead of just cutting the power usage by 1/2, I'm
actually cutting it to just 1/4. Should be saving about $55
a month in electric cost, making for a quick payback.

Also, found out something else interesting. Before measuring
via the power meter, I used a clamp-on ammeter. Looking at
amps going from full speed to half only cut the amps by just
a little over half. I new this wasn't accurate, but thought
that if the power factor was about the same at high and low
speed, then it would be a proxy for true power. But obviously
the PF must change substantially, because as reported above
as measured at the electric meter, the true power used drops
to 1/4 at low speed, not just by 1/2 as would be indicated
by measuring amps. I guess as the speed drops, more of the
power is reactive and less is real.

Bottom line, what I've measured is consistent with what I've
read about the substantial savings you can get by going to
a dual speed pump. In this case, all I had to change was the
motor ($180) and an additonal box, some switches, etc. Still
have to add that relay stuff. All in, probably cost $230
total.

Trader,

About a few years ago I changed my pool pump out, doubled the filter
sq.ft. with a new filter system. Solar pool heat.

I went with the Pentair Variable Speed Pump and Hayward filter.
Against all the negative reviews. I sorted them out for the
solutions. This gadget can be programmed for 8 speeds. I only use 2
for now. Power bill went down. Prior to that I put in new efficient
HAVC units. I don't recall a recent high power bill. They used to
run ~$350 a month in summer.

Both save me money