Pentair Dynamo Power Consumption

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RussH

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Mar 15, 2014
59
Central AL
We bought a house with a pool last fall and we are getting the pool opened up now for this season. The pump is a Pentair Dynamo 1.5 hp with 110V service run to the pool. The filter is a Pentair SD60. Both filter and pump are probably 8 years old.

I put a clamp ammeter on the motor yesterday and got that it is pulling 10 amps. The name plate shows 12 amps at full load. 10 amps works out to about $100/mo if run 24/7. I know the run time can be cut down a lot, but this pump seems to be really inefficient. I would like to have the flexibility of being able to run it longer, if needed, without a major power bill impact.

Is there a different pump similar to this one's output that is more efficient? Most higher efficiency pumps seem to be 230V. I dont want to re-wire for 230V, if possible.

Is the pump supposed to pull this much power in this application or is there something wrong with it? I have changed out the sand in the filter, new laterals and a new multiport valve, so I dont think the filter is having a negative effect on it.


Thanks,

Russ
 
That measurement is typical for pumps that size. Efficiency is mostly a function of pump size, larger pumps are less efficient, smaller pumps are more efficient. There are some other secondary factors that affect efficiency, but pump size is by far the largest factor. Two speed pumps and variable speed pumps run at low speed are effectively smaller pumps, and so more efficient.

Typically you would run the pump roughly four hours a day, so more like $17/month in average conditions.

If efficiency is a big deal for you, you could replace the motor on your current pump with a two speed motor, and run it on low speed. That will save you roughly 50% of your electrical costs to run the pump, however given your electrical rates that would be unlikely to pay back the initial investment fast enough to be worth doing.
 
Mine runs about 11 amps so you're real close to that. I run my pump about 8 hours a day during the summer and that's about $30 a month.

I'd cut the run time back to about 6 hours a day and see how clean the pool stays. You want to aim the eyeball so that it circulates the water by the skimmer as efficiently as possible.
 
Thanks for the responses guys. Ok, so it's normal for it to use this much power. I can work from there by adding a timer to it. The timer can pay for itself in a month.

I have the eyeball directed to the side and down which seems to have the skimmer working well getting leaves and such out.

Is this pump and filter undersized for this 25,000 gal pool? I ask because last fall I went by a local pool store to get a winter cover. I've never dealt with a pool before, so you can imagine what that turned into... Fortunately I found TFP over the winter. In talking to the person at the store, they tried to convince me that this filter/pump was undersized for an AGP pool of this size and that I should run it 24/7 or algae would result. Obviously if its well chlorinated, its not going to break out in algae just because the water isnt moving. It is at 7 ppm FC with ~35ppm stabilizer.

When there is dust or dirt on the bottom, I can brush it up and it disappears but the water flow never really seems to pick it up and get it back to the skimmer. It returns in the next day or so. Maybe its too small for the filter to catch and hold. I dont think its a bloom or anything as it passed an OCLT at SLAM levels and the water just looks great. With the eyeball set as described, there is a pretty decent rotational speed to the pool water at the perimeter, maybe a foot every 2-3 seconds or so, just guessing. It forms a dead spot in the center where a lot of the stuff ends up. So is the filter/pump size okay?

Thanks,

Russ
 
For a 25k pool, a sand filter of at least 29" diameter would be a good fit with a 4.6 sqft filter area. Yours is 2.3 sqft so about half what we would recommend. All that really means is that you will have to clean it twice as often.

The pump is plenty big. In fact, you would save money by have a smaller 1HP 2-speed.

As you surmised, the pool store employee did not know what they are talking about. Chlorine is the only thing required to prevent algae. I had NO pump on my pool for over 2 weeks in the AZ summer a few years ago ... maintained adequate FC and no algae started ... the pool was dirty, but no algae.
 
Jason,

How did you get the chlorine to mix with the pool water with no circulation?

There were a lot of red lights flashing in the pool store that day. They wanted $300 to replace $40 worth of sand in the filter, telling me the filter was fragile and very difficult to keep sand out of the centerpipe. Please... All that did was make me determined to try it.

I didnt have many options at the time for closing the pool. I needed to get it done as I was fighting a lot of other fires with getting moved into the new house. I ended up with two 5 lb(?) jugs of Poolife Turboshock in the pool and one thing of an algae killer. Fortunately the pool survived relatively clear when we opened it. It's something of a mystery, the CYA was only around 30 ppm after opening and I know the previous owner was using a lot of Turboshock and tablets. I caused around 25ppm of that with my closing additions. I found his shock/tablet receipts from last year with some other documentation. If all of that went in the pool, the CYA should have been a *lot* higher. All I can figure is that he must have had a pool disaster resulting in most of the water getting drained before we came along looking at the house. There are several patches along the perimeter of the liner at the bottom. Maybe he had leaks and drained it to patch them before selling the house.
 
That was back after I had found this site, but still had a pool service that would use chlorine gas injection into the pool. They had my CYA crazy high and would also raise the FC very high and it stayed high enough while I did not have a pump.

One method though is to stir the pool with an oar or just brush it really well to mix the chlorine in.
 
A 1.5 HP Dynamo is more pump than you really need, but as stated - you really can't get too big of a filter. I'd look at replacing the filter before the pump as long as it's still working well - but when the pump goes - you REALLY need to replace it - think of it as the "heart" of your pool. As you run the pump - take note of what your initial pressure is, then you want to backflush when it gets 25% larger.

That being said - yes - get a timer for it (needs to be one that can handle 15 Amp 120 V), and for safety - use a GFCI circuit. Experiment with the timer - I tend to run about 12 hours /day, but then - I live in a forest. You may need more or less, depending on your circumstances and preferences.
 
The 1.5 HP Dynamo is a SPL rated pump so in reality, it is identical to the 1 HP UR Dynamo. There actually aren't that many pumps which are "smaller". The 3/4 HP Dynamo, Superflo, Optiflo, Maxflo are about the only pumps that are truly "smaller" and not by much.
 

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SPL is "Special" rating. UR is "Up Rated". I explain the differences in this sticky: http://www.troublefreepool.com/thre...you-lost-your-head?p=6230&viewfull=1#post6230

There is also a chart of flow rates for various pumps which is a more accurate way of comparing pump sizes than using the HP rating.

Most in the industry have long understood that pump motor nameplates can be very deceiving which often leads to incorrect sizing. It is bad enough that manufactures have chosen to have two classes of IG pumps, up rated vs full rated, but AG pumps also come in an "Special HP" (SPL) version which is basically a double up rated pump.

So what do all these terms mean?

The horsepower required to turn an impeller at a specific RPM is called brake HP (BHP). The required BHP changes along a pump's head curve and reaches a maximum near the right side of the curve. A motor will typically be rated at a service factor HP (SFHP) or total HP (THP) which is greater than the maximum BHP required for the pump. The SFHP/THP is the true measure of a motors power capability and is determined by multiplying the pump's service factor by the label HP. This is where a lot of the confusion originates. As a general rule of thumb, here is how a pump's service factor relate to the ratings:

Full Rated: Service Factor > 1.3
Up Rated: 1.0 < Service Factor < 1.3
SPL Rated: Service Factor < 1.0


Within the same pump line, sometimes you will see two pumps with different label HP and service factors but identical head curves and identical THP (service factor * label HP). Don't be fooled by this, if the head curves are the same, the pumps are identical. Only the labels are different. So the lesson here is that you cannot judge a pump's power or strength just by just the nameplate HP rating.
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