# Thread: Do we have a 1.5 HP or a 1.0 HP Pentair Dynamo?

1. ## Do we have a 1.5 HP or a 1.0 HP Pentair Dynamo?

Hi all. I was servicing our pool this week when I saw a tag pulling loose on the new 2-speed Dynamo we installed in November. I pulled it off, so I could keep it and when I did, I realized it had been taped over the original production tag. The original tag says "HP 1.5 - .18 SPL" and the tag that came untaped reads "HP 1.0 - .12 SF 1.0". We ordered the HP 1.0 2-speed pump.

How do we go about figuring out if this is really a 1.0 or a 1.5? And will a 1.5 use more electricity than a 1.0? And what is the significance of .18 SPL and .12? My formula for figuring electrical usage doesn't use HP. It only uses amps and voltage.

Any help would be appreciated. Thanks.

2. ## Re: Do we have a 1.5 HP or a 1.0 HP Pentair Dynamo?

SPL stands for "split phase" which is just to say that it has low and high speed windings. The lower numbers (.18 and .12) are the HP ratings on low speed. As for your actual horsepower, if you know the amp draw of the pump, multiply that by your voltage and divide by 746.

A x v = W
1HP = 746W

3. ## Re: Do we have a 1.5 HP or a 1.0 HP Pentair Dynamo?

This probably has to do with SF or service factor. A 1.0 HP motor with a SF of 1.0 is exactly the same motor as a 1.5 HP motor with a SF of 0.67. You didn't mention the original label having an SF rating, but I suspect it is 0.67. The actual HP available to turn the shaft is called the brake HP. Rated HP times SF gives you brake HP. 1.0 HP and 1.0 SF means 1.0 brake HP. 1.5 HP and 0.67 SF also means 1.0 brake HP.

This has to do with distortions in the listed HP invented for marketing purposes. Some marketing genus discovered that they could relabel a 1.0 HP motor as a 1.5 HP motor and people would think it was a good deal. The phrases full rated, up rated, and max rated are used to hint about how the listed HP corresponds to the amount of work the motor can actually do. A 1.0 HP full rated motor is typically the exact same motor as a 1.5 HP up rated motor. You frequently see motors with different combinations of listed HP and SF that are all the exact same motor with the same brake HP.

There are many different definitions of HP, way beyond the simple variation in SF discussed above. The formula spishex gave for calculating HP from amps and volts is one definition. There are also other definitions based on various ways of measuring the amount of work the motor can do. Different kinds of motors have different inherent efficiencies, so the electrical HP and work HP don't always match up.

4. ## Re: Do we have a 1.5 HP or a 1.0 HP Pentair Dynamo?

The original sticker on the unit does not list the SF. That's why I was wondering how we could tell if this is truly a 1.0 or 1.5. But it may be a moot issue if the 1.5 doesn't use much more electricity than the 1.0. This unit shows to be a 11/2.9 amp (high/low, respectively). And our single speed was, I believe, either a 12 or 15 amp. The formula I used to figure what our new electricity usage would be is:

Amps X Volts ÷ 1,000 X (cost of kwh) X (hrs used per day) X 30 (days) = monthly cost.

So it sounds like I need to contact the company again (depending on where they bounce me to this time!) and give them the serial number and have them tell me if it's full-rated or uprated, right?

5. ## Re: Do we have a 1.5 HP or a 1.0 HP Pentair Dynamo?

If it is indeed a Pentair Dynamo two speed that uses 11 or 2.9 amps then it is the 1 HP model. There is a chart of the amps for each version of the Dynamo pump on this Pentair page. The 1 1/2 HP two speed draws 16.4 or 4.4 amps.

What probably happened is that they sourced the motor from a company who rates the motor in a different way. With a few exceptions, the pump manufacturers buy their motors from others and combine them with a pump that they build themselves. Sometimes you see the motor label from the original motor company, but other times the pump manufacturer replaces it or covers it up.

6. ## Re: Do we have a 1.5 HP or a 1.0 HP Pentair Dynamo?

Originally Posted by Cherie
The formula I used to figure what our new electricity usage would be is:

Amps X Volts ÷ 1,000 X (cost of kwh) X (hrs used per day) X 30 (days) = monthly cost.
Picking nits here, because this is essentially correct, but just an FYI: your actual power draw will probably be about 80-90% of the apparent watts in your VxA calculation depending on the power factor (not on the label) of your motor. Your actual amps are probably lower than the label reads as well since that is the motor's maximum capacity.

7. ## Re: Do we have a 1.5 HP or a 1.0 HP Pentair Dynamo?

Originally Posted by JasonLion
This probably has to do with SF or service factor. A 1.0 HP motor with a SF of 1.0 is exactly the same motor as a 1.5 HP motor with a SF of 0.67. You didn't mention the original label having an SF rating, but I suspect it is 0.67. The actual HP available to turn the shaft is called the brake HP. Rated HP times SF gives you brake HP. 1.0 HP and 1.0 SF means 1.0 brake HP. 1.5 HP and 0.67 SF also means 1.0 brake HP.
This is moot now that we have the amps, but I've never seen a motor with a SF below 1.0. Since it's overload capacity, it wouldn't make much sense to market motors at a HP above their actual ability (not that market HP makes a lot of sense anyway). Is this something you've come across?

8. ## Re: Do we have a 1.5 HP or a 1.0 HP Pentair Dynamo?

Sigh, you are right. It doesn't make any sense to have a SF lower than 1.0. I guess that means the 1.5 HP name plate is just plain wrong.

9. ## Re: Do we have a 1.5 HP or a 1.0 HP Pentair Dynamo?

I believe Sta-Rite has the dubious honor of introducing the SF marketing concept. BTW, quite a number of years ago you could purchase a motor with a SF of less than 1.0.

10. ## Re: Do we have a 1.5 HP or a 1.0 HP Pentair Dynamo?

Old thread Good info , just what I needed today thanks

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