Misleading horsepower?

[cj133]

Hi all,

I don't recall this being talked about but I wanted to ask about something I noticed recently.
I'm using a Hayward Matrix 1.5HP 2 speed pump. A good friend recently bought a AquaPro 2HP pump.

I compared 3 pumps. My dad's Hayward Powerflow II 1HP from 1990 which stated 12A @ 115V on the tag. This was a very strong pump for it's size.
My 1.5HP 2 speed which claims 11A and my friends AquaPro 2HP which says 10.5A on the tag. These are all at 115V.

Both my 1.5 and the 2HP do not seem any stronger at all than the old Powerflow II. Also, none of them have capacitors so I do not see how the current could be lower on the same type motor. It looks like the current Powerflow II being sold today still says 12A on the tag.

I just looked at some of Hayward's inground pumps and they appear to have more reasonable current specs, such as 19.4A for 2HP at 115V. Makes me think the real difference between the in ground and above ground pumps are actually "Economy series vs quality series" rather than the elevation of the pool.

I suspect the cheaper pumps have inflated numbers and so called 1.5HP and 2HP pumps for AGP's aren't what they claim. Kind of like the 6HP 120V shop vacuums that are lucky if they're 1HP.
But I have no way to actually test this. The 1.5HP Matrix pump was drawing just under 900W in high, but it's hooked to a filter and the eyeball in the return restricts some as well.

Thoughts?

 

[cj133]

If you look up the two part numbers listed for the Matrix pumps they were also used on the older Powerflo LX and Powerflo 1500 series and the only ones I can find are 3/4Hp and 1HP impellers.

 

[MITBeta]

My thoughts on this are that my Hayward Powerflo Matrix 1.5HP 2-speed pump is way more powerful than necessary for my 24' 13kgal AGP. So I'm not sure what your issue is.

 

[cj133]

My thoughts on this are that my Hayward Powerflo Matrix 1.5HP 2-speed pump is way more powerful than necessary for my 24' 13kgal AGP. So I'm not sure what your issue is.

Curiosity.
Nothing else.

 

[CJadamec]

My thoughts on this are that my Hayward Powerflo Matrix 1.5HP 2-speed pump is way more powerful than necessary for my 24' 13kgal AGP. So I'm not sure what your issue is.

The superflo VS pump is way overkill on my 13k gallon 15x30 pool but I still have it.

Pool pump manufacturers love to hype the HP rating of their pumps particularly when marketed to the AGP folks. We Americans just love our HP and if 1 HP is good 2HP must be twice as good.

Electric motor nameplate ratings get rather confusing at times but when trying to compare one to another by HP you have to look at the service factor SF number as well. SF is listed typically as 0.5, 1, and 1.5. the higher the SF the "stronger" The motor will be when compared to the same HP rated motor with a lower SF.

That 2HP pump with 10amps of current draw is likely a 2HP 0.5 SF motor coupled to a small impeller. So yes the motor could make 2HP if pushed hard enough but it would burn out very quickly if run that hard all the time. So that cheap motor with all that extra HP is just smoke and mirrors because the impeller on the pump could be run by a much lower rated HP motor.

The only way pump companies cant lie to you and is the only true way to compare pump power across pumps is to look at the flow charts for the pump. It takes power to move water under pressure. The pump that can move the most water at a given pressure is the strongest pump regardless of what the motor running it claims for HP.

 

[cj133]

The superflo VS pump is way overkill on my 13k gallon 15x30 pool but I still have it.

Pool pump manufacturers love to hype the HP rating of their pumps particularly when marketed to the AGP folks. We Americans just love our HP and if 1 HP is good 2HP must be twice as good.

Electric motor nameplate ratings get rather confusing at times but when trying to compare one to another by HP you have to look at the service factor SF number as well. SF is listed typically as 0.5, 1, and 1.5. the higher the SF the "stronger" The motor will be when compared to the same HP rated motor with a lower SF.

That 2HP pump with 10amps of current draw is likely a 2HP 0.5 SF motor coupled to a small impeller. So yes the motor could make 2HP if pushed hard enough but it would burn out very quickly if run that hard all the time. So that cheap motor with all that extra HP is just smoke and mirrors because the impeller on the pump could be run by a much lower rated HP motor.

The only way pump companies cant lie to you and is the only true way to compare pump power across pumps is to look at the flow charts for the pump. It takes power to move water under pressure. The pump that can move the most water at a given pressure is the strongest pump regardless of what the motor running it claims for HP.

Interesting.
And sure enough the Powerflow Matrix shows the SF as SPL.

Why Your Spa Pump’s HP Is a Lie

A lie, I say! Pump manufacturers may categorize it as a “fudging of the numbers” but let’s call a spade a spade. They are at best trying to mislead the homeowner. We take phone calls from customers every day attempting to match their current motor label information to a new replacement motor and...

www.inyopools.com

For a long time I've wondered what the difference between AGP and In ground pool pumps was.
It's seeming more and more to me like what it really is economy vs premium rather than the elevation of the pool.

 

[CJadamec]

Interesting.
And sure enough the Powerflow Matrix shows the SF as SPL.

Why Your Spa Pump’s HP Is a Lie

A lie, I say! Pump manufacturers may categorize it as a “fudging of the numbers” but let’s call a spade a spade. They are at best trying to mislead the homeowner. We take phone calls from customers every day attempting to match their current motor label information to a new replacement motor and...

www.inyopools.com

For a long time I've wondered what the difference between AGP and In ground pool pumps was.
It's seeming more and more to me like what it really is economy vs premium rather than the elevation of the pool.

The primary difference between AGP pumps and in ground pumps is the "self priming" aspect of the pump.

AGP pumps are almost always situated below water level and always have water flowing into them thru the skimmer. There is no need to have a more costly self priming pump design.

In ground pools almost always have the pump above water level so the pump is actually sucking water out of the pool when it starts up. A self priming pump will be able to draw water out of the pool so long as you start it with a full basket of water.

That's really the only difference between the two. A self priming pump can be used for an AGP but it's not needed.

A non self priming pump with die a quick melted plastic death if you try to use it above the water line.

"Inground" pumps are typically marketed differently and dont inflate HP numbers to increase sales nearly as often.

 

[jseyfert3]

So one horsepower is 746 watts. It is impossible for the steady state output power of a motor to be more than the power it consumes, because physics.

If you assume 90% motor efficiency, then a true 1 HP motor would draw 829 watts (6.9 A at 120 V) and a true 2 HP motor would draw 1492 watts (12.4 A at 120 V).

Now 90% may be generous for a cheap motor but with that assumption I get an actual 1.52 HP for your 1.5 HP pump. So your dad’s pump if anything may be conservatively rated, your pump seems spot on, and your friends pump has an exaggerated rating. Of course the service factor may play in, that is a pure marketing thing IMO…

If you want over-rating though: My spa motors, OEM from 2008, are listed at 13 A, 240 volts and 6 HP. That is 3120 watts, assuming the same 90% efficiency it works out to 3.8 HP. Way lower than 6…

As an engineer I find it really annoying how over-inflated and inconsistent motor HP ratings are.

 

[cj133]

So one horsepower is 746 watts. It is impossible for the steady state output power of a motor to be more than the power it consumes, because physics.

If you assume 90% motor efficiency, then a true 1 HP motor would draw 829 watts (6.9 A at 120 V) and a true 2 HP motor would draw 1492 watts (12.4 A at 120 V).

Now 90% may be generous for a cheap motor but with that assumption I get an actual 1.52 HP for your 1.5 HP pump. So your dad’s pump if anything may be conservatively rated, your pump seems spot on, and your friends pump has an exaggerated rating. Of course the service factor may play in, that is a pure marketing thing IMO…

If you want over-rating though: My spa motors, OEM from 2008, are listed at 13 A, 240 volts and 6 HP. That is 3120 watts, assuming the same 90% efficiency it works out to 3.8 HP. Way lower than 6…

As an engineer I find it really annoying how over-inflated and inconsistent motor HP ratings are.

True,
Except these motors most certainly do not have a PF of 1. They're single phase and there's no capacitor.
I didn't actually check mine at the time but I'd bet 0.6 to 0.7 would be likely. So 11 amps at 120 volts should be 800 to 900 watts.

I'm not sure about the others you mentioned. I've seen many of the better pumps with capacitors but I don't know if they're start only, or run capacitors etc.

 

[CJadamec]

Very few residential pool pumps have a run capacitor. Most any capacitor you see on them is for start only.

PF ratings are going to be around 0.8. They are just typical squirrel cage motors with very few efficiency enhancements.

Of course this is why there are all the 2-speed and variable speed pump mandates out there. The pool industry flooded the market with in-effcient over powered boat anchors.

I'm happy to let my VS pump sip away at 140watts keeping my pool clean as can be. Its already paid for itself in electrical costs.

 

[cj133]

Very few residential pool pumps have a run capacitor. Most any capacitor you see on them is for start only.

PF ratings are going to be around 0.8. They are just typical squirrel cage motors with very few efficiency enhancements.

Of course this is why there are all the 2-speed and variable speed pump mandates out there. The pool industry flooded the market with in-effcient over powered boat anchors.

I'm happy to let my VS pump sip away at 140watts keeping my pool clean as can be. Its already paid for itself in electrical costs.

Actually, turns out I took pictures of the watt meter for my pump.

896 watts, 9.82A in high
171 watts, 2.85 amps in low.

Assuming 120 volts, which is usually right around where mine runs, that gives a PF of .76 in high and .5 in low which I suppose isn't surprising considering there isn't much load on the motor for it's size. My 1930s refrigerators usually run around 0.5 to 0.6 unless there's a heavy load on the compressor.


So 725 watts less in low speed and the skimmer works 100% just as good, if not better than in high speed. If I did the math right that's about $18 a month to run it 24/7 vs $92 in high speed.

 

[mas985]

Very few residential pool pumps have a run capacitor. Most any capacitor you see on them is for start only.

Actually, quite a few have run capacitors. See this database column Type. PSC is permanent split capacitor and CSCR is capacitor start, capacitor run. Both types use run capacitors.

Pump Database

docs.google.com

As for motor ratings, they are just that, just a rating (i.e. maximum load). They tell little about the true performance of the pump (wet end) which is a separate machine. The pump's head curve is the proper way to compare pump performance.

Also, induction motors are in usually in the range of 60%-80% efficient with low THP at the low end and high THP at the high end.

 

[cj133]

Actually, quite a few have run capacitors. See this database column Type. PSC is permanent split capacitor and CSCR is capacitor start, capacitor run. Both types use run capacitors.

Pump Database

docs.google.com

As for motor ratings, they are just that, just a rating (i.e. maximum load). They tell little about the true performance of the pump (wet end) which is a separate machine. The pump's head curve is the proper way to compare pump performance.

Also, induction motors are in usually in the range of 60%-80% efficient with low THP at the low end and high THP at the high end.

That is true...
But when they sell a pump as a "1 HP pump" you'd expect it to actually be that, in some form.
Not a pump intended for continuous load that comes with a motor that cannot handle the claim so the pump is undersized to work with the motor. If the motor can only do 3/4HP continuously and the pump is sized accordingly, that's a 3/4HP pump not a 1.5HP.

Of course, this applies to almost everything anymore. 1000W home theater receivers that can't do more than 100-200 watts. 6HP Shop vacs that can't do more than 1HP.

 

[mas985]

First, pump motors are rated for continuous operation at the THP rating (Label HP * Service Factor). So a pump motor rated at 1.0 HP with a 1.65 service factor is a 1.65 THP motor rated for continuous operation. However, a 1.0 HP impeller is really a 1.0 HP "full rated" impeller which could potentially create a maximum load of up to 1.65 BHP, depending on the head curve. So there is definitely some confusion about that.

Second, pumps have a very wide BHP operating range over the entire head curve. So the motor has to be sized for the maximum load which is a single point on the head curve (usually BEP). However, motors are not built in an infinite range of the THP values. They generally are in 1/2 HP increments to minimize the number of models in order to keep costs down. A pump manufacture (e.g. Hayward or Pentair) will first design a pump head and then choose a pump motor from a existing line of motors from the motor manufacture (e.g. US Motors, Regal Beloit) . However, the pump head curve may place the maximum load between two motor THP ratings so the larger one must be chosen. But this is also why one should avoid using the motor THP to size a pump because it may not actually reflect the true power of the pump. Only the pump's head curve should be used when sizing a pump.

 

[cj133]

First, pump motors are rated for continuous operation at the THP rating (Label HP * Service Factor). So a pump motor rated at 1.0 HP with a 1.65 service factor is a 1.65 THP motor rated for continuous operation. However, a 1.0 HP impeller is really a 1.0 HP "full rated" impeller which could potentially create a maximum load of up to 1.65 BHP, depending on the head curve. So there is definitely some confusion about that.

Second, pumps have a very wide BHP operating range over the entire head curve. So the motor has to be sized for the maximum load which is a single point on the head curve (usually BEP). However, motors are not built in an infinite range of the THP values. They generally are in 1/2 HP increments to minimize the number of models in order to keep costs down. A pump manufacture (e.g. Hayward or Pentair) will first design a pump head and then choose a pump motor from a existing line of motors from the motor manufacture (e.g. US Motors, Regal Beloit) . However, the pump head curve may place the maximum load between two motor THP ratings so the larger one must be chosen. But this is also why one should avoid using the motor THP to size a pump because it may not actually reflect the true power of the pump. Only the pump's head curve should be used when sizing a pump.

Hi Mark,

Thank you for responding.
How do you figure that out when the SF rating on the pump motor is "SPL".
I tried searching for what that meant exactly and all I came up with was "It's less than 1.0". Why would a motor manufacturer sell a motor with a SF of less than 1?

In your opinion, what brand of pump do you feel is best (price aside) for swimming pools? Where does Hayward fall in the list?

 

[mas985]

A SPL rating has a service factor of less than 1.0. The reason for this is basically a marketing ploy. Long ago when electricity was cheap, pool owners wanted more "powerful" pumps and pool builders knew that the larger pumps could actually cause more issues (especially with AG pools) so the motor manufactures created an SPL rating such the pump looked like it had more power when in fact it is exactly the same as the uprated version with a lower label HP or the full rated version with the even lower label HP. This has long been a complaint of the industry but there is a lot of history and legacy that is hard to shed.

BTW, in the water distribution industry, the pump heads and the motors are sold separately. This is so the engineers can trim the impellers for the specific application and then mate the appropriately sized motor for the given head curve. This is much more efficient for very high flow or head applications.

In your opinion, what brand of pump do you feel is best (price aside) for swimming pools?

Depends on what you mean by best. I don't really have a strong opinion in this area. If you are looking for energy efficiency, there is a spreadsheet in my signature that lets you compare pumps on an apples to apples operational efficiency basis but in reality, it doesn't matter all that much. Higher flow rates result in higher energy use and lower flow rates results in lower energy use no matter which pump you decide on.

 

[jseyfert3]

Except these motors most certainly do not have a PF of 1. They're single phase and there's no capacitor.
I didn't actually check mine at the time but I'd bet 0.6 to 0.7 would be likely. So 11 amps at 120 volts should be 800 to 900 watts.

I'm not sure about the others you mentioned. I've seen many of the better pumps with capacitors but I don't know if they're start only, or run capacitors etc.

Ah yes, fair point. Forgot about the inductive power factor.

I don't have a power meter handy that could measure the power of my 240 volt spa pumps though. Could probably borrow something from work though on a weekend if I was super curious. My pumps definitely have caps though. Here is one of the OEM "6 HP" pumps along with it's replacement, which was rated at 3 HP.