General > Beating a dead horse
Horse power
Chas:
--- Quote ---Those who say horsepower means nothing are wrong.
Improperly applied, large horsepower pumps can be made to feel inadequate due to long piping runs and improper line sizing or poorly designed jet quantities or sizes. Just as smaller horsepower pumps utilizing properly sized lines and lengths combined with well engineered jets and air induction can be made to feel more than adequate.
The plain fact is that all other factors being equal, higher horsepower pumps simply have the ability to do more work (move larger volumes of water) than their lower horsepower counterparts.
--- End quote ---
You just contradicted yourself. Your opening line says we are wrong, but then you go on to point out exactly what we have been saying: that HP numbers do not take into account the many variable such as good/poor plumbing, long/short plumbing lines, well designed/poorly designed jets, jet quantities and jet sizes.
You also mentioned air induction - some spas use a blower to force air into the jet system, and others use recycled heat as the air source - there are about as many variables as there are tub makers, times two.
Next - look at the line in your post where you said, "All other factors being equal, higher horsepower pumps simply have the ability to do more work..."
But in comparing different tubs, especially from different makers, all other factors are far from equal. Better tub makers us better designs on plumbing, jets, layout, plumbing size, and many other factors including hydraulic balance and flow characteristics. And if a system is well designed, it will flow just about as much water as the pump can put out, and simply adding a larger motor or motor/pump combination will not net higher flow. You would need to redesign the entire plumbing system, or add some jets, or up size some of the jets, or remove some plumbing restrictions, or increase filter area, or perhaps all of the above before the larger pump could move more water.
Sorry, but shopping by HP numbers on the brochure or web site simply will not tell you anything about how well or poorly a particular spa is going to work.
One more thing - three five horsepower pumps will require (750watts X 15= 11250 watts, which will take 52 amps at 220volts. To run just those three pumps, you need to have a 70 amp breaker feeding the spa. That means that no additional blowers or heaters could run at the same time. NEC only allows 80% of the breaker's rating, so 70 amps X .8 = 56 amps max. That may require a larger main electrical panel in your home!
But relax, I have repaired plenty of spas which have three pumps labeled as "5HP" and they are actually 3HP pumps with over sized impellers, or some other combination - but they are NOT truly Five Horsepower pumps.
The rating plate on the motor will prove it. In each of the cases replacing the motors with the same amp/voltage required buying 3 HP motors. In fact, recently I replaced two bad motors in a spa which had three pumps with 5HP stickers on them - and one of them was only a 1.5 HP two-speed for heating/filtering. It had a completely different motor, the pump housing was smaller, the plumbing was smaller, needless to say the impeller was smaller, and yet it had it's very own "5HP" sticker just like it's big brothers. I looked at the rating plates on the bad motors, ordered new wet end pumps accordingly, and the new pump/motor combos were 3HP with 2" plumbing. The spa worked exactly as it did when new.
So again, if the customer shopped and bought because the maker told them they had three five horse motors, they were misled. If they shopped and bought because they turned one of these tubs on in the showroom and were pleased by the amount of water moving - and if that held true to the spa which was delivered to their home, then once again I say, the HP claims and/or markings on the brochure and even the tub mean nothing.
OK, one more thing - if you can get good jet action out of smaller pump/motor combos, why wouldn't you? I mean, why pay the extra energy bill if you don't have to? Most of my customers report that they run the jets at reduced power - that is easily accomplished in HotSpring and Tiger River tubs - and I haven't had folks complain about lack of power at the jets.
Yes, some have come in and put their hand in front of the jets and reported that it wasn't as strong as brand X they had just looked at. And they were right! I have sold Caldera, and they can be set to put out far more kick at the jets than HS and many other tubs. But long-term owners tell me that too much power at the jets is just too much power. It is not comfortable, and it not used in reality, at least not on a regular basis. HS puts in a few extra-large jets for when you need the extra punch, but I think they have come up with a pretty good system using far less power overall. Even my Caldera owners tell me that they move diverters and adjust jet settings to mellow out the jets for regular use.
So again, I say to shoppers - wet test, or at least stick and hand/arm in front of working jets in a running spa to determine if you are going to get enough power from the jets.
8-)
In Canada eh:
To All,
What Chas has said is correct although perhaps a little long winded ;) A quick and easy look at the motor HP to pump GPM ratio would go like this.
Say you have two different spas that both have one 200 GPM pump. Spa "A" has a well designed low head or back pressure plumbing layout. That spa may only require a 2.5 HP motor to move the 200 GPM the pump is capable of delivering. Spa "B" has a poorly designed plumbing layout, higher head pressure with a lot of bends and elbows in the system and a lot of small jets. That spa would require 4.5 HP to deliver the same 200 GPM.
Its all about the pump GPM and the plumbing or head pressure in the spa, the HP is some what irrelevant. Motor performance is measured in amps and that can be converted to HP. Pumps are measured in GPM only. The term "4.8 HP pump" makes no sense. The correct way to say it is 200 GPM pump with a 4.8 HP motor.
Just my 2 cents worth
Repeat_Offender:
Chas,
Excellent points, and you're right. "All things being equal" is non-existant in the hot tub world. I guess simply put, more horsepower gives you greater "potential" for greater pressure, water movement, etc..
Joe
Chas:
--- Quote ---To All,
What Chas has said is correct although perhaps a little long winded ;)
--- End quote ---
A LITTLE!? Wow, I just looked it over - I guess I have battled this for a long time.
Sorry to get so verbose....
Breathe Chas, breathe.
8-)
Zep:
could one also make many of the same "horse power means nothing"
arguments about cars?......because many cars are designed different
and some may be "designed better"?
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