Motors and Pool Pumps

When comparing the motors the power delivered will depends on the loading on the motors and rotational speed. As suggested, a 1 HP motor can deliver 1 HP at specific rotational speed and load. So you must verify the rotational speed rating of the pump motor, since the pumping capacity will depend on the rotational speed at which the pump is operated. Motors tend to vary somewhat also, and their are varying efficiencies at which the transfer power to a pump. I would say if it is the same manufacturer and model number it is like for like, else they need to supplied the motor efficiencies and curves to show equivalence or better to standards.

The OP seems to me to be concerned about motor speed and the effect on turnover.

I assume that you will concur that the motor will run at 3450 RPM.

We assume that a competent pool servicer will replace the motor like for like.

Thanks.

And this is why they must provide paperwork, to show the service was condcuted by someone competent and who performed a proper job. I would never allow a well pump or motor to be replaced with out proper documentation on the replacement showing it conforms to project requirements. BTW, pump motors tend to be 1700 and 3450, and 1100, but a closer inspection of the power curves would allow you to see they aren't actually exactly 1700, sometimes they are set to perform at 1850 rpms. Also, the pump needs to deliver pumping HP to the water to achieve turn over rates.

Lynlynch,

There is a flaw in your reasoning: "competent pump repairman". You cannot assume the competence of the person doing the work. The purpose of the OP's job is to verify that the work was done in a way which will not compromise public safety, sanitation and health. Many municipal pools use their own employees to do this kind of work. Places like the YMCA or a health club may have the custodian or a handyman do it. The managers usually have no clue whether or not their staff is capable of this type of work.

Case in point: several years ago the local YMCA upgraded their aquatic center. After replacing 3 brand new pump motors, the service tech asked our utility if we could raise the voltage to the building. The service is 208V, and he had burned up three 240V motors, each time causing a building evacuation and fire response. He seemed incapable of understanding that he needed a 208V motor, or that raising the voltage would damage all of the other equipment which was properly rated. One of my staff finally took pity and walked him through ordering the correct motor.

How do you get the motor to not run at standard speed?

change the frequency

Then you are using a VVFD that isn't mentioned. İ would think they would be rare for pool pumps as well.

I will repeat myself in answer to your question.

To get/have a motor NOT run at a standard speed, you can use a Variable Speed Drive.

Now do they use VSD's for speed control of pool pumps in this particular application that the OP mentions? Who knows!

I know of several pools in the UK & Canada that do, their application is to increase the circulation of the water dependent on several factors and to make waves.

But this is off topic

Standard speeds vary. I just did a quick search online and found motors for pool pumps in the Us that run at 1800, 1700, 3450 and 3600. That was just looking at 2 manufacturers sites and reviewing the specifications. Plus if you look they allow a variance in thats standard speed for the motor. So some actually run at 1850 instead of 1800. Plus there are other electric motors you can purchase for pumps that operate at 1100 or 1200. There really isn't one standard, just some more commonly used speeds.

Please - The electrical frequency and number of poles set the motor speed. One of the electrical guys can possibly explain this to you. Or can you find a fixed speed motor running on 60 Hz at 1400 RPM?

I have not seen a 1400 RPM motor as I can recall, just the ones i looked up really quick at a couple of manufacturers websites. The bearings and other components set a load internal which impacts the efficiency. Just the fact that there are manufacturers showing other standard operating speeds for just pool pump motors in the US, should indicate the two operating speed of 1700 and 3450 are not standard.

Like LynLynch says, The Pool motor pumps I see operate at 3450 RPM. As they are powered by induction motors the armature speed is determined by the frequency of the AC current powering it. So generally you will see speeds of 1725 or 3450. Ideally it would be 1800 or 3600, but there is some slip. The pumps are centrifugal, so you need good rotor speed at the impeller to push water through a filter. Some smaller spas have two speed motors to maintain flow through the heater when not in use, but that is not common in swimming pools. If they have changed the pump motor then I imagine they have replaced it with one of the same RPM. They would almost have to go out of their way to find one with the wrong speed to fit the pump. As the speed would probably be half what it should be, the sound of the pump would be immediately and noticeably different. -Illya

Or do motors of the same horsepower potentially have different characteristics such as rotation rate that would affect the output of the pump and therefore change the flow rate/turnover rate of the pool?

Yes. A 1 hp 1725 rpm motor will not pump the same volume as a 1 hp 3450 rpm motor. If both speed and hp are the same, then the motors could be considered "like for like".

Depending on how many pools you have to inspect, and how good the maintenance of the pools has been before you started as the Pool inspector, you might ask at each pool if they have a maintenance log book, and a general equipment layout/plan/plant design (is there a maintenance man?). I would guess that as you work for the local authorities, then the pools were built by the local city council and therefore designs/layouts/equipment installed will be part of public record. I 'm sure that someone could help you understand those plans

If those plans are available either in the records department or at the pools, it might tell you what type/size of motors are currently in use, that is, the HP of motors and any other information that you require.

The maintenance log book might tell you when motors/valves were changed etc.

If no log book, then start a maintenance log book AND maintenance work sheets so you can keep a record of what work has been done, when it was completed and what was repaired/replaced.

If there is a maintenance man or department or even the pool manager, then it can be their responsibility to keep the log updated, it would not be difficult or complicated

Here we go again. Instead of providing a simple answer to a simple question, you geniuses have to go out of your way to prove your superior intelligence and vast knowledge of any subject that comes along.

For example, " 1700 and 3450, and 1100, but a closer inspection of the power curves would allow"

Or, "I would guess that as you work for the local authorities, then the pools were built by the local city council and therefore designs/layouts/equipment installed will be part of public record."

"To get/have a motor NOT run at a standard speed, you can use a Variable Speed Drive."

The poor OP couldn't care less about VFD's or the local city council.

Get over it people! I cannot believe the egos here. You are not helping the guy, you're just confusing the issue in your zeal to be recognized as the world's smartest person.

Here in the UK we have a pump manufacturer ( GRUNDFOSS) that supply pumps with three different speed settings. These speed settings are for adjustments to the pipe sizes being used. For instance if the pump speed is to fast through a small sized pipe then you will get a situation of water heating inside the pump and causing bubbles to be generated and in turn causes wear on the inside of the pump known as wiring.(spiraled lines) coming from the impeller on the pump body. this in turn will also wear out the pipe work and fittings more quickly. So when fitting a new pump the operating pressure and pump speed should be checked for the right amount of pump lift,(How far up a pipe the water will be raised before it will no longer be raised by the pump).

I would suggest to you to look at the pipe work to locate any pressure gauges and any pressure reducing valves (PRV's). Once you have located these items look for any lines that may have been drawn on them to see if the gauge needle still is within its operating limits. It is a bit of a hit or miss situation when you are only on the premises for about an hour to know what you are ment to be looking for. Even if a pump has been changed like for like it dose not mean that it has been setup correctly.

But that is not realy your responsability?. If you are going that far into the work that has been carried out you will need to have flow charts and pressure reading being made before and after the work is implimented.

While correct replacement is important, what makes me nervous about public pools/water features, is correct wiring methods.

Mr VanCuran,

Typical swimming pool pumps use a motor that is with a "C face"--in other words, it has a flat end with a machined rib and bolt holes to allow its connection directly to the pump. I consider three factors being required to rate the replacement as being " like for like":

1. Same horsepower.
2. Same or higher service factor.
3. Same or nearly same speed (such as 1700 or 1725 or 1740 or 1750 RPM, meaning a speed difference less than 5%).

I believe the original documentation filed when the pool was permitted and built should give the first motor's data. The nameplate information would give the second one. If any of the three items I listed above fail, then I would agree that the entire application needs proper design review because it is a modification from the original design.

If it is the installation of an entirely new pump and motor, then I could agree with insisting on filing the necessary paperwork (pump curves, and flow calculations) for the pool to be approved as meeting the requirements for turnover rate, etc.

--JMM