RPM to GPM estimates for VS-SVRS?

[mas985]

The California Energy Commission (CEC) contracted a thrid party to perform some measurements for numerous pool pumps and posted the data to their web site. So far, it is the most comprehensive set of data for pool pumps that I have seen and allows one to directly compare the energy efficiency of pumps. The CEC performs measurements for two theoretical plumbing curves, soon to be three. From these four points (2 curves, 2 speeds), a pump energy curve and head curve can be inferred which is what the spreadsheet does.

The pump energy curve requires the knowledge of GPM, RPM and Watts for at least three operating points in order to do the curve fit. The head curve only requires two points of both GPM and Head for the curve fit, preferably at a high RPM.

Once the coefficients for the curves are known, you can then look up any other point. So for those without a GPM readout on their pump, they only need to know RPM and Watts to determine what the GPM and head is likely to be.

With the data you have, you could replace the head curve calculation to more accurately represent your pump's head curve although it shouldn't vary that much from the CEC data. If you had a watts measurement as well, then you could also replace the default pump's energy curve with your own. But first, you might want to confirm your measurements with what the tables indicate to see if there is much error.

 

[PoolGuyNJ]

CEC is the California Energy Commission.

Scott

 

[jt-cali]

Hi,
I need help with the IntelliFlo spreadsheet. I have the VS-3050 and used the electric meter to measure the wattage (PG&E SmartMeter). The wattage I got seem pretty low and I'm not sure if there's a power factor that needs to be taken into consideration.

Direct Calculation
RPM Setting 3450 3110 2350 1500 1000 750
Watts Reading 2039 1509 688 220 97 60
RPM Ratio 100% 90% 68% 43% 29% 22%
GPM Estimate 46.92 41.83 30.60 13.34 (11.25) (49.81)
Head Estimate 91.54 74.49 42.69 17.92 7.84 (1.83)

 

[mas985]

Your watts do seem quite low for the RPM setting. Do have a filter pressure for each of those settings?

 

[jt-cali]

Here's the PSI numbers:
3450 - 37
3110 - 30
2350 - 16
1500 - 2
1000 - 0
750 - 0

 

[mas985]

The PSI values are consistent with both the watts and head values. You must have 1 1/2" plumbing or something in the return that has a lot of head loss. 37 PSI with only 47 GPM is quite large and would indicate very restrictive flow.

However, the pump should not draw less than about 75 watts according to the published data so I don't know why it would read lower than that for the low end. In fact if you look at the tab labeled "Energy Table", you see what the minimum is for each RPM (column C).

The plumbing curve systems to deviate from 1500 RPM on down. I have noticed on some plumbing systems that when flow rate drops the plumbing equivalent length increases. Do you happen to have any spring loaded check valves? If so, how many? Also, tell me a little about your plumbing.

 

[jt-cali]

I'm not sure what's in my plumbing as I bought the house last year with the pool. I think there are check valves, but not exactly sure what type they are. There are 1 1/2" pipes from the filter to the heater. I'll take some pictures when I get home from work.

 

[jt-cali]

Here are some pics of my setup. The intake is 2" to the pump. But the rest is smaller. The filter has 1-1/2" in/out and same with the heater. The returns are also 1-1/2". The distance to the spa is about 6ft (3 jets) and the pool returns are at about 25ft and 34ft.
There's a check valve right after the filter, before the heater. But I'm not sure what type it is. I've attached a picture.

PUMP AREA

PIPES

CHECK VALVE

 

[mas985]

I see a couple things that could be an issue.

Is that 1" pipe that the returns step down to? Also, the suction ports look like they are pretty small too. All of this will add significant head loss to the plumbing which may be why you are seeing high pressure and low flow rates.

Also, the check valve in the picture could be either the flapper type or axial spring. The latter takes a significant amount of pressure to open so low speed may be blocked which is why you are getting the results you are. Also, the flapper type sometimes fails and will block the return pipe.

Has the pressure always been this high or only recently?

Did you have the Intelliflo installed?

What was the pump and pressure before?

 

[jt-cali]

The 1" pipe goes to the booster pump. The 1-1/2" return was hidden behind the step down connector in the picture.
The suction side are all 2" pipes.
The pressure has been the same since I got the house.
The IntelliFlo was already installed when I bought the house.

 

[mas985]

The pipe coming out of the ground on the suction side looks smaller than 2" are you sure all 2" is used to the pool. Same on the return side, it looks smaller than 1 1/2" going into the ground. The pipe going to and from the pool is what really matters in terms of size not so much the size that connects to the pump although that can be important too.

 

[jt-cali]

The caliper measured 2.134" and 1.632" for the pipes that come out of the ground.

 

[mas985]

Ok, must be an optical delusion on my part.

Still, when I model your setup, I had to guess a lot, I need to add an additional 1500' of 2" pipe before I get those pressure levels. What this might mean is that there is a lot of unaccounted head loss in your plumbing somewhere. My first guees would be either the check valve or the filter. I would check the filter first as it is easier to deal with. Has the filter been backwashed/cleaned recently? If the filter is a DE, it may need a grid cleaning.

 

[jt-cali]

I cleaned out the DE filter back in Sep 09. Lightly pressure washed the grids to remove all the gunk. I didn't jot down the PSI's before I cleaned it, only after. And the pressure's been the same since then. To re-coat the grids with DE, I introduced it via the skimmer. I did it a little at a time, making sure that the DE is well dispersed and not just dumped in. Do you think it might have collected somewhere in an elbow and blocking the pipes?

NEW READINGS (edited - changed multi-meter batteries to get accurate readings):
I finally figured out how to attach an amp meter to the setup without taking too many things apart. The wattage as calculated using V*A is a bit higher now for the lower RPM values. Also, when it's not running, there's a .22A draw (53W).

I just added another 3" of water in my pool, so the electric meter readings are about 10W higher from the previous results. The voltage on the line is 240v (inside 120v).

RPM Setting 3450 3110 2350 1500 1000 750
Watts Reading 2057 1514 686 242 125 101
Meter Watts 2069 1539 701 230 92 58
Amps 9.9 7.3 3.33 1.18 0.63 0.51
PF 1.006 1.016 1.021 0.949 0.737 0.575
Amps 8.57 6.31 2.86 1.01 0.52 0.42
RPM Ratio 100% 90% 68% 43% 29% 22%
GPM Estimate 48.34 42.36 30.32 22.82 15.22 19.25
Head Estimate (ft) 91.19 74.37 42.74 17.03 7.57 3.64
PSI 37 30 16 2 0 0

 

[PoolGuyNJ]

Sorry for going off topic a bit.

That's one ancient system!

How are you chlorinating? I hope you're not using tabs in the skimmer(s). Tabs plus copper pipe = copper in the water. High speed water flow and coper = eroding pipes. The two together = failure before long.

Scott

 

[jt-cali]

The filter looks old outside. But when I opened it up last year, the inside looks great and shinny after I cleaned it.
The heater box is rusted. I don't really use it as the temp. controller is not working.

I had put tabs in the skimmer when I first got the house... maybe 2 dozen or so. Then I got a floating dispenser.
I chlorinate with liquid bleach now, dispensing in front of the booster pump return with the Polaris cleaner disconnected.
There's a couple of tabs in the floater now for CYA.

How can I tell if my pipes underground have eroded to the point of failure?

 

[mas985]

If the pipes had eroded to the point of leaking, you would know by the water loss and perhaps wet ground.

Also, the power factor for the Intelliflo should be very nearly 1 since it coverts the AC to DC in the first stage. Also, others have reported that VA is pretty close to their power meters. So the difference between VA and the power meter is probably just accuracy in either measurement although it seems to deviate by quite a bit.

 

[jt-cali]

I finally realized that my multi-meter was probably out of whack after contemplating on the 260V line voltage. I changed the battery and now it's reading 120v/240v. I took a new set of readings and they match up well on the higher RPMs. But the lower ones are still off.

I updated my earlier post with the correct readings.

 

[mas985]

I am more inclined to believe the amps reading as they make more "sense". Given the problem PG&E has had with their meters, it wouldn't surprise me if they are reading wrong at low values. Also, when you do those readings are you turning off the rest of the house power or just subtracting the baseline power from the house? Sometimes things can turn on or off in the middle of a measurement, such as a refrigerator, that can mess with the measurement.

 

[jt-cali]

I turned power off to the rest of the house for one set of readings. Subsequent tests were done using subtraction method and comparing with first set. If the readings were more than 5 watts off, I would shut off the fridge. I had forgotten to turn it back on once and it was off for half a day.