2-speed pump, or just a 2-speed motor?

[DaveAZ]

Ok now that you have the pump figured out, there is another issue.

With a pump that large I would have expected a lot more head loss on 2"/1.5" plumbing. 48' of head loss is very low for 1.5" plumbing and would put the flow rate at 90 GPM. Is there only a single 1 1/2" return line from pool to pad or are there actually 4 separate return lines that split at the pad, one to each eyeball?

My existing equipment has a 1HP impeller and the side of the housing front is marked 1HP. For the purposes of their curve, 1HP applies, not 3/4 HP . Shouldn't that be 84 GPM @ 46' of head?

That sounds pretty close, but to make matters more confusing, the pump I'm using for these readings is an unknown spare pump. This one is marked Challenger Centurian and has 2 capacitors, while my original pump has only one capacitor. When I started my pool a month ago I discovered that the original pump has trashed bearings, which led me to decide to get a two-speed pump now. The spare pump (now in use) has no model number anywhere and I never looked at it's impeller to see it's size.

The discharge side plumbing has a single 1-1/2" line from the backflow valve to below ground. I doubt the builders would have gone to the expense in extra pipe and labor to manifold them underground, and the nearest eyeball absolutely gets a lot more flow than the farthest. At most, they may have an underground Tee fitting and have gone in both directions around the pool.

Also, the other thing that doesn't make sense is that when you have the KK fully engaged, you have less head loss than when you have two suction ports, 37' of head vs 48' with both suction ports open. That is impossible so one or more of the measurements must be incorrect. Because of the excess head loss on the suction side, this makes the pressure readings very low so I suspect there is a lot of error in the pressure reading. Are you confident that both gauges are operating correctly?

All the gauges are new and seem to be fine. I have no idea of their accuracy.

At this point, I can't tell you what is going on since nothing seems to make sense.

Ok, just I went out and took a new set of consecutive readings with the diverter valve in different positions. The filter is no longer clean, so these will not be the best to establish a TDH for selection puposes. My pool is still dirty from the huge dust storm (Haboob) that passed through last week and the filter gets full in only a few days of running. I'd be willing to do this again with a clean filter if the results would get me an answer to the question of "Will the KK work on low speed and still have a little left over flow for the skimmer?" (I'm not sure what we are looking for in these calcs.)

1. Skimmer closed: 1 to 2 PSI / -22 in. Wg.= 32.48 ft.H2O
2. KK closed: 16 PSI / -7 in. Wg.= 47.87 ft.H2O
3. Diverter not obstructing: 16 PSI / -5 in. Wg. (Vacuum needle bouncing a lot) 45.61 ft.H2O
4. Diverter partially obstructing skimmer. 10 PSI / -17 In. Wg. = 45.31 ft. H2O
5. Diverter partially obstructing skimmer. 12 PSI / -15 In. Wg. = 47.67 ft.H2O
6. Diverter partially obstructing skimmer. 14 PSI / -12 to -13 In. Wg. =50.03 ft.H2O
7. Diverter partially obstructing skimmer. 16 PSI / -9 In. Wg = 50.13 ft.H2O

My very first readings, done with a clean filter and the diverter in my usual running position, which I based my original calculation on: 14 PSI / 9 In. Wg = 45.51 ft.H2O

Have you thought about a VS pump? In situations such as this, it takes the guess work out of things. Of course it costs a lot more too.

Definitely not. My pool budget is steering me towards a remanufactured 2 speed pump. My family uses my pool a handful of times a year, mostly when guests are here.

I'm under the impression that my pool plumbing can get by with the smallest 220V 3/4 HP 2-speed that I can find. I can start out running it with the 1HP impeller and see what results it gives me. I doubt I'd need to switch to a 3/4 HP impeller for any reason.

I'm thinking my motor selection choices would be any of the following, based on rebuilt availability or least price new:
B2980
B862SE
B980
SQS1072R (48Y)
UQS1102R (48Y, 1HP, up-rated)

I'd like to compare them, but no curves are available for specific motors.

 

[mas985]

Again. The motor does not set the head curve. The head curve is determined by the impeller. If you don't change the impeller, the head curve does not change. If you go with a 3/4 HP impeller then use the 3/4 HP Challenger pump curve.

If you stay with 1 HP impeller, you will need to have a two speed motor to match. The B2982 is a 1 HP full rated motor that would be a good match. You can only use the B2980 if you also downsize the impeller to 3/4 HP.

 

[DaveAZ]

Again. The motor does not set the head curve. The head curve is determined by the impeller. If you don't change the impeller, the head curve does not change.

The differing amps thing is confusing me. I was thinking that if the amps are greater at 1/2 speed it will spin faster. You are correct, they should all have identical output with the same impeller and I should be able to use the challenger pump curve.

I have located a used SQS1072R (48Y) for $200.00 from a rebuilder.
I have an extra 2hp pump that I will bring with me to see if I can cut the price in half.
I have also located a 3/4 hp impeller for $20.00.

If you were to replace the motor with a two speed, the high speed operating point would not change and on low speed, the operating point would be around 34 GPM @ 11' of head.

However, since you are drawing from both the skimmer and the KK, that 34 GPM would be split between the two. If you want to run the KK on low speed, you will probably need to run 100% on that port to get the target flow rate. Doing so, will increase the suction head loss and therefore, you may not get 34 GPM. If you can measure the suction again but with just the KK engage and no draw from the skimmer, I can then tell you if there will be enough flow rate for just the KK alone. This would be worst case but at least you would know if it worked at all.

I'd love to be able to calculate the TDH at 1725 rpm. The Hydraulics 101 didn't establish how I would create a plumbing curve to do that and I have no idea as to how people are able to use the low-speed portions of the pump curve without it.

Actually, the third post has a spreadsheet that allows you to do just that. But again, I think what you really want is to determine what the flow rate is which the spreadsheet will also do.

Where is the third post with the spreadsheet? I can't find it. I'm still not sure if the KK will operate at half speed, and Mark (mas985) didn't explain how the TDH readings I took would determine that. Should I somehow be able to use the 32.48 ft.H2O to determine it? The MFG. told me on the phone that 25-28 GPM is enough for it to run. I see that 34 GPM @11 ft. head is on the 3/4 hp curve...

 

[DaveAZ]

Bump before I go shopping...

 

[mas985]

1. Skimmer closed: 1 to 2 PSI / -22 in. Wg.= 32.48 ft.H2O
2. KK closed: 16 PSI / -7 in. Wg.= 47.87 ft.H2O
3. Diverter not obstructing: 16 PSI / -5 in. Wg. (Vacuum needle bouncing a lot) 45.61 ft.H2O
4. Diverter partially obstructing skimmer. 10 PSI / -17 In. Wg. = 45.31 ft. H2O
5. Diverter partially obstructing skimmer. 12 PSI / -15 In. Wg. = 47.67 ft.H2O
6. Diverter partially obstructing skimmer. 14 PSI / -12 to -13 In. Wg. =50.03 ft.H2O
7. Diverter partially obstructing skimmer. 16 PSI / -9 In. Wg = 50.13 ft.H2O

These measurements still do not make sense to me. #1 should have the highest head loss of all meassurements and not the lowest. Also, total head loss should be higher in 4 than 7, not the other way around.

Also, the head loss for #2 seems very low for that pump. Based upon just on the description of your pool plumbing, I would have expected #2 to be 18.3 PSI/10.5" of suction for a total head of 63' @ 78 GPM.

Is there a lot of air being sucked into the pump basket during these tests?

Also, when you had the pump apart, did you inspect the impeller for damage?

One thing that I would like to point out is that most people who have two speed pumps, like myself, run the cleaner on high speed a couple of hours a day and the rest of the time on low speed. This is beneficial in a couple of ways. #1, you will not have to close of the skimmer as much to get the cleaner to work and #2, the skimmers work much better at high speed that low. Running the cleaner on low speed, will reduce the effectivness of the skimmers so any floating debris will sink to the bottom and the cleaner will have more work to do.

If I were you, I would consider downsizing the motor/impeller and running the cleaner on high speed for a few hours a day and then drop down to low speed for just filtering and circulation. This is what I do and it has worked out pretty well for me. My pump is only a 1/2 HP and I can still run the cleaner with the skimmers (2) working and have solar running at the same time.

 

[DaveAZ]

1. Skimmer closed: 1 to 2 PSI / -22 in. Wg.= 32.48 ft.H2O
2. KK closed: 16 PSI / -7 in. Wg.= 47.87 ft.H2O
3. Diverter not obstructing: 16 PSI / -5 in. Wg. (Vacuum needle bouncing a lot) 45.61 ft.H2O
4. Diverter partially obstructing skimmer. 10 PSI / -17 In. Wg. = 45.31 ft. H2O
5. Diverter partially obstructing skimmer. 12 PSI / -15 In. Wg. = 47.67 ft.H2O
6. Diverter partially obstructing skimmer. 14 PSI / -12 to -13 In. Wg. =50.03 ft.H2O
7. Diverter partially obstructing skimmer. 16 PSI / -9 In. Wg = 50.13 ft.H2O

These measurements still do not make sense to me. #1 should have the highest head loss of all meassurements and not the lowest. Also, total head loss should be higher in 4 than 7, not the other way around.

Also, the head loss for #2 seems very low for that pump. Based upon just on the description of your pool plumbing, I would have expected #2 to be 18.3 PSI/10.5" of suction for a total head of 63' @ 78 GPM.

Is there a lot of air being sucked into the pump basket during these tests?

Also, when you had the pump apart, did you inspect the impeller for damage?

One thing that I would like to point out is that most people who have two speed pumps, like myself, run the cleaner on high speed a couple of hours a day and the rest of the time on low speed. This is beneficial in a couple of ways. #1, you will not have to close of the skimmer as much to get the cleaner to work and #2, the skimmers work much better at high speed that low. Running the cleaner on low speed, will reduce the effectivness of the skimmers so any floating debris will sink to the bottom and the cleaner will have more work to do.

If I were you, I would consider downsizing the motor/impeller and running the cleaner on high speed for a few hours a day and then drop down to low speed for just filtering and circulation. This is what I do and it has worked out pretty well for me. My pump is only a 1/2 HP and I can still run the cleaner with the skimmers (2) working and have solar running at the same time.

This isn't the 1hp pump, it is an unknown pump that a neighbor gave to me after they upsized for their new water feature. I recently had the rear ceramic seal replaced in it, so the shop had to pull the impeller and they didn't say it was damaged. I don't know the size of this impeller, either. I will be checking the impeller when I have the two-speed to put in it's place.

I agree that the readings are odd- I was referring to the KK plumbing run as my high static run on paper, but it didn't turn out that way in reality. I have no idea why, either. The skimmer wasn't sucking air. I had it open and was checking the surface for movement to verify if it was active or not. I even double-checked because after I did my math I went to verify that I didn't confuse the KK/skimmer readings. Now I'm imagining an obstruction in my skimmer line, but these readings are the sole basis for it. The basket was always in place...

I really want the KK cleaner to function on low. I tossed my navigator and bought the KK a few weeks ago for this very purpose. My plan was to run it on high when it starts, since it needs to prime any way, and to let it run for perhaps the first hour on high so that the skimmer can do its job. Then switch to low to allow the KK to continue doing it's thing for the rest of the time. The KK is far more important than the skimmer in my pool. Floating debris is rare, but the bottom gets a lot of dirt. If I need it to run on high for the KK, I may as well stick to a single speed based on the needs of the pool.

 

[mas985]

I found a small silver sticker on the housing front. it reads: CHII -N1-1FE 2-13-A02
The correct Pentair equivelent part number is 345205.

This isn't the 1hp pump, it is an unknown pump that a neighbor gave to me after they upsized for their new water feature. I recently had the rear ceramic seal replaced in it, so the shop had to pull the impeller and they didn't say it was damaged. I don't know the size of this impeller, either. I will be checking the impeller when I have the two-speed to put in it's place.

??

I am getting conflicting information. I would like to help but unless you know what pump you have, any measurements are meaningless.

 

[DaveAZ]

I found a small silver sticker on the housing front. it reads: CHII -N1-1FE 2-13-A02
The correct Pentair equivelent part number is 345205.

This isn't the 1hp pump, it is an unknown pump that a neighbor gave to me after they upsized for their new water feature. I recently had the rear ceramic seal replaced in it, so the shop had to pull the impeller and they didn't say it was damaged. I don't know the size of this impeller, either. I will be checking the impeller when I have the two-speed to put in it's place.

??

I am getting conflicting information. I would like to help but unless you know what pump you have, any measurements are meaningless.

This wasn't new information:

That sounds pretty close, but to make matters more confusing, the pump I'm using for these readings is an unknown spare pump. This one is marked Challenger Centurian and has 2 capacitors, while my original pump has only one capacitor. When I started my pool a month ago I discovered that the original pump has trashed bearings, which led me to decide to get a two-speed pump now. The spare pump (now in use) has no model number anywhere and I never looked at it's impeller to see it's size.

The post you quoted on top was in reference to the OE pump that the pool was built with. First I was told in this thread that I need to match or go greater than my original equipment, which I was convinced was oversized because I calc'ed the TDH (by using this 1-1/2hp pump) and that I referenced the pump curve with the TDH and desired GPM and I believed a 3/4hp was appropriate. Unfortunately I had the wrong pentair number for the OE pump, which led you to believe I had an uprated 1hp motor with a 3/4hp impeller on the OE pump. I then checked the impeller and searched the half of the pump plastic housing that stays with the pool plumbing and I found the actual pump part number, confirming it as a 1hp.

Does the pump size change the TDH readings? I tried having this discussion at the pool store, and they had no idea how to adjust the calculation for the impeller size/pump hp.

I just checked the impeller on the operating pump. It is 35-5315. 1-1/2 hp. Does this clear anything up? If not, let me know what I can do in order to get measurements that have meaning. I have the 1-hp impeller from the original pump and I can mount it onto the 1-1/2hp pump for measurements.

I went to a pool motor shop today and they are rebuilding a 3/4hp 2-speed 230V motor for me for $200.00. If I need a different size (with expectation to operate the kreepy krawly on low speed) I'd need to know on Monday so I can call them and change my request before they begin working on my order.

Thanks for your help, Mark!

 

[mas985]

I had assumed that the Challenger pump that you were talking about all along was the one that was connected to the plumbing since that is the only one that really matters.

Does the pump size change the TDH readings?

Definitely! The larger the pump, the higher the flow rate, the higher the flow rate, the more TDH.

I just checked the impeller on the operating pump. It is 35-5315. 1-1/2 hp. Does this clear anything up?

Yes and no. That impeller is for a full rated 1 1/2 HP pump but the pressure and suction you are measuring for #2 is much too low for that sized pump and your plumbing. If you had 2.5" plumbing, then I might believe those measurements but with such small diameter plumbing, the head loss should be much higher. Based on the description of your plumbing, you should have a filter pressure of around 19 PSI and suction of 11" hg. Either there is something wrong with the pump or there is a large amount of head loss between the pump and filter. This is the only section of your plumbing that is not accounted for with the filter pressure or the suction measurement.

You might be able to resolve the difference with a pressure measurement at the pump itself via the drain plug. If it is a lot higher than the filter, then that could explain the difference. BTW, you are measuring the suction at the pump drain plug, correct?

I don't think you will be able to resolve this by Monday but if you are willing to risk it, I would say there is a pretty good chance that you will be able to hit at least 25 GPM on low speed with a 3/4 HP full rated pump but at this point I cannot be 100% certain. The worst case is that you run the pump at full speed for the cleaner and low speed the rest of the time. You will still save money on energy costs.

The motor they are rebuilding for you, is that full rated or up rated? It makes a difference for the impleller size. If it is a full rated 3/4 HP motor, then you will need to replace the impeller with a 3/4 HP impeller (35-5187).

 

[DaveAZ]

I installed my two-speed setup.

I got a 3/4 motor, which I believe to be a rebuilt EB980 (Emerson.) I had to make two trips to the motor rebuilder shop 30 miles away and I paid $220.00 for it with me supplying the pump parts and rear seal. It would have been better to just buy a new one online for 180.00 plus shipping. It does have impeller 35-5187. Too late for regrets...

After I installed the pump and set the diverter to the optimum position for the Kreepy Krawly to run at high I took some readings. (The KK doesn't work on low. Too bad, but this may make the KK pad last longer.)
The filter may be a little dirty, so these may be a bit high.
On high:
10psi @ top of filter
-10"wg @ drain in front of pump
37.4 TDH

On low:
0psi @ top of filter
-4"wg @ drain in front of pump
12.24 TDH

My initial settings have it on high for 1.5 hours, followed by 5.5 hours on low.
I will be adjusting the high time duration until I see the KK is doing a good enough job.

I haven't tried to figure out my GPM, turnover, etc. yet. I may need to add more low speed runtime.

So far so good... Thanks again for the help!

 

[mas985]

74 GPM on high and 37 GPM on low.

 

[DaveAZ]

74 GPM on high and 37 GPM on low.

Not bad. I was targeting 63GPM on high and a minimum of 28 gpm on low.
63 GPM was because of the 1-1/2" supply piping from filter to jets. 28 was because the Kreepy Krawly claims it only needs 28 to run. I'm calling B***sh** on that, because it refused to run with the diverter at full force at 37.

The pool had a 1hp motor for over a decade (as installed by builder) and I downsized to 3/4hp. I'm glad I did. 74 won't do damage.

I think I'm set. Now I need to decide what turnover rate I am comfortable with on a residential pool which gets very little use.

 

[mas985]

When you put the diverter on full kk, head loss goes up because of the extra restriction and therfore flow rate goes down which is probably why the kk will not work on low speed. On low speed, the head curve is 1/4 that of high speed so it doesn't take much head to significantly reduce flow rates.

 

[DaveAZ]

While the pump was set to low, I gradually adjusted the diverter, one click at a time, while checking the KK with each adjustment. The KK was doing it's normal click thing, but the pad was not sticking to the bottom of the pool sufficiently enough for it to move.