Sizing a new pump

[lstinthot]

We live in Central Virginia. We have a hurricane season.

[mas985]

You can use this map to determine your vulnerability.

http://www.vaisala.com/VaisalaImages...01997-2010.png

[lstinthot]

Looks like we are in the 9-12 region.

[lstinthot]

Looks like these two pumps pull the same amps. The WFDS-4 is one HP and the WFDS-26 is 1.5 HP. The -4 costs about $75 more than the -26. Does it make sense they both have the same amp rating? Wouldn't make more sense to go with the 1.5 in my case then for the higher lift?

Thanks

The UltraFlow is a high head pump so priming is probably as good as it gets with this pump. You can either replace the entire pump or just the motor. It usually makes more sense to just replace the motor if the wet end is in good condition and you don't need to change any plumbing. But since you have to change the plumbing anyway, it may make more sense to replace the entire pump. Either way is fine, it is basically an economic decision.

However, when looking at a replacement, you need to focus on max head because that is the only thing you can go on for priming ability. The higher the pump head, the larger the impeller and more effective the pump will be at priming. However, in most pump lines, the max head is the same for the various HP ratings so you can lower the HP to save some on electricity costs.

If you want to stick with Pentair, the Whisperflo is a good pump line but for priming reasons, I wouldn't go below 1 HP (full rated). So either the WFDS-4 or the WFDS-26 would be a good choice.

BTW, where is your location and how much do you pay for electricity? A VS may or may not be a good solution for you.

[lstinthot]

Will these pumps move water on slow speed in my application? I am figuring 50 Ft of head, looks like slow speed graph tops out at 22 lbs.

[mas985]

Looks like these two pumps pull the same amps. The WFDS-4 is one HP and the WFDS-26 is 1.5 HP. The -4 costs about $75 more than the -26. Does it make sense they both have the same amp rating? Wouldn't make more sense to go with the 1.5 in my case then for the higher lift?

The WFDS-26 is an up rated pump while the WFDS-4 a full rated pump but other than the label, they are identical in performance. So it doesn't matter which you get. One of the problems with pump ratings is that it causes confusion.

Will these pumps move water on slow speed in my application? I am figuring 50 Ft of head, looks like slow speed graph tops out at 22 lbs.

Yes, they will still move the water on low speed. But head loss is dependent on flow rate so on low speed, head loss is about 1/4th that of high speed. If you indeed have 50' of head on high speed, on low speed you would have 12.5' of head. But you don't need to figure head loss to know that low speed is always around 1/2 the flow rate of high speed.

But because of the lift, you will need to always prime on full speed and then switch to low speed. The pump should not lose prime when shut off but if does, it will need to be started on high speed. If you get a two speed timer, that should solve any priming issues because you can always start the pump on high speed and then switch to low speed.

[lstinthot]

I installed the WFDS-26 today. Went pretty good. Took a little longer than expected to complete. The discharge pressure on high is 16# and maybe 2# on slow speed. Not sure what others are seeing for slow speed discharge pressure. I did change the piping on the return of the filter. It now comes out of the filter and goes back to the pool without going through the heater or clear water metal copper system. Very little water comes out of the vent when I open the vent on top of the filter in slow speed. I am returning to the bottom drain of the pool. We keep this lineup during the spring to help heat the pool. Have not tried going back to the return jets.
Pump is significantly quieter then the ultraflow 2HP even on high speed.

New filter elements will be in Friday.

[mas985]

Low speed will have lower pressure and theoretically should be about 3 PSI but gauges get inaccurate at low PSI. 1/2 the flow rate results 1/4 the head loss in the plumbing.

But is the pump basket staying full between pump runs?

[lstinthot]

The pump started up immediately the following day. Pump was full pressure came right up to 16# . Best it has ever done. I'm thinking slow speed could have started moving water from the start.

[mas985]

As long as the the pump doesn't lose prime after being off, you can start it on low speed if you want.