Should you use a vf pump

[dalehileman]

Notwithstanding the probability of drowning an interloper I advise no winter cover since it not only blocks your view of what might be going on underneath and requires occasional tedious sweeping of debris, in spite of a potentially reduced electric bill I also question the advisability of vf:

Since our inlets are at the head (W) surface flow carries flotsam to skimmer port at foot (NE) where it's deposited in the basket. Furthermore (for anyone considering new pool construction) our prevailing wind by the sheerest chance comes from exactly the right direction (SW)

Anyone considering vf, however, might judge whether a minimal flow rate might hinder the former action especially where a summer solar cover might limit the period during which this flow is possible

Apologize if the following is a breach of protocol but it's pertinent

http://ths.gardenweb.com/forums/load/po ... 99247.html

[chem geek]

As Mark noted on the GardenWeb thread, with the IntelliFlo VF you can set the flow rate to whatever you want for whenever you want. Like him, I have solar on part of the time at 48 GPM so with 3 returns that's 16 GPM per return while with the solar off it's 26 GPM so around 9 GPM per return though I have an IntelliFlo VF. I haven't notice any problems with debris getting to the skimmer, but I have an electric safety cover on the pool so debris is only an issue for the 1-2 hours per day the pool is open on weekdays and the 3-4 hours per day on weekends. Even on windy days, most leaves and debris get to the skimmer, but our prevailing winds tend to be towards the direction of the skimmer anyway.

[dalehileman]

Geek thank you for that report as we are considering vf

Wondering how you change pump speed, whether there's external electronics or simply a switch on the pump itself. If both how is the external electronics unit situated to protect it from the weather and are you confident when it fails that you will be able to easily fix it. For instance, will the maker likely remain in business and if so is it easily serviced, eg, by simply replacing a circuit board etc

Thanks once more

[chem geek]

You can program some things on the pump itself -- up to 4 programs, I believe. However, if you want these programs to change based on external events, such as a thermal sensor for a solar system, then you'll need an external controller. Pentair offers several at different levels of sophistication and pricing. The controller is a circuit board and panel put into a metal box with a cover so is weather proof. In my case, all of my equipment is in a pool shed designed for that purpose so this isn't a problem.

[dalehileman]

geek thanks for that report. If you can program your pump I assume that means it uses semiconductor logic and switching which in an environment like mine--the Mojave Desert--bodes ill with future maintenance. I had hoped to find a simple, inexpensive vf with no semiconductors but only mechanical switches to vary its speed. During the time I worked in the Electronics Industry high-voltage high-current semiconductor devices weren't very reliable even in a laboratory environment but from what I've heard so far evidently nobody else shares my apprehensions so maybe the sort of simplistic pump I imagine doesn't even exist today

Still I hope given no choice in the matter that its maker is well established and that the semiconductor electronics is easily and inexpensively replaced but thank you once more for your input

[dalehileman]

TO geek but by the way in a fabulous modern forum like this with intricacies such as confirmation codes etc how on earth does one edit one's post if previewing doesn't catch all the errors and typos

[chem geek]

There should be an "Edit" button to the left of the "Quote" button in the upper right of every post that you have written.

As for the IntelliFlo VF electronics, I believe they are a unit that can be replaced separately (i.e. they attach to the pump), but you should contact Pentair about that and about your specific operating conditions.

[mas985]

A two speed pump doesn't use any electronics other than a second set of windings in the motor and perhaps a capacitor or two. A mechanical switch is sometimes used to switch between speeds but you can also use a mechanical timer to switch between speeds. Mutliple speeds without electronics requires a multi-pole motor which beyond 4-poles (2-speeds) is hard to come by and probably very expensive.

As to the VF electronics, I have seen the drive advertised but the prices seem to be about 2/3rds the cost of the entire pump.

[dalehileman]

There should be an "Edit" button to the left of the "Quote" button in the upper right of every post that you have written.

You're right, there should be, but there isn't

As for the IntelliFlo VF electronics, I believe they are a unit that can be replaced separately (i.e. they attach to the pump), but you should contact Pentair about that and about your specific operating conditions.

Thanks I will look into that but in the meantime do you understand that this external unit is necessary for speed control, in other words, if you had no need for the kind of complex programming it provides (depending only on the existing timer), could you acquire the pump without that accouterment

[chem geek]

I don't believe so, but ask Pentair about your options. As Mark pointed out, a 2-speed pump wouldn't need special electronics and would be less expensive as well, though you obviously don't get the full variable speed range nor as high efficiency at lower speeds compared to the IntelliFlo.

[dalehileman]

Thanks once more geek. The 2-speed then is out since the entire purpose of switching to vf is diminution of our electric bill. Looks more and more, alas, as if I'm at the mercy of expensive complex subminiature weather-prone electronics

[mas985]

While the energy savings for an Intelliflo may be more than a two speed pump, a two speed pump can still save you quite a bit of money.

I went from a 1 HP single speed to a 1/2 HP two speed and was able to reduce the energy consumption by about 50%. Had I gone with an Intelliflo, it would of reduced the energy consumption by 65% so a bit more.

[ddalehileman]

Thank you again mas. From Internet reports I understand that savings even significantly higher than 65% are possible at even lower flow rates presumably without loss of other functions

[dalehileman]

....the question being whether pumps are made at these lower rates but without the electronics. So far it seems not though if someone in the know should provide a link to a pertinent catalog I'd be much indebted

[mas985]

Cost savings that you see published by variable speed vendors are usually unrealistic. They assume you are only running the pump at the absolute most efficient RPM possible. My numbers assume a more reaslistic scenario where I run the pump at least 2 hours a day at higher speed for solar and for my suction cleaner.

I have a pump cost comparison spreadsheet located here which is setup to help you determine the lifetime costs of various pumps. The scenarios are setup so that you can compare a single speed pump to both two speed pumps and variable speed pumps. The lifetime costs are determine with both the cost of the pump and the energy costs over the lifetime of the pump. Because the variables cost more, the lifetime costs are not that much better than a two speed pump but it does depend a lot on what you pay for electricity and how long you run the pumps.