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Switching to vf?

Posted by dalehileman ( on
Thu, Nov 18, 10 at 17:02

Anyone planning a switch from conventional pump to Variable Flow might find interesting the following email message I recently intercepted from someone trying out his new Intelliflow installation:

Set for lowest speed, when it first came on didn't pump at all, it just sucked air whereupon my Friendly Engineer Installer Ike programmed it to start at full speed running there for 5 minutes to ensure prime before dropping back

A side benefit to this 5-minute run: It provided a flow rate suitable to backwashing the filter which requires only a minute or two. Notwithstanding some misgivings I made the attempt this noon (its programmed start time) and was successful. Sure enough when I shut down to select backwash, then afterward reenergized the system it remembered that it had been going full speed so didn't require reprising.

Amazing forethought on the part of commercial programmers who otherwise fall down so miserably in many areas. Typical example of such programming incompetence above, God help me, by sheer chance: Mac didn't understand "repriming" and without even asking replaced it with "reprising"

I had previously asked Ike if he could instead initiate a subroutine making it possible to backwash just any time at all, say with the press of a button, whereupon he promised to look into the possibility. Meanwhile depending on any difficulty writing or using such a subroutine I therefore might consider no changes whatever, I shall just have to cultivate my routine to suit the habits of Ike's program, bless him and my No. 1 Son who had helped with the job

There is an interesting side issue, though. Formerly pressure at the input to the (sand) filter provided continual indication of its condition. Starting out clean at say 18 psi it increased over a period of weeks to about 28 psi at which level I was advised to backflush after which of course it drops back to 18 psi. With Intelliflow the initial pressure this morning was 25 psi apparently indicating a high level of contamination but after a successful back flush this pressure still measured 25 psi


Thanks guys

Follow-Up Postings:

RE: Switching to vf?

The answer to your final "Why?" is simple. At full speed, Intelliflows are 3 HP pumps. Thats a lot of water flow.


RE: Switching to vf?

Thread closed, next.

RE: Switching to vf?


RE: Switching to vf?

"The answer to your final "Why?" is simple. At full speed, Intelliflows are 3 HP pumps. Thats a lot of water flow."

Thanks Scott for that observation but I am still wondering because one might suppose the capacity of a pump to maintain constant flow should become more nearly independent of load as horsepower increases. Thus with a more powerful pump but the same max rpm I'd expect the difference in pressure to be greater not less

But I'll present this to my engineer buddy Ike and if I'm wrong I'll so sheepishly admit

RE: Switching to vf?

The fact that this is a Dale post makes me happy.
His verbosity never fails to satisfy my penchant for powerful forum foreplay.


RE: Switching to vf?

Why thank you Goy I am honored

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