About to drill well - Need Advice

[pettrix]

About to drill a well in Northern AZ. The well depth will be around 350-400 feet deep with around 30GPM.

I have been given 2 options for the well pump:

Grundfos 1.5 HP 10GPM (10SQE 15-330) and the CU301 Controller - $3,800 installed
Goulds VFD 2.0 HP 13GPM (13GS20) and the AquaDrive Controller - $4,700 installed

The well drilling costs are around $6,800 (400' deep, casing, etc)

The house has not been built so the well is being put in to provide water for the job site, compaction, etc.

[Cary Austin]

If the water level turns out to be at 300', that Grundfos SQE will only pump about 7 GPM.  If the water level is any deeper than 300', that pump just won't cut it.  I believe the 1.5 HP is the largest SQE they make, which is why that is what they offered.

The Goulds 13GS20 will deliver 14 GPM from 300', and will still pump 8 GPM from 400'.  A Grundfos 16S20 will do the same, if you like Grundfos better, which I do because they have Stainless Steel impellers and a good drop in amps at low flow.  The Goulds has plastic impellers and not as good an amp drop.  The SQE has plastic composite impellers and spins at 10,700 rpm as compared to the normal 3450 rpm from the other two normal type pumps.

They are going to tell you that the 3 phase motor needed with the Goulds "Aquadrive" will be more efficient and save money because it can use smaller wire down hole.  The difference in efficiency between the 3 phase motor and a normal single phase motor is not even worth mentioning.  And you will be able to use smaller wire down hole with the 3 phase.  But that is how they lock you into replacing that expensive and short lived VFD "Aquadrive" several times, because once you have a 3 phase motor, you must have the "Aquadrive" to convert your single phase house power to three phase to be able to run that motor.  So that makes it expensive to pull the pump, replace the wire with larger wire, to be able to change to a standard single phase motor.

Constant pressure systems are a very good idea, but how you get that constant pressure is important.  The variable speed systems like the SQE and Aquadrive use a $1200+ computer to vary the speed of the motor, while we can do the same thing with a simple and dependable CSV1A valve for maybe $200.  Plus the CSV uses a standard single phase motor spinning at normal 3450 RPM, and doesn't have any of the electrical problems associated with variable speed drive systems.

Of course the CSV system will cost at least $1000 less than the variable speed systems and will last much longer, which is why they are not offering you the CSV system.  They will even try to tell you the CSV is bad for pumps and anything they can say to get you stuck with a variable speed system, which I believe is a lot like the old story of the Tar Baby.

Either the 13GS20 or the 16S20 with a single phase motor will work with the CSV. The only concern with the CSV is that the water level in the well needs to be deeper than 135', which I would think it is, so as not to put too much pressure on the CSV.

You are wise to do your own research, because now you actually know more about it than the pump guy who is trying to sell you a variable speed system.  If he really knew what he was doing and was trying to do the right thing for you, he would have priced you a system with a CSV to start with.

[pettrix]

I really do like the "modern" capabilities of the Grundfos SQE but like you mentioned, it doesn't have the GPM capacity and the control unit is sketchy (Although Grundfos claims they ironed out the issues with the electronic controller).

How many GPM's do I need for 2 single family homes?

One driller recommends Franklin pumps and the Franklin Controller. He said it was the SubDrive Constant Pressure System and he claims the Franklin control boards are bullet-proof when compared to the Grundfos systems.

[Cary Austin]

Yeah Grundfos has said they have the "bugs ironed out" at least 8 times since 1999.  They have "upgraded" or redesigned the SQE and CU301 at least 8 times that I know of.  And while they have come up with a few BandAids, mother nature will never let them completely iron out the bugs with any VFD.  Harmonics, voltage spikes, resonance frequency vibrations, and other things are simply laws of physics associated with varying the pumps speed that they just can't get around.

Same with Franklin.  They haven't been at it as long as Grundfos, so they are only in the third or forth generation of redesigns on their Subdrive.  And what do you expect an installer to say when he is going to make a cool 2500 bucks if he can sell you on a variable speed type system, as compared to only making a thousand or so if he sells you a regular and dependable pump system using a CSV?

The CSV is actually more "modern" than any VFD.  They have been redesigning and "upgrading" VFD's, trying to solve some of the inherent problems since they were invented in 1964.  We have been using CSV's to replace VFD's only since 1993.  And while we have added or changed a few of our valve models since then, the original idea and function has not changed since 1993, as there is nothing left to improve on.

"More modern" or not, the most important thing about a water system is that the water actually comes out of the faucet when it is opened.  And when there are two or more ways to accomplish the same job, the simplest way is always the best way, which is the CSV.  There is nothing "bullet proof" about any VFD.  They are designed to make you think they are saving energy, which they do not, and  make you think the "new capabilities" are important, which they are not, so you don't mind paying 3 to 4 times as much to keep your water flowing over the years.

A good pump man would know enough about how pumps work to understand the problems associated with VFD control, and the absence of problems with the CSV control.