Well pump help

[Leeelson]

In another thread (https://terrylove.com/forums/index....franklin-subdrive-150-model-5870204150.63646/) I chronicled the impending failure of a VFD controller. I am now convinced that it would make sense to abandon the VFD in favor of a conventional system with a CSV. I would like to be knowledgeable as I try to search for an installer who won't rip me off like the last one apparently did. In order to understand what I'm getting, I have some basic questions about well pump systems, starting with the following:

In sizing the system, as I understand it, one needs a desired flow rate (among other things). The flow rate should satisfy household needs, while not being over sized to prevent energy inefficiency. It should also allow the well to re-charge so as not to run the system dry. In my case, a typical tap in my 4 bedroom house runs about 3 GPM. We also have several yard hydrants, probably capable of at least 6 GPM as well as some drip irrigation systems. Does a 20 GPM pump make sense? As for the well, the well report claims at least 35 GPM over 1.5 hours ("air lift" test method) so I suspect a pump could support that flow. Suggestions?

 

[Reach4]

Does a 20 GPM pump make sense?

Consider if a 10 GPM may fit your use. You don't normally run everything at once, and do you really want to size for every thing on? Note that a "10 GPM" pump can usually pump more.

In selecting a pump, you would like to know the depth to water, and you would like to have the pump efficient at that depth. You would like to know the PSI range you will be generating, such as 40/60PSI. You would like the pump to be able to lift water from deeper than usual as margin, although a reduced GPM at the deeper depth is OK... reducing flow as the well is ready to run dry is a feature, not a problem. So how deep is the pump set? Is there a rise or fall in altititude from the well to the house?

 

[Sponsor]

 

[Valveman]

A 10 gpm pump would probably be fine for the house. But you need to size the pump for the irrigation plus the house. The CSV will let you put in as large a pump as needed for peak demands while still making the pump work like a small pump when running a little drip. Now because drip is usually run for long periods of time, you don't want to oversize the pump much to keep the drip as efficient as possible.

A frost free yard hydrant can let out 15+ gpm without anything on the end of the hose. But it will only let out as much as an attached sprinkler will let out.

I would say a 20 gpm pump with a CSV would be about right.

 

[Boycedrilling]

As Valveman said, you need to allow for outside watering. Many areas of the country don't have to factor this in. I live in eastern Washington. It is a semi desert. We get maybe 12" of precipitation a year. The average impact sprinkler uses 5 gpm or more. Most people want 20-30 gom to irrigate their yards. Yes 5-10 gpm is sufficient for most residences, but not for outside irrigation. Western Washington is a different story. They don't need outside irrigation in most areas. You can't apply one criteria and use it universally.

Valveman you will appreciate this being in an irrigation area in Lubbock. I spent 5 years working for a dealer that sells Zimmatic center pivots. The average center pivot in my area runs in excess of 2000 hours per year. We used to nozzle them at 10 gallons per minutes per acre, with overhead impacts. With rotators on drops, we run them at 8.5 gpm per acre. A wiper gets nozzled at 6.5 gpm/acre.

 

[Valveman]

Have you seen the variable rate pivots in your area yet?

 

[Boycedrilling]

I don't really work in that end of it any more. Nelson is here in Washington, I think that's what most people run here. The irrigation company I worked for in the '90's had nelson's sprinkler package software. I ran 100's of sprinkler charts per year. That's when Nelson was developing the nutator to compete with senninger's wobbler.

You've had a relationship with senninger haven't you?

It's probably been 7-8 years since I've driven thru Lubbock. A lot of circles were using drag hoses there if I recall.

 

[Leeelson]

OK. Got a handle on flow. Now for TDH. I used this link:
http://www.buypumpswholesale.com/page/tdhcalculator_w/help
Static water level= 128'
Friction loss =6'
Cutoff pressure=115'
TDH=250'

Sound reasonable?

 

[Leeelson]

A side question. Is this correct?
A Franklin Subdrive controls a VFD using 4 wires (3-phase + ground?) by changing the frequency of the motor and therefore it's speed.

A Monodrive is described as a 3-wire device . Does it also change the frequency/speed of the motor? What is the difference between it and a Subdrive?

 

[Boycedrilling]

Leeelson, yes you have the basics of TDH, except for one part. Your static level is 128 feet. Your pumping level will be lower than this. Every well will vary. This is what is called specific capacity. This is a term that tells us how many gallons per minute can be pumped for every foot of drawdown. For example, the pumping level in your well at 20 gpm may only be a few feet lower than the static level, say another 5 or 10 feet. But what if 20 gpm draws the well down 100 ft?

Specific capacity can vary greatly. I have drilled wells that would pump over 1500 gpm with less than 6" of drawdown. This would be a specific capacity of over 3000 gom/ foot. I have drilled wells that yielded 1/2 gpm with 200 ft of drawdown. This would be a specific capacity of 0.005 gpm/foot. The average specific capacity for all wells is around 5 gpm/foot, however this means absolutely nothing when you are looking at an individual well. All you know for your well is that your driller indicated that it was capable of around 35 gpm estimated by airlifting, as I recall. What that doesn't tell you how far the water level will drop in YOUR well at that flow.

We do know that you haven't run out of water at the rate that you have been pumping so far. How much outside irrigation do you do in your part of Nevada? This is your greatest water usage. The average house only uses about 300-600 gallons per day. And this usage is concentrated in a few hours in the morning and evening. By contrast, if you have ONE impact sprinkler running for 24 hours, it will use over 5000 gallons.

 

[Boycedrilling]

a Franklin SubDrive is a VFD that takes single phase 230 volt 60 hertz input and has three phase 230 volt 0-80 hertz output. It varies the hertz output to vary the speed of the 3 phase motor.

A Monodrive does not convert the output to 3 phase and works with single phase motors. A SubDrive will not work with a single phase motor and a Monodrive will not work with a three phase motor.

When I install a domestic VFD, I use the Pentair Intellidrive. It will run either single phase or three phase motors.

A 3 phase motor is less expensive than a single phase motor. It can also use smaller gauge wires, because the amps are evenly distributed between 3 wires. This can be important on deep set pumps. Most residences do not have 3 phase power, just single phase.

You presently have a 3 phase motor in the well. You only have single phase power available. The VFD is being used as a phase converter to supply 3 phase power. It also varies the hertz of the output to vary the speed of the motor. The VFD also causes the pump to run as long as there is any water demand. It variesZ the speed of the motor to maintain a preset pressure.

A cycle stop valves causes the pump to run as long as there is minimum demand (1-5 gpm depending upon model). With a single phase motor no VFD IS NEEDED. if you still keep the 3 phase motor, you still have to use a VFD to convert your single phase power to three phase, even if you are using a cycle stop valve. Now if you have 3 phase incoming power of course, a VFD wouldn't be needed with a cycle stop valve.

 

[Craigpump]

I believe you could ditch the VFD and go with an static phase converter and contractor utilizing a pressure switch and not have to change the pump & motor.

 

[Leeelson]

Leeelson, yes you have the basics of TDH, except for one part. Your static level is 128 feet. Your pumping level will be lower than this. Every well will vary. This is what is called specific capacity. This is a term that tells us how many gallons per minute can be pumped for every foot of drawdown. For example, the pumping level in your well at 20 gpm may only be a few feet lower than the static level, say another 5 or 10 feet. But what if 20 gpm draws the well down 100 ft?

Makes sense.

Specific capacity can vary greatly. I have drilled wells that would pump over 1500 gpm with less than 6" of drawdown. This would be a specific capacity of over 3000 gom/ foot. I have drilled wells that yielded 1/2 gpm with 200 ft of drawdown. This would be a specific capacity of 0.005 gpm/foot. The average specific capacity for all wells is around 5 gpm/foot, however this means absolutely nothing when you are looking at an individual well. All you know for your well is that your driller indicated that it was capable of around 35 gpm estimated by airlifting, as I recall. What that doesn't tell you how far the water level will drop in YOUR well at that flow.

Unfortunately, the well report is my only information. I recall that the driller said that he was able to produce 35+ GPM for 1.5 hours so I'm guessing that the drawdown is minimal, but I could be wrong. The bottom line is that I don't know how to add in this factor with the data I have, so I'll have to leave it out. Hopefully its small.

We do know that you haven't run out of water at the rate that you have been pumping so far. How much outside irrigation do you do in your part of Nevada? This is your greatest water usage. The average house only uses about 300-600 gallons per day. And this usage is concentrated in a few hours in the morning and evening. By contrast, if you have ONE impact sprinkler running for 24 hours, it will use over 5000 gallons.

Good questions. We are in a very dry part of the state. Typical annual rainfall is less than 10". In addition to low flow devices in the house, we have a drip irrigation system that handles up to 100 drip heads at a time. I'm guessing this translates into about 6-10 GPM for each zone since the main line is about 1/2". The drip system runs 1 or 2 zones at a time so demand is not that great but run time can be hours in the summer. In addition, we have several yard hydrants that are usually used with hoses (relatively low flow) but sometimes used without for brief periods (16 gpm?)

 

[Leeelson]

a Franklin SubDrive is a VFD that takes single phase 230 volt 60 hertz input and has three phase 230 volt 0-80 hertz output. It varies the hertz output to vary the speed of the 3 phase motor.

A Monodrive does not convert the output to 3 phase and works with single phase motors. A SubDrive will not work with a single phase motor and a Monodrive will not work with a three phase motor.

Does the Monodrive change the speed of the motor? How?

When I install a domestic VFD, I use the Pentair Intellidrive. It will run either single phase or three phase motors.

What do you like about it? Price? Reliability? It looks like the PID20 model would work for me (2 hp 3 phase output). I can't find a price. Is it less than a SubDrive 75?

A 3 phase motor is less expensive than a single phase motor. It can also use smaller gauge wires, because the amps are evenly distributed between 3 wires. This can be important on deep set pumps. Most residences do not have 3 phase power, just single phase.

You presently have a 3 phase motor in the well. You only have single phase power available. The VFD is being used as a phase converter to supply 3 phase power. It also varies the hertz of the output to vary the speed of the motor. The VFD also causes the pump to run as long as there is any water demand. It variesZ the speed of the motor to maintain a preset pressure.

A cycle stop valves causes the pump to run as long as there is minimum demand (1-5 gpm depending upon model). With a single phase motor no VFD IS NEEDED. if you still keep the 3 phase motor, you still have to use a VFD to convert your single phase power to three phase, even if you are using a cycle stop valve. Now if you have 3 phase incoming power of course, a VFD wouldn't be needed with a cycle stop valve.

Yes. I have single phase so without replacing the motor, I need a VFD. The question remains: does it make more sense to replace a VFD on a 9 year old 3 phase motor or throw it all away for a conventional system. Seems like I could do the latter for around $1500 plus labor.

 

[Boycedrilling]

I've only ever installed one Monodrive. It was a retro fit. I don't know the specifics but yes the Monodrive varies the speed of a single phase motor.

Pentair does not authorize Intellidrive sales direct to consumers. They are not supposed to be sold in the Internet. Prntair will not warranty them unless there are installed by an authorized and trained dealer.

Here's my opinion. If you want to get by for now, replace the SubDrive with an inexpensive VFD, an ABB or Hitachi. under $300. You would need to be comfortable with learning and programming the VFD. If you're not comfortable with that, then probably need to go to option 2.

Option 2 would be to replace everything at once. You would gain a new warranty. You would need to decide if you want; A Conventional system working on a 20 psi differential. A conventional system with a cycle stop valve, so that the pump doesn't cycle when water is being used. Or a VFD system with either a single phase or 3 phase motor. You are much more knowledgeable that you were a few weeks ago. You can make an educated decision now.

Then you will need to find an installer that will install the system that you specify.

 

[Leeelson]

I believe you could ditch the VFD and go with an static phase converter and contractor utilizing a pressure switch and not have to change the pump & motor.

OK. Can you provide some reference links and more explanation of how this works, some idea of costs, sizing. What happens when the pump and motor quit (with my luck a few days after repair)? Can I replace them with something relatively inexpensive, energy efficient and durable? Will this work with my existing 8 gallon pressure tank? Do I need a CSV?

 

[Craigpump]

A static converter is about $150 plus a contactor, maybe $250 total parts plus wiring it up?

I don't see why it wouldn't work with a CSV.

Cary would be able to do a schematic.

 

[Leeelson]

Putting it all together....

My #1 choice would be to put in a conventional system. Here are my specs: I need a 25 gpm capability. My TDH is about 250 ft. People seem to like Grundfos, so looking at their offerings for 25 gpm, I look at the performance curve. I choose 25 gpm and go up until I intersect a curve at 250'. This is the curve for model 25S20-11 pump and I choose the single phase 230 V version which is 2 hp. Next I select the appropriate control box and a CSV valve: looks like the CSV1A should work.

Does this capture the essentials? It's just an example but I want to make sure I understand how to make the right choices.

 

[Valveman]

The 25S 20-11 will give you 20 GPM form 250' total head. But if your water level drops 50', it will only produce 8 GPM.

Having already been spinning that 3450 rpm pump at 4700 rpm for 9 years, I don't know if it is worth replacing the VFD controller. The pump may go out the next day. You can use one of the cheap VFD controllers from driveswharehouse as a phase converter and use a CSV to control the pump. You just don't need a pressure transducer. Set the VFD to ramp up to 80hz 0r 4700 rpm in 1 second. Then you can tie two wires from a pressure switch to the controller to make it work like a phase converter/soft starter. This way when the pump does give out you will have the CSV and everything you need to replace the three phase motor with a normal single phase and let the CSV and pressure switch be in control.

 

[Leeelson]

With the discovery that the motor in place is very likely a 3 hp device (pump still unknown). It becomes a little more unclear what replacement (single phase) Grundfos pump to use. 2 questions:

1) Is it better to over estimate or underestimate the pump capacity?

2) If I consider a larger pump, am I better off having a higher capacity pump (e.g. 40 gpm 40S30-9) or one with a greater TDH ( 25 gpm 25S30-15). Both have a 3 hp motor. A reminder: I still don't know my draw down so my estimate of TDH=250 is a lower limit.

 

[Reach4]

See http://www.blumenauerpumps.com/groundwater/SP4performanceSpec.pdf The tables are are easier to read than the graphs.

In a 40/60 PSI system, it is the 40 PSI row that determines available GPM, and if you are using a CSV set for 50, you could look at the 50 PSI row for the GPM available at normal max pressure seen during irrigation, showers etc.

Do you think the 16S15-14 would be inadequate? If your well dropped 50 ft, do you think having it pump fewer GPM would be a bad thing? I don't.