Rural water pressure from well and how to improve

[North Idaho Wolfman]

You will use pretty much the same amount of electricity to pump the same volume of water with a variable pump vs a fixed speed one.

The fixed speed one fills the bladder tank and then is off until you've used enough water to drop down to cut-in pressure. The variable speed pump does pretty much the same thing only the pressure drop to trigger it is smaller and then the pump will shut off when you stop using water and the pressure reaches its cut-off pressure.

The pressure differential is like 20 psi on the fixed pump system, while the variable speed system will only be a psi or two differential which you don't notice. Either way if you use 10 gal of water you are paying for the electricity to pump 10 gal of water. There is no electricity savings, just the extra cost of the variable system to get you the non-noticeable pressure drops.

That's not really the real result.
Full flow system:
Runs the pump at full amperage/ wattage through the whole cycle of the pump.
Where a variable speed pump runs it at a lower amperage/ lower wattage and does so as needed.
Electric is billed for demand wattage used, it's not linear.
The higher the demand wattage the higher the billing.
So if your constantly pulling high wattage it equates to higher billing for water usage.
Lower wattage demand equates to lowering billing for water usage.
It's on the same line as LED's, you can get the same light output at a much lower cost for that output.

 

[wp6529]

That's not really the real result.
Full flow system:
Runs the pump at full amperage/ wattage through the whole cycle of the pump.
Where a variable speed pump runs it at a lower amperage/ lower wattage and does so as needed.
Electric is billed for demand wattage used, it's not linear.
The higher the demand wattage the higher the billing.
So if your constantly pulling high wattage it equates to higher billing for water usage.
Lower wattage demand equates to lowering billing for water usage.
It's on the same line as LED's, you can get the same light output at a much lower cost for that output.

Sorry, you are incorrect.

- Both the fixed speed and variable speed pumps run only as needed. If you use 10 gal they both will pump 10 gal. The fixed speed one may pump a little longer and more volume if the tank was below cut-off pressure when it started however that water it pumps is stored in the tank and will be used the next time you use water before the tank reaches the cut in pressure. The bottom line is they both pump what you use and no more other than a little standby volume which is in now way wasted.

- Residential electricity is billed by killoWatt hours, and either pump is going to use the same kWh to pump the same volume of water, that is just physics. The energy required to get the water up out of the well and to pressure is the same regardless of how fast you pump it. Commercial electricity is demand metered, but not many commercial buildings with wells are running variable speed pumps.

- There is no efficiency difference in the pumps between fixed speed and variable speed if you are comparing pumps of the same quality and age. If you perhaps replaced an old worn out fixed speed pump that was bypassing in the impeller stages and not producing it's rated flow with a shiny new variable speed pump you might see a power savings, but it has nothing to do with variable speed.

- Lower Wattage demand does not equal a lower bill on a kWh metered service if the lower demand pump is pumping for a longer time to move the same amount of water as the higher wattage pump. There is no free lunch, the energy required is the same no mater whether it's 1 KW for 30 min = 0.5 kWh or 0.5 Kw for 60 min = 0.5 kWh.

 

[DustyRusty]

"Still in the cellar, because I can't find enough people to drag it up the cellar stairs".

Outside access cellar stairs ????

Not a problem!
Don't you have a BH?
Lower BH boom into stairwell to lift Bock heater up/out.
I used my hoe to set my 850 lb safe in.

The tank probably weighs as much as my BX23S backhoe does. I would probably wind up with the tractor in the cellar.

 

[Dave_eng]

I am surprised by the number of comments and differing opinions. I did not thinnk anyone much read this section of the forum.

I certainly don't want to argue with anyone who thinks the system they currently have is as good as it should be but rather inform those who do not like what they currently have of an option

Franklin Electric is the supplier of many submersible pump motors so from a motor point of view their engineers know what the motor can do and live long.

I have no water hammer issues.

I have a cottage which is across the road from a new very large municipal water system. My 3/4" pex plumbing easily handles the 100 psi coming from the plant.

Garden hoses are where the cheap products cannot stand the pressure especially when left with pressure in them and exposed to the sun.

Before the Subdrive system, Franklin Electric had a number of products which did the same variable speed operation. The subdrive is just designed to handle a wide variety of pumps in one product.

The operation of the motor as a variable speed unit is not all that different than the soft start kits people trying to run large central AC's off small generators use.

Dave

 

[wp6529]

The operation of the motor as a variable speed unit is not all that different than the soft start kits people trying to run large central AC's off small generators use.

Dave

Actually the hard start kits as they are called in the HVAC world are very different than that sub drive unit which is apparently operating a 3 wire pump a bit like an inverter drive.

The hard start kits are just a bigger starting capacitor and a potential relay to take the extra capacitor out of the circuit once the compressor manages to get up to speed.

Actual soft start drives don't really exist in the residential HVAC world these days, you now have the old single speed compressors or newer inverter drive units that run both the compressors and fans at variable speeds optimized for the current heating or cooling demand.

 

[RCW]

@Dave_eng - does this system eliminate a pressure tank? Don’t see any reason it needs to if I understand correctly.

That is a really neat setup.

Had no idea a VFD-type system could be used in a household well application.

Was normal for municipal systems and saved energy dollars by reducing demand charges. Seen them on submersible and vertical turbines from 5 HP to 125 HP.

For some talking water pressure, I tested my own kitchen sink at 94 psi with calibrated gauges 30 years ago.

We’re on a public water system in a hilly area. It happens.

I’ve seen as high as 120 on public systems, which is way too high. Unfortunately, PRV’s can be a maintenance issue.

 

[The Evil Twin]

Submersible well pump motors are typically oil filled and they are mounted at the bottom of the pump with the intake and impeller stack above them. The water does not flow through the pump motor at all, though in the typical well casing there will be water flow going past the motor casing while it is running. In any case, the motor windings are immersed in oil which provides thermal coupling to the motor housing which is immersed in water which provides thermal coupling to a whole lot of thermal mass from the aquifer.

As for the comments on my 70psi setting, if you plumbing is in such bad shape that it can't handle 70psi you have much bigger problems. Typical city water pressure is above 70psi, often quite a bit higher.

Ok....

 

[wp6529]

Ok....

Yes, oil filled motor at the bottom of the pump with no external flow through it. The water intake at the middle of the unit, impeller stack above and outlet at the top, exactly as I stated.

 

[BAP]

Nobody seems to understand that these Variable Speed Drives are actually Variable Frequency Drives which are converting 1 phase electric into 3 phase electric to be able to change the speed of the motor to meet the demand. The motor on the pump is now a 3 phase instead of 1 phase. The 3 phase motors can handle slow speed without overheating and burning up. They also will use less electricity. We installed a 10hp vacuum pump on the farm 25 years ago with a VFD to milk cows. It replaced 2- 7.5hp vacuum pumps to do the same job. At times it slowed down so much that you could almost count the revolution but it never got too warm. Electric bill went down big time. It would speed and slow as needed.

 

[wp6529]

Nobody seems to understand that these Variable Speed Drives are actually Variable Frequency Drives which are converting 1 phase electric into 3 phase electric to be able to change the speed of the motor to meet the demand. The motor on the pump is now a 3 phase instead of 1 phase. The 3 phase motors can handle slow speed without overheating and burning up. They also will use less electricity. We installed a 10hp vacuum pump on the farm 25 years ago with a VFD to milk cows. It replaced 2- 7.5hp vacuum pumps to do the same job. At times it slowed down so much that you could almost count the revolution but it never got too warm. Electric bill went down big time. It would speed and slow as needed.

I'm quite familiar with VFDs, I use several driving 3 phase machines from my single phase residential power. I also use a rotary phase converter for some things.

Your farm is on commercial peak metered power? That is where you will see a cost savings, not from actual efficiency. If you ran on residential power with straight Watt/Hour metering there would be no real difference between intermittent high load pumps vs. a continuous lower load pump.

Some of the variable speed residential well pump systems on the market Goulds? are indeed VFDs driving an actual 3 phase pump. It appears that this Franklin Sub Drive unit is slightly different in that it's driving a single phase 3 wire (remote starting capacitor) pump motor in a similar fashion.

 

[Dave_eng]

@Dave_eng - does this system eliminate a pressure tank? Don’t see any reason it needs to if I understand correctly.

That is a really neat setup.

Had no idea a VFD-type system could be used in a household well setting.

Was normal for municipal systems and saved energy dollars by reducing demand charges. Seen them on submersible and vertical turbines from 5 HP to 125 HP.

For some talking water pressure, I tested my own kitchen sink at 94 psi with calibrated gauges 30 years ago.

We’re on a public water system in a hilly area. It happens.

I’ve seen as high as 120 on public systems, which is way too high. Unfortunately, PRV’s can be a maintenance issue.

The installation manual suggests using a 4 gal pressure tank pressurized at 70% of what you have the subdrive sensor to. My pump is a 3/4 hp with around 7 stages.

The subdrive has settings for 1/2 hp pumps

Dave

 

[GreensvilleJay]

sorry BAP, you're in error about how this 'subdrive' works. I downloaded the manual, specs are in the back...

VFD is a 'generic' term, though most associate it to the 'magic' box that allows guys to hookup their surplus 3 phase motor powered lathes/milling machines to regular house power (single phase ).VFD can be single phase, like this unit, 2,3 or even 6 phase.

It just a single phase VFD unit that can adjust the frequency between 35 and 63 Hertz. It 'reads' the water pressure using an industry standard sensor and controls the frequency of the power going to the motor.

The big thing to remember is that you need to use a 'VFD' capable motor ! You just can't slap any old more to VFD and be 100% sure it'll run.

 

[Dave_eng]

Actually the hard start kits as they are called in the HVAC world are very different than that sub drive unit which is apparently operating a 3 wire pump a bit like an inverter drive.

The hard start kits are just a bigger starting capacitor and a potential relay to take the extra capacitor out of the circuit once the compressor manages to get up to speed.

Actual soft start drives don't really exist in the residential HVAC world these days, you now have the old single speed compressors or newer inverter drive units that run both the compressors and fans at variable speeds optimized for the current heating or cooling demand.

I agree my comparison was not the best but I was trying to respond to those who saw future problems.

For those commenting on over heating the sub motor, there is this solution from Franklin Electric:

Cooling sleeve for submersible motor pumps
The heat loss generated by the submersible motor must be dissipated to the pumped medium by means of convection. If the minimum cooling speed along the submersible motor cannot be guaranteed, it is mandatory to install a cooling jacket in order to generate sufficient cooling.
To provide cooling, the pump-motor unit is supplemented by a cooling sleeve. This separate „sheet metal jacket“ is sealed above the pump inlet. The pumped medium is thus sucked in from below and directed past the motor in order to dissipate the generated motor heat loss (convection).
Appropriate brackets and inlet strainers are available for horizontal installation in an open body of water, e.g. a tank, a lake or a flowing body of water.

Cooling sleeve

In my 40+ years dealing with wells this sleeve was only needed once and this was in a large water storage tank where the school had a low yield well so water would be pumped at 5 gpm 24 hrs a day and then a sub pump in the storage tank provided high flows for times when students were in the school..

Dave

 

[wp6529]

I agree my comparison was not the best but I was trying to respond to those who saw future problems.

For those commenting on over heating the sub motor, there is this solution from Franklin Electric:

Cooling sleeve for submersible motor pumps
The heat loss generated by the submersible motor must be dissipated to the pumped medium by means of convection. If the minimum cooling speed along the submersible motor cannot be guaranteed, it is mandatory to install a cooling jacket in order to generate sufficient cooling.
To provide cooling, the pump-motor unit is supplemented by a cooling sleeve. This separate „sheet metal jacket“ is sealed above the pump inlet. The pumped medium is thus sucked in from below and directed past the motor in order to dissipate the generated motor heat loss (convection).
Appropriate brackets and inlet strainers are available for horizontal installation in an open body of water, e.g. a tank, a lake or a flowing body of water.

Cooling sleeve

In my 40+ years dealing with wells this sleeve was only needed once and this was in a large water storage tank where the school had a low yield well so water would be pumped at 5 gpm 24 hrs a day and then a sub pump in the storage tank provided high flows for times when students were in the school..

Dave

Yep, in a typical well casing the water will flow along the outside of the motor housing on it's way to the pump inlet. I have a 1,100 gal cistern tank here due to low yield well and I have a similar cooling jacket setup on the submersible pump in it, though mine is made just using regular PVC pipe and a cap with the pump output feeding through at the top. Either way it ensures the water flow over the motor housing when in operation.

 

[The Evil Twin]

I agree my comparison was not the best but I was trying to respond to those who saw future problems.

For those commenting on over heating the sub motor, there is this solution from Franklin Electric:

Cooling sleeve for submersible motor pumps
The heat loss generated by the submersible motor must be dissipated to the pumped medium by means of convection. If the minimum cooling speed along the submersible motor cannot be guaranteed, it is mandatory to install a cooling jacket in order to generate sufficient cooling.
To provide cooling, the pump-motor unit is supplemented by a cooling sleeve. This separate „sheet metal jacket“ is sealed above the pump inlet. The pumped medium is thus sucked in from below and directed past the motor in order to dissipate the generated motor heat loss (convection).
Appropriate brackets and inlet strainers are available for horizontal installation in an open body of water, e.g. a tank, a lake or a flowing body of water.

Cooling sleeve

In my 40+ years dealing with wells this sleeve was only needed once and this was in a large water storage tank where the school had a low yield well so water would be pumped at 5 gpm 24 hrs a day and then a sub pump in the storage tank provided high flows for times when students were in the school..

Dave

EXACTLY what I said! If you reduce the flow, you reduce the cooling. Not sure why you were so confused about this. Especially when the video I posted shows the cooling impeller moving the water or oil to evacuate heat.

 

[wp6529]

EXACTLY what I said! If you reduce the flow, you reduce the cooling. Not sure why you were so confused about this. Especially when the video I posted shows the cooling impeller moving the water or oil to evacuate heat.

The video shows internal oil circulation, which is separate from external flow. If you are pumping, you will have flow outside past the pump motor unless it is an unusual (for residential) situation where the pump is in a very large casing or such where the pump inlet is not drawing any water past the motor.

 

[Dave_eng]

Sorry I even posted this...... most everyone is an expert and few feel they can learn.
If anyone has personal questions PM me and I will do my best to assist.
Dave

 

[Biker1mike]

Sorry I even posted this...... most everyone is an expert and few feel they can learn.
If anyone has personal questions PM me and I will do my best to assist.
Dave

I found the thread interesting.
As for me. There is a 650 foot shaft in my yard with an expensive and almost new pump in it.
When something goes wrong I break out the checkbook and call the guys with the big drill rig.

 

[jimh406]

most everyone is an expert and few feel they can learn

Don't take it so hard.

There's obviously a lot of ways to solve similar issues. Your approach is unusual, but that doesn't mean it's wrong or perfect. That's ok with me, but as noted, the conventional approach is simply to use pressure tanks.

Maybe I'm the only one who wonders why you didn't just use pressure tanks.

 

[AndyM]

Dave_eng, thanks for posting this. I found all the commentary very informative. Good to know of the options / issues I had not considered.