- Occupation
- Licensed Electrician
These two statements are in conflict with each other. The motors are being maxed out. The first likely culprit is too much flow.
Motor Issues?
- Thread starter jahilliard
- Start date
- Status
jahilliard
Senior Member
Please keep in mind my ignorance with these motors....so if these are in fact 30hp motors the issue based upon the info, is that they are being maxed out? Does the 53A rating seem to be typical? from what I am seeing from Franklin, SEI, FARDINE, etc, they all seem to show approx. 47-48A max rating at that voltage, nit when I reference a 30KW/40Hp motor the infoprmation seems to fit perfectly. I guess what I am asking is that does it seem likely that these motors if 30Hp would offer the current info...53A FLA. And a potential solution if 30Hp would be to reduce the flow/increase back pressure?
I looked up the SHAKTI (motor manu.) Manual and it has a 30Hp 460v 3ph motor FLA at 41.8A.
I looked up the SHAKTI (motor manu.) Manual and it has a 30Hp 460v 3ph motor FLA at 41.8A.
Last edited:
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
" I do know that the fountain contractor adjusted the fountain head and the amperage dropped a few amps."
I rather doubt the contractor actually adjusted the head. He probably decreased the flow, causing the fountain stream(s) to be lower. Maybe he just did not adjust it far enough.
I rather doubt the contractor actually adjusted the head. He probably decreased the flow, causing the fountain stream(s) to be lower. Maybe he just did not adjust it far enough.
jahilliard
Senior Member
Another question about motors..I am noticing most offer a rewindable motor. What if any, is the advantage of that option, and how often would someone actually want a motor to be rewound vs. buying new?
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Let's look at it another way.
HP to FLA = 746 x HP / 1.732 x V x Eff x PF. so we can assume a .8PF and we know it is 460V, 30HP and 53A already, so indirectly the Efficiency would need to be 746 x 30 / 1.732 x 460 x 53 x .8, so the motor would need to be no better than 66% efficient! If so, FIND A NEW MOTOR!!!
It just means that most likely, the non-rewindable motor is encapsulated, probably using VPI (Vacuum Pressure Impregnation), which makes it a lot more expensive. In other parts of the world, equipment that has treated with VPI encapsulation is no longer able to be repaired or rewound, because the process of removing the VPI material is too environmentally nasty. That's actually not the case here in North America (yet), but the cost of doing so is likely not worth it on a 40HP motor. VPI however will likely make the motor last forever, as long as it isn't overloaded or single phased. How long do you want the fountain motor to last though? 25 years would not be unheard of, so is that fountain still going to be running 25 years from now, or will some landscape designer change the entire area and get rid of the fountains by then anyway?
- Occupation
- Licensed Electrician
If the nameplate or factory specs says 41.8A then that is what the motor is designed to run at. The pump should produce x number of gallons per minute. The pump and the motor have to work together. Too many gallons per minute, i.e not enough back pressure, means the pump is moving more water than the motor has horses to keep up with for very long. Reducing the flow will mean the motor is doing less work so the amps will go down. I don't know what effect that will have on the fountain. It may stop it from being a fountain and make it just a bubbler.
- Occupation
- Licensed Electrician
In terms of this discussion there is no advantage to rewinding the motor. We won't even touch a submersible pump. They are a GIANT pain in the posterior.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Yeah, with the new efficiency standards, most of the shops around here now will not even quote on rewinding anything below 50HP unless there is something really special or odd about the motor. They would quote and quote and never get the order because a new motor was cheaper in the long run. So they just stopped quoting on them. Customers get pissed, but it's just the reality.
For anyone interested, there was a study done by MIT on this issue in 2010.
http://web.mit.edu/ebm/www/Publications/MITEI-1-c-2010.pdf
Most commercial fountains have adjustable/replaceable nozzle
as others have said throttling flow will reduce hp/current
and reducing the orifice will increase height and reduce flow
hydraulic hp = gpm x ft hd x 8.34 / 33000
essentially linear with flow and pressure
as others have said throttling flow will reduce hp/current
and reducing the orifice will increase height and reduce flow
hydraulic hp = gpm x ft hd x 8.34 / 33000
essentially linear with flow and pressure
- Occupation
- Licensed Electrician
That's where we're at. Most every time our motor guy will go up a size in wire and all we have is class H wire, so overall a rewind will result in a better motor, but even if you take that away you can't rewind a motor cheaper than you can buy a new one unless it's big enough or hard enough to replace.
Not to hijack this thread, I would like to ask, what minimum size do you think a motor rewind is favorable as compared with buying a new unit, in your opinion? (460V motors).
- Occupation
- Licensed Electrician
It's not about the size, it's about how hard it is to get a replacement. Keep in mind we are a small shop in a small town, but I think the same principles apply to bigger shops with more overhead.
jahilliard
Senior Member
Update...
Update...
To update everything...turns out these motors are rewindable submersible 30hp 460v...they run at 51A FLA 53 Max. Problem is that the system was designed for an encapsulated submersible, same size/voltage with an FLA of 40A. The 10-11A difference is creating problems with the wire, breakers, etc. I recomended that they reduce the flow by slightly closing the valve on the floating fountain. There is a ball valve but i am not sure if it is before or after the motor/pump - I am curious if that would matter. When I recomended that the response was that they tried that and it increased the amperage. Does the position of the valve matter, or should they try to create more back pressure by adjusting the nozzle?? Ultimately I want to understand how to reduce the flow therefore reducing the work/amperage.
Update...
To update everything...turns out these motors are rewindable submersible 30hp 460v...they run at 51A FLA 53 Max. Problem is that the system was designed for an encapsulated submersible, same size/voltage with an FLA of 40A. The 10-11A difference is creating problems with the wire, breakers, etc. I recomended that they reduce the flow by slightly closing the valve on the floating fountain. There is a ball valve but i am not sure if it is before or after the motor/pump - I am curious if that would matter. When I recomended that the response was that they tried that and it increased the amperage. Does the position of the valve matter, or should they try to create more back pressure by adjusting the nozzle?? Ultimately I want to understand how to reduce the flow therefore reducing the work/amperage.
- Occupation
- Licensed Electrician
That's kinda whacko. There are some manufacturers that try and stuff more wire inside the same size stator and sell it as a higher HP motor, usually with poor results.
I don't see how you can reduce the water going into a submersible pump unless you pull it out of the water. Closing a valve or a smaller nozzle on the outlet is the same result. That trick will only get you so far though, and if you have a poorly designed system, which it starting to sound like you have, then it won't overcome that.
jahilliard
Senior Member
So I'm not sure..are you saying that adjusting the valve should or should not have the same result as reducing the flow some other way. There is a PVC sleeve with a screen...the motor and pump are inside the sleeve mounted horizontally under the float and fountain head.
ptonsparky
Tom
- Occupation
- EC - retired
Are these centrifugal pumps?
Normal submersibles are hung vertically. Horizontal is a No No.
Normal submersibles are hung vertically. Horizontal is a No No.
Last edited:
jahilliard
Senior Member
yes. Actually I am trying to be SURE that they are...
ptonsparky
Tom
- Occupation
- EC - retired
Sounds like the proverbial CF to me.
View attachment 14805
Yes above a representative curve
it will increase head/pressure drop thereby reducing flow
Assuming a centrifugal pump
look at head flow and power curves
as head increases capacity or flow and power decrease
Yes above a representative curve
it will increase head/pressure drop thereby reducing flow
Assuming a centrifugal pump
look at head flow and power curves
as head increases capacity or flow and power decrease
- Occupation
- Licensed Electrician
Moving less water is moving less water, either by putting less water in or restricting how much water can get out, but it's better to do it on the outlet so you don't starve the pump for water. Also, you don't get an infinite amount of adjustment just by turning a valve as the pump curve chart posted shows.
The thing I don't understand is how you have a submersible pump that has a valve on the inlet. They sit under water, usually in a pond or a well casing full of water.
- Status