Soft Start Single Phase Pump

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Ravenvalor

Ravenvalor

Senior Member
Location
Triad region of NC
Occupation
Electrician
Hello,

Does anyone know of a Soft Start that will operate a single phase pump? I've got a customer with a GRUNDFOS S-25S 20 well pump and it is jerking bad when it starts.

Thanks,
 
ActionDave said:
Can't use a soft start on a single phase pump. Franklin makes a VFD, single phase in three phase out well pump controller. Pretty much plug and play. I don't know how slow they start the pump but they do vary the speed.
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I've installed a few single phase to three phase VFD's before but never knew that a single phase motor could not start with a soft start until my supply house informed me yesterday. I am surprised that no one's figured out how to make one. I guess the market for one is not large enough.
 
Ravenvalor said:
Hello,

Does anyone know of a Soft Start that will operate a single phase pump? I've got a customer with a GRUNDFOS S-25S 20 well pump and it is jerking bad when it starts.

Thanks,
Click to expand...
Dos the motor have a centrifugal starting switch?
Also, are you sure it isn't a hydraulic problem where the water is causing the jerking? There could be an Oscillation issue where the pump comes up to speed developing pressure (water hammer?) then there is s drop in pressure then the pimp starts to bring the pressure up again repeating the cycle.
 
templdl said:
Dos the motor have a centrifugal starting switch?
Also, are you sure it isn't a hydraulic problem where the water is causing the jerking? There could be an Oscillation issue where the pump comes up to speed developing pressure (water hammer?) then there is s drop in pressure then the pimp starts to bring the pressure up again repeating the cycle.
Click to expand...

I will try to find out.

What you are describing to me reminds me of a ship's screws cavitating.
 
ActionDave said:
Can't use a soft start on a single phase pump. Franklin makes a VFD, single phase in three phase out well pump controller. Pretty much plug and play. I don't know how slow they start the pump but they do vary the speed.
Click to expand...
Same drive will run a single phase three wire submersible pump - you have to set a parameter for the motor type you are driving, then remove the start capacitor/potential relay controller and let the drive regulate current. They ramp up instead of full torque starting which is hard on a pump anyway.
 
Ravenvalor said:
I've installed a few single phase to three phase VFD's before but never knew that a single phase motor could not start with a soft start until my supply house informed me yesterday. I am surprised that no one's figured out how to make one. I guess the market for one is not large enough.
Click to expand...
Ability to "soft start" really depends on a few things. I think all motors will take some reduced voltage at startup and will result in less instant torque and less inrush current, but there hasn't been much demand for such application. Universal (brush type) motors are easier to do this as well as shaded pole or PSC motors, and in fact all those types are speed controlled by varying voltage. But a motor with a start capacitor needs full voltage pretty quickly and must be able to accelerate to the right speed to cut out the start capacitor in a fairly short time or you will have troubles with start capacitors. They don't take long energize time very well.

I have a table saw that "soft starts". Not really sure what kind of motor it has - never had to work on it. It is a newer (maybe up to 7-8 years old) Dewalt. Turn on the switch and there is a short delay and it ramps up to speed, where many older saws have such a hard inrush they trip circuit breakers on some sites this one never does at startup.
 
Ravenvalor said:
I've installed a few single phase to three phase VFD's before but never knew that a single phase motor could not start with a soft start until my supply house informed me yesterday. I am surprised that no one's figured out how to make one. I guess the market for one is not large enough.
Click to expand...
It's not about finding a market it's about the physics of single phase power.
 
kwired said:
Same drive will run a single phase three wire submersible pump - you have to set a parameter for the motor type you are driving, then remove the start capacitor/potential relay controller and let the drive regulate current. They ramp up instead of full torque starting which is hard on a pump anyway.
Click to expand...
Interesting. I did not know that. I have run power to a few of them but the well guys take over after that.

kwired said:
I have a table saw that "soft starts". Not really sure what kind of motor it has - never had to work on it. It is a newer (maybe up to 7-8 years old) Dewalt. Turn on the switch and there is a short delay and it ramps up to speed, where many older saws have such a hard inrush they trip circuit breakers on some sites this one never does at startup.
Click to expand...
Not related to this topic but I'd be curious to know if it would trip an AFCI. It was this style of power tool that showed me, for the first time, solid evidence of a nuisance trip.
 
ActionDave said:
Interesting. I did not know that. I have run power to a few of them but the well guys take over after that.

Not related to this topic but I'd be curious to know if it would trip an AFCI. It was this style of power tool that showed me, for the first time, solid evidence of a nuisance trip.
Click to expand...

I have a Pentek Intellidrive on my well pump, basically about same thing as Franklins Monodrive. I am driving a single phase three wire submersible with it. I used to replace pump motor nearly annually - always because splines on motor shaft get sheared off from full torque at starting. Last pump still only lasted about a year then a seal went out and bearing went bad:( - but the shaft splines were in great shape:).

Haven't run the table saw on an AFCI that I am aware of, it doesn't leave the shop all that often either though.
 
Ravenvalor said:
Hello,

Does anyone know of a Soft Start that will operate a single phase pump? I've got a customer with a GRUNDFOS S-25S 20 well pump and it is jerking bad when it starts.

Thanks,
Click to expand...

Some one didn't install the torque arrestors on the pipe near the pump. If not fixed it can and will break the pipe then you have more problems on your hands.
 
Ravenvalor said:
It is a 1.5" pipe I am told. I will ask the customer about the torque arrestors.
Click to expand...

Torque arrestor braces the pipe to protect it, now the pump shaft and impeller are absorbing even more of the surge of starting torque - you still may want to soft start this motor somehow.
 
ptonsparky said:
Add some wire to your well. Create some voltage drop. If a 14 will run the pump. Use it. Don't oversize in this instance. Franklins manual touches on this problem.
Click to expand...

Good idea. Lower the voltage going to the pump. I will look it up in the Franklin manual.

As far as soft starts are concerned I have not found anything that Grundfos will approve of for this particular single phase 2 - horse power pump. The Pentek PID-20 should work but if Grundfos does not approve of it then I will not install it. Franklin does not make a starter for anything over 1.5 horse power and single phase and even if they did Grundfos probably would not recommend it.

I gave all of the options to the customer and he is exploring a couple of torgue arrestors.

Thanks for the help.
 
Ravenvalor said:
Good idea. Lower the voltage going to the pump. I will look it up in the Franklin manual.

As far as soft starts are concerned I have not found anything that Grundfos will approve of for this particular single phase 2 - horse power pump. The Pentek PID-20 should work but if Grundfos does not approve of it then I will not install it. Franklin does not make a starter for anything over 1.5 horse power and single phase and even if they did Grundfos probably would not recommend it.

I gave all of the options to the customer and he is exploring a couple of torgue arrestors.

Thanks for the help.
Click to expand...

The tech support person talked me into a Franklin MonoDrive XT Constant Pressure drive because it has soft start capabilities. I'll report on the outcome if the customer decides to use it.
 
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