Capacitor start contactor

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jmo103

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I am looking to replace a contactor (for a well pump on an irrigation system). The existing contactor has a capacitor start. I have never seen one of these before and am looking for more information. Is that capacitor start going to be critical? Can I replace the 230 v 5 hp contactor with a more readily available contactor, without the capacitor start? I have very little experience with irrigation systems so any input or advice would be greatly appreciated. Thank you.
 
You will need the capacitor...you should be able to find a replacement at Well/Irrigation Supplier.

jmo103 said:
I am looking to replace a contactor (for a well pump on an irrigation system). The existing contactor has a capacitor start. I have never seen one of these before and am looking for more information. Is that capacitor start going to be critical? Can I replace the 230 v 5 hp contactor with a more readily available contactor, without the capacitor start? I have very little experience with irrigation systems so any input or advice would be greatly appreciated. Thank you.
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Never heard the term “capacitor start contactor”. A contactor is just a contactor, it doesn’t need a capacitor.

What you might have is a single phase capacitor start MOTOR that is submersible, so the capacitor is relocated into the pump panel above ground, and instead of a centrifugal switch in the motor, they use a “potential relay” that switches the capacitor out once the motor gets up to speed. If it’s a 5HP single phase motor, that capacitor might be too big for the potential relay to handle on its own, so it pulls in a contactor to control that capacitor, at the same time as the motor contactor, then drops it out a second later. I’ve seen it done with timers too, but that’s dangerous, you can smoke the cap or the motor or both of you get it wrong.

If this is 3 phase (you didn’t specify), then any capacitor is for power factor correction. Typically that capacitor is wired down stream of the motor starter so that it’s only on line when the motor is. So in that case I’m not sure what your issue is here.
 
It is single phase. I actually have a picture of the wiring diagram that I have been trying to upload a picture all afternoon but can’t figure out how to do it. There are actually 2 capacitors, a start capacitor and a run capacitor, with a relay in between the contactor and the capacitors. There are also 3 wires (plus the ground) going to the motor. I will be returning tomorrow and will see if I can’t make more sense of it.
 
Are you dealing with a Franklin 5 hp single phase control box? If so, here is the Franklin AIM manual in PDF. It has part numbers for the components in the control box

http://www.franklinwater.com/media/110562/M1311_60_Hz_AIM_12-14-WEB.pdf

and yes, you need the capacitors. You could probably use a different definite purpose contractor, but why half-ass it? Blake equipment in Greenfield is probably your closest Franklin distributor.
 
jmo103 said:
It is single phase. I actually have a picture of the wiring diagram that I have been trying to upload a picture all afternoon but can’t figure out how to do it. There are actually 2 capacitors, a start capacitor and a run capacitor, with a relay in between the contactor and the capacitors. There are also 3 wires (plus the ground) going to the motor. I will be returning tomorrow and will see if I can’t make more sense of it.
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You can use other contactors for the main contactor, but the other relay is a "potential" relay, and is needed to cut out the start capacitor after starting the motor. (The run capacitor is always connected in the circuit.)

A capacitor-less option is to get a "Mono drive" (Franklin) or "Intellidrive" (Pentair). Those are variable frequency drives specifically designed to drive this type of motor and direct connects to the motor without the relays and capacitors. Will make your capacitors and relays look pretty inexpensive though.
 
kwired said:
A capacitor-less option is to get a "Mono drive" (Franklin) or "Intellidrive" (Pentair). Those are variable frequency drives specifically designed to drive this type of motor and direct connects to the motor without the relays and capacitors. Will make your capacitors and relays look pretty inexpensive though.
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That would mean a new controller and new pump. You can't run a single phase, cap start motor off a VFD.
 
ActionDave said:
I've never heard of that.
How do you keep starting cap out of the circuit when the pump slows down?
Since you have a vfd why wouldn't just use a three phase motor?
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1. There is no centrifugal switch and the start winding lead is brought to the controller at the top of the well.
2. Maybe because you already have a motor integrated with a pump and it is at the bottom of a well. Not necessarily the OP's situation.

Sent from my XT1585 using Tapatalk
 
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From the original posters information, he has a 5 hp single phase 230 volt submersible motor. These are capacitor start, capacitor run motors. The capacitors are located in a control box at the surface. The control box also contains klixon overloads, a start relay and it may or may not contain a 2 pole contactor. The original posters question was about replacing the contactor.

the standard Square D FSG pressure switch is rated for up to 2 hp at 230 volts. So on a 2 hp or under Pump, the incoming power goes to the pressure switch, then to the control box, then To the Pump motor. At 2 hp and above, you have the option of buying a control box with or without a contactor.

If you utilize a control box without a contactor, you then have two options. One is to use a heavy duty pressure switch rated for the horsepower. The other option is to use an external contactor. The standard FSG pressure switch is then used, but it’s only a pilot circuit to activate the contactor. Any definite purpose contactor can be used.

i prefer to use the control box with a contactor built into it. I’m replacing a 1 1/2 sub Pump right now with a 2 hp. I installed the original pump 24 years ago in 1994. It hasn't failed, but is starting to get a little noisy. The new 2 hp control box has a contactor, so I’m changing the wiring. Now the incoming power goes directly to the contol box,not the pressure switch. There is just a pilot circuit to the pressure switch for the heavier duty contractor

even though the FSG pressure switch is rated for 2 hp, and has had a 1 1/2 hp load, it has been replaced a number of times in the last 24 years. The point are burnt now and a new switch is going in.

the subject of VFD’s came up, but not from the OP. A single phase motor up to 2 hp can be run at variable speeds on a Franklin Monodrive or Pentair Intellidrive. 3 hp and larger require a 3 phase motor to use a VFD.

A 5 hp single phase control box with a contactor costs in the area of $300. A Pentair Intellidrive to run a 5 ho 3 phase sub motor is about $1,600 my cost.
 
ActionDave said:
I've never heard of that.
How do you keep starting cap out of the circuit when the pump slows down?
Since you have a vfd why wouldn't just use a three phase motor?
Click to expand...

You replace the control box that contains the capacitor and the potential relay. The drive isn't your average general purpose drive, it is specifically designed for submersible motors, and cost much more than a similar kVA rated general purpose drive. The single phase submersible has three leads, you must connect to correct terminals on the drive output. It is programmed to put out the right current to drive said single phase motor, and is not even current on all three lines like it would be with a three phase motor.

Same drives often will run a three phase motor also, but you have to enter correct parameters to tell it whether you are powering a single or three phase motor.

I happen to have Pentair Intellidrive on my water system, it is driving a 1 HP single phase submersible, same submersible that once had a start capacitor and potential relay in a control box located about where this drive is now located. Dry contact pressure switch gets replaced with a pressure transducer that gives input to the drive.

I installed it because of the amount of water usage I have the frequent starting of the pump kept shearing splines off the motor shaft at the motor to pump coupling point. Never had that failure again since installing the drive because it "soft starts" now.
 
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