Can I Add A Capacitor To Help A Pump Motor Start? - Electrical - DIY Chatroom Home Improvement Forum

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Old 03-22-2012, 11:21 PM   #1
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Can I add a capacitor to help a pump motor start?

Hi, I live in rural Panama, where I have a small house that is about 2000 ft away from the nearest transformer. Unfortunately the electrical company will not run a secondary electrical line up the road for me. I was on a budget when I installed the wiring, so I have 220V #6AWG aluminum cables running this distance, which I know is a long ways for this size wire. As I only have a few light bulbs and a small fridge, this hasn't been a problem, and I've had this set up for 2 years without incident. I do notice that the electrical system is taxed when the fridge's compressor clicks on (the lights in the house get very bright, I'm assuming this is an amperage spike to make up for the voltage drop).

However, I recently installed a pressure-tank system that draws water from an above-ground storage tank and pumps it into the house. The system uses a 1/2HP, 110V centrifugal pump to send water into the pressure tank and beyond into the house. The pump clicks on and off with a pressure switch. However, due to the electrical, occasionally the pump doesn't start well. I have notice that if I throw the breaker, and run out to the pump, I am able to get it going by spinning the fan on the back of the pump. Once I do that, it (mostly) starts and stops just fine with the pressure switch. However, if it sits too long and cools down, it generally needs to be helped again to start.

I'm worried that I (or someone else) will burnout the pump (or worse) at some point when they open the tap and don't realize it's trying to start. Is there a way to wire a capacitor to the pump to assist with the large current demands when the motor starts? I think this would solve the problem.

Thanks for your tips!
Drew in Panama


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Old 03-23-2012, 06:57 AM   #2
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Sounds like starter windings and or starter cap isn 't working

This isn't normal. I'd fix that first


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Old 03-23-2012, 07:37 AM   #3
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Lights getting brighter is the classic symptom of a loose neutral connection. Check all your connections between the POCO feed and your main panel. Have the POCO check theirs as well, including in the meter pan.
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Old 03-23-2012, 08:37 AM   #4
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If its not a cap start motor i wouldnt add one
"facts" have no relevance to this discusion
Posting from a concrete bunker under a non descript barn
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Old 03-23-2012, 10:22 PM   #5
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I doubt if the pump has any problem at all. 2000' of #6 AL causes too much voltage drop.

#6 AL is 0.8Ω per 1000'. 2000' out and 2000' back = 3.2Ω.

The resistance of both the start and run windings of a typical 1/21HP 120 volt motor would be less than 1Ω. this means that most of the voltage is dropped across the incoming wiring, leaving very little for the motor. There's a lot more than simple math to the equation, but I'd guess the motor is trying to start on about 40 or 50 volts.

If possible, change the motor to 230 volts. It'll still have greatly reduced voltage at startup, but it'll very likely start.

Also, I don't think the lights getting brighter is a loose neutral, I think it's because of the length of the wire.

2000' is a LONG way to push 120 volts, heck it's a long way for 480.

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Old 03-26-2012, 09:18 AM   #6
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Hey Rob,

Thanks for this, I did check the neutral and it wasn't loose - seems the most logical that it is just the distance. I found a cheap 220V 1/2 HP pump, I think I'm going to buy this one and give it a shot.

Eventually I'll need to rewire with thicker gauge, or get the power company to put an extension at least some of the way to the house.

Much obliged! Drew


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capacitor , pump motor , wiring

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