OFF TOPIC: Electricians & electric motor?

Submitted: Sunday, Mar 16, 2003 at 13:24
ThreadID: 3872 Views:2876 Replies:14 FollowUps:3
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Hi all.

Sorry to post this off topic but I would like some impartial information and I think there may be a few electricians on this Forum that may fit the bill.

I have a 2.2 HP single phase electric pump driving my reticulation, The pump is in as new condition and weather protected. It is less that 3 years old.

Recently I have been experiencing the problem that the motor does not at times kick in as per timer. I have to physically press the 'reset' button to make it work. As such it is no longer reliable.

I have just come back from a 3 weeks camping trip to find my lawn almost dead because of this.

My questions:

What could be causing this,
and, is there any way to overcome this problem?

Regards
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Reply By: Member - Cocka - Sunday, Mar 16, 2003 at 14:29

Sunday, Mar 16, 2003 at 14:29
Firstly I'm not a licenced electrician. I have however had many electric motors in past business and had to solve problems. A couple of things worth checking. I take it the motor and pump are an intergrated unit. Does the enclosure allow sufficient ventilation to prevent overheating ? Is there a guaranteed water supply to the pump, if it runs dry it will run hot and could cease - overloading the motor. Reset buttons usually trip to prevent burn out if overloaded. With the power turned off - does the pump/motor turn easily by hand? Is the pump and motor big enough to do the job, have you added any extras to the line ?
Reset buttons do not reset themselves when they trip, its a matter of trying to find the cause if it 'goes off" whilst you are there to observe.
Make sure there a no obstructions around the cooling vents of the motor like leaves, spiders etc. Disconnect and bench test, try blowing out with high pressure air any accumulated gunk.
If its the trip switch you will have to find an electric motor rewind/service workshop to have a look at it.
So much to do - and so little time
AnswerID: 15307

Reply By: Voxson - Sunday, Mar 16, 2003 at 14:46

Sunday, Mar 16, 2003 at 14:46
I agree with everything that Cocka said.. Sounds like he has his fair share of motor problems...
The other problems that can occur with single phase electric motors to cause them to trip the manual overload is faulty capacitor, centrifugal switchgear not working properly or the windings have a fault......
So if you check the things that Cocka said and all is ok,, then it will be most probably be one of the things i said...
If it is just a capacitor approx $30,, a switchgear adjustment approx $90,, if it is a rewind,, $$$$ heaps.......
If it is one of the first two,, make sure you change the bearings also.. Never know when you will get another chance..
If it is burnt out (windings),, check your household insurance policy for "fusion" and claim it..
Plus if you pull it out and put it back in yourself,, charge them for your time.
Labour normally about $120...._____________________________________________
Countin the days till July 5th. *Cape York Trip*
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AnswerID: 15309

Reply By: GOB - Sunday, Mar 16, 2003 at 16:45

Sunday, Mar 16, 2003 at 16:45
without looking at the unit it is hard to diagnose the problem as said above they could be one of many if you have a motor rewinder not to far away the quickest and easiest is to undo pipe work at pump and take to motor rewinder he should be able to tell you what is wrong and how much to fix on the spot or whether it would be cheaper to replace.most rewinders are happy to do this for you at no cost (althuogh dont quote me on it) can you post some more details of what it does when you press the reset does it try to go, does it squeal or does it just pop the reset again
AnswerID: 15312

Reply By: AK - Sunday, Mar 16, 2003 at 20:11

Sunday, Mar 16, 2003 at 20:11
janset
Provided you are talking about the reset button on the actual motor you have a thermal overload problem. This thermal overload is designed to open circuit when the windings in the motor draw more current then they are designed to. There are several things that would cause the motor to draw more current. 1 heat build up - ensure adequate ventilation and that the cooling fins are free from dust build up. 2 the rotor spins freely - bearings could be no good or a blockage in the impelor system. 3 The biggest killer of electric motors is under voltage, for any motor of the same size if you reduce the voltage the current increases ( P=Vi ). Depending on your location some places can experience what is called a brown out this is when the lounge room lights go dim, this is caused by someone in your area who shares the same supply transformer starts a very large load causing your supply voltage to drop.Question does the motor cut out at the same time of day?


You have a couple of options measure your supply voltage ( anything under 228 volts is a concern). disconect the plumbing and get it checked - note motor rewinders are notorous for ripping people off ( motor rewinds are usuallly priced at 2/3 the cost of a new motor.You could call an electrician to come and have a look but trust me this can be like finding a needle in a haystack particularlly if a under voltage fault is the cause .
Best of luck
AK
AnswerID: 15323

Follow Up By: Voxson - Sunday, Mar 16, 2003 at 22:49

Sunday, Mar 16, 2003 at 22:49
note motor rewinders are notorious for ripping people off

Yes.. If you live in the eastern states.....

_____________________________________________
Countin the days till July 5th. *Cape York Trip*
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0
FollowupID: 9341

Reply By: Mark - Sunday, Mar 16, 2003 at 23:05

Sunday, Mar 16, 2003 at 23:05
Janset,

On the side of the motor there should be a plate that tells you the FULL LOAD CURRENT, Now open up the enclosure with the reset button and there will be a contactor and a set of thermal overloads. On the overloads there will be a slide to vary the cut out current, make sure that it is set to the same as the plate on the motor. Also make sure that the pump hasn't sucked up any crap and that the bearings let it turn freely.
Being single phase there is a good chance that it is the 440v capacitor normaly located on the outside of the motor in an enclosure.
AnswerID: 15343

Follow Up By: Member - Cocka - Monday, Mar 17, 2003 at 00:11

Monday, Mar 17, 2003 at 00:11
That all sounds like good professional advice to follow. But please, please disconnect the unit from any power supply before you touch it, and I don't mean turn off the switch. Either pull the plug or the power fuse in the fuse box - if in doubt pull the main.

I got a motor rewound in Sydney a few years ago and the guy offered me a brand new Korean motor for just $60.00 more. There used to be 32 rewinding workshops in Syd 25 years ago, now there are 3. They can't compete with the throw away cheap motors.
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FollowupID: 9346

Reply By: Nordave - Monday, Mar 17, 2003 at 23:24

Monday, Mar 17, 2003 at 23:24
Janset.
AnswerID: 15431

Reply By: Nordave - Monday, Mar 17, 2003 at 23:24

Monday, Mar 17, 2003 at 23:24
Janset.
AnswerID: 15432

Reply By: Nordave - Monday, Mar 17, 2003 at 23:24

Monday, Mar 17, 2003 at 23:24
Janset.
AnswerID: 15433

Reply By: Nordave - Monday, Mar 17, 2003 at 23:24

Monday, Mar 17, 2003 at 23:24
Janset.
AnswerID: 15434

Reply By: Nordave - Monday, Mar 17, 2003 at 23:24

Monday, Mar 17, 2003 at 23:24
Janset.
AnswerID: 15435

Reply By: Nordave - Monday, Mar 17, 2003 at 23:24

Monday, Mar 17, 2003 at 23:24
Janset.
AnswerID: 15436

Reply By: Nordave - Monday, Mar 17, 2003 at 23:40

Monday, Mar 17, 2003 at 23:40
Janset.
One thing not covered is the fact that the most common fault In all my years fixing these small motors is the overload itself. The overload on small kw motors is a bimetal strip which heats up with excessive current. You will find it will not reset until it cools down. Contary to a previous post there is no adjustable part to this if it is faulty and it may be that it has operated a few times as they loose their "spring" after a while.
Please do not open the unit, before any attempt to adjust any thing get a registered electrician. I say this not to protect the trade but because of the many hundred people who have been killed due to a small mistake made by people not familiar with how electricity works. Most electrians would be able to diagnose this in a few minutes or tell you if the motor is the problem. I have no reason to defend motor rewinders but I have found most of them to be fair. I believe most people do not realise how much work is involved in rewinding a motor. That by the way is why it is usually not worth rewinding them as the price of a new one is not that much. Any reputable electrician will tell you that.
AnswerID: 15440

Follow Up By: Nordave - Monday, Mar 17, 2003 at 23:46

Monday, Mar 17, 2003 at 23:46
Whooooo
Sorry about all the posts don't know what happened there.
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FollowupID: 9387

Reply By: Eric - Tuesday, Mar 18, 2003 at 01:18

Tuesday, Mar 18, 2003 at 01:18
Janset.
Sorry to ad to the already long replys but the answer could be a combination of facts, its true that low voltage is a motor killer. Another cause of low voltage is to thin supply wire, a single phase motor requires 5 times its runing current to start it so the wire has to be heavy if the pump is a long way from the meter box. Measure the voltage drop when it is ruuing and x 5 if the answer is 10 run a thicker wire. Eric.
AnswerID: 15459

Reply By: Janset - Tuesday, Mar 18, 2003 at 11:57

Tuesday, Mar 18, 2003 at 11:57
Hi all.

I thank you one and all for all the good advice given. It is more than I could hope for. Most of the suggestions I have either already tried before submitting this post or have now tried.

The indications all seem to point to overheating and also power fluctuations are very common in my area.

I try to over come the fluctuations by running the bore in the early hours of the morning. Still the motor throw-out does happen randomly, (I live rather close to a light industrial area).

An interesting point was suggested that I had not entered into the equation and that is a blockage.

I know that there is no blockage in the suction side of the pump, but what I do have quite a bit of trouble with are the solenoids as they tend to jamb because of sand being sucked up resulting in one or more valves only partly opening and as such it is quite conceivable that one or more could at times even not open at all.

This sand problem I try to overcome by stripping the solenoids every 5-6 weeks and cleaning them out but at time I seem to get more sand then at other times. I have tried filtering the water though a strainer but that gets blocked up in a very short period of one watering cycle, so hence, no more filter.

The old pump that I had on for nearly 20 years was a 1.5 HP single phase but that did not have a cut-out button so I guess it just slogged on coping with possible over heating until it finally gave up the ghost.

Thanks again. Regards

I will look around for a more sand friendly solenoid and try those as they usually do not cost too much
AnswerID: 15481

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