Armsrtong motor continuity to ground

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i_blew_up_my_linemans

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I have a 120v 1 phase pump motor that has continuity hot to ground, hot to neutral and neutral to ground. The motor runs very hot but doesn't trip the breaker. What should i start checking in order to fix the problem? This pump motor is for my
house boiler heat. It ran all last winter at a fairly high temp. I could touch it and keep my hand on it, but it wasn't very fun to do. Ive kept it oiled. Where should i start?
 
i_blew_up_my_linemans said:
I have a 120v 1 phase pump motor that has continuity hot to ground, hot to neutral and neutral to ground. The motor runs very hot but doesn't trip the breaker. What should i start checking in order to fix the problem? This pump motor is for my
house boiler heat. It ran all last winter at a fairly high temp. I could touch it and keep my hand on it, but it wasn't very fun to do. Ive kept it oiled. Where should i start?
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Do not assume that there is a problem just because it is hot to touch. It could be a lot hotter than that and still be within the rating of the motor.
Look at the nameplate and measure the current in all conductors including EGC.
If the motor has been disconnected from the house wiring when you measure continuity to ground, then there is a short inside the motor somewhere, one which does not impair the motor performance too much nor draw too much extra current. Possibly just neutral to ground at the terminals?
 
i_blew_up_my_linemans said:
I have a 120v 1 phase pump motor that has continuity hot to ground, hot to neutral and neutral to ground. The motor runs very hot but doesn't trip the breaker. What should i start checking in order to fix the problem? This pump motor is for my
house boiler heat. It ran all last winter at a fairly high temp. I could touch it and keep my hand on it, but it wasn't very fun to do. Ive kept it oiled. Where should i start?
Click to expand...
Are you competent and qualified to accurately test this motor? What are you using to test it and how? The reason I ask is this:
... hot to neutral and neutral to ground.
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A first year apprentice should already know that you will read continuity from hot to neutral through the motor windings themselves, and neutral and ground are SUPPOSED to be connected at the service, so of COURSE they would read continuity. Basically, what you have posted as evidence of a possible issue means nothing.

So giving you the benefit of the doubt as an apprentice, the main lesson here is, if you don't know what you are doing yet, don't take it on yet.

Other lessons for your growth as an electrician:
1) Motor health is checked with a megohmeter, often called a "megger". It charges up a DC voltage with a capacitor from a battery, or a hand cranked generator, and you look at the resistance between the windings and ground as that DC voltage leaks through the winding insulation to the case, looking for it being less than a certain value (different for different motors, but the megger will come with a guide book) to know it is bad.

2) Putting your hand on a motor is not a valid determination of motor health either. Motor insulation is rated for MUCH higher temperatures than the human hand can even BEGIN to stand. For example, Class H insulation, common on modern energy efficient motors now, is OK at temperatures of up to 357 degrees F. Your hand will jerk back at somewhere around 120 F. So again, that means nothing.

So aside from these two invalid results, was there any other reason for you to suspect a problem with that motor?
 
is it disconnected

is it disconnected

If you disconnected the wires and still have a reading from hot to ground the motor has a problem. If you did not disconnect it, that why you have a reading from hot to ground it is the bonding of ground to neutral. Start with wires disconnected and let us know in ohms what the readings are getting, not just continuity. Note if you do have a reading from hot to ground it probaly has current on the ground and is not safe to run.
 
Jraef said:
Are you competent and qualified to accurately test this motor? What are you using to test it and how? The reason I ask is this:

A first year apprentice should already know that you will read continuity from hot to neutral through the motor windings themselves, and neutral and ground are SUPPOSED to be connected at the service, so of COURSE they would read continuity. Basically, what you have posted as evidence of a possible issue means nothing.

So giving you the benefit of the doubt as an apprentice, the main lesson here is, if you don't know what you are doing yet, don't take it on yet.

Other lessons for your growth as an electrician:
1) Motor health is checked with a megohmeter, often called a "megger". It charges up a DC voltage with a capacitor from a battery, or a hand cranked generator, and you look at the resistance between the windings and ground as that DC voltage leaks through the winding insulation to the case, looking for it being less than a certain value (different for different motors, but the megger will come with a guide book) to know it is bad.

2) Putting your hand on a motor is not a valid determination of motor health either. Motor insulation is rated for MUCH higher temperatures than the human hand can even BEGIN to stand. For example, Class H insulation, common on modern energy efficient motors now, is OK at temperatures of up to 357 degrees F. Your hand will jerk back at somewhere around 120 F. So again, that means nothing.

So aside from these two invalid results, was there any other reason for you to suspect a problem with that motor?
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Thanks. as for qualified, i doubt anyone coming out of my apprenticeship is where they should be, most of my instruction comes from OTJ and at that point its just a lot of running pipe and pulling wire. But yes I did understand that i would get
a reading from hot to neutral, i was just adding anything i could. As for the temp part of the question, that is something my Journeyman told me to check. i was under the impression that it shouldn't be too hot at all. My experience with motor is somewhat slim (i only had the opportunity to take one apart/ hook up in class. and it was a blown motor so i don't know if i did it correctly), but i did open it up to clean it out, all the leads were flaking and showing conductors, it was covered in oil, and had a ton of lint in it. FYI, Ive only been in the house since last spring, so the condition of the motor was not something i was aware of till i tore it apart.(just in case someone wants to yell about maintenance).

As for a name plate. it doesnt have one. the only info i have is a nameplate on the pump section. - Armstrong 816549-091 . Do these pumps come as an assembly already married together? when i looked up the pump number all i could find was the pump without a motor.

@just the cowboy-

Thanks i did disconnect it, it did not read to ground after this. I didnt think about it going all the way back to the panel from the neutral. Kind of a "Duh" moment.
Hot --->ground--->Main bonding J---->neutral--->motor windings--->back to hot.

At this point Should i try to clean up this motor and replace the leads? What is safe to use to clean the windings ? they are covered with oil and lint all the way through. The thing is really a mess, which is probably the cause of the heat.

Thanks for the help everyone.
 
I doubt a little lint makes it run hot. A lot of motors run too hot to touch comfortably.

If it bothers you a rag and some isopropyl alcohol is about as good as it gets for this kind of cleaning.
 
Also remember if this is a boiler pump it is likely pumping 180 degree water if it is in the "supply line" if in the "return line" it will be cooler but still possibly more then 120 degrees, just depends on the system, that will transfer some heat to the motor even if it wouldn't be running very warm otherwise.
 
kwired said:
Also remember if this is a boiler pump it is likely pumping 180 degree water if it is in the "supply line" if in the "return line" it will be cooler but still possibly more then 120 degrees, just depends on the system, that will transfer some heat to the motor even if it wouldn't be running very warm otherwise.
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good to know. for future reference,and i know it will be different for the environment/specific motor, what would be a general temp for a motor in a room temp environment? or is there no way to tell? just wondering for my own sake.
 
i_blew_up_my_linemans said:
well, i kinda already opened it up. Would rubbing alcohol hurt the winding coatings?
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That being the case clean away. We use a plain old solvent and a nylon brush in our shop. Can't say anything about alcohol, never tried it. I would stay away from any harsh cleaners like xylene or naptha.

While you have it open wipe the end bells good and clean soak the wicking with some good bearing oil.
 
when i opened it up i noticed that the leads were cracked and showing the conductor. is a crimp and some heat shrink ok to use when i replace them? the winding lead is pretty small. not sure if a crimp would work on it.
 
i_blew_up_my_linemans said:
when i opened it up i noticed that the leads were cracked and showing the conductor. is a crimp and some heat shrink ok to use when i replace them? the winding lead is pretty small. not sure if a crimp would work on it.
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We have some fiberglass material that I only have heard called spaghetti that can slide over the leads. If you can find something like that it would be your best bet .
 
ActionDave said:
We have some fiberglass material that I only have heard called spaghetti that can slide over the leads. If you can find something like that it would be your best bet .
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Spaghetti came before heat shrink, and in my experience just describes the colorful thin insulating tubing and does not imply any particular material. It could range from thermoplastic (not the best choice for motor leads) to varnished cambric (very durable but not flexible) to woven fiberglass.
 
all i could find is some fiberglass tape. its a class B insulator. gonna go with that for now. i think im gonna test to see if i get a voltage drop on start up. i have a feeling i might have bad bearings.
 
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