Troubleshooting tip for submersible well pump users

Stargazer

Surin Legend
Arriving back in Thailand, my grandpa job is 'Mr. Fixit'. Amazing how many things can break in 6 months! I do have pretty good troubleshooting experience. My successful isolation of problem may help someone else.

One of the two well pumps, ½ hp about 40 meters down, had stopped working. (Franklin pumps) Power OK, pump controller OK, just kept tripping breaker. Two possibilities left: pump wiring connections at pump failed, allowing short. Or pump motor seal failed, flooding motor, allowing short. Ugh. Time to pull the pump, not fun.

Wait! I examine main breaker for rice field buildings. It has a little RSQP switch about the size of a pencil lead. I remembered that we had some problems at our house with a safety breaker always tripping on the pump line. So I tried turning off RSQP. Pump then worked fine, nothing wrong.

Analysis: (I am not an electrical engineer, but was a licensed electrical contractor as part of design/building homes in California) It is my understanding that sensitive ground fault breakers can be activated by either too many connected devices that shunt power surge peaks to ground (which, added up, look like a ground fault), or by long wire runs with inductive losses, or connected induction motors. My theory is that typical pump installations in Thailand can create the latter condition.

In the case of our home, the solution that worked was to bypass the whole house safety breaker just for the pump circuit, and connect the pump top metal connector to ground stake. One way to test if there is significant leakage current is to measure from top of well to ground.

As there are some safety risks involved here, I do not recommend following my solution without professional help. But it works for us. I have no idea what PEA's position is about this issue, and I prefer to not involve them lest it get bureaucratic. Certainly, you do want most house circuits protected by RSQP, which in Thailand works a bit differently than in USA, as it simply measures the current going out the hot and compares to that returning on the neutral. If there is a difference above a certain (sometimes adjustable) threshold, it reasons that there is a ground fault, and trips off.
 
Pardon my ignorance but what does RSQP mean? You are on the right track being something to do with inductance. Circuit breakers world wide have three characteristics set out by a T1 or T2 curve then a definition of B, C and D which defines the tripping characteristics
  • Trip characteristic B is the standard characteristic for wall outlet circuits in domestic and utility buildings
  • Trip characteristic C is advantageous when using electrical equipment with higher inrush currents as for example of lamps and motors
  • Trip characteristic D is adapted to electrical equipment that can produce strong current surges such as transformers, electromagnetic valves or capacitors

MCB Trip curves

If you have not been using a type D most likely the energy dispersal from the motor winding fields have destroyed the breaker and it needs to be replaced.
If you have worked as an electrical contractor you should know this.
 
Arriving back in Thailand, my grandpa job is 'Mr. Fixit'. Amazing how many things can break in 6 months! I do have pretty good troubleshooting experience. My successful isolation of problem may help someone else.

One of the two well pumps, ½ hp about 40 meters down, had stopped working. (Franklin pumps) Power OK, pump controller OK, just kept tripping breaker. Two possibilities left: pump wiring connections at pump failed, allowing short. Or pump motor seal failed, flooding motor, allowing short. Ugh. Time to pull the pump, not fun.

Wait! I examine main breaker for rice field buildings. It has a little RSQP switch about the size of a pencil lead. I remembered that we had some problems at our house with a safety breaker always tripping on the pump line. So I tried turning off RSQP. Pump then worked fine, nothing wrong.

Analysis: (I am not an electrical engineer, but was a licensed electrical contractor as part of design/building homes in California) It is my understanding that sensitive ground fault breakers can be activated by either too many connected devices that shunt power surge peaks to ground (which, added up, look like a ground fault), or by long wire runs with inductive losses, or connected induction motors. My theory is that typical pump installations in Thailand can create the latter condition.

In the case of our home, the solution that worked was to bypass the whole house safety breaker just for the pump circuit, and connect the pump top metal connector to ground stake. One way to test if there is significant leakage current is to measure from top of well to ground.

As there are some safety risks involved here, I do not recommend following my solution without professional help. But it works for us. I have no idea what PEA's position is about this issue, and I prefer to not involve them lest it get bureaucratic. Certainly, you do want most house circuits protected by RSQP, which in Thailand works a bit differently than in USA, as it simply measures the current going out the hot and compares to that returning on the neutral. If there is a difference above a certain (sometimes adjustable) threshold, it reasons that there is a ground fault, and trips off.
JESUS.png
 
I hope Jesus was not trying to test an RCD while standing on water.
I had to stop company fire man from using a stream of water to put out a transformer fire. The only water would be demineralize water.
 
Pardon my ignorance but what does RSQP mean? You are on the right track being something to do with inductance. Circuit breakers world wide have three characteristics set out by a T1 or T2 curve then a definition of B, C and D which defines the tripping characteristics
  • Trip characteristic B is the standard characteristic for wall outlet circuits in domestic and utility buildings
  • Trip characteristic C is advantageous when using electrical equipment with higher inrush currents as for example of lamps and motors
  • Trip characteristic D is adapted to electrical equipment that can produce strong current surges such as transformers, electromagnetic valves or capacitors



If you have worked as an electrical contractor you should know this.
Next time I'm over to the farm I'll photo the breaker. My recollection of 'RSQP' may be incorrect. It's in 1 point type or less on a switch so tiny(1mm wide) it is funny! In our own house, we have a SafeLife whole house RCBO unit in front of the main breaker panel.

However, I think we're talking pomelo vs. star fruit here. The issue is not breaking on current fault, but on ground fault. The graphic you provided is about current fault.

On the unit in the picture, MCB probably means 'Main Circuit Breaker', as it is the unit solely tripping based on total current. RCBO means 'Residual Current Breaker Overcurrent perhaps', the mfg calls it Residual Current Circuit Breaker with Over Current Protection (RCBO) ) where the sensitivity can be set to 6 to 30 mA. 6 is very sensitive, and in our house we have to set it to 20 to avoid frequent spurious trips. I've never seen such a unit in the USA.

Perhaps it's an Asian or European standard. I am not familiar with international codes, because I have not worked abroad, but I should study up. The norm in USA is 'GFCI' or 'Ground Fault Circuit Interrupt' in an individual breaker, or a GFI outlet that can have downstream plugs protected. Electrical code in USA also now requires an AFCI in some cases (Arc Fault Circuit Interrupt), which protects against cases where the fault current is below the breaker trip current, but large enough to cause an arc and fire (such as if a faulty lamp cord breaks due to fatigue). I have not seen such breakers on sale here.
 

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However, I think we're talking pomelo vs. star fruit here. The issue is not breaking on current fault, but on ground fault. The graphic you provided is about current fault.
How can you be so sure? The breaker may of failed due to excessive EMF inrush currents. You should replace the breaker. If it was still tripping. One way to tell if its earth leakage is to place an earth stake at the supply and bond the neutral to that. If it still trips your pump has lost double insulation and is faulty.
 
How can you be so sure? The breaker may of failed due to excessive EMF inrush currents. You should replace the breaker. If it was still tripping. One way to tell if its earth leakage is to place an earth stake at the supply and bond the neutral to that. If it still trips your pump has lost double insulation and is faulty.
FKIN SPA.png
 
How can you be so sure? The breaker may of failed due to excessive EMF inrush currents. You should replace the breaker. If it was still tripping. One way to tell if its earth leakage is to place an earth stake at the supply and bond the neutral to that. If it still trips your pump has lost double insulation and is faulty.
Thanks, Rice. I appreciate your comments and suggestions. The panel is already bonded to an earth stake (it was installed by a licensed Thai electrical contractor, as I'm not allowed to work here).

As I said myself earlier, a good check is whether there is any voltage (which is what EMF is) from the well top to the earth stake. The startup amperage (inrush current as you put it) is always higher, but that is not the cause here, or the branch circuit breaker would trip rather than the much higher rated main breaker. I will thoroughly test whether there is leakage to ground with a good digital VOM.

My main point here is that these GFI/RCBO devices can be an issue that bears looking into when deep well pumps are involved, IMHO.

I did only residential electrical, not commercial, and though I was licensed, it was not my main work, so you may know more about it than me (I designed and built custom homes, and then started a building supply business). One of my kids lives in New York City, and I installed a whole house surge protector there in the main panel. That is becoming popular in premium homes, as it provides much better protection than the little multistrip units (best practice is to use both). I have not seen the whole house units for sale here.
 
Thanks, Rice. I appreciate your comments and suggestions. The panel is already bonded to an earth stake (it was installed by a licensed Thai electrical contractor, as I'm not allowed to work here).
You say the panel is bonded. Bonded where? Is the neaetral bonded to earth in the panel. That is the most important question. A low-resistance path is created for the earth fault currents by the distribution of the neutral conductor. Its ‘potential rise’ is kept in control by connecting it to earth. If it is a long run it should be connected at a few locations all through its length.
FYI Working for your wife on her farm is not employment. Even if she pays you in kind. :)
 
Of course it is. Code standard is bond neutral to ground in main panel, but not in subpanels.
By the way: the tiny type on the 63A main breaker at the fields is the same, MCB/RCBO. It's got to be the tiniest slide switch I've ever seen (bottom left corner) which is why I didn't notice it at first:

I'll have to take up the 'in kind payments' with my wife. Getting too much in arrears might necessitate foreclosure. :smirk:
 

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Where did you get that idea. This is where you are terribly wrong!
Any way you do what you like. No further comment from me.
From the National Electrical Code: "NEC 2008 states that the neutral and ground wires should be “bonded” together at the main panel (only) to the grounding rod." I don't think we disagree about this. What is your point?
 
Where did you get that idea. This is where you are terribly wrong!
Any way you do what you like. No further comment from me.
I'm sorry that I have apparently offended you. It was not my intention. I value your comments and suggestions, and appreciate all you do to enrich the forum.
 
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