Baboon Getting Shocks

[Marvo]

Re: Any Ideas

I have a quick pop-quiz type question for the trainees;

A 400 kilogram baboon is frying a couple of dozen burgers for his breakfast on an electric flat top grill. Due to him being lethargic because he's overweight, he's sitting on a stainless steel table which is a couple of feet away from the grill whilst he's cooking. Every time he flips a burger with his stainless steel spatula he gets a strong tingling sensation up his arm.

View attachment 29352 View attachment 29353

He doesn't know the first thing about electricity so he calls you out to have a look for the fault.

Question 1; What's the minimum number of faults you're going to be looking for?


Discuss some of the possible fault scenarios.(please don't say static because of his fur )

 

[Marvo]

Okay I've moved this into a new thread.

I've managed to find an earth leakage clamp meter with a 2.5 meter clamp opening, I placed the clamp around the overweight baboons waist whilst he was burger flipping and it shows a leakage current of 25 mA flowing through his lard --- so we've definitely got problems.

Any suggestions what they could be?

 

[pennychew]

Hmmm. First things i can think of are a L-E fault (blown element?) on the Grill and it either has no earth or a high resistance earth so its not tripping.

Not sure if its relevant that the steel is stainless but sitting on a conductive metal table will be grounding him and hes completing the circuit to earth when he touches the grill with the spatula.

 

[Marvo]

Hmmm. First things i can think of are a L-E fault (blown element?) on the Grill

Correct......

and it either has no earth or a high resistance earth so its not tripping.

....and correct again. Nice one Pennychew.

Your first suggestion of a L-E fault is a good call but if it was a full low resistance contact then the protective device would trip. This means it must be a high resistance contact which is more commonly known as an earth leakage fault. This could be caused by a blown element or even a frayed wire or something that got damp.....there's lots of possible causes.

Not sure if its relevant that the steel is stainless but sitting on a conductive metal table will be grounding him and hes completing the circuit to earth when he touches the grill with the spatula.

There is a good chance that sitting on the stainless table could increase the parallel path to earth and amplify the shock the baboon is getting.

So in answer to my original question there's two faults that must occur simultaneously for the baboon to get a shock. If either fault was repaired then the shocks would stop but the appliance or the circuit could still be faulty.

The one thing I wanted to drive home is that if someone gets a shock there's almost always two separate faults you need to find.

 

[Marvo]

Okay the grill has just been IR tested and it passed with flying colours; >500Mohms L-E. I also tested the earth impedance with a trailing lead from the chassis of the grill to the MET of the CU and it was 0.5 ohms. I couldn't believe there was no fault so I quizzed the baboon about his shocks, he said he doesn't get a shock during burger flipping when stands in front of the grill, only when he sits on the table.

He seems a bit dimwitted even for a primate and I'm not sure whether I believe him. Is there even a possible fault scenario that could cause that or can I safely sign the fault off now??

 

[pennychew]

Re: Any Ideas

The fault on the grill may only be once it's up to temperature and the elements have expanded.

Could another scenario be the table introducing the potential from something else it is touching and using the earth of the grill to complete the circuit

 

[Marvo]

Gezz Pennychew, you're on a roll. Both are very valid points.

Earth leakage faults by their nature are prone to being intermittent or varied.

The other suggestion is also a very important one, just because you get a shock when you touch something it doesn't necessarily mean that the thing you touch is at an elevated voltage, it could be the thing you're standing on or sitting on or something else you're in contact with that's causing the hazard.

In this case it would be possible for the grill and its supply circuit to be in perfect and compliant condition but the table is in contact with something causing it in turn to be at an elevated voltage and giving the shocks.

 

[pennychew]

Gezz Pennychew, you're on a roll. Both are very valid points.

Earth leakage faults by their nature are prone to being intermittent or varied.

The other suggestion is also a very important one, just because you get a shock when you touch something it doesn't necessarily mean that the thing you touch is at an elevated voltage, it could be the thing you're standing on or sitting on or something else you're in contact with that's causing the hazard.

In this case it would be possible for the grill and its supply circuit to be in perfect and compliant condition but the table is in contact with something causing it in turn to be at an elevated voltage and giving the shocks.

Thanks Marvo, good little challenge set!

 

[telectrix]

still think it's fleas. baboons and all primates have them.

 

[GMES]

still think it's fleas. baboons and all primates have them.

I've also got feelings Tel and I'm a bloody APE

 

[telectrix]

never mind, glenn. sit back and have 'er indoors give you a good scratch.

 

[Marvo]

I've also got feelings Tel and I'm a bloody APE

Ape, baboon, gibbon, chimp ....didn't realise there was a difference, they're all furry pests where I live.

 

[telectrix]

Ape, baboon, gibbon, chimp ....didn't realise there was a difference, they're all furry pests where I live.

pests maybe, but at the end of the day, you've still got to pay them their wages.

 

[happysteve]

I came a bit late to this thread/challenge, it's all done and dusted now. Gotta say, I'm very impressed by pennychew's answers! Great way of posing a question too, Marvo, and makes the whole thing memorable in a way that a text book won't. Great stuff!

 

[Marvo]

Yeah it was a short and sweet one and Pennychew was on the ball and got all the glory I'm afraid. I'll see if I can come up with another one over the next day or so .