oyb:


hmmm. the real question is what corners were cut while wiring that house
1) if there is overload on the cable, the breaker should trip first
2) in all honesty, a water pump is max 2hp 1500w . a 13amp socket should carry that easily.

of course everything i've posted assumes the house was wired in a competent and honest manner.

unfortunately, i have seen that even artisans who i have seen to be competent will cut corners if they feel they can get away with it.

and the proliferation of fake /substandard materials . . .

there was one instance where for three months straight we kept getting fire alarms in a site server room. we could not figure out the problem.
then one day we took the server room raised floor apart and we found that an ac supply cable had been joined. the joint was the source of all the smoke triggering the fire alarms.

artisans cutting corners.

Wow the more you think you learn the more revelation been expose every day. Very big lesson learn here today, I love ❤️ this platform.

You can search for houses on Zilllow.Com with keywords "fire sprinkler"

EgunMogaji:


My three year old cannot operate the extinguisher but she knows what it is and where it is. We do trimonthly security check in my household. And we actually activate one of the extinguisher.

I must commend such a proactive safety approach.

Just the type of neighbours one would pray to have in an emergency.

Duplicate post

kopell:
Wow the more you think you learn the more revelation been expose every day. Very big lesson learn here today, I love ❤️ this platform.

I wanted to let this go but I think it best to clarify some things.

1st off, circuit breakers unlike surge arrestors and ELCBs et al do not have provision for periodic function tests, hence user might not be able to predetermine functionality status. Remember they are not SIL3 rated

For a 2hp submersible pump, it should be 1492 watts
Divide by 220v gives 6.78amps

As a standard induction motor, it uses between 3-5times rated current as the starting/ surge current. Assuming we take avg of 4x, starting amps will be 27.12amps or 5968watts.

At the time the fridge was running on the same line. Let me assume the fridge is just 600watts (600w/220v) which gives 2.73amps
So total 29.85 amps gives 6567watts.

This is the actual watts / current delivered to the already running fridge and the starting pump and not the volt-amps or apparent power which is always greater.

For the volt-amps when you add the length of wire from the distribution board to the socket outlet to the borehole wellhead and then vertically down to the wellbore where pump is located, due to wire resistance plus ac peak frequency, will be greater but we will ignore this for simplicity.

If I remember correctly, the max current 2.5 sq.mm can handle is 27amps, so providing the breaker failed to tripped on time at 25amps, 30amps can heat up the wire and if due to partial contact on the socket the pump stops and starts again...

44chux:
Duplicate post

44chux:

For the volt-amps when you add the length of wire from the distribution board to the socket outlet to the borehole wellhead and then vertically down to the wellbore where pump is located, due to wire resistance plus ac peak frequency, will be greater but we will ignore this for simplicity.

If I remember correctly, the max current 2.5 sq.mm can handle is 27amps, so providing the breaker failed to tripped on time at 25amps, 30amps can heat up the wire and if due to partial contact on the socket the pump stops and starts again...

Good constructive thinking but ...

Your last paragraph (reproduced above) is a very unlikely scenario but let's humor you.

I refer you to the penultimate paragraph (also reproduced). The immediate supply wire to the pump is likely to be thermally overwhelmed first in a situation where starting current is permanently drawn, given it's lower gauge than the main DB cable. When that happens, you would likely have triggered an earth fault trip anyway. I hope you have an RCD somewhere.

44chux:


I must commend such a proactive safety approach.

Just the type of neighbors one would pray to have in an emergency.

Thank you, Sir.

The older kids who are now of to colleges were trained on how to use an escape ladder from their second story bedrooms.

Training and then practise are the keys.

44chux:

I wanted to let this go but I think it best to clarify some things.

1st off, circuit breakers unlike surge arrestors and ELCBs et al do not have provision for periodic function tests, hence user might not be able to predetermine functionality status. Remember they are not SIL3 rated

For a 2hp submersible pump, it should be 1492 watts
Divide by 220v gives 6.78amps

As a standard induction motor, it uses between 3-5times rated current as the starting/ surge current. Assuming we take avg of 4x, starting amps will be 27.12amps or 5968watts.

At the time the fridge was running on the same line. Let me assume the fridge is just 600watts (600w/220v) which gives 2.73amps
So total 29.85 amps gives 6567watts.

This is the actual watts / current delivered to the already running fridge and the starting pump and not the volt-amps or apparent power which is always greater.

For the volt-amps when you add the length of wire from the distribution board to the socket outlet to the borehole wellhead and then vertically down to the wellbore where pump is located, due to wire resistance plus ac peak frequency, will be greater but we will ignore this for simplicity.

If I remember correctly, the max current 2.5 sq.mm can handle is 27amps, so providing the breaker failed to tripped on time at 25amps, 30amps can heat up the wire and if due to partial contact on the socket the pump stops and starts again...

30amps will not heat up a wire rated for 27amps, a high starting current will not lead to a wire immediately catching fire.

The starting current is not significant.
You dont need to conduct periodic checks of run of the mill circuit breakers.

The implications of the long circuit is voltage drop.


Unless it's an old fridge, most fridges today operate in 100w to 200 w range. It is your water coolers that operate at 400 to 500 w, probably because they also warm water.

From your account, this issue happened immediately

Even in normal conditions, when a cable is overloaded it first gets warm. To get to catching fire conditions, it has to be consistently subjected to the high current. As the cable is in a pvc conduit in a wall or screed floor, I have to wonder what it even came in contact with.

I had an experience where a 70mm cable was substituted for a 95mm application. The cable got warm, but there was no fire. We simply replaced it


Sometimes you pull cables out of conduits and see the signs of charring of the insulation due to overheating.


It's actually an interesting scenario, and there is probably more than one factor involved.

Even with respect to the pump 2hp is an assumption.

It may be 1hp or 1.5.

Possible issues.
Partial contact like you said.
Cheap /fake socket outlets or plugs
Undersized or substandard cable
Those cheape 'British standard' extensions sold everywhere
Flammable material in the vicinity, Eg carpet ing

Theres a lot of talk about gypsum boards. These are fire resistant and can thus limit spread of fire. You however must also consider wall to wall carpeting which is another way fires can spread. Some people turn electrical rooms to stores

EgunMogaji:


Thank you, Sir.

The older kids who are now of to colleges were trained on how to use an escape ladder from their second story bedrooms.

Training and then practise are the keys.

The horrors of burglar proofing.

EgunMogaji:


Erico2k2, stop that Sir

Many houses have fire sprinkler per code.

I just checked,and found out loads of your houses over there do have them, down here nahhhh
Una to like fire for that unu country,I4got you guys have wild fires we dont here.
I checked down here there is a company that has a system that brings mist that suppress fire.

44chux:
I used to laugh at EgunMogaji when he didn't import all the stuff he said he would, but given what I know now, his new approach is the best. After this my first and only build, I have decided to go back to buying completed houses provided they were built by reputable companies or their Cooperative societies.

I made a lot of regrettable mistakes like:

Not bonding my lightening arrestor with my house earthing system which costed me millions in damages.


And the list goes on.

could you explain whats wrong with your approach in this scenario?.
i though a good lightening protector would absorb all the energy from the lightening strike and safely transmit it to ground...that linking your normal earthing to the lightening protector could expose your appliances to harmful volatges if per chance a stike happens to hit ur arrestor

erico2k2:

I just checked,and found out loads of your houses over there do have them, down here nahhhh
Una to like fire for that unu country,I4got you guys have wild fires we dont here.
I checked down here there is a company that has a system that brings mist that suppress fire.

I think you mean fm200, which is aimed mostly at it infrastructure. Typically your fire suppression solutions aim to kill fire without destroying the items being protected. Fire extinguishing solutions aim for a killing the fire and anything else

oyb:


I think you mean fm200, which is aimed mostly at it infrastructure. Typically your fire suppression solutions aim to kill fire without destroying the items being protected. Fire extinguishing solutions aim for a killing the fire and anything else

Hello Boss,

From experience, How do you recognize sub-standard cables??

Your summary in house wiring, Does diversity not apply??

I realise some thime when calculating loads and using diversity,it seem to always reduce cable size, What do you have to say about that?

Thanks

oyb:


30amps will not heat up a wire rated for 27amps, a high starting current will not lead to a wire immediately catching fire.

The starting current is not significant.
You dont need to conduct periodic checks of run of the mill circuit breakers.

The implications of the long circuit is voltage drop.


Unless it's an old fridge, most fridges today operate in 100w to 200 w range. It is your water coolers that operate at 400 to 500 w, probably because they also warm water.

From your account, this issue happened immediately

Even in normal conditions, when a cable is overloaded it first gets warm. To get to catching fire conditions, it has to be consistently subjected to the high current. As the cable is in a pvc conduit in a wall or screed floor, I have to wonder what it even came in contact with.

I had an experience where a 70mm cable was substituted for a 95mm application. The cable got warm, but there was no fire. We simply replaced it


Sometimes you pull cables out of conduits and see the signs of charring of the insulation due to overheating.


It's actually an interesting scenario, and there is probably more than one factor involved.

Even with respect to the pump 2hp is an assumption.

It may be 1hp or 1.5.

Possible issues.
Partial contact like you said.
Cheap /fake socket outlets or plugs
Undersized or substandard cable
Those cheape 'British standard' extensions sold everywhere
Flammable material in the vicinity, Eg carpet ing

Theres a lot of talk about gypsum boards. These are fire resistant and can thus limit spread of fire. You however must also consider wall to wall carpeting which is another way fires can spread. Some people turn electrical rooms to stores

It was a double side by side door fridge with auto defrost and one innovative green ion tech (something lg said preserved food better). So its definitely greater than 200w although I never bothered to check.

The pump was 2hp rated at slightly less than 11amps. And that's normal for submersible pumps am familiar with.

The house was surface wired and covered with the fancy white surface conduit plastic.

I cannot rule out substandard products. But I can tell you it wasn't immediate. It happened while he was still pumping but not immediately.

You seem to have a habbit of estimating based on optimistic assumptions. I was trained the otherway, to use worst case scenarios and sometimes double jeopardy (simultaneously occurrence of independent unrelated events or scenarios) in mind so as not to overlook a credible failure scenario (Layers Of Protection analysis).

oyb:


I think you mean fm200, which is aimed mostly at it infrastructure. Typically your fire suppression solutions aim to kill fire without destroying the items being protected. Fire extinguishing solutions aim for a killing the fire and anything else

Water mist is different from fm200.
FM200 is being phased out due to longterm health issues. In fact it has a deadline date.

The mist suppression is very high pressure water system that passes the water through tiny holes to produce very tiny droplets to fall down essentially as a mist rather than as a sprinkler/shower

temi4fash:


Hello Boss,

From experience, How do you recognize sub-standard cables??

Your summary in house wiring, Does diversity not apply??

I realise some thime when calculating loads and using diversity,it seem to always reduce cable size, What do you have to say about that?

Thanks

your best bet is to buy as close from source as possible

stick to the known names coleman, nigerchin, kabelmetal

for your larger cables, you can get a micrometer or even a ruler to do a quick check to confirm the radius of the conductors- this is because som e traders will relable cable sizes. this was the issue i had with a 79mm vs 95 mm cable. i had sized the cable properly, but somewhere along the chain, someone had relabelled a 70mm cable as 95mm. so once we started operating, the cable started overheating.

check the labelling on the cable insulation of any cable very carefully; fake or adjusted cables usually have signs

you can also run continuity checks [some cables are joined inside and insulation wrapped over them. if your tester is stuttering, then there may be a problem with the cable

load sizing is always a very tricky business, and it is more of an art than a science. it is a big deal in nigeria because of generators.

typically we place .8 diversity - but your challenge when designing for a house is you do not have an actual schedule of all the items that will be conncted to the sockets. so you cannot really tell, will your ring ccit be assigned 2000w, or 3000, or 4000? will you decide based on the ring cct location? eg upstairs low , downstairs high?

i would say identify a period when you exect the house to be at full occupation and calculate based on that. eg evening is typically a time when a house will be full and appliances maxed out. at that time, all lights would be on, tvs would be on, acs would be on

earthrealm:


could you explain whats wrong with your approach in this scenario?.
i though a good lightening protector would absorb all the energy from the lightening strike and safely transmit it to ground...that linking your normal earthing to the lightening protector could expose your appliances to harmful volatges if per chance a stike happens to hit ur arrestor

Its the other way round.

If the ground has enough conductivity, it will quickly absorb all the high voltage, but if not (as is normally the case), then hv will want to also use ur earthing system to ground itself, but because the path of least electrical resistance to ur earthing system is through ur household electrical equipments, it will arc back to the nearest wire to pass through them to get to ground via the earthing

However if your earthing system has a direct underground link to the lightening system, that becomes the path of least resistance and the high voltage flows underground to the earthing system and equally grounded to earth there. So in essence, both the lightening rods piled to the ground, and the house earthing system equally share the job of safely transmitting the lightening strike to ground.

At that microsecond, all the electrical equipment earthed in the house receive that hv on their earthing / chassis but there is no danger as there is no current flow. And if someone was to touch that equipment at that time, nothing would happen because there will always be least resistance at the earthing system than through the person's feet.

No lightening protection is better than an incomplete lightening protection.

jabolo:


Good constructive thinking but ...

Your last paragraph (reproduced above) is a very unlikely scenario but let's humor you.

I refer you to the penultimate paragraph (also reproduced). The immediate supply wire to the pump is likely to be thermally overwhelmed first in a situation where starting current is permanently drawn, given it's lower gauge than the main DB cable. When that happens, you would likely have triggered an earth fault trip anyway. I hope you have an RCD somewhere.

In Nigeria, RCD or ELCB is an unusual electrical luxury for a rented apartment and mine was no exception.
Twinskenny and co can confirm this.

44chux:


It was a double side by side door fridge with auto defrost and one innovative green ion tech (something lg said preserved food better). So its definitely greater than 200w although I never bothered to check.

The pump was 2hp rated at slightly less than 11amps. And that's normal for submersible pumps am familiar with.

The house was surface wired and covered with the fancy white surface conduit plastic.

I cannot rule out substandard products. But I can tell you it wasn't immediate. It happened while he was still pumping but not immediately.

You seem to have a habbit of estimating based on optimistic assumptions. I was trained the otherway, to use worst case scenarios and sometimes double jeopardy (simultaneously occurrence of independent unrelated events or scenarios) in mind so as not to overlook a credible failure scenario (Layers Of Protection analysis).

worst case scenarios introduce a lot of additional and unnecessary costs

the typical fallout of worst case scenario calculations is over sizing of generators

believe me it is very ugly when you have done agressive worst case scenario and proposed a generator of 100kva, and the total load at any time comes to 60kva


also, when doing calculations, you must understand your client.

a domestic residence is unlikely to be scaled upwards
however commercial or industrial facilities have a high potential for future expansion. if you are designing for a high rise, or a factory, you can throw in 25 to 50% additional on mains cables [ with your caveats in place]

It was a double side by side door fridge with auto defrost and one innovative green ion tech (something lg said preserved food better). So its definitely greater than 200w although I never bothered to check.

The pump was 2hp rated at slightly less than 11amps. And that's normal for submersible pumps am familiar with.

2hp motor is 1490w - an electric kettle uses more power ; your big fridge may even be 150w - thats what green refers to.

all in all, not more that 2100w max on the circuit. even 1.5mm can carry that

it does not pay to go all out without clearly identifying the real cause of the fault. if you go that route, you can end up looking incompetent very quickly. buy stabilizer, surge arrester, ups, etc etc, and the equipment keeps burning/failing after over 200k investment - there is a limit to your clients patience.

oyb:


worst case scenarios introduce a lot of additional and unnecessary costs

the typical fallout of worst case scenario calculations is over sizing of generators

believe me it is very ugly when you have done agressive worst case scenario and proposed a generator of 100kva, and the total load at any time comes to 60kva


also, when doing calculations, you must understand your client.

a domestic residence is unlikely to be scaled upwards
however commercial or industrial facilities have a high potential for future expansion. if you are designing for a high rise, or a factory, you can throw in 25 to 50% additional on mains cables [ with your caveats in place]

Unfortunately I prefer to have something I might never ever need (waste) than to one day need it and not have it.

Other than that, I think all is well.

oyb:


The horrors of burglar proofing.

True Sir but one of my burglary bar is designed to be openable here in Nigeria.

44chux:

Unfortunately I prefer to have something I might never ever need (waste) than to one day need it and not have it.

Other than that, I think all is well.

that is risk management. it also depends on your clients pockets

oyb:


that is risk management. it also depends on your clients pockets

So you know the guy

Sometimes, I think engineers like you don't take out time to explain well enough to the clients.

Given, there are clients who don't care probably cause they cannot afford the extras and stressing it might mean you loose the bid.

But I happen to know a lot of clients who do care but just that they were never told how important such redundancies were. And when they do find out, they try to modify but then it becomes more expensive to implement.

EgunMogaji:


True Sir but one of my burglary bar is designed to be openable here in Nigeria.

Would you be so kind as to share pictures, and possibly, the details of the fabricator

44chux:


Would you be so kind as to share pictures, and possibly, the details of the fabricator

Once he finishes it I will share it. It's such an important thing to have.

EgunMogaji:


Once he finishes it I will share it. It's such an important thing to have.

I eagerly await.
If I may ask, is it that Brabus design?

44chux:

I eagerly await.
If I may ask, is it that Brabus design?

Not at all.

My guy says he has done one before so I've asked him to do one for me too.

This is for my garage apartment. For the main house I'm going to be on the ground to supervise my own creation that I designed in SketchUp.

44chux:

Water mist is different from fm200.
FM200 is being phased out due to longterm health issues. In fact it has a deadline date.

The mist suppression is very high pressure water system that passes the water through tiny holes to produce very tiny droplets to fall down essentially as a mist rather than as a sprinkler/shower

I think who ever designed this had electrics in mind.But kudos to them

EgunMogaji:


Not at all.

My guy says he has done one before so I've asked him to do one for me too.

This is for my garage apartment. For the main house I'm going to be on the ground to supervise my own creation that I designed in SketchUp.

Una too like long thing, HAjji don promise to show me the Engineer wey do his own security proof, we only need Broom and palmwine.any intruder will sweep TDB no long thing

erico2k2:

I just checked,and found out loads of your houses over there do have them, down here nahhhh
Una to like fire for that unu country,I4got you guys have wild fires we dont here.
I checked down here there is a company that has a system that brings mist that suppress fire.

Lot of house? have sprinkler system-- Misinformation
Really Please HOMES?
0ne out of 30,000
sprinkler system for lawns? --Yes

erico2k2:

Una too like long thing, HAjji don promise to show me the Engineer wey do his own security proof, we only need Broom and palmwine.any intruder will sweep TDB no long thing

Erico, I'm Ijebu man now, from Ijebu Ode proper.

Forget sweeping. Shebi na house wey you see na him you go sweep?

"You no see gate? Which gate? This one for front of this house. You dey craze, where you see house talk less of gate"

Na so the thieves go argue with each othertill OPC come carry dem comot

GoodFaith:

Lot of house? have sprinkler system-- Misinformation
Really Please HOMES?
0ne out of 30,000

Keep fooling yourself.

Many cities have ordinances that require fire sprinkler systems.