Incoming neutral fail..

[TPES]

I've had a customer call saying all lights in the building are flickering, all sorts of strange things happening, there has been thousands of pounds worth of damage caused to a huge list of appliances, washing machines, dryers, fridges, phones, alarms, entry system, TV's... The list is endless. It's a big residential place..

This faulty, extremely hot neutral was not strapped down correctly, causing a high resistance in the neutral which is trying to be compensated for by the line conductor pushing more and more current down as there is no neutral to disperse of unused current.. Which has caused all this damage to the appliances and damage to fluorescent lighting.

I know I could word this to the insurance company in a far better way with a better description of what's caused these faults and why the appliances will no longer work... It seems anything with a PCB in has fried, amongst other things.

Could anyone offer more advice on how to word this in a letter with a better explanation..?

Any help appreciated

 

[thekingiam]

faulty loose connection on neutral caused overload causing any equipment attached to fry

 

[Deleted member 9648]

I've had a customer call saying all lights in the building are flickering, all sorts of strange things happening, there has been thousands of pounds worth of damage caused to a huge list of appliances, washing machines, dryers, fridges, phones, alarms, entry system, TV's... The list is endless. It's a big residential place..

This faulty, extremely hot neutral was not strapped down correctly, causing a high resistance in the neutral which is trying to be compensated for by the line conductor pushing more and more current down as there is no neutral to disperse of unused current.. Which has caused all this damage to the appliances and damage to fluorescent lighting.

I know I could word this to the insurance company in a far better way with a better description of what's caused these faults and why the appliances will no longer work... It seems anything with a PCB in has fried, amongst other things.

Could anyone offer more advice on how to word this in a letter with a better explanation..?

Any help appreciated

Not sure on the theory of the highlighted bit....if there's no return path there wont be any current,it cant just disappear,or be 'unused'..........more likely voltage all over the place has caused the damage.

 

[brman]

Not sure on the theory of the highlighted bit....if there's no return path there wont be any current,it cant just disappear,or be 'unused'..........more likely voltage all over the place has caused the damage.

I agree. On the other hand, I guess intermittent high resistance in either the line or neutral could cause inductive surges which could damage equipment. Is this what you mean?

I am only talking theoretically here as I haven't experienced this but could the causes of failure be some or a combination of the following....
1) High resistance giving low voltage to motors, causing them to stall, overheat and burn out? (might affect washing machines, fridges, dryers etc
2) Inductive equipment (such as that with motors) causing voltage spikes when the supply intermittently drops/rises. These spikes could fry sensitive equipment
3) Rapid and continues power cycling of electronic equipment can cause failure due to internal power spikes or just thermal cycling.

EDIT: BTW. If this is a large place is it supplied by its own substation (or taking a significant part of the load from the substation)? If so then it could be the inductive nature of the supply transformer causing significant surges in the supply voltage, damaging equipment with over-voltage.
I am beginning to thing that might be what wirepuller meant by "voltage all over the place"

 

[brman]

Ok. Now I have thought about it a bit better, how about this for an explanation....
"Due to the inductive nature of the installation and supply, intermittent connection at the incoming supply neutral (as evident by the reports of flickering lights and other problems) has induced voltage surges which have damaged voltage sensitive equipment".

 

[SYKRAPS]

When was the installation last inspected TPES?

I would be surprised if the insurance company will pick up the tab if it was a long time ago, also if it was recently inspected I feel that they will try and push it onto the inspection engineers PI insurance "if they have any".

I can't see what the insurance peril would come under if it is a loose connection causing the problems.

 

[TPES]

When was the installation last inspected TPES?

I would be surprised if the insurance company will pick up the tab if it was a long time ago, also if it was recently inspected I feel that they will try and push it onto the inspection engineers PI insurance "if they have any".

I can't see what the insurance peril would come under if it is a loose connection causing the problems.

The place was last tested 6-8 months ago.

 

[TPES]

Not sure on the theory of the highlighted bit....if there's no return path there wont be any current,it cant just disappear,or be 'unused'..........more likely voltage all over the place has caused the damage.

There is a return path, it's just a very poor connection, causing a high resistance.. Isn't the voltage stabilised by the sub before it even enters the property? The poor neutral connection isn't going to make the voltage rise... Is it?

 

[jeremy]

Is it single or three phase?

 

[Deleted member 9648]

There is a return path, it's just a very poor connection, causing a high resistance.. Isn't the voltage stabilised by the sub before it even enters the property? The poor neutral connection isn't going to make the voltage rise... Is it?

Hmmmm!......the voltage would undoubtably be all over the shop I feel...as a high resistance would cause a volt drop across the neutral connection. If there was arcing as well is it not possible that capacitors in circuit could cause voltage spikes?
Thats my take on it,but happy to be corrected by those with more technical knowledge than me.

 

[brman]

Hmmmm!......the voltage would undoubtably be all over the shop I feel...as a high resistance would cause a volt drop across the neutral connection. If there was arcing as well is it not possible that capacitors in circuit could cause voltage spikes?
Thats my take on it,but happy to be corrected by those with more technical knowledge than me.

it would be inductance rather than capacitance I think but yes, intermittent connection could cause voltage spikes. Which I was what I tried to say above

 

[Richard]

There is a return path, it's just a very poor connection, causing a high resistance.. Isn't the voltage stabilised by the sub before it even enters the property? The poor neutral connection isn't going to make the voltage rise... Is it?

You say that, but if the supply's three phase (which i'm assuming it is) and you remove a main neutral, wouldn't you be left with 400V between things?

 

[TPES]

It is 3 phase, but there's nothing 3 phase in the building, it's just 3 domestic 10 way boards on a different phase each..

 

[CrazyScozzese]

Not anymore!

 

[Farmelectrics]

a phone call to the contractor who tested it 6 8 months ago would be interesting ive no doubt they will say the same well it was allright when we tested it interesting

 

[Edd]

If you have a high resistance on a neutral in a 3 phase system, even if no items are 3 phase the common neutral bar becomes a central point for all things connected, so a current will go up from one phase off through a load back down the neutral then up the next item on a diffrent phase (the lowest resistance path) If an item on the second phase is a high load (low resistance)(or inductive)this will produce a high voltage across the other items even up to 400v if the neutral is shot.

 

[MDJ]

Sounds like a hung Neutral could have done it, this is one reason why I would never put a neutral through a contactor with 3 phases as 230 volt could easily become 400 if the coil packs up and the poles don't connect properly, out of interest is there a contactor at all in line with the DB?

 

[SirKit Breaker]

a phone call to the contractor who tested it 6 8 months ago would be interesting ive no doubt they will say the same well it was allright when we tested it interesting

It probably was. When does it cease to be the inspectors responsibility? He cant be held accountable for the duration until his next recommended retest date. If its anything like the car MOT, its only valid at the time the test was carried out, and i see no reason why electrical installations should be any different. No end of stuff could have been done in the eight months since it was I&T'd. I know what my reply would be if someone tried to hold me to account in this situation. It would get me a long ban on here from Jason anyway.

Cheers..........Howard

 

[nickblake]

problem is if you loose a neutral on the DNO side especially on TNCS three phase you can get a back feed down the other phases so basically you end up with 400 volts across the appliances on a single phase , other things that can happen is flashing florescents if the are switch start normally go bang if HF and the voltages can peak way higher than 400 had a domestic board with RCBOs all RCBO's tripped when the neutral; was lost measured 680 volts across the switch and it set fire to the incomming supply of a garage 2 doors away

 

[SparkyJoe]

Seen a lot of equipment in a comms room / IT room, Go BOOM due to no neutral, smoke and everything.

 

[Richard]

If you have a high resistance on a neutral in a 3 phase system, even if no items are 3 phase the common neutral bar becomes a central point for all things connected, so a current will go up from one phase off through a load back down the neutral then up the next item on a diffrent phase (the lowest resistance path) If an item on the second phase is a high load (low resistance)(or inductive)this will produce a high voltage across the other items even up to 400v if the neutral is shot.

I was trying to word that the otherday, but eventually gave up! nice one