Voltage sensative eqipment disaster

[liamraffo]

Hi,
i am an Electrical contractor but also carry out Mechanical works. On this particular project we were only carrying out the Mechanical installation. This was a boiler house replacement that consisted of a mechanical control panel and BMS system. The control panel was manufactured by a sub contractor and they also carried out the field wiring and supplied all the sensors and controls. The testing and commissioning was completed on all the equipment on a temporary supply. However, when the electrical contractor put his 3 phase supply to the mech panel it blew all the controls, including the field controls.

Does anything spring to mind as to how this may have been caused? It is as if there was transiant voltage but i cant see how this may have been caused?

The blame is with somebody but the electrical contractor will not accept it is him as he says he only put the supply to the panel. However, the controls sub contractor did put type D mcbs in. Would this have caused the circuits not to trip out under fault conditions?

Any input would be much appriciated.
Thanks

 

[nickblake]

The D type mcb would trip under fault conditions , the D type can handle higher inrush currents ,only problem with the D type is the max Zs readings are lower and some times can be difficult to obtain,as for the panel blowing up ,with out seeing the panel ,alot of control panels that i have worked on use 230 v to control the circuits ,and then switch the 400 3 phase through contactors etc what could have happened is that if the installation is a TNCS and the neutral was not connected you could have ended up with back feed down the earth , this may well have cause 400 volts to flow across the 230 v controls ,or the panel was incorrectly wire , like i have said without seeing the panel its difficult to give an acurated reason ,i may well be wrong

 

[liamraffo]

Yes i appriciate it is very difficult to diagnose a fault without actually been there

Obviusly the electrical contractors argument is that his responsability ends at the rotory isolator hes has installed with 32A 3 phase. But from our point of view the equipment was fine before he undertook any works as we have commissioning reports to prove that.

The electrical contractor did say that when he connected the permanant supply the components in the panel started to chatter and vibrate after this the gas solinoid went bang.

I dont think it was a lose/disconnected neutral as this would have affected the entire installation but nothing else is damaged.

I just cant think what else could have caused it. If he accidently put a phase on the neutral that would have tripped out on short circuit but some how it appears that we have got 400v down 230v controls?

Thanks

 

[ian.settle1]

In my opinion who ever carried out the testing and commisioning with the temporay supply is at fault.

They should have waited until the permanent supply was installed, connected and had been inspected and tested to ensure it was correct before connecting the Mech panel etc.

 

[davelerave]

sounds like overvoltage anyhow

a problem with the neutral to panel would only affect panel equipment afaik


his supply should have been tested and left at isolator in off postion
-he may have corrected any mistake obviously

 

[auto1]

sounds like overvoltage anyhow

a problem with the neutral to panel would only affect panel equipment afaik


his supply should have been tested and left at isolator in off postion
-he may have corrected any mistake obviously

I have seen this happen when the neutral and a feed get confused saw it a couple of times when the harmanisansation of cables first occurred and have found it recently during testing.
Does the installation have old and new colours?

Why change it when it wasn’t broken

 

[davelerave]

line/phase + neutral reversal would cause a few fireworks i think

never came across it

you'd have a couple of line voltages where you'd be expecting phase voltages

 

[mike3671]

As someone else has previously mentioned a lack of neutral can have serious consequences. The neutral on one of our machines burnt away a few years ago and instead of 240v to the transformers we had 415V feeding back through neons etc which did quite a bit of damage.

I think you are looking at a pretty basic error somewhere along the line that may have been covered up by now

 

[mikejashley]

I would say its a case of neutral and phase wrong way round. plug in....BANG.....Oops (realising mistake), quick swap around of the wires and act as if nothing happened !!!! Impossible one to prove i'm afraid. I take it you have a test cert from the sparkie, which probably thinking about it wouldnt be of much use if it is a case of the above.

 

[davelerave]

he may not remember swapping the wires after could've been a reflex reaction