Anyone for a widowmaker ?

[SimonH2]

Late last week we had a call from one of our customers (we do their IT). They are having their power turned off again (makes three times in about 2 years I think) for works on the network. Last time, at short notice (as in my boss calling me during breakfast, plan A having failed) I took my own small genny up to keep the servers running for remote users. This time they've found that their neighbour in the next unit has a genny with spare capacity - so I think you can guess what the question was ...

Yup, can they run a cable from next door and plug it into a socket to power up the building ? At least they knew enough to turn off the main switch first. So I explained that this arrangement is called a widow maker for good reason, plus I think they are on a 3 phase supply and so they'd only get 1/3 of their circuits live.
I went on to add that the only safe way to do it is to have a proper inlet and changeover switch installed - though less than a week is a bit short notice.
Alternatively, it's a load of extension leads to plug stuff into - not exactly ideal given their sprawling office.


Got a call back today. Their electrician is going to see if he can get an inlet/switch fitted in time - and has also advised that a widowmaker isn't safe even under supervision.
Oh yes, and that genny with spare capacity ? Unless something got lost in translation, it should be fairly adequate at 80kVA

 

[securespark]

 

[Lectrician]

80KVA - That's a baby

 

[ricicle]

Do you want to borrow my 800 kva genny ?

 

[plugwash]

playing devils advocate here but if you locked the main isolator off and locked the plug into an interlocked CEEform (IIRC you have to drill an extral hole to do this but it can be done) would it really be unsafe?

 

[ban-all-sheds]

Do you want to borrow my 800 kva genny ?

Will it go in the back of my car?

 

[ricicle]

Do you want to borrow my 800 kva genny ?

Will it go in the back of my car?

Only if you have a rather large low-loader extension on it

 

[SimonH2]

playing devils advocate here but if you locked the main isolator off and locked the plug into an interlocked CEEform (IIRC you have to drill an extral hole to do this but it can be done) would it really be unsafe?

Well that's a minimum of 3 locks :

one to lock off the main incomer

another to lock the supply cable into the outlet

and another to lock the other end of the supply cable into the genny - and that's if there's a facility or the owner is prepared to let you drill holes in the socket. You might argue that this third lock isn't necessary, but if unplugged and the rest of the system not operated correctly, you have the potential to make the exposed pins live.
Or, you need a means of locking a protective cover over the plug once it is unplugged from the genny - so still a third lock.

That last bit is also an issue. It's one thing having a safe method of working when the widowmaker is in use - you also need a safe method of working when it isn't, ie a means of preventing it being plugged in and exposing live pins when there's no-one around to operate the safe working methods. Unless you remove both plugs, you need to lock a cover over at least one end - so that end cannot be plugged in, and if the other end is plugged in, then the live pins aren't accessible.


But I can see where you are coming from. It's no different really to working in a busbar chamber, or distribution board with the terminal covers off, etc - potential for there to be live exposed parts with the only safety barrier being methods to isolate and lock off supplies as appropriate to the situation.

Where I think the biggest problem lies is that once someone sees one of these in use, and especially if it's being used "by an electrician" - then they may well assume that it's an acceptable way to operate, but without having the knowledge to do it safely.


But since this customer doesn't have any CEEform sockets, it would have to be a standard 13A plug - not very easy to lock in. Also loading would be an issue. The server room takes about 2kVA, so that doesn't leave a lot of headroom to run an office full of computers, printers, lights, ... and you can guarantee someone will insist on brewing up.

 

[SimonH2]

Do you want to borrow my 800 kva genny ?

Only if you don't want it back !

 

[ban-all-sheds]

Only if you have a rather large low-loader extension on it

Mine's the red one.

 

[ban-all-sheds]

That last bit is also an issue. It's one thing having a safe method of working when the widowmaker is in use - you also need a safe method of working when it isn't, ie a means of preventing it being plugged in and exposing live pins when there's no-one around to operate the safe working methods. Unless you remove both plugs, you need to lock a cover over at least one end - so that end cannot be plugged in, and if the other end is plugged in, then the live pins aren't accessible.

Somewhere in a box in the loft I have a BS 1363 plug with a length of flex from it - on the other end of the flex are a couple of spade connectors.

 

[SimonH2]

Somewhere in a box in the loft I have a BS 1363 plug with a length of flex from it - on the other end of the flex are a couple of spade connectors.

And ? In our garage there are similar leads hanging up (but with bare ends/choc blocks rather than spades).
Given your encyclopaedic knowledge of regs and safety systems, I'd say it's probably safe there - ditto the ones in our garage since only two people have free access and we both know not to plug them in without the ends being terminated.

However, would you leave it lying around where anyone could pick it up and plug it in ? In the sort of situation I'm talking about, unless the electrician (ie skilled person) took the lead away with him once disconnected, then it would be "lying around" and accessible to unskilled people.

So we come back to, yes a lead with two plugs on could be used safely, but ...
1) You also need to consider it's safety when not in use.
2) You also need to consider the message it sends to a non skilled person seeing it in use.

 

[plugwash]

Another possibility to consider, what if you locked off the main isolator and then just connected the cable from the generator to a spare way in the DB?

 

[westie101]

The problem with finding a solution other than a changeover switch is that the safety of staff working on our side of the meter is not assured.

The only way we find it acceptable without one is if cables are physically disconnected to prevent the risk of a backfeed.

Generally if we fit one it would be to the input terminals of the meter (if whole currect metering) or for larger installations on the input terminals of the maiin isolator but with the cable from our supply disconnected.

The widowmaker is well named as that is what one did during the "hurricane" in 1987.

As an aside, genarally if we come across a "non-standard" set up we will remove our fuses and disconnect tails to ensure our safety. There, of course, could be some delay in us restoring supply later in the day.

 

[ban-all-sheds]

Somewhere in a box in the loft I have a BS 1363 plug with a length of flex from it - on the other end of the flex are a couple of spade connectors.

And ?

And it's not made anybody a widow yet.

Or widower.

In our garage there are similar leads hanging up (but with bare ends/choc blocks rather than spades).

I needed spades on mine - I had a UPS with the utterly brilliant design feature of needing the batteries to have (some) life in them for a relay to operate the charging circuitry. Batteries which were (too) dead could not be charged without a bit of bypassing. There probably was a good reason, but it was a tad annoying when trying to resurrect the thing.