mortar silo

[Derek Preece]

I've been offered a bit of work installing the supply for a 3 phase mortar silo on a building site (I'm not sure if I'm going to do it though, I might pass it on), so I was wondering if anyone could give me a bit of advice.

The supply is 3 phase TN-S though I haven't measured Ze as I haven't been on site yet. It is currently supplying three single phase consumer units- one phase to each from the meter and 3 neutrals from a henley block. My first question is- is it acceptable to use henley blocks to 'tap' into the three phase supply to supply a 3 phase distribution board to supply three phase equipment, without changing anything on the existing installation or should I take the supply to the 3 existing consumer units from the new three phase distribution board and install appropriate breakers. I am trying to think of ways to keep the costs minimal but obviously don't want to do anything that is unsafe.

As the supply is for temp equipment on a building site would a three phase socket outlet incorporating an RCD and appropriate IP rating suffice or does the cable (which is going to be SWA in buried conduit) need to be protected by an RCD at the origin/dist board.

Does the lockable isolator have to isolate the whole installation or just the part that is going to be on the building site (which is the property next door).

Does 10% volt drop apply (I've been struggling to get through to anyone in the company who can answer this due to the christmas period). Thanks in advance

 

[NozSpark]

Pass it on mate,,

 

[Sidewinder]

Derek,

Where is the job mate?

I would take it on! ; )

I'm not being funny, I find it really hard to advise from written descriptions on the forum, sorry.

 

[steptoe]

I would normally say if someone is going to have to do it, it may as well be you,

but, in all honesty with the number and level of questions you have regarding this, and your own thoughts about passing it on,

that is probably your best decision here.

get someone else to do it.

 

[NozSpark]

I would normally say if someone is going to have to do it, it may as well be you,but, in all honesty with the number and level of questions you have regarding this, and your own thoughts about passing it on,

that is probably your best decision here.

get someone else to do it.

Thats exactly what I was trying to say, but couldn't think of how to say it nicely

 

[Derek Preece]

To be honest I was asking so I could learn for future reference, I've worked out the cable calculations and protective device rating but I don't know a great deal about the requirements for meter tails.

Thanks for the replys though the job is in essex

 

[Sidewinder]

Ahh, too far for me for it to be viable probably mate!

 

[ProDave]

I would personally have no issues henley blocking into the 3 phase to feed a small 3 phase board. As it's only feeding one circuit, you might as well have the RCD in the 3 phase board, then you don't need one in the socket.

As it's only a temporary install, you will be taking the 3 phase board away again later, so then just leave the henley's in line with each single phase feed.

If you routed the single phase boards via the 3 phase board, then you have changed the installation and would have to test the whole lot. By just tapping into the supply, you haven't changed the single phase installations to any degree, so I wouldn't get too bothered testing them.

 

[steptoe]

To be honest I was asking so I could learn for future reference, I've worked out the cable calculations and protective device rating but I don't know a great deal about the requirements for meter tails. Thanks for the replys though the job is in essex

it depends on just how confident you feel,

and if you feel the need to have a second opinion on anything then ask, but its not the sort of thing we could walk you through holding your hand without being there,

too many variables for temp supplies to building sites.

the call is yours,

as Canoey says, we will try to help & guide you, but we are not there so cant actually tell you.

 

[revjames]

so who's doing it? is there anything concrete yet?.... :coat

 

[Derek Preece]

Thanks, I'm going to get my head back in my regs book now