IET logo
Decrease font size
Increase font size
Topic Title: Builders - Construction Sites
Topic Summary: Is it just me?
Created On: 11 October 2012 10:56 PM
Status: Read Only
Linear : Threading : Single : Branch
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 11 October 2012 10:56 PM
User is offline View Users Profile Print this message


Posts: 1634
Joined: 24 January 2008

Was asked by a builder to attend site to connect up the 110V transformer and site cabin, initial request was to supply the transformer from the site cabin.

Got there to discover the site cabin is 50m from the DB and the transformer is 10kVA Single Phase.

On the phone to the builder to explain I am going to need 50m of cable to make it work, his answer was "Can't you plug it into the socket in the house", my answer was NO

Closer inspection reveals that the site cabin has been running off a 13A plug. Talking to the guys on site it transpires this arrangement was used on the previous job and they did have problems because the fuse kept blowing. Not sure what the transformer was plugged into because on the end of the SWA from the transformer was a 32A CEE from plug; socket not available.

How are others wiring up site cabins?

Is it just me, or do others have these problems with builders and site electrics, as a few years ago I had another bunch of problems with another construction site?
 11 October 2012 11:14 PM
User is offline View Users Profile Print this message


Posts: 3715
Joined: 31 March 2005

Just builders for you.

Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 12 October 2012 08:21 AM
User is offline View Users Profile Print this message


Posts: 2547
Joined: 07 August 2007

I do not see why a SMALL site transformer can not be supplied from a 13 amp socket, if not on a PME system. And some might argue that is acceptable even on PME.

A 10KVA transformer though, no way.
Even if very lightly loaded It would probably blow plug fuses regularly, leading to the temptation to bypass the fuse, or use an unfused plug.
 12 October 2012 09:33 AM
User is offline View Users Profile Print this message


Posts: 22467
Joined: 23 March 2004

I once did a bit of an academic study on the power consumption during construction phases of a project. This was for an intelligent client that wanted the site temps designed by the building designer and not the builder. No problem with that ( BS 7375 is useful for this). We also decided to monitor real time the energy consumption, relevant currents and voltages etc as a record and as the basis of understanding relevant energy benchmarks - links to BREEAM credits etc and potential recharges to main contractors we they use client supplies.

It just so happens that each floor of the building had a 10KVA transformer supplying PDU's that then fed 110V fluorescents as temp lighting and the usual 110v tools. There was also a quantity of 230V RCD protected sockets for charging battery tools and a complete prohibition on exporting the 230V outside the dedicated charging enclosure.

The actual demand was suprisingly small, the base load was low (and quite predictable), current for time on 110v power tools was peaky but short lived.

Like Broadgage, I could quite easily see a small development operating off a 13A supply - I'd ask the builder where the 32A to 13A "adaptor" went to -



Let the wind blow you, across a big floor.
 12 October 2012 01:24 PM
User is offline View Users Profile Print this message


Posts: 7856
Joined: 18 April 2006

"the transformer is 10kVA Single Phase."

That might need a 50 A type C due to inrush....... I sold mine for that reason and now have a 5 kVA that runs on a 32 A type C. Unless festoon lighting is on it, hand held power tools hardly make a dent

Generally, a 3.3 kVA tool Tx will only be rated at 2 kVA continuous.


 14 October 2012 01:07 PM
User is offline View Users Profile Print this message


Posts: 607
Joined: 08 June 2010

I do site temps as my bread and butter and can concur with OMS statements. Loading is usually small.

However, I wouldn't be happy with the set-up the OP described either. Totally unsuitable for purpose from a design POV.

I take it Mike that this building firm is medium-small, or a concrete-bashers (your Expandeds and PCH who seem to have the opinion that if it's concrete it doesn't matter.)??

New here?

See Also:

FuseTalk Standard Edition v3.2 - © 1999-2018 FuseTalk Inc. All rights reserved.