Magic Electric

Hi all,
need to test a busbar circuit and was wondering if anyone has done this before. i have done loads of testing but never a busbar. My thought are to test the busbar where it is supplied from rather than at each point where equipment is powerd up. reason being is that as soon as you open the busbar conection the power is lost to the equipment. Would i be doing the right thing by testing the busbar at the point it is supplied from. Also the instalation has sockets powerd by the busbar. as the busbar is not protected by an rcd so too the socket connected to it are not. due to the 17th edition all socket outlets must be protected by an rcd. putting an rcd socket in it my best option. what do you think.

frank

Majic



We first need to determine what you mean by Bus bar. We also need to determine location and use. If the busbar is domestic ( as within a consumer unit ) this determines one approach

If the bus bar is industrial ( within a chamber and supplying switchgear etc) then another approach applies. But then again are you thinking of a busbar dado/skirting trunking.

Come back with more info;

Frank

Magic Electric

the type that i am talking about is busbar in an industreal building that supplies machines and sockets round the building. in some of the building we have busbars feeding other busbars and everything that is powerd by the busbar has its own fuse but the sockets are on fuse only and not rcd. this is my main issue as i think that even these sockets need some rcd protection in some way as they are used often with extension leads. most of the sockets powerd by the busbar are radial circuts and not rings. 20 am fuse bs88 in them.


now here is another chalenge. if one busbar is powerd from the other how do you test the cable between them... all up the wall at the moment.
hay i am all ears..lol

nick

Well i may be out of line , may i ask what are you testing just voltage on the buss ? or load testing down stream to see if the tees and elbows are tight and are in good connection ? are you talking about buss bars or buss duck ? we test a buss duck with infared on joints tees elbows verticals up downs .we also use a voltage tester to test for drops directly in sockets , we call them plugins in usa , is this what you are asking ?

Magic Electric

All Tests that that the regs requirs us in the uk to do. you will find them in bs7671 Part 6.
you may do things a little diferent over the pond

sparkie

check your reg's it is permissible to have non rcd protected sockets on a commercial site if overseen by a competent or instructed person.
Basically if the person isn't an ordinary person and only equipment is authorized.
eg factory with welding equipment and maintenance guy who pat tests and repairs machines= okay

office where people bring in their own untested equipment and there is no supervision = unaccepttable

Magic Electric

Yes i understand that the regs says that if there is a ppm in place and the electrics are always checked and all that. but still there must be a method for testing a busbar. does anyone know? or am i barking up the wrong tree.

chrisb271

Hi Bud,testing your bus-bar system is no different to testing any other circuit,isolate it,short it out one end ( i usually do it mains feed end then don't forget to take it off before its re-energised )
Disconnect any neutral links ,megger , short out phase(s) to earth R1+r2 , reconnect then earth loop,obviously you need to be at the furthest point of utilisation on the bars,job jobbed

The tap off boxs are tested seperate,like a mini installation if you like,so you would take a loop reading at your box (that now becomes your external loop within the system Ze) from your tap off box to the socket is the bit you now test and get the Zs at the furthest point.
Any Rcd would be installed at this point to feed the sockets.

There would be no need to protect the bus bars with an RCD.

Hope this helps Bud

Chris

Magic Electric

Hello Again, What i did was. i did all the tests that are in the regs but i did the tests at the point where the feed meets the busbar. from this point all the reading that i took were acceptable. ie megger reading was greater than 0.5 mega ohms. zs withing acceptable range and continuity was less than one ohm.so far all readings acceptable. i was going to do the test from the longist run but as the box was open was out of reach. if it was within reach i would have done all the test from that point. Thanks anyway.

nick

Well now i know what you were asking ,yes thats no different than we do here in the usa megging a buss bar in a switchboard or megging a buss duck in a commercial or industrial building ,rule of thumb= 1000 volts to one megg ohm is normally used . didnt know if you were testing hot or testing with power off in your post , we do it everyday every piece of equipment new must be megged to factory specs. insulation is insulation it maybe wire ,or a insulated buss bar its a simple insulation test . take care