Small industrial unit, advice on pricing

[Echo]

Haha engineer I was just about to google it....Not a term I have ever come across before!

 

[soulman]

hi engneer54 i would like to know what a staggered ring circuit is. i am aware of the leapfrog method for long corridors but never heard of a staggered ring
cheers

 

[Engineer54]

Echo, Soulman,

I would imagine there are several given names for this type of wired ring circuit, but i was brought up with the term ''Staggered'' and most of the older sparks i've come accross, also called it by this name.
Probably ''leapfrog'' is another name for it too!! lol!!

Echo,

Basically, from the CU/DB you take the first pair of the ring to the first socket, then take the second pair to the second socket. From the first socket you take a pair to the third socket, then from the second socket you take a pair to the forth socket. and continue on until you link the final socket with the previous socket (omitted cpc, easier to say ''pair''...lol!!)

This configuration spreads the rings loading across the the whole ring circuit and not to just one leg. It eliminates unloaded long return runs back to the CU/DB. Can be used with multi-core cables, MICC, or more usually in conduit/trunking installations with single core wiring.... Not much call for using in domestic installations, because if ring designed properly there will no long unloaded return runs back to the CU.

 

[bugsy]

Basically, from the CU/DB you take the first pair of the ring to the first socket, then take the second pair to the second socket. From the first socket you take a pair to the third socket, then from the second socket you take a pair to the forth socket. and continue on until you link the final socket with the previous socket

Never done it any other way!

 

[Engineer54]

Good to hear!!! You'ld be surprised how many Don't!! lol!!

 

[soulman]

cheers for that i thought there was something i was missing. yeah we call that the leapfrog method.

 

[mgnelec09]

Cheers guys,
I am aware of staggering the ring mains and would usually do this instead of one side of the ring taking all the load. by doing this your zs readings are more consistent too.

If there are 12 machines all rated between 5.5kva and 10 kva,. would it be best to split it into 3x 2.5mm 3ph ring mains on a 32amp 3p type c breaker?

This meaning 4 machines on each.

I agree with the trunking and dropping in steel conduit to steel sockets.

the roof of this unit is very high, I,m talking at least 10 metres and there are a couple of machines plonked in the middle of the workshop floor.

i will have a scissor lift on site so i can get up there.

im thinking that to drop threaded rod and hangers to get to the machine would be a bit wobbly.

was thinking maybe unistrut mounted vertically, to suspend the trunking, any suggestions???

Any suggestions

 

[Engineer54]

Yes, no problem using 3 x 32A rings for your 3 phase distribution outlets, try and keep the loadings within each circuit similar. Ask your client to see the proposed machines manuals, that will give you a better idea of type of MCBs, but C type sounds good as an initial assumption.

Fix uni-strut to the floor at a convenient location by the machine's then, depending on length/distance to the wall, horizontal support between, and fix trunking to this. You may need more than one floor mounted vertical support, for each of these 2 centrally located machines, but that's a site based decision...

What about lighting requirements?? Are they existing, if so, are they adequate/fit for purpose, to the factory units new usage/layout of your client??

 

[mgnelec09]

Hi there, the lights are existing.

There are 4x 250watt son floods wall mounted at high level and 2 x 250 watt hqi high bays.
There are a couple of partition walls going in but he just wants twin 6ft flourescents.
Oh and a small paint bays in which i was going to install anti- corrosice ip reated flourescents

 

[remer1957]

Have a think about fire alarms if there is a paint/laquer spray area. There might be zone 1 (flame proof-ouch!) regs involved in a paint/laquer spray area, unless they are in the form of purpose made booths. Sometimes chasing out the floor to the machine positions is a good idea. Bear in mind moving machines and flourescent lights as well; re stroboscopic effects-i.e. sometimes the machines moving parts can look like they're still whilst actually turning under flourescent lighting.

 

[davelerave]

Have a think about fire alarms if there is a paint/laquer spray area. There might be zone 1 (flame proof-ouch!) regs involved in a paint/laquer spray area, unless they are in the form of purpose made booths. Sometimes chasing out the floor to the machine positions is a good idea. Bear in mind moving machines and flourescent lights as well; re stroboscopic effects-i.e. sometimes the machines moving parts can look like they're still whilst actually turning under flourescent lighting.

no stroboscopic with newer HF ballasts afaik

 

[netblindpaul]

OK, quick post.
Skimmed only everything since my last post so sorry for any mistakes.
As far as the reg for 3ph supplies on a ring, no one mentioned sockets as far as I could see when I commented, I would not put all the machines hard wired onto a ring as if one tripped the ring then all machines would go off, a couple of £100's worth of timber ruined would not be good! Minimise inconvenience in the event of a fault.
Also consider BE2.
Next 7671 is not the only reg you need to consider.
Wood machines may well have DC/Regenerative braking which means they must be kept under power in emerency situations.
Also any central emergency switching system as you are hinting at i.e. run through a contactor as is often seen in schools is acceptable for that environment, though hardly ever implemented correctly. These types of switching systems must not interfere with any installed safety systems, e.g. braking LEV, etc. STATUTORY requirements.
Also 7671 is not the only regs to consider there are other STATUTORY REGULATIONS to consider here as well.
If you start putting control systems into the wiring in the structure of the building then you will need to consider other standards and these would become safety related parts of controls systems, AKA SRPCS these are covered by another raft of EN & BS std's, you will find that 7671 has to bow out in this scenario, you would be looking at redundancy and other control system requirements.

Got to dash, loads to do, sorry not been back before, been working lots to try to pay the bills!

 

[somersetsparks]

Have a think about fire alarms if there is a paint/laquer spray area. There might be zone 1 (flame proof-ouch!) regs involved in a paint/laquer spray area, unless they are in the form of purpose made booths. Sometimes chasing out the floor to the machine positions is a good idea. Bear in mind moving machines and flourescent lights as well; re stroboscopic effects-i.e. sometimes the machines moving parts can look like they're still whilst actually turning under flourescent lighting.

If its not to difficult, i would go with chasing the floor, can be the easiest/cheapest/neatest way, especially if there is not any vehicle traffic over the area.

 

[davelerave]

ya-school workshops is where i see the 'central' emergency switching

prob no need here