New 3 phase installation

[Tony Way]

Doing a favour for a friend and using it as a learning experience as well.
Guy is going into a new unit with an existing 1ph board. he has a 3ph machine so wants to upgrade mains etc. New board will supply everything in the small industrial unit from heating/lights through kitchen sockets.
I've done the calcs for A/phase etc but then started thinking about what equipment to specify. Most boards come with a main switch included and an option to upgrade to RCD incomer. However with this you get no diversity to circuits. So I was thinking that any new install has to have a c type 100mA rcd incomer with b type 30mA rcbos to any single phase circuit on the board................. Or am i just complicating things?

Many thanks in advance for the advice.

Tony

 

[Knobhead]

Use a standard incoming isolator. The 3ph loads can be fed via 3 pole MCB’s, where as the single-phase loads via RCBO’s.

You could fit a type S RCD to cover the entire board. But you have to weigh up the pro’s and con’s of the situation

 

[johnboy6083]

the discrimination rule of x3 for RCD's only works ifthe fault curent is near the nominal I delta n of the closest device. much more than that and you dont acheive discrimination. This is why nowadays'its more common to use S-types as Tony has said. Definately fit a normal mains switch.

 

[mogga]

merlin gerin "VIGI" units do 3 ph rcds check schnider cat or google merlin vigi

 

[Tony Way]

Many thanks guys. Most helpful

Tony

 

[Chr!s]

Doing a favour for a friend and using it as a learning experience as well.
Guy is going into a new unit with an existing 1ph board. he has a 3ph machine so wants to upgrade mains etc. New board will supply everything in the small industrial unit from heating/lights through kitchen sockets.
I've done the calcs for A/phase etc but then started thinking about what equipment to specify. Most boards come with a main switch included and an option to upgrade to RCD incomer. However with this you get no diversity to circuits. So I was thinking that any new install has to have a c type 100mA rcd incomer with b type 30mA rcbos to any single phase circuit on the board................. Or am i just complicating things?

Many thanks in advance for the advice.

Tony

And what happens if you develop a neutral fault?

 

[Knobhead]

You probably don’t notice it. There must be 1000,s upon 1000’s of boards through out industry without E/L protection. It's the exception not the rule to fit them.

 

[Engineer54]

I agree with those that have stated to leave the main switch as a 4 pole isolator. As for choices as to what type of breakers you install, that would very much depend on what that breaker is supplying. A b type breaker may be of no use at all, on some machinery with high in-rush currents, be they 3 phase or single phase. You need to match the breaker type, to the type of load it's feeding. This could mean a mixture of B's, C's and even D's in your DB.

Any circuits requiring RCD device protection, can be accommodated with either RCBO's for single phase, or Vigi type units, for single or multi phase circuits.

When working on Industrial and to some extent Commercial installations, you have to forget about your usual domestic CU set-ups. In the main they will be somewhat/completely different, both in make-up, and in the type of loads they will be supplying....