Combining circuits

[Gardner]

What regs are in America?

This: http://ecx.images-amazon.com/images/I/81oFJBtzhSL._SL1500_.jpg

PDF: https://ia700505.us.archive.org/35/items/nfpa.nec.2014/nfpa.nec.2014.pdf


From the code on dwellings:

210.11 Branch Circuits Required. Branch circuits for
lighting and for appliances, including motor-operated appliances,
shall be provided to supply the loads calculated in
accordance with 220.10. In addition, branch circuits shall
be provided for specific loads not covered by 220.10 where
required elsewhere in this Code and for dwelling unit loads
as specified in 210.11(C).

(A) Number of Branch Circuits. The minimum number
of branch circuits shall be determined from the total calculated
load and the size or rating of the circuits used. In all
installations, the number of circuits shall be sufficient to
supply the load served. In no case shall the load on any
circuit exceed the maximum specified by 220.18.

(B) Load Evenly Proportioned Among Branch Circuits.
Where the load is calculated on the basis of volt-amperes
per square meter or per square foot, the wiring system up to
and including the branch-circuit panelboard(s) shall be provided
to serve not less than the calculated load. This load
shall be evenly proportioned among multioutlet branch circuits
within the panelboard(s). Branch-circuit overcurrent
devices and circuits shall be required to be installed only to
serve the connected load.

(C) Dwelling Units.

(1) Small Appliance Branch Circuits. In addition to the
number of branch circuits required by other parts of this
section, two or more 20-ampere small-appliance branch circuits
shall be provided for all receptacle outlets specified by
210.52(B).

(2) Laundry Branch Circuits. In addition to the number
of branch circuits required by other parts of this section, at
least one additional 20-ampere branch circuit shall be provided
to supply the laundry receptacle outlet(s) required by
210.52(F). This circuit shall have no other outlets.

(3) Bathroom Branch Circuits. In addition to the number
of branch circuits required by other parts of this section, at
least one 120-volt, 20-ampere branch circuit shall be provided
to supply a bathroom receptacle outlet(s). Such circuits
shall have no other outlets.

Exception: Where the 20-ampere circuit supplies a single
bathroom, outlets for other equipment 'within the same
bathroom shall be permitted to be supplied in accordance
with 210.23(A)( J) and (A)(2).


Basically for these areas having a dedicated circuit(s) is mandatory and cant share anything else. :6:

 

[jamie-spark]

As in 2 x separate 2.5mm cables leaving the mcb. Supplying separate 1 gang sockets. Then no hell you could have a 32a mcb as the OCPD as its only there for short circuit protection as the cable won't be subjected to overload

 

[Gardner]

What voltage are they on?
I believe you chaps over there have different voltages than us here in Blighty.

230 volts, but this is not within the US where everything is 120 or 120&240 like dryers and cookers.

 

[Gardner]

As in 2 x separate 2.5mm cables leaving the mcb. Supplying separate 1 gang sockets. Then no hell you could have a 32a mcb as the OCPD as its only there for short circuit protection as the cable won't be subjected to overload

Single 20amp MCB and single 2.5mm2 T&E from the board for both units.

 

[andyb]

and then that's that little factor known as diversity.

Is that when I dress up as a lady?

 

[Gardner]

Is that when I dress up as a lady?

:rofl: lol, I hope its that easy.

 

[ian.settle1]

and then that's that little factor known as diversity.

Whats a dance group got to do with it?

 

[davesparks]

Normally in a the average domestic installation the washing machine and the dishwasher would both be connected to ring final circuit, along with the tumble dryer, microwave, fridge, freezer etc etc.

 

[Engineer54]

Single 20amp MCB and single 2.5mm2 T&E from the board for both units.

If you don't have a ring circuit in the area, then preferably 2 X 2.5mm circuits each on a 16A MCB, or a single 4mm radial on a 25A MCB to supply both appliances via socket outlets or FCU's... You'll not go far wrong using either method.

Those that keep going on about NFPA 70 (NEC), THE OP's company supply Portable type cabins to the UK, so the electrical installation to these cabins needs to comply to BS7671...

 

[Knobhead]

230 volts, but this is not within the US where everything is 120 or 120&240 like dryers and cookers.

So where is it?

 

[Gardner]

But where rings are not present, what would be typical? Or would a 32 amp 6mm2 radial take over as long as nothing is hard wired?

Ok, never mine I see Engineer's response.

So it boils down to this:

Fused sockets means many appliances can be combined.

If direct wired I can not go over 16 amps or what ever the manufacturer states?

 

[davesparks]

We don't use fused sockets full stop, the plugs are fused.
If you want multiple hard wired appliances on the same circuit just use switched fused spurs for the isolators.

 

[Knobhead]

If you don't have a ring circuit in the area, then preferably 2 X 2.5mm circuits each on a 16A MCB, or a single 4mm radial on a 25A MCB to supply both appliances via socket outlets or FCU's... You'll not go far wrong using either method.

Those that keep going on about NFPA 70 (NEC), THE OP's company supply Portable type cabins to the UK, so the electrical installation to these cabins needs to comply to BS7671...

BS7671 is available in the US just as the NFPA 70 is available here.

If the OP is supplying equipment to the UK he should be conversant and comply with the regulations.

 

[SPARTYKUS]

I still don't know where this is all happening!!

 

[Knobhead]

The OP hasn’t said where so we’re all in the dark.

 

[Engineer54]

But where rings are not present, what would be typical? Or would a 32 amp 6mm2 radial take over as long as nothing is hard wired? No, A 32A 4mm radial could be used in place of a say a ring circuit, so long as all other circuit criteria is considered. My suggestion above, was basically solving your problem of connecting two fixed appliances of 2KW or over...

Ok, never mine I see Engineer's response.

So it boils down to this:

Fused sockets means many appliances can be combined.

No, the plug top fuses as well as the fuses in FCU are there to protect the leads/cords connected to the plug top/FCU, NOT the appliance itself. Any circuit must be designed to be suitable for the load it is expected to carry.

I think the ''terminology'' as in ''combined'' is getting confused here, Running two cables (radial) from a single MCB/OCPD is not considered as being suitable or good practice. There is not a problem supplying two or more fixed appliances on a given or dedicated circuit that has been adequately designed to carry the total expected load. You need to distinguish between general socket outlet provision, and a dedicated provision for fixed or multiple fixed appliances of 2KW and over. Something along the lines mentioned in your own NEC...

If direct wired I can not go over 16 amps or what ever the manufacturer states?

Direct wired in the UK generally means connection via an FCU (fused connection unit) for fixed appliances loads up to 3KW. Loads higher than 3KW, then a suitably sized OCPD in the DB is used...

Is this porta cabin unit(s) you're working on for site living accommodation set up, as in a communal kitchen/canteen/laundry?? I ask because on a recent previous i'm sure you mentioned a 42 way DB... It would help a great deal to give a few details of the type of installation your working on, it can often get confusing commenting on off the cuff situations....

 

[Gardner]

Yes, some will have a compact kitchen plus laundry. I only mentioned a 42 way consumer unit because this is what most panels are rated in the US (32, 24 and 12 also common), in reality the ways will be much less for the trailers.

 

[BLBelfast]

You boys wouod love it here in Oz. Two 16A power circuits if your lucky. All spider wired and soldered. Or alot if the time they are spider wired from the MCB......