Single phase appliance from a 32a 5 pin trailing socket

[pennychew]

Hi all

What are the thoughts on fitting a male 5 pin plug to a single phase appliance then connecting it to a 5 pin three phase socket. Obviously only using one phase.

Rough but as a temporary measure is it against the regulations?

Found these distribution boxes which appear to do similar..

Thoughts?

 

[Bobster]

Rough, but as a get out of jail temporary measure I wouldn't worry.

Just make sure the circuit protection is adequate.

 

[Darkwood]

It's not uncommon to just tap of one or two phases in a 3ph plug, it's more convenience and cost effective than installing new, I also wouldn't call it rough tbh but one should consider whether the load requires RCD protection which may not be fitted to the 3ph source of the outlet as that is what may sway it to been more suited to its own dedicated circuit.

 

[pennychew]

Thanks both, its being suggested by an external company to fit their coffee machines with red plugs to plug into the existing supplies at various sites. It feels rough to me but cant really justify why.

Due to the age of the installations none of them will be on an RCBO but i don't think plugging a different appliance in would merit this (although it would be an improvement).

Were not involved with this but it got me thinking last night when i was reading the emails!

 

[Darkwood]

If you forget the single phase equipment and just think about 2 phase appliances like some old portable welders etc then this was how we connected them, there is no demand for 2p+E 400v red sockets and plugs so getting suitable equipment was expensive and hard to source and meant you were limited to just using it for that one purpose, using 3 or 4 pin and earth made for a cost effective method that could be used for 3ph as well.

 

[pennychew]

That makes perfect sense, thank you

 

[Lucien Nunes]

This is quite standard in some industries. 3P+N+E sockets are provided as standard, single or 3-phase equipment is connected as required.

One disadvantage is that if all single-phase loads are wired to the same phase of their plugs, and the sockets are mostly used for single-phase equipment, 2/3 of the supply capacity is left unused and VD can be unbalanced needlessly. At least when using the 1x3 to 3x1-phase splitter box, you get to use all three phases on each outlet.

 

[pennychew]

I suppose most people would probably gravitate to using L1, which would like you say could cause an imbalance with a lot of appliances connected at once. Can I ask what you mean by VD?

Just realised what you mean regarding those splitter boxes, I assume you mean one of the blue outlets is on L1, one on L2 and one on L3. That’s so simple when you think of it but improves the chances of a more balanced system.

Anyway I’m really happy that 3 of the forum heavyweights have cleared that up for me... I haven’t been on the forum for a couple of years but Still remember the usernames and have massive respect for you three in particular

 

[Lucien Nunes]

Volt Drop. If the total supply capacity is sufficient for however many 3-phase loads of the full circuit rating, then it will be sufficient for that many single-phase loads all on one phase (albeit totalling only 1/3 of the available power). So the unbalance isn't a problem as far as loading is concerned. But it will unbalance the voltage drop all the way to the final circuit, which is not always an issue but can be undesirable if there are genuine 3-phase loads sharing it.

 

[pennychew]

I’ve got you now, so if L1 is pulled down by a lot of single phase loads a genuine 3 phase load elsewhere on the same supply will have unequal voltages across the three phases. Any particular equipment this could effect? I’d imagine fixed loads like heating elements and such would be ok. Would it cause issues with motors? Maybe cause overloads to trip or motors overheat or is that too dramatic?

Didn’t even consider volt drop as tend to just (incorrectly) associate it with initial design.