Three phase circuit breaker - Utilising only one phase

[daavvee]

I have a scenario where there is a three phase DB in a commercial property where there are mixture of three phase and single phase washing machines.

All the washing machines including those that are single phase have triple pole MCBs installed and wired in 5-core to 16A rotary isolator. from the same isolator a 5-core rubber flex is used and then of those five cores two of the phase L2 and L3 have been WAGO'd in the next single phase washing machine, exactly the same but L1 and L3 have been WAGO'd

Googling this type of things has yielded a mix bag of opinion from stating remove the TP breaker and install a single pole breaker, some have said this is fine as some machine would utilise only a single phase on low-load in any case. Other have said it is okay as the TP breaker would still trip on overload of the single phase being used or on short circuit and have gone as far as saying it's possibly been done where a pre-existing machine used the three phases and now only utilise one.

Would you recommend making safe the other two phases at each end of the cable and installing a single pole MCB? or Would you say that there aren't any issues for this setup?

Any insights or opinions on this one would be grateful.

 

[davesparks]

Nothing wrong with a single phase load supplied from a 3 pole breaker.

However I would disconnect the unused outgoing cores at the isolator so that those cores aren't sitting in the machine live.

 

[Flanders]

Agree with Dave disconnect unused
Phases on the outgoing side of the isolator. No reason to replace mcbs with single pole, unless you need room in the DB to add other circuits and it also sounds like the loads of been spread out over the 3 phases so all good there.