tripping infra reds

[dynamic]

I have got a slight puzzler here. A community hall with 6 three bar single phase IR wall hung units (3kw each) running on a 2 phase system, 3 units from each phase wired individually through B32 MCBs. Said heaters will run for many hours with no problem, then on other occasions odd ones will trip their MCB. I have now noticed that it is always the ones on phase 2 that trip, but not always together. I have done all the basic checks, terminations and connections, IR, continuity & fault current checks to establish resistance values etc but nothing untoward is springing out. voltage on both phases is usually 232 - 244. Any suggestions what I may be missing?

 

[Thefailsafe2012]

2 phase?

May you be missing a phase? :disguise:

 

[dynamic]

Yes, strange as it may seem, there are only 2 separate phases on this installation. both run separately as singles. It runs through 2 DBs. the first runs all the usual single phase circuits, lighting sockets ect, (balanced between the 2) then they are linked into the 2nd and balanced with 3 heaters off each 230 v phase (and neutral of course)

 

[Thefailsafe2012]

Hmmm not ever come across this and was under the impression 2 phase supplies were rather rare in the UK. That said, I could be very wrong, hopefully one of the forums more learned members will have a gander and put me right! Would have possibly suggested that the inrush current might be throwing the breakers but as they're on separate 32A (though seems a bit high for 1 x 3KW load) they should hold. If the Zs permits you could try a C type breaker?

 

[somersetsparks]

Is it split phase? Fairly common around our way in rural areas? What voltage do you get between phases?