Breaker Sizing/Type Problem

[Northdude]

Got called out to a job yesterday which had been butchered by cowboys, a guy had 3 multideck display cabinets installed with remote condensors. Apparently he kicked them off the job and then called me to pick up where they left off. The problem is with the 3 condensing units supplying the multidecks. The condensing units are Kooltech KTM54Z, Max start amps 84A, Full load amps 14.4A. They also installed the DB board, they had condensor 1 wired to a CMB132 breaker and condensor 2 & 3 BOTH wired to the same CMB132 breaker?? So as you can imagine as soon as 2 & 3 started up the whole of the guys shop was tripping out. To run the systems individually i terminated condensor 3 to a spare B32A breaker, problem is that when 2 & 3 run together now its popping the RCD (80A), i know these are the wrong breakers but its been a while since i did an install, wondering if anyone can tell me the type of breakers to get for high starting amps and if i maybe need to replace the RCD? The DB board and breakers are CLIPSAL. Thanks in advance!

[Quality]

The RCD may be doing its job properly i.e. operating on earth leakage as it may be the equipment at fault.
But type D for high start currents

[frank]

From memory, and I stand to be corrected, but if the starting current is over 50A/phase then you should use Star/Delta starters.

Your breaker should be rated in excess of the motor FLC but as near to it as possible, and your cable should be rated in excess of your breaker size.

For motors, your breaker should have a 'C' (3) tripping curve.

[chemi-cool]

Any breaker should be set to 1.05 of the currant draw.
The make is up to you to choose, depend of availability.

I can only recommend the types I use such as ABB, AB, klockner moeller, etc..

If what you want is a currant protection in the main electric board than use 20A type C.

[charlie patt]

use type c breakers on all fridge motor rated kit i always go for individual suplies 105 percent as above quote. if your pushed to get running fit a delay timer on second unit on contactor to split load so at least it dont take shop out be lucky ta charlie

[Quality]

Depends what you work with type D or fuses for real proper stuff.
My fault I did not read the OP properly. Type C for small equipment like this

[mad fridgie]

Your breakers (fuses, MCB) are there to protect your cable, not the machine, this done with an adjustable overload.
The rating C/D is time related and corrosponds with the predicted in rush.

[richardb14]

can I ask, how big are the multidecks? condensing units seem on the large side.

http://www.kooltech.co.uk/clientfiles/File/10_SLIMLINE_HERMETIC_COND_UNIT.pdf

[Northdude]

Thanks guys, i will pick up 3 type C breakers tomorrow and fit them. The condensing units are brand new and they only tripped the RCD when unit 2 and 3 ran at the same time, i ran and tested each system individually and all was ok. The multidecks are second hand arnegs which are about 4 metres long (dont know the models as the data plates are missing). Is it possible for the RCD to trip because of the wrong breakers being installed and because of the high ampage when all 3 units start up?

[frank]

Is it possible for the RCD to trip because of the wrong breakers being installed and because of the high ampage when all 3 units start up?
The RCD may be tripping on overload as the 2 units operating simultaneously exceed the RCD rating.

Or, 1 or both of the second hand units may have an earth leakage problem. Have you meggered the second hand units?

Check what the drawn current is for each unit running seperately, add the results together and compare the total drawn current against the RCD rating