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Brendo

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Hi all.
Don't have much experience on this topic.

Called to a job with an electric boiler. It has a dedicated 10mm supply from a 50A MCB. I narrowed down the fault the the contactor which was only feedig 1 of tge 3 elements and had scorching marks around the other 2 terminals. And is currently a 20A. The boiler has 3 x 3kw elements.
My query is surely the 20A is insufficient for the 9kw load from the elements and shouldn't I fit a 40A contactor in it's place.

Thanks
 
Firstly is this 1ph or 3ph and if the latter is this 9Kw per phase or 3Kw a phase would be my first few questions, have you clamped the load to see what 1 element pulls if you are in doubt?
I guess 1ph but that would rely on the fact the installer got it right and we should never assume in this game.
 
Your contactor is 20amp per pole so it is sufficient for a resistive load a 3kw element per pole, the problem is likely to be poor termination, this is a high current load, have the cable ends been suitable dressed with rated crimps or lugs?
What is the brand of contactor - is it a recognised reliable brand or cheap import.
 
Firstly is this 1ph or 3ph and if the latter is this 9Kw per phase or 3Kw a phase would be my first few questions, have you clamped the load to see what 1 element pulls if you are in doubt?
I guess 1ph but that would rely on the fact the installer got it right and we should never assume in this game.
There is usually an electronic control board which is installed with his system but it's blew in the past and someone has hard wired it up with this 20A contactor and a 16A timer
 
Your contactor is 20amp per pole so it is sufficient for a resistive load a 3kw element per pole, the problem is likely to be poor termination, this is a high current load, have the cable ends been suitable dressed with rated crimps or lugs?
What is the brand of contactor - is it a recognised reliable brand or cheap import.
I've attached a photo of the contactor which is a Chint NC1-0910

[ElectriciansForums.net] What contactor size for a 9kw electric boiler
 
No I would never install this.
The black box/housing above the contactor usually would contain the main pc control board with digital display. Someone just removed that and fitted.this instead
if i was you i wouldnt try and improve upon this install without starting from fresh

id say the "fault" is down to poor installation than the boiler or contactors themselves
 

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What contactor size for a 9kw electric boiler
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