What contactor size for a 9kw electric boiler

Brendo · Jun 1, 2018

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

telectrix · Jun 1, 2018

you can't blame Chint for the installer fitting an under rated contactor. I've installed a few Chint CUs, and 1 3 phase board. been in for 10 years with no problems.

Darkwood · Jun 1, 2018

@telectrix was referring to there contactors, if you can get one for 7-quid it says a lot for the quality of it tbh, I talk from experience with them, I have faulted and stripped enough out to to give them a low rating, they are also crap at handling faults so would never put one on elements which tend to go with a bang... now that I realise the OP has a 4kw version then looking at other low end budget range like lovato you are still looking at twice that cost and about 20 -30 quid for a mid range while a high end would cost 40-100 ish but probably a mid range would be fine for this job imho.
Chint is a Chinese group which is actually about 4th largest in the world in its placement, it mainly does transmission gear HV/MV and LV but they also flood the world with mass produced budget/cheap stuff and like I said before, you get what you pay for, I don't argue that you may have had no issues as the mcbs have to meet the same standards but its the quality and build of the consumer units that turn me away, you can now get better more rigid solid constructed equivalent boards for similar prices and given my experience with the contactors I simply wouldn't have peace of mind fitting one regardless of them doing exactly what it says on the tin.

westward10 · Jun 1, 2018

Wouldn't touch Chint for any product as I like to maintain standards. Contactors I would be looking at Schneider or ABB.

buzzlightyear · Jun 1, 2018

Brendo said:
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

FFS, why. why. Delilah and you are asking about that ,sort it out before asking a post .