installing 3ph and single ph wiring into new workshop

[Outspoken]

I will agree to disagree here, when using mcb's on motor circuits manufactures guidelines must be referred to to ensure nuisance tripping is not ever going to be an issue due to inrush.... and with said compressor been a fixed load and as long as you dont fit it as a plug and socket arrangement the the cabling can be wired as per load and cable calcs and the mcb can overrate the ccc of the cable meaning no additional costings and would still fall within the BS7671.... the number of times ive corrected others installs because the mcb's are nuisance tripping because they stuck basic calcs and believing that the mcb only need be rated the next size up and typed as a (c) in the case of a motor. It dosn't work like this as the trip threshold of the next size up mcb is often too low regardless of type fitted....this is especially the case with compressors as they start on load.

And do you know how many motor installs I have done in the last 32 years...I work with motors continually, and most a lot higher rated than 5.6kW and I have never had any issues with using Type C or D MCB's when the calcs have been done with accurate information. I am used to dealing with motors that start under load that make the 5.6 spoken of seem like the piggy back starter. Your also likely forgetting that at this rating I would think the starter will be YΔ. As for your satisfaction of over-rating the CC of the cable..on that we will have to disagree because I will never agree with that being satisfactory or acceptable.

 

[Darkwood]

And do you know how many motor installs I have done in the last 32 years...I work with motors continually, and most a lot higher rated than 5.6kW and I have never had any issues with using Type C or D MCB's when the calcs have been done with accurate information. I am used to dealing with motors that start under load that make the 5.6 spoken of seem like the piggy back starter. Your also likely forgetting that at this rating I would think the starter will be YΔ. As for your satisfaction of over-rating the CC of the cable..on that we will have to disagree because I will never agree with that being satisfactory or acceptable.

Well this says it all you are clearly a man stuck in his own ways and if it not your way then its wrong.... firstly the compressor has its own overload protection so how the hell can an over rated mcb to the ccc of the cable be an issue.... this is why they introduced this regulation to save the wasteful costs of larger cables.
I also have spent many decades doing motor supplies well above the example the OP gives and what concerns me here is you think that star delta affords you a lesser rating of mcb which you are incorrect the spike from the change over from star to delta means you must treat the mcb rating the same as if it was direct on line ..... i realise you picked your name as outspoken on here but look at the evidence so far you have been re-educated on numerous occasions so far but you seem to be a little stubborn to accept it. Im not pulling you for a debate im pointing out when i think you are wrong and im not by far the Mr know it all and will accept when im wrong and hold my hands up but from you joining this site i see you find it difficult to accept if you may be wrong.... wouldn't surprise me if you have been kicked off other sites as usage of terms like ffs etc etc show a short temper and a intolerance to differing opinion.

Please dont get me wrong i believe you are well educated and good at your job from your posts but you come across as a bloke who refuses to be wrong..... from the opening on this debate your calcs disagreed with the OP motor plate and you got sarcy then edited about PF then you refute the use of a 32 amp mcb when im quoting from schneiders own tables which was the mcb brand you recommended, then you have a self opinion of the regulation regarding omiting overload protection of a fixed load just because you have never factored it into your designs yet it used often on large scale project to save costs on fixed motor supplies and even stated for it use on motor circuits in the IET guidlines to circuit design. I can only say if you have a problem with this regulation take it up with the IET and stop throwing your negative opinions about it in numerous threads where its completely acceptable to apply it (yes ill agree domestic isn't really a place for it but it can be applied in certain circumstaces).... .

I sit back on new members with who give a lot of input to assess them and realising your character i only contradict you if i can give good back-up but yet this still seems to not change your opinion if you are unwilling to be flexible and accept contradiction without a negative response or a derogatory comment you are in my books a lost cause stuck in your ways. Ive given responses on this thread and can back everyone of them up with Spec's, tables ill happily forward regarding trip thresholds and mcb recommended ratings... like it or not they are in black and white and IMHO over-rule any of your responses.

 

[Knobhead]

This is getting funny. Carry on boys.:90:

 

[snowhead]

This is getting funny. Carry on boys.:90:

More tea, and would you like some Scotch in yours, it may be a long evening?

 

[guest119]

How much is the popcorn?

 

[Outspoken]

This is getting funny. Carry on boys.:90:

Sorry Tony, I do not do juvenile games anymore so the entertainment is one sided here.

 

[Knobhead]

Don’t apologise to me. It’s funny watching the squabble going on.
All I can say is I’m glad neither of you worked on our MCC’s. Nothing would be working.

 

[Darkwood]

With respect Tony your MCC's are a whole different ball park and mcb's wouldn't be a suitable upfront device to start with as would the motors i normally fit (30kw+) this little debate was only with regards to the OP set-up.

 

[Knobhead]

Depends how you look at them, they are after all a collection of lots of starters. Some large some small.

 

[Outspoken]

Don’t apologise to me. It’s funny watching the squabble going on.
All I can say is I’m glad neither of you worked on our MCC’s. Nothing would be working.

Whatever you want to think your welcome to.