40 Amp MCB supply to a 100 Amp Distribution Panel Help!!!!!!!!

[JonScott53]

My industrial unit is supplied via solar power.

All the switchgear and mains supply etc. for the solar is in the unit next to mine to which I have no access unless the tenant is in.

The landlord has got the supply coming from the solar unit through a 40amp MCB into our main distribution panel which has a 100 amp DP isolator.

I frequently trip the 40 Amp MCB and have to go into the unit next door to reset it.

The landlord seems to think that 40 Amp is a substantial supply.

I'm concerned for several reasons but mainly I keep having to go next door to reset the MCB. It screws up several CNC jobs on the laser cutters and finally I don't think what he's had done is correct.

Any advice or help appreciated.

Jon

 

[westward10]

If you have that sort of machinery it is bound to trip at some point either through overcurrent or incorrect characteristics of the 40A device.

 

[Wilko]

Sounds like you have a single phase 40A supply via a sub main cable from next door. Its likely you are drawing considerably more than 40A at some point as Westie says. If the mcb trips when a machine starts, it's possible a simple upgrade of the mcb type (from B to C say) may assist. Or perhaps your feed could be separated through an appropriately rated switch fuse. An Electrician could assess the available power, measure the load and advise how best to resolve this. It may be quite simple

 

[Des 56]

With a wave of the magic wand,the solution was made simple
Employ a decent electrician or get more suitable premises

 

[Darkwood]

When you took the tenancy you specify the supply you require thus see if there is a suitable place available, this is not just about the average load you need to run your business, your machines would possibly be high on inrush demand when motors start or even Lasers fire up, thus I would say the existing supply isn't suitable, without really knowing the size and ratings of the machines it hard to call what would be required but tbh, running a machine shed with front end 40amper is very bad design, you have little to no discrimination between most of your fuses and the front end 40amp. I would suggest the blame lies partly at both your feet.

 

[ruston]

I am a bit confused - are you relying completely on solar power ?

 

[JonScott53]

I am a bit confused - are you relying completely on solar power ?

In a word No.

Long story is:- electric was supposed to be free due to the solar. Landlord then decided that he couldn't work out was was used from the solar and the grid so put a 40 amp MCB in the supply with a meter and then charge us for all electric used at a reduced rate.

I suppose the question is should I have an MCB in my supply line before the 100 amp isolator?
It seems odd to me to do that!

Thanks for the previous replies

 

[Des 56]

It would be interesting to hear the reasoning behind the 2 disagree feedbacks to well structured advice by darkwood ,any takers?

 

[JonScott53]

It would be interesting to hear the reasoning behind the 2 disagree feedbacks to well structured advice by darkwood ,any takers?

Yep.

Sorry! I understand what's been said but disagree with it lying at my feet as this happened sometime after we moved in.

When we moved in there was no MCB in place and no mention of restriction on the supply.

As I said above it just seems an odd thing to do .

 

[ruston]

Did he tell you you were to have a 100 amp supply . Many isolators are rated at 100 amps , but that does not mean the supply is 100 amps

 

[Darkwood]

Yep.

Sorry! I understand what's been said but disagree with it lying at my feet as this happened sometime after we moved in.

When we moved in there was no MCB in place and no mention of restriction on the supply.

As I said above it just seems an odd thing to do .

I have no issue with your disagree but without explanation it means little, now you have explained I retract that part of the post and place this on the landlord and whoever did his electrics to add this 40amp mcb, although I still stand by the rest of the post, it all poor design and even though full discrimination cannot often be met on smaller supplies, it is still required to achieve the best partial discrimination you can, even if this means having a 100amp front end fuse and cable size to suit. (Even if you have no intention of using that amount.)

 

[Des 56]

Whatever solution is forthcoming,having to reset a breaker on a regular basis suggests for reasons of safety only,the current arrangement cannot and should not continue

The breaker may be rated for the size of the supply cable,it may be a considered share of a limited supply, it may be complete guesswork on the landlords part,either way the system is not fit for purpose and you need to thrash this issue out with the landlord

 

[JonScott53]

I have no issue with your disagree but without explanation it means little, now you have explained I retract that part of the post and place this on the landlord and whoever did his electrics to add this 40amp mcb, although I still stand by the rest of the post, it all poor design and even though full discrimination cannot often be met on smaller supplies, it is still required to achieve the best partial discrimination you can, even if this means having a 100amp front end fuse and cable size to suit. (Even if you have no intention of using that amount.)

Sorry I didn't want to fill the post with all the blurb about how and why we'd got to where we are but see know I should have put a bit of an explanation in.
Thanks

Whatever solution is forthcoming,having to reset a breaker on a regular basis suggests for reasons of safety only,the current arrangement cannot and should not continue

The breaker may be rated for the size of the supply cable,it may be a considered share of a limited supply, it may be complete guesswork on the landlords part,either way the system is not fit for purpose and you need to thrash this issue out with the landlord

Thank you all for your answers. Your advice is much appreciated

 

[Darkwood]

@JonScott53
Your issue her as well especially with the CNC machinery is regular power crashes can damage the electronics of your machine and be a costly repair, on top of that you are suffering productions hits so I would be going to the landlord asking for an immediate solutions, I would be quite clear that it isn't acceptable and until it is rectified you may withhold some of the rent to cover incurred costs, this will probably do the trick ... although I don't know your personal level of relationship with the landlord, I would be weary of been fobbed off etc.

If the landlord is an amicable and reasonable chap(ess) then I'm sure this will be resolved quickly but if your having any problems with him/her then I would start taking notes and possibly sending a formal email so all correspondance can be logged, I seen some nasty landlords in my time and when the weather turns cloudy they will look after their own regardless of the position they leave you in.

 

[marc8]

Hi All
you might want to check your contract that you have with the landlord for the premises before you do anything. just done some work on a rented commercial property myself for a tenant on a new lease & the electrics were shockingly bad I mentioned that this would be a good idea to have chat with landlord about it, they had a chat with him & he laughed check the contract they were liable for any changes they required at no cost to landlord.
myself I would measure the supply cable to your board the next time it trips from their side & yours, calculate the load you require on your side (machine start up plate or booklet) look at size of your cable work out if the CB can be changed in the supply board or not due to cable size.
check see if 3 phase or single phase next door if 3 phase consider upgrading your board to a 3 phase if possible changing cable & CB.
also if possible leave old cable in place keep old consumer unit & CB breaker, when you give notice or if you ever do change it back.