"One is an 8 way wylex with MCBs, but no RCD, that is for the house.
There seems to be an earth connection to the end of a rod in the ground just below the consumer units. I don’t know if there are any earths with the incoming cable from the street."

Firstly, it would appear that you have what is known as a TT mains supply.

There should be a Type S time delayed RCD connected between the meter and your consumer units.

All of the sub circuits leaving your 8 way wylex should be 30ma RCD protected too.

That said, the exact characteristics of your supply and earthing arrangements will have to be determined. Then an assessment can be made as to how the new building shouild be earthed.
From your description, it sounds like TT,  but without seeing it.............

That aside -

You will need to determine the total design current for your brewery, a rule of thumb method is to add up the ratings of each all of the pieces of current-using equipment you wish to install.
Make a list and add up the total wattage ratings.

Not knowing enough about how a brewery works in practise, I can't advise much further on this aspect. For example, will both of your 3KW boilers be on all of the time together?

Yes you can add new ccts in your new outbuilding.

Yes it is a good idea to bond all exposed metalwork together, but again you will have to determine you mains earthing characteristics first.

New consumer units in the house? Good idea.

The most cost effective method is to go for an old conventional split load consumer unit, with one half of the board protected by a single RCD and the other half - lighting ccts etc, protected by what is known as RCBOs, that way, you won't lose all power to all ccts in the event of a fault on just one of them.

The SWA feed out of the house doesn't need RCD protection because it has mechanical protection via the armouring, and so long as it is not concealed behind plaster etc at the house end before it goes outside, it should be ok.
It will also be no doubt rated well above 20A.




Sadly yes, you do need a Part P person for this, but make sure the business you engage is one which has been trading since before Jan 2005. I say this because there are many folk who have sought new careers in the electrical industry and have gained entry just by completing a 5 day 'training course' of dubious quality.
Suffice to say, that although registered & qualified in the loosest sense of the word, these guys will not have the requisite experience for such an undertaking.

Just for information -

Here's a short description of a small commercial microbrewery -

This one has a 3 phase 400V supply.

Electric pumps fill and empty the vats, and he has a filling station to fill bottles and kegs.  Everything is back washed with steaming water after use.

He has two large vats with 63amp three phase heaters controlled by a thermostat via a contactor.

There is a 32amp keg cleaner.

Everything in the brew room is IP rated.  

The walls and ceilings are all PVC clad, and the floor quarry tiled with a slope to a drain.

There is also a large walk in fridge for the beer.

Come back here if you get stuck.

TT

Thanks for your replies, TT and Lectrician. I’m new to this forum and already you have helped me understand some of this stuff, thanks, it’s a great place.  

I’m not an electrical person, so please forgive me is any of the following sounds rubbish to you.

I will take some photos soon, I don’t have a digital camera, but I’m going to get one. I’ll need to take up the floor in the hall to see the incoming cable. The meter and 3 x 100amp fuses are outside in a cupboard. The incoming cable goes into a black box and a separate thick green cable comes up into another black box connecting to the meter. It then looks like two green cables (1 thick, 1 thin) and a large grey cable go down to the CU.

The house is 1930s and was re-wired 20 years ago when I moved in. The original Wylex CU that was in at the time was re-used and the fuse wire holders replaced with MCBs (coloured type). I cannot see any RCDs between the meter and the CU the only one there, is latest one supplying the shed SWA cable.

NB:  I have a letter from the electric company wanting to change the meter to a new type. Could I get them to tell me what this system is ?

My original shed used to power my pond equipment as well, so I would like to get that back on. (Sorry for making it more complex).

I have been adding up the brewery equipment and done a diagram (see below).



   



I’ve rounded things up a bit, but the kettle elements are 3KW each. Also not everything will be on at the same time; there could be all kinds of variations. I’ve listed the main permutations. I’ve used power/230v to estimate current (hope that’s ok). You can see the worst operating case would consume 70Amps, but only for 1 ½ hours, when boiling. Also I might only brew once a week or less. There might also be a few extra things plugged in now and then, i.e steam washer etc…

I guess it’s all down for me to manually control the items that are switched on, e.g I wouldn’t wash my hands with the instant water heater during the full boil phase. I’d also tell ‘swmbo’ not to do any baking at the same time etc (100A fuse for the whole house)!!

I looked at a 3 core 16mmsq cable at TLC (for interest) and it was rated (max) at 94amps. I’ve not took the distance or any voltdrop into account in any of the above.

Will my existing cable suffice or do I need to get a new one, is there any problem with these old colours and this part P person doing the work and interfacing with new stuff at both ends. ( I only ask because it was very expensive at the time) ?

As I mentioned, I think it’s best to have a new CU/s in the house and something in the outbuilding (see diagram for example only). I’m not sure whether the pond wants to be on it’s own CU. Given the above information can anyone advise on a good solution for CUs at the house and the outbuilding ? I’m not sure on MCB sizes, maybe 16A for each element. A drawing would be great for my understanding.

Thanks again for any comments, much appreciated.

Cheers, Bill

And... If you were to go 3 phase you could reduce the new submain to say 4 x 10mm instead and stick it on a 40a MCB.

If you have got another 100a service available it would probably be easier to have another single phase meter installed and keep it dedicated to the brewery. Will also help when working out your production costs ...