Info on a dedicated circuit for a welding machine required.

[Isol8or]

The welder is a 180 ac/dc inverter.
It's spec is as follows.
Single phase 230v
Input frequency 50/60Hz
Fuse rating 16 A Slow Blow
Open circuit voltage 50 - 60 V
Max primary current 29.5 A
Max power consumption 6.8 kVA
Main supply protection 25 A
Power factor (Cos) 0.98

The circuit I want to install for the welder will be in a new garage fed from a new CCU with a 63A RCD which is fed from another CCU with 16mm XLPE SWA (3core) I'm not sure what to protect this feed with on the other CCU, it's a split board with 80A RCD's....Anyway I digress.

In the garage I will have a washing machine, tumble dryer and a small chest freezer. The washing machine and tumble dryer will be on at the same time so a 25A load will happen sometimes.

I'm assuming 0.5A for a 100L chest freezer.

I plan to use a 2.5mm t&e ring (32A MCB) with single switches spurred to 1gang unswitched 13A outlets for the washing machine, tumble dryer and chest freezer then another 2.5mm t&e ring (32A MCB) with 4x2gang 13A outlets for strimmers, general portable devices etc.
Also a 1.5mm lighting circuit (6A MCB)

Should I run a 6mm t&e radial to a switched 32A commando socket with a 32A MCB Type C?
The reason I'm contemplating this is because the welder has a max power consumption of nearly 28A and its max primary current (I assume when starting up or striking an arc) is 29.5A
It would be a bonus if someone can explain how the welders electrical design works. I mean 29.5A with 25A protection and 16A Slow Blow fuse confuses me and I don't know exactly how the duty cycle effects these figures (50% @ 180A & 100% @ 140A)

TIA

 

[winston1]

The circuit I want to install for the welder will be in a new garage fed from a new CCU with a 63A RCD which is fed from another CCU with 16mm XLPE SWA (3core) I'm not sure what to protect this feed with on the other CCU, it's a split board with 80A RCD's

Two RCDs in line is pointless. With a fault they will both trip.

 

[Isol8or]

Two RCDs in line is pointless. With a fault they will both trip.

I don't know what kind of circuit breaker to get to protect the CCU in the garage. Maybe I should put a 45A RCD in the garage CCU and protect it with a 50A MCB in the other CCU that feeds it. I just mentioned what type of CCU I have so that someone might give me suggestions. The other option "might" be to come from the tails instead using a Henley block and a 100A switch fused isolator.

 

[bernardgreen]

Water Heating:
Gas Electric (Storage & Direct) Electric Boiler
Ground/Air Source Heat Pump Other fuel
Number of Instantaneous Showers and size: .. ............ kW each
Should you require your connection to accommodate large loads, welders or motors, please provide us with full details.

Most DNOs seem to consider 1kW or above as a large load when discussing welders and motors due to the large inrush currents and the effect they can have on the network.

Read more: http://www.diynot.com/diy/threads/wiring-diagram.467863/#ixzz4N2cCUcpV

 

[Isol8or]

Most DNOs seem to consider 1kW or above as a large load when discussing welders and motors due to the large inrush currents and the effect they can have on the network

Ok thanks for clarifying that I will need a 32A MCB and a 32A switched Commando socket.
Any more suggestions for the supply to the CCU in the garage?
I'll try and do a wiring diagram for it all when I'm off shift.

 

[bernardgreen]

The point I was making is that you should inform the DNO that you will be using a welder on your ( I assume ) domestic supply.

 

[Isol8or]

Yeah thanks I did get your point.

 

[winston1]

I don't know what kind of circuit breaker to get to protect the CCU in the garage. Maybe I should put a 45A RCD in the garage CCU and protect it with a 50A MCB in the other CCU that feeds it. I just mentioned what type of CCU I have so that someone might give me suggestions.

NO. As I said two RCDs in line is pointless. RCDs do not trip on over current, they protect against imbalance typically caused by leakage to earth. The current rating is the safe load not a trip.

 

[Isol8or]

As above. The welding circuit will be protected by a 32A MCB (possibly a C type if that's what is recommended for a welder) The RCD question is seperate to the welding circuit question.

 

[Isol8or]

NO. As I said two RCDs in line is pointless. RCDs do not trip on over current, they protect against imbalance typically caused by leakage to earth. The current rating is the safe load not a trip.

I did mention a 50A MCB protecting the CCU in the garage for the 2x32A + 1x6A circuits but if this isn't adequate I would like to know wether I can do something from the CCU or do I have to come from the tails.

 

[Isol8or]

I understand what you are saying, put a CCU without an RCD in the garage. Just incase you think I don't understand that part

 

[Risteard]

A welder circuit is not something to DIY.

 

[Isol8or]

Disregard this thread I know what to do now, all I had to do was ask a qualified electrician and he told me what I needed to know, he explained everything with minimum effort.

 

[EFLImpudence]

Perhaps it's easier in person than writing or perhaps he just told you what to do whilst being on site and seeing it.

Take this for example:

I don't know what kind of circuit breaker to get to protect the CCU in the garage. Maybe I should put a 45A RCD in the garage CCU and protect it with a 50A MCB in the other CCU that feeds it.

Circuit breakers do not protect CUs; they protect cables - and as said RCDs do not do that for overload.

So a lot of writing required to counter your lack of knowledge.

 

[bernardgreen]

ask a qualified electrician and he told me what I needed to know, he explained everything with minimum effort.

So out of interest can you tell us what the qualified electrician told you was necessary fopr a safe and compliant installation ? After all we might learn something that we need to know.