Electricians: internal or external, electricity cables to garage.

Gloomendoom

I am planning new garage/workshop that will be attached to an outbuilding that is itself attached to the main house (old with an higgledy piggledy layout.) I will need to get electricity to it. I am re-roofing the outbuilding at the moment and wondering if I should make provision for routing the cables in a duct under the new roof or just run them around the external walls to the garage when it is built.

BTW the cables will need to be heavy gauge as I will be using electric welding sets in the finished workshop.

DVardysShadow

As you know what your plans are, you are in pole position to make the decision. I would be putting in a cable route if I knew I needed the cables

DevCoder

I'd also be putting in a cable route/duct (along with pull string to pull the cable through.

You'll probably want to use SWA cable for the run. The CSA depends on the load you are going to put on it.

Gloomendoom

DVardysShadow wrote: »

As you know what your plans are, you are in pole position to make the decision. I would be putting in a cable route if I knew I needed the cables

I wasn't sure if regs would insist that the cables ran externally or through a duct. I've set it up now so that either is an option. The sparky can choose.

krisdorey wrote: »

I'd also be putting in a cable route/duct (along with pull string to pull the cable through.

You'll probably want to use SWA cable for the run. The CSA depends on the load you are going to put on it.

I was hoping to avoid the expense of SWA cable but you are right, it might be the safest way to do it.

DevCoder

Also ask youe electrician about how you should earth your welding connections as I believe there are certain regs/rules on what you can connect the earth lead of the welding ends to (ie not to something which is then crossbonded with the houses earth supply, so possible not framework etc)

Gloomendoom

krisdorey wrote: »

Also ask youe electrician about how you should earth your welding connections as I believe there are certain regs/rules on what you can connect the earth lead of the welding ends to (ie not to something which is then crossbonded with the houses earth supply, so possible not framework etc)

Thanks for the heads up. I was actually wondering how an RCD would cope with welding. I intend to have a dedicated welder circuit with blue 16A sockets.

DVardysShadow

Gloomendoom wrote: »

Thanks for the heads up. I was actually wondering how an RCD would cope with welding. I intend to have a dedicated welder circuit with blue 16A sockets.

A welder should use a double wound transformer, IIRC. An RCD will be oblivious to this.

However, I would be minded to take off a separate supply before the consumer unit, with its own protection and have a distribution board in the workshop with protection tailored to the workshop cirguits

Gloomendoom

DVardysShadow wrote: »

A welder should use a double wound transformer, IIRC. An RCD will be oblivious to this.

However, I would be minded to take off a separate supply before the consumer unit, with its own protection and have a distribution board in the workshop with protection tailored to the workshop cirguits

The newer TIG units use an inverter but not sure if that makes a difference.

Yes, the garage supply would be tapped off before the the main house consumer unit. It's actually more convenient that way as the the house consumer unit is remote from the meter.

Unusually, I've got a completely separate unused supply coming into the meter board but that would probably mean a separate meter and associated billing costs.

DVardysShadow

Gloomendoom wrote: »

The newer TIG units use an inverter but not sure if that makes a difference.

There should be a double wound device in the power circuit somewhere. With an inverter, you may find that the incoming 230V ac is immediately rectified to dc and then inverted at high frequency to go through a double wound high frequency transformer before being further conditioned for welding. You need to check out the welder specs to get to the bottom of this, but personally, I would not expect it to be any other way than the welding supply to have galvanic isolation from the mains.

Gloomendoom

DVardysShadow wrote: »

There should be a double wound device in the power circuit somewhere. With an inverter, you may find that the incoming 230V ac is immediately rectified to dc and then inverted at high frequency to go through a double wound high frequency transformer before being further conditioned for welding. You need to check out the welder specs to get to the bottom of this, but personally, I would not expect it to be any other way than the welding supply to have galvanic isolation from the mains.

Interesting. I'm not sure how the inverter welding sets work but they certainly don't have a stonking great transformer in them. My 220 amp MIG has a massive transformer and it weighs a ton. My 200 amp TIG is tiny by comparison and seems to be all solid state electronics.

DVardysShadow

Gloomendoom wrote: »

Interesting. I'm not sure how the inverter welding sets work but they certainly don't have a stonking great transformer in them. My 220 amp MIG has a massive transformer and it weighs a ton. My 200 amp TIG is tiny by comparison and seems to be all solid state electronics.

With a high frequency inverter the transformer will be small - to a first approximation proportional to the energy transferred in a half cycle at the operating frequency.