16A sockets in shed for welder and compressor

[bayzoo]

Hi,

I want to have installed 2 x 16A commando sockets in my shed. I want to run a MIG welder which has a max output of 180A @ 23V and a 3hp 2.2kW compressor. They wouldn’t be running at the same time. Both manufacturers state each needs a 16A supply however I’ve been running the welder from a 13A socket to date.

I’m in a 11 year old 3 storey town house with a concrete floor and there is a bathroom in between the CU and the utility room on the ground floor. I have 2 double sockets on the downstairs ring main in the utility room; this is where the cable would leave my house to the shed.

A spark came round to assess and said because of where the CU is located it would be difficult to connect the sockets direct to the CU; I'd need to spur off the ring main in the utility room however I’m lead to believe this wouldn’t work for my set up?

The spark left looking rather doubtful and asked me to send me the power rating on my welder. After he left I thought about putting a cable up behind the CU to the attic, and then dropping it down the other side to the utility room.

I checked in the attic and there is a small gap that would appear to go all the way down, in between the concrete blocks that separate my neighbours house and the plasterboard. I estimated the total length would be around 35m if I did it this way.

Can anyone offer any advice? Should I just drop the idea? I also thought about running a cable in trunking through the bathroom but I don’t even know if this is allowed.

I have a good understanding of current/voltage/power etc. but my knowledge on domestic electrics is very basic, so some of my terminology used might be incorrect.

Thanks.

Fraser

 

[littlespark]

Hi,

I want to have installed 2 x 16A commando sockets in my shed. I want to run a MIG welder which has a max output of 180A @ 23V and a 3hp 2.2kW compressor. They wouldn’t be running at the same time. Both manufacturers state each needs a 16A supply however I’ve been running the welder from a 13A socket to date.

I’m in a 11 year old 3 storey town house with a concrete floor and there is a bathroom in between the CU and the utility room on the ground floor. I have 2 double sockets on the downstairs ring main in the utility room; this is where the cable would leave my house to the shed.

A spark came round to assess and said because of where the CU is located it would be difficult to connect the sockets direct to the CU; I'd need to spur off the ring main in the utility room however I’m lead to believe this wouldn’t work for my set up?

The spark left looking rather doubtful and asked me to send me the power rating on my welder. After he left I thought about putting a cable up behind the CU to the attic, and then dropping it down the other side to the utility room.

I checked in the attic and there is a small gap that would appear to go all the way down, in between the concrete blocks that separate my neighbours house and the plasterboard. I estimated the total length would be around 35m if I did it this way.

Can anyone offer any advice? Should I just drop the idea? I also thought about running a cable in trunking through the bathroom but I don’t even know if this is allowed.

I have a good understanding of current/voltage/power etc. but my knowledge on domestic electrics is very basic, so some of my terminology used might be incorrect.

Thanks.

Fraser

There’s always a way to get power to where you need it, it’s just down to how much disruption you would put up with.

I’m surprised the electrician that looked at it didn’t suggest alternative routes.

Where in Scotland are you, as there’s a few forum members could offer a second opinion.

 

[plugsandsparks]

Hi,

I want to have installed 2 x 16A commando sockets in my shed. I want to run a MIG welder which has a max output of 180A @ 23V and a 3hp 2.2kW compressor. They wouldn’t be running at the same time. Both manufacturers state each needs a 16A supply however I’ve been running the welder from a 13A socket to date.

I’m in a 11 year old 3 storey town house with a concrete floor and there is a bathroom in between the CU and the utility room on the ground floor. I have 2 double sockets on the downstairs ring main in the utility room; this is where the cable would leave my house to the shed.

A spark came round to assess and said because of where the CU is located it would be difficult to connect the sockets direct to the CU; I'd need to spur off the ring main in the utility room however I’m lead to believe this wouldn’t work for my set up?

The spark left looking rather doubtful and asked me to send me the power rating on my welder. After he left I thought about putting a cable up behind the CU to the attic, and then dropping it down the other side to the utility room.

I checked in the attic and there is a small gap that would appear to go all the way down, in between the concrete blocks that separate my neighbours house and the plasterboard. I estimated the total length would be around 35m if I did it this way.

Can anyone offer any advice? Should I just drop the idea? I also thought about running a cable in trunking through the bathroom but I don’t even know if this is allowed.

I have a good understanding of current/voltage/power etc. but my knowledge on domestic electrics is very basic, so some of my terminology used might be incorrect.

Thanks.

Fraser

Did the electrician have a look at the meter location, i.e. do you have an external meter box. Pulling power off the house ring could cause you some issues .
Look into the external meter box first,
If its really important for you, then suck up the house trauma and get a decent cable in to the CU.

 

[bayzoo]

There’s always a way to get power to where you need it, it’s just down to how much disruption you would put up with.

I’m surprised the electrician that looked at it didn’t suggest alternative routes.

Where in Scotland are you, as there’s a few forum members could offer a second opinion

Thanks - I'm based in Midlothian, just south of Edinburgh.

Did the electrician have a look at the meter location, i.e. do you have an external meter box. Pulling power off the house ring could cause you some issues .
Look into the external meter box first,
If its really important for you, then suck up the house trauma and get a decent cable in to the CU.

I just have the one metre box inside I think... I've only one box outside and that's for the gas supply. I don't mind house trauma; if I know all the possible options then I can make a decision based on time and cost. The spark was helpful just to add, I think he just wanted to get home after waiting in traffic for 40 min to get to me... don't blame him.

 

[pc1966]

You can run cables through the bathroom if that is physically easiest, however, there are some implications for doing so as it is classed as a 'special location' in the regulations. But for new socket outlets they would need to be on a RCD-protected circuit anyway, which should cover the main point for any cables traversing that region.

Those 16A sockets don't have fuses, so they must to be fed from a supply with a 16A MCB (and RCD, or a RCBO) for overload protection. You could have two on one 16A supply if you are absolutely sure they won't be used at the same time (cheaper option), or you could have a 32A feed and a small local CU with a pair of 16A MCBs, etc to allow simultaneous usage (not much more cost, but clearly better long-term).

For 32A you would be looking at 6mm supply cable and it should be OK for 35m is that route is taken, but if it goes outdoors at any point then it needs to be either UV-tolerant cable or protected in suitable conduit, etc. For a 16A feed then 2.5mm cable would be adequate, but given a significant portion of cost is going to be labour for install and test you might be better to size the cable for any future needs.

As above, there may be someone on this forum who can take a look.

 

[bayzoo]

You can run cables through the bathroom if that is physically easiest, however, there are some implications for doing so as it is classed as a 'special location' in the regulations. But for new socket outlets they would need to be on a RCD-protected circuit anyway, which should cover the main point for any cables traversing that region.

Those 16A sockets don't have fuses, so they must to be fed from a supply with a 16A MCB (and RCD, or a RCBO) for overload protection. You could have two on one 16A supply if you are absolutely sure they won't be used at the same time (cheaper option), or you could have a 32A feed and a small local CU with a pair of 16A MCBs, etc to allow simultaneous usage (not much more cost, but clearly better long-term).

For 32A you would be looking at 6mm supply cable and it should be OK for 35m is that route is taken, but if it goes outdoors at any point then it needs to be either UV-tolerant cable or protected in suitable conduit, etc. For a 16A feed then 2.5mm cable would be adequate, but given a significant portion of cost is going to be labour for install and test you might be better to size the cable for any future needs.

As above, there may be someone on this forum who can take a look.

Many thanks for your detailed reply - that's good to know 6mm cable would be fine for 32A, and I agree this might be the best option in the long run. I have found another spark who is coming later today hopefully, so we'll see what they say and I'd welcome any input from sparks local to me.

Also is it possible to make more room for this on my CU or would a new CU be required?

 

[littlespark]

Many thanks for your detailed reply - that's good to know 6mm cable would be fine for 32A, and I agree this might be the best option in the long run. I have found another spark who is coming later today hopefully, so we'll see what they say and I'd welcome any input from sparks local to me.

Also is it possible to make more room for this on my CU or would a new CU be required?

View attachment 92952

You’ve got spare way extreme left, but as you can see, there’s a number of circuits protected by each rcd. Any fault with the additional circuit would trip off half the house.

A dedicated RCBO at this end would satisfy protecting the cable route through the house, with a small garage type CU in the shed for supplying the 16A sockets.

Unfortunately, you’re just outside my area.

 

[bayzoo]

You’ve got spare way extreme left, but as you can see, there’s a number of circuits protected by each rcd. Any fault with the additional circuit would trip off half the house.

A dedicated RCBO at this end would satisfy protecting the cable route through the house, with a small garage type CU in the shed for supplying the 16A sockets.

Unfortunately, you’re just outside my area.

I can see it now to the left... OK so thanks to you all I'm armed with a lot more information to discuss with a spark(s). I do have 2 more questions:

When a manufacturer says an appliance needs 16A, does that mean that 16A is the highest current it will draw?

I'm trying to work out the highest power draw from my welder. The highest output is 180A at 23V, so going by P = IV I get 4.1kW, is this correct or should it be the input figures I work this out from?

 

[timhoward]

I know these seem strange questions, but shed is made of wood and has no water pipes / outside tap ?

 

[bayzoo]

I know these seem strange questions, but shed is made of wood and has no water pipes / outside tap ?

Yes it's made of wood and no it doesn't have any water pipes.

 

[plugsandsparks]

I can see it now to the left... OK so thanks to you all I'm armed with a lot more information to discuss with a spark(s). I do have 2 more questions:

When a manufacturer says an appliance needs 16A, does that mean that 16A is the highest current it will draw?

I'm trying to work out the highest power draw from my welder. The highest output is 180A at 23V, so going by P = IV I get 4.1kW, is this correct or should it be the input figures I work this out from?

Those figures are the output, what you need is the input max current, if the welder needs a 16A supply then assume at some point it will draw it,

 

[bayzoo]

So had a nice young lad from a local firm just round today. At first he had that look of doubt, but I suggested running the cable up to the loft and out of the house, and then down outside the house and it came together. As mentioned above he suggested a 32a supply, just in case I wanted to run both appliances at once, with the shed having its on small CU. He also suggested 6mm armoured cable, which will be needed the whole route - I know this will be pricey.

He reckoned it will be a days work for 2 sparks so I appreciate this will be likely more than I had budgeted for but I don't mind paying for a proper job to be done; I see it as a good sales point should I want to sell in the near future.

 

[littlespark]

What’s the fire risk of a welder inside a wooden shed?

 

[bayzoo]

What’s the fire risk of a welder inside a wooden shed?

I’d imagine quite high but I’m not welding in the shed, but outside it. I have a welding tent for days when there’s a breeze. Having power in the shed means I don’t have to keep the back door open as well.

 

[pc1966]

So had a nice young lad from a local firm just round today. At first he had that look of doubt, but I suggested running the cable up to the loft and out of the house, and then down outside the house and it came together. As mentioned above he suggested a 32a supply, just in case I wanted to run both appliances at once, with the shed having its on small CU. He also suggested 6mm armoured cable, which will be needed the whole route - I know this will be pricey.

He reckoned it will be a days work for 2 sparks so I appreciate this will be likely more than I had budgeted for but I don't mind paying for a proper job to be done; I see it as a good sales point should I want to sell in the near future.

That sounds like a reasonable solution that would make any future use possible. Over the summer we saw quite a few questions like this but for hot tubs! So if you tire of welding you have another use

With SWA (steel wire armoured) cable you do not need RCD protection for the cable itself, depending on the supply earth characteristics. So you might be better to ask for them not to have the RCD in the house CU in that case, but to have it in the garage CU (as you do need RCD protection for the socket outlets). That way if the welder trips it you can reset it easily.

Another minor thing you might want to consider if the garage is very much a workshop is what would happen if it tripped (or power failed for any other reason) and the lights go out. You might want to look at having some emergency lights (e.g built in to a LED baton style unit) if you are doing anything that could be dangerous if suddenly very dark at night, etc.