Advice on running electrics to shed

[Agent_zed]

I'll stand corrected (or sitting at the computer) if wrong but I was taught to never use a coiled cord as it increases the resistance creating heat in the wire coils. Either pull all the cable out of the reel or get a shorter cord instead.

Pete

Pretty much any coiled extension lead sold that I have seen in the UK has a rating marked on the side. My 25m cable for example can run 750w coiled or 3000w uncoiled. They often have a thermal overload protection switch as well.

I was at a party last year in an unheated space so someone plugged a 2kw heater into a coiled extension which already had some halogen lights in it. It was quite toasty by the time we noticed. It smelt hot.

 

[Sideways]

OK, seeing as pulling out old OSB in the new workshop is boring, and physics is interesting, I did the test.

2kW filament heater alone:
236.2 V
8.75 A
2058 W
PF: 1.00

2kW heater + 30m coiled extension lead (ten seconds only!):
236.4 V
8.53 A
2071 W
PF: 1.00

As you see, the coiled lead isn’t sucking (or pumping) any VARs. What you say about displacement PF is correct, but doesn’t apply in this case.

Work out the resistances on those two and they differ by about 0.71 Ohms.
That sounds like a reasonable number for the resistance of 2x 30m lengths of copper.

 

[Katomi woodsmith]

Get a qualified electrician in for the mains
Or
I have fitted my own solar panels battery’s and inverter
Note
If using lithium batts you will prob have to speak to local fire station as when I asked they record lithium battery applications re fire risk

 

[Spectric]

If using lithium batts you will prob have to speak to local fire station as when I asked they record lithium battery applications re fire risk

I think this depends upon the number and size of your lithium battery banks, but it is always good practice to put a hazzard warning label on a shed door or place where you have anything that could be classed as a hazzard such as gas bottles or compressed air.

 

[John Brown]

Get a qualified electrician in for the mains
Or
I have fitted my own solar panels battery’s and inverter
Note
If using lithium batts you will prob have to speak to local fire station as when I asked they record lithium battery applications re fire risk

LiFePo4 batteries are, as far as I know, extremely unlikely to catch fire.
I also have a "solar shed". 410w panel, 24v 100ah lifepo4 battery and 4000w pure sine wave inverter. Works for me, but I don't live out there.

 

[Hypnotic Chimera]

Since posting original question, I've had a few more thoughts about this.

First, my current use case includes the following; and has done for over 17 years since we moved in here.

I have a twin socket, coiled reel extension lead that I use regularly. It is labelled for "outdoor use" has 1.5mm2 triple core rubber sheathed cable and is 43 metres fully uncoiled. Labelled as Max Current Fully Coiled = 5A; Max Current Fully Uncoiled = 13A.
I've regularly plugged this into my garage socket and hooked up my shop vac (1000W) and my old Einhell table saw (2000W) - (recently replaced with 1500W Rage5-S)

This would, for a layman, and in the absence of any other further professional advice or warning, appear to be a reasonable thing to do. Notionally, this would not appear to have exceeded any basic electrical parameters. The lawn is 15 metres from the closest garage socket and a lawnmower cable is an extra 10 or 15 metres on top of the 43 metres of extension cable. The garage socket would be the primary choice to run an electrical lawnmower - commonly 1700W or 1800W.

Question would be - is what I've been doing "safe"?? A common homeowner wouldn't have any notion of loop impedance, etc... so would not hesitate to do what I have done for many years.


Bearing that in mind, how would a simple 15metre length of 2.5mm triple core running from the same socket, into a far, FAR lighter electrical load (sub 200W total) somehow be something to be concerned about, given that it ought to have been considered safe, to a layman, to run the 3000W load off a 43 metre 1.5mm2 cable?

 

[Spectric]

Question would be - is what I've been doing "safe"?? A common homeowner wouldn't have any notion of loop impedance, etc... so would not hesitate to do what I have done for many years.

That is why some people get themselves into trouble and there are electrical thermal events because they know no different and have no concept of electricity except that it is not cheap. Without any electrical background people do some incredable work because they just do not realise the dangers but when it all works they think they have done a great job because their logic is "it's working so must be safe". Another issue is that they also believe that the fuse is going to protect them, luckily we now have residual current protection so safer from an electrocution perspective but that fuse needs a certain amount of current to actually cause it to blow, if you are pulling almost enough current but not quite enough you have a potential overload and now things get warm.

 

[Dabop]

LiFePo4 batteries are, as far as I know, extremely unlikely to catch fire.
I also have a "solar shed". 410w panel, 24v 100ah lifepo4 battery and 4000w pure sine wave inverter. Works for me, but I don't live out there.

LFP/LYP batteries are EXTREMELY unlikely to 'catch fire' especially from the cells themselves (they are a completely different animal to the phone/powertool/laptop etc batteries ie LiPO for phones etc versus LiFePO4 (LFP) or LiFeYPO4 (LYP)...
LiPO (what most people think of when they hear 'lithium battery- also what many call 'lithium-ion') are the 'easily catch fire'/can't put out batteries/cells, where LFP/LYP are far more stable (but have a lower energy density per kg)...

Think of them like petrol and diesel- both 'fuel' but completely different in characteristics- one I wouldn't wave a lit oxy torch anywhere around it, the other I would happily use one right next to it- lithium batteries are the same- LiPO is the 'dangerous one' LFP/LYP is very safe in comparison, yet ignorant people lump them all in together...

"LITHIUM - runs away screaming in fear...."

 

[Dabop]

Since posting original question, I've had a few more thoughts about this.

First, my current use case includes the following; and has done for over 17 years since we moved in here.

I have a twin socket, coiled reel extension lead that I use regularly. It is labelled for "outdoor use" has 1.5mm2 triple core rubber sheathed cable and is 43 metres fully uncoiled. Labelled as Max Current Fully Coiled = 5A; Max Current Fully Uncoiled = 13A.
I've regularly plugged this into my garage socket and hooked up my shop vac (1000W) and my old Einhell table saw (2000W) - (recently replaced with 1500W Rage5-S)

This would, for a layman, and in the absence of any other further professional advice or warning, appear to be a reasonable thing to do. Notionally, this would not appear to have exceeded any basic electrical parameters. The lawn is 15 metres from the closest garage socket and a lawnmower cable is an extra 10 or 15 metres on top of the 43 metres of extension cable. The garage socket would be the primary choice to run an electrical lawnmower - commonly 1700W or 1800W.

Question would be - is what I've been doing "safe"?? A common homeowner wouldn't have any notion of loop impedance, etc... so would not hesitate to do what I have done for many years.


Bearing that in mind, how would a simple 15metre length of 2.5mm triple core running from the same socket, into a far, FAR lighter electrical load (sub 200W total) somehow be something to be concerned about, given that it ought to have been considered safe, to a layman, to run the 3000W load off a 43 metre 1.5mm2 cable?

Just for gits and shiggles, I ran your numbers through the AS/NZ electrical standards calculator- and this was the result (which I fully agree with...)

In particular...

It may have 'worked'- but in no way was it 'safe' in doing so...

(note that the first 'all green' cable size for that distance/load is 6mm^2- your extension cord is 1.5mm^2!!!)

Your voltage drop is abysmal (down from 230v nominal to 208.5v, the cable is running past its maximum rated current and any RCD/RCBO would have its sensitivity degraded with those figures...

Luckily you likely weren't hitting them all the time- but still- that combination is really well over what is considered 'safe'- even if it did 'work'...

 

[Hypnotic Chimera]

Just for gits and shiggles, I ran your numbers through the AS/NZ electrical standards calculator- and this was the result (which I fully agree with...)

View attachment 191617
In particular...
View attachment 191618

It may have 'worked'- but in no way was it 'safe' in doing so...

(note that the first 'all green' cable size for that distance/load is 6mm^2- your extension cord is 1.5mm^2!!!)

Your voltage drop is abysmal (down from 230v nominal to 208.5v, the cable is running past its maximum rated current and any RCD/RCBO would have its sensitivity degraded with those figures...

Luckily you likely weren't hitting them all the time- but still- that combination is really well over what is considered 'safe'- even if it did 'work'...

Wow - thank you - and just goes to show that "normal people" don't give this kind of nuance with electrics any consideration or second thought.

I'm gonna have to retire that extension for anything other than light loads and buy a new cable... (thinking about what might be "safe") ... ...


... ... thinking about what would be considered "safe", then, I used the same calculator as above, with your entries, and changed just the active size to 2.5 and the Cable distance to 15m - and this went through "all green" on the 2.5mm2.

Before I go ahead and purchase - do you think I need a visit from an electrician to advise on the garage electrics setup?

 

[Dabop]

Wow - thank you - and just goes to show that "normal people" don't give this kind of nuance with electrics any consideration or second thought.

I'm gonna have to retire that extension for anything other than light loads and buy a new cable... (thinking about what might be "safe") ... ...


... ... thinking about what would be considered "safe", then, I used the same calculator as above, with your entries, and changed just the active size to 2.5 and the Cable distance to 15m - and this went through "all green" on the 2.5mm2.

Before I go ahead and purchase - do you think I need a visit from an electrician to advise on the garage electrics setup?

Wouldn't hurt, especially if its an older 'add-on' on a spur- It might already be at the upper limits of 'acceptable' just at the shed/garage (plus at nearly 20 year old if I remember correctly. its had plenty of time for corrosion/insulation leakage etc to rear its ugly head, a quick check with a mega and a visual of the feed will say for sure what its limits are, rather than us trying to second guess what you 'might' have there... )

You are chucking some pretty heavy loads on it after all- many 'garage' installs are minimum cost installs designed for a light or two, and maybe some light occasional handtool use, rather than the bigger 'hobby' loads...

Many are only wired in only 2.5mm^2 armoured, and with a 20m plus possible run on the feed, it would already be right at its limits at the outlet by itself!!!
Adding 'any' extension cord might be risky with that 3000w hanging off the end...

Only an onsite inspection by someone with the right gear can determine that (and the overall health of the install)...

Thats what a 2.5 armoured buried would be like direct buried- only 'just' up to the job of handling a 3000w actual load right at the outlet!!!
Chuck another 15m on the end, and yeah...

 

[Hypnotic Chimera]

Thanks mate, appreciate the efforts

 

[Hypnotic Chimera]

Thanks mate, appreciate the efforts

One more question, if I may?

Can I even plan to run my hobbyist electricals off my house mains, with a decent extension, if this is such a safety issue?

 

[Dabop]

Most 'hobby level' electricals are fine- IF there is a good feed from the consumer unit rated for the intended purpose...

(ie a 4mm or 6mm single armoured circuit from the consumer unit to the shed would be more than adequate for almost all 'hobby level' equipment...)

It is just that very few HAVE such an existing feed already installed...

(as I mentioned before, most 'garage/shed' feeds are specced for just a couple of lights and a single powerpoint really meant for lighter duty applications- running a vacuum through the car or the occasional light powertool use...)

Upgrading it to a 'hobby workshop' with multiple larger machines running at once (dust extractor plus a larger saw for example) means a heavier feed is needed (not installed to 'all garages' simply because probably 90% of the population never would use it, and it costs more to have done than the standard 'light duty' specced feed... especially as it is usually both one of the longest feeds in the place, and the least used...

It basically means that anyone who is looking at running anything more than the most basic and smaller tools on a regular basis really SHOULD (if they haven't done it already) look at what their power demands are, and what their circuits are really capable of handling... (especially if long extension cords are thrown into the mix...)

Length is the real enemy here- the longer the length of cable, the bigger it has to be to handle the same load (look at that 300m run I mentioned before on page 1- a HUGE cable was needed even for a 'light duty' 10A outlet and a single light at the shed end)- true that is an extreme example but shows how adding length can mean ALL the cable in-between starts to matter at the far end...