3kw Heater on a 13a Socket

[Adskee]

Hope I'm posting this in the correct place, couldn't find a "new post" button in the DIY forum.

I have built a 100l kettle using a large pot and an immersion heater. The original heater I tried was 5.5kw, wired using 2.5mm cable to a standard plug. The plug got very hot after 3 minutes. After some discussions and research, I determined that trying to pull 23a down through a standard 13a socket was a very bad idea.

So I downgraded to a 3kw heater - 12.5a, should be fine. Same cable, same plug got very hot again.

So then I thought it might be the wiring in the plug (or the plug itself) so I bought a moulded plug with 1.5mm cable. Cut it down to 2m in length so the run wasn't too long. This time, the cable started getting warm (very slightly) after a 3-4 minutes. I left it running for 10 minutes, by which point the cable was warmer, the plug wasn't warm yet but the bit where the cable leaves the plug was getting warm too. I unpplugged at this point and the Live and Neutral pins were pretty hot. Too hot to touch. The socket felt fine.

My question is, why is this getting so hot? I've tried it on different sockets, one in my house, one in the new shed (which is where the kettle will live) so I don't think it's faulty sockets. I've used two different plugs and two different cables. I need this running for about 1.5 - 2 hours at a time so if it's hot after 10 mins it's a worry.

Will it reach a level of heat and stop or just keep getting hotter and hotter until my house melts? From what I've read online (not always a good idea), I should get a little heat but this setup should be OK as it's under 13a.

Where am I going wrong? Cheap heating element??

 

[Darkwood]

Welcome to the forum, I will notify Admin' to tag your name with DIY so members can respond appropriately for you level.

 

[Risteard]

The use of 2.5mm^2 flex with a BS 1363 plugtop is prohibited.

 

[Adskee]

The use of 2.5mm^2 flex with a BS 1363 plugtop is prohibited.

When you say 2 flex, do you mean the number of cores? If so, it was a 2.5mm, 3 core cable. It's now a 1.5mm, 3 core cable.

 

[davesparks]

The use of 2.5mm^2 flex with a BS 1363 plugtop is prohibited.

Is it? By whom?

 

[Dave OCD]

Is it? By whom?

By Risteard. :laugh3:

 

[Risteard]

Is it? By whom?

By BS 1363.

 

[Leesparkykent]

A decent plug top like the old school MK ones and a bit of 1.5mm butyl. TBH I wouldn't like this as a permanent solution and would be better if you had a dedicated 16A radial with double pole switch.

 

[7029 dave]

A decent plug top like the old school MK ones and a bit of 1.5mm butyl. TBH I wouldn't like this as a permanent solution and would be better if you had a dedicated 16A radial with double pole switch.

Had that in my house for years (old mk plug top to) , had CH so it was only for back up. I considered wiring dedicated radial but never got round to it.

 

[Lucien Nunes]

3kW is fine, in theory, on a 13A plug with 1.5mm² flex. It will get warm due to resistance in the fuse and contacts, but will not carry on getting warmer once it has reached equilibrium. However, if either the plug or the socket is not of best quality and in good condition with tight contacts and clean pins, there is a tendency to overheat at 3kW. For this reason it is not a recommended method for making permanent connections to appliances with a continuous load of 3kW.

When you say 2 flex, do you mean the number of cores

No, he said ^2 which is shorthand for squared if you can't type a superscript ² on your keyboard.

 

[UKMeterman]

A decent plug top like the old school MK ones and a bit of 1.5mm butyl. TBH I wouldn't like this as a permanent solution and would be better if you had a dedicated 16A radial with double pole switch.

If you want to try the old school plug try http://uk.farnell.com/mk-electric/646whi/plug-safety-13a-white/dp/107754

and you will need a decent make of socket, not the 99p special from screwfix....

and for cable try http://uk.farnell.com/pro-power/h07rnf3-1-5/cable-3core-1-5mm-per-m/dp/1494813

 

[Spoon]

The use of 2.5mm^2 flex with a BS 1363 plugtop is prohibited.

I can't find anything about this. Please can you post some info.

 

[UKMeterman]

Look at the link for the plug above maximum conductor size 1.5mm

 

[Spoon]

Look at the link for the plug above maximum conductor size 1.5mm

So it does. Thanks.

 

[Adam W]

The more current you draw through a cable the warmer it will get. If you constantly pull 12.5A through a system designed to handle 13A it will be a lot more noticeable than, say, boiling a domestic kettle. Obviously this will put more strain on the wiring in the same way as redlining your car's engine.

My question would be why do you need a homemade 100 litre kettle in your shed?

 

[Andy78]

The more current you draw through a cable the warmer it will get. If you constantly pull 12.5A through a system designed to handle 13A it will be a lot more noticeable than, say, boiling a domestic kettle. Obviously this will put more strain on the wiring in the same way as redlining your car's engine.

My question would be why do you need a homemade 100 litre kettle in your shed?

I'm going to guess homebrew, on a very respectable scale

 

[7029 dave]

I'm going to guess homebrew, on a very respectable scale

Ooh white lightening as the Americans call it.

 

[7029 dave]

I nicked your smiley Andy. oops

 

[Adskee]

We're making Kombucha actually. It's fermentation, but of green tea. Results in a fizzy, mildly alcoholic, delicious drink thats very good for you.

It's a new business venture and we have 2 x 300l tanks that need to be filled.

Warm I don't mind, but the pins being too hot to touch after 10 mins? I could keep going and see if it reaches a level but I'd rather not melt the socket in the process. I'm going to look at a dedicated feed but I understand people are using this setup so am not why I'm getting souch heat.

 

[Andy78]

We're making Kombucha actually. It's fermentation, but of green tea. Results in a fizzy, mildly alcoholic, delicious drink thats very good for you.

It's a new business venture and we have 2 x 300l tanks that need to be filled.

Warm I don't mind, but the pins being too hot to touch after 10 mins? I could keep going and see if it reaches a level but I'd rather not melt the socket in the process. I'm going to look at a dedicated feed but I understand people are using this setup so am not why I'm getting souch heat.

Sounds interesting. The plug is getting hot due to it pulling a large amount of current for its rating. This can be entirely normal. Other effects such as looseness of the plug and socket connection and duration of use can add to the heating, but I'm only repeating earlier advice in this thread.
See a local electrician about a permanent connection, maybe for your original larger heating element to suit your needs.

 

[telectrix]

put it on a 32A MCB, 6mm cable, 45A cooker isolator. then a 4mm butyl flex to the heater.

 

[UKMeterman]

Hi,
How quickly do you want the 100l or 300L heated and over what temprature range?

 

[Adskee]

Hi,
How quickly do you want the 100l or 300L heated and over what temprature range?

We're only heating 100l at a time but even with the 3kw heater it will take around 2 hours just to get to 80 degrees.

We'll probably have to do this at least twice every time so anything slower would take too long.

 

[telectrix]

which side of manchester are you. the west and south is just on my patch.

 

[Dizzy_Maskell]

If go for an isolator and a separate supply myself.
Cooler isolator be ideal and correct overload protection (fuse or mcb)


Sent from my iPhone using Tapatalk

 

[Andy78]

I might be teaching you to suck eggs here, but have you explored gas burner systems ? I believe they can be quite popular with large batch homebrewers so it might work for you ?

I know my local garage based microbrewer manages on a single 3kW immersion heater for his 150l batches but have no idea of his heating times or if his needs are similar to yours.

 

[LeeH]

Are you a fellow home brewer Andy? I have a system half built in the garage at the moment.

 

[Karin]

2 x 2,2kw elements across two different outlets/circuits for me

 

[Andy78]

Are you a fellow home brewer Andy? I have a system half built in the garage at the moment.

I do a little bit but only kits with the occasional batch of cider or ginger beer or similar. Not got the time or space for grain brewing unfortunately. I think I've seen your setup on one of the brewing forums in all its shiny glory.

I am stuck with buying my proper beer from a local guy who brews in his garage and supplies local bars and restaurants. But that's great really as his prices are good, his beer is delicious, and he does 7 different styles currently.