Immersion heaters on 32A cable?

[ScottyMc]

I am wanting to power two 3kw immersion heaters that have a 12.5A 240v thermostat. I will be using 16A plugs & sockets as a 13A plug wouldn't be able to take it

I have a cable run already that is rated at 32A. The plan is to run the cable to a new fusebox, onto a 16A breaker.

Is this feasible?

 

[ColJack]

immersion heaters should be hard wired, not on a plug and socket.. it's not like you'll be unplugging them every few days to move them is it..?

3KW is about 12.5A.. so by 12.5A thermostat do you mean the built in one?

as you'll be running 2 I take it that it's supposed to be a ECO7 setup? one for off peak and one for top up?
these may require 2 seperate feeds depending on your setup..
it can be done with a timer and a "boost" button..

running the circuit to a new breaker means that it's notifiable under Part P.. so you have to pay a fee to the LABC or employ the services of a registered electrician..

 

[ban-all-sheds]

Is this feasible?

Yes, apart from:

1. 16A isn't enough for 6kW
2. you aren't supposed to use EN60309 plugs and sockets
3. a BS 1363 is OK for a 3kW load
4. it's unusual to plug immersion heaters in
5. water heaters with a storage capacity of over 15 litres should be fed from their own dedicated supply
6. you're supposed to notify LABC before you start

Are you sure you know what you're doing?

[EDIT]Doh![/EDIT]

 

[electronicsuk]

BAS, I think you may have misunderstood the op...

Yes, apart from:

1. 16A isn't enough for 6kW

1. 
   
   To my mind, OP seems to be suggesting 32A submain to small DB (near the immersions) with 2x 16A MCBs onto 2x 16A sockets. I know he says 'A 16A breaker', but this wouldn't make any sense.
   
   

   [*] you aren't supposed to use EN60309 plugs and sockets

   
   Why not?
   
   

   [*] a BS 1363 is OK for a 3kW load
   [*] it's unusual to plug immersion heaters in

   
   Agree on both counts, they would be much better hardwired.
   
   

   [*] water heaters with a storage capacity of over 15 litres should be fed from their own dedicated supply

   
   If there will indeed be a DB at the end of the submain witted with 2x 16A MCBs, then this will provide the dedicated circuits as required.
   
   

   [*] you're supposed to notify LABC before you start

Are you sure you know what you're doing?

I suspect your suspicions are correct, too.

 

[ericmark]

I am wanting to power two 3kw immersion heaters that have a 12.5A 240v thermostat. I will be using 16A plugs & sockets as a 13A plug wouldn't be able to take it

I have a cable run already that is rated at 32A. The plan is to run the cable to a new fusebox, onto a 16A breaker.

Is this feasible?

Working through what you say:-
1) Although 3Kw is 0.04348A over the 13A that is not enough to worry about and there will work A1 without using 16A MCB and unfused plug and socket.
2) How do you know the cable is ratted 32A only flex cable is ratted in amps and page 292 and 296 in regs shows 4mm sq as being 30A and 32A but this cable must be visible for its whole length and so I wonder if you have selected the correct cable?

There is nothing wrong with the idea and I have seen the old 15A plugs used with immersion heaters to allow easy isolation and maintenance.

There is no requirement for immersion heaters to be hard wired. But there is a requirement to have good earths on high earth leakage equipment and as a result normally they are not plugged in. With the new regulations and RCD protection on near everything likely the earth leakage is no longer a problem but in a cupboard where cloths may prevent the plug from cooling I would not use a 13A plug. Any fuse will produce heat and any unit with a fuse needs to be able to get rid of that heat.

So although some of the statements made my not be strictly true the advice they give is still sound.

So maybe you can expand and say what you are really trying to do? For all we know you may be setting you portable showers for your employees and it could be all on a commercial premises. And if so our advice would likely change. So where, and why do you want to do this?

 

[ColJack]

don't be so condesending eric..

3KW is between 12.5 and 13.04A depending on whether the rating is given for 230V or 240V...

the 32A rating would likely be for the hardwiring that he has installed already...

immersion heaters are recomended their own circuit of 16A or 20A and are to be hardwired with a 20A DP switch ( REG 554.3.3 )

no one mentioned electric showers, and a tank full of water with a heating element is hardly the best way for portable showers...

 

[kai]

This photo shows a setup, where the Day and Night immersions are fed from two 13amp fuse-connection units, via two Industrial 16amp plugs and sockets - meaning the plumber can simply unplug to isolate the elements, in order to carry out maintenance or replacement!

 

[Steve]

I knew I'd seen that before!

 

[ColJack]

so, how stupid is that then?
well for a start you can plug the wrong element into the wrong socket, so you'll be heating the top of the tank on eco7, and heating the whole of the tank on boost..
secondly, why bother with 16A blue plugs when there are 13A fuses in the FCU's? might as well have just used single switched sockets.. does the same job...
thirdly, any plumber changing an element should know how to disconnect it anyway.. they'll have to change the cable from the old one onto the new one so it's a waste of time...

 

[londonboy]

That picture looks pretty

I like the bonding at the top of the cylinder too.

God knows why two 16a radials havent been run in, one off peak and one on.
Terminated in a double pole switch with flex outlet.

 

[SUNRAY]

I am wanting to power two 3kw immersion heaters that have a 12.5A 240v thermostat. A 13A plug wouldn't be able to take it

a BS 1363 is OK for a 3kW load

Sorry BAS i'm with Scotty on this one, seen too many burnt ones.

you aren't supposed to use EN60309 plugs and sockets

Why not? I would certainly prefer 4343 over 1363.

Although I wouldn't normally use plugs on immersions if the're not portable.

 

[ColJack]

what's a 4343? not in the BS mentioned in the regs?
and not the one BAS mentioned..

and stop buying cheap plugs then..
if it's rated for 13A then it can take 13A continuous..

 

[SUNRAY]

what's a 4343? not in the BS mentioned in the regs?
and not the one BAS mentioned..

and stop buying cheap plugs then..
if it's rated for 13A then it can take 13A continuous..

I'd love to find 1363 plugs that can take 13A continuousely, can you suggest a suitable make?

Please dont mention MK!

 

[ColJack]

what's the point of making them then?
might as well just re-classify them as 10A plugs and start only selling 10A fuses for them...

what you are seeing is probably heating caused by old sockets.. lets not blame the plugs here..
the socket connections are worn and loose and heat up because of the poor connection between the solid pins on the plug and the flexible connections of the socket..

 

[NotHimAgain]

BS 1363 plugs are designed to work in 'normal temperatures'. The standard requires that performance tests are carried out in an ambient temperature of 20 +/- 5 degrees.

The ambient temperature in many airing cupboards would exceed this - so the use of 1363 plug and sockets is usually discouraged in that environment.