External Pond Heater Question

[sdlangford]

Hi there,

I have a koi pond and have decided to heat it this year after losing koi last year due to the low temps.

I havea 3KW heater that is on a 3 core 1.5mm cable with a 13 amp plug.

This is what the heater came with.

It plug direct into the mains, which will be the garage for my installation.

I have extended the cable so that it reaches my garage, same cable 3 core 1.5mm.

My question is, should the plug at the socket be warm ? It is, but not Hot.

The cable is not warm.

Anything to be worried about ?

Many Thanks

Simon

 

[RF Lighting]

You are running the plug right at it's limit, with a sustained load of 3kW

It shouldn't really be getting warm, and chances are you will find either the plug, socket or both will burn out over time.

You really ought to have a dedicated 16A radial circuit installed for this heater and then connect the heater to the circuit with either a 16A plug and socket or a 20A double pole isolator.

 

[ericmark]

When a fuse does as the name says fuses it melts. i.e. enough heat to melt the metal the fuse wire inside the cartridge is made of. So any fuse must heat up. There is a balance between how much it is heated and how quickly the heat can be removed.

In a plug when the power is used for a short time the plug does not have enough time to get warm. But with an extended time the material the plug is made from becomes very important.

Years ago when the 13A plug was first designed there was more metal in the plug but to add an extra safety feature metal was removed from the live pins and a plastic finger guard added. As a result the 13A plug although it can handle 13A for a short time is not really good enough to handle 13A for an extended time.

Items like immersion heaters are normally supplied using a fused connection unit (FCU) which is larger so better able to radiate the heat. For maintenance some times the old 15A plug is used the socket being supplied from the FCU. Since the 15A socket does not have a fuse inside it does not heat up as much.

I have never tested the plug in RCD units. Since these are much larger these may radiate the heat better than a simple plug. You can get 10ma versions of the plug in RCD units and these may be a good idea so should any moisture get into the heater or cable it will trip the 10ma RCD rather than take out the 30ma RCD which of course you would have supplying a device of that type.

The problem with the plug in RCD units is most are what is called active. That means if the supply is lost it will need resetting. This is done as the device needs power to work and if the loop impedance is not good enough a fault could reduce the voltage to a level where it will not work.

With RCD FCU because it is fixed you can get both active and passive types. Which you use would depend on the loop impedance at the device. However although the 30ma are reasonable price the 10ma versions are very expensive.

I would assume you already have RCD protection?

 

[sdlangford]

Thanks for the replies.

Just to answer a few of the points raised.

The double socket i have the heater pluged into is protected by a RCD in the garage and this circuit is then direct to the man house and RCD so if there are any issues in the garage it is protected.

My house is only a few years old and the garage electrics were installed as part of the build, the incoming cable is very substantial to the garage.

My cocern is that it sounds as though the product suggestions to plug straight into the mains is incorrect ?

The heaters are widely used and are profi-pond heaters 3kw.

I purchased this because is was a simple plug and go.

Regards

Simon