which size fuse for boiler?

The plug should not get hot. This indicates a poor connection or faulty plug. Pop out and buy an MK plug. It will already have a 13 amp fuse in it. Make sure the wires are not burned. Cut them back to good wire if needed. Make sure the connections are tight and try again. If the plug gets hot again you need a new wall socket. MK or Crabtree are the best. At worst the plug may get slightly warm after a long time, but never hot.

Hi There,

===First of all: when sizing wiring and fusing for a circuit===

1. Check the nameplate on the device( boiler in this instance )

2. For example: if the boiler nameplate reads " 13 amps" then you will need a wire rated for no less than 15 amps.....but usually a 20 amp wire size is recommended. this is #12 AWG.

3. The job of the fuse is to protect the wire from overcurrent and a 20 amp fuse will keep the wire from overheating while providing adequate power for the load

.

4. So now you have a 20 amp fuse and a wire rated at 20 amps feeding a load of 13 amps and that is correct for the application.

But the problem is that the plug is overheating. That indicates a high resistance at that point.

My guess is that either the plug is dirty, loose in the receptacle or the receptacle itself has worn out and not making a good connection between the plug and receptacle.

Of course there can be a loose wire connection at the back of the receptacle.

To fix this problem:

Check the nameplate for the rated current on the boiler.

Look at the wiring an make sure it is the correct size for the load.

Check the fuse rating to make sure it is the correct size for the wire.

Next put an Amprobe on the wiring to see exactly how much current is being used by the boiler to see if is matches the nameplate rating. There might be a problem with the boiler causing excess current draw.

If the wire, fuse and current draw on the boiler are OK then the problem has to be with either the receptacle or plug.....dirty, loose, or just plain "worn out".

When troubleshooting an electrical problem the entire circuit must be checked and the cause of the problem can then be diagnosed and repaired. A "piecemeal" approach is not a good idea and is a waste of time and money. An electrician can and should diagnose the problem for a proper repair.

It is good you found the problem before it became worse. Now it can be fixed with nothing bad happening.

Hope this helps,

Al

I think you mean an immersion heater, a boiler would not take enough current to heat a plug.

It's not uncommon for big loads like electric heaters to cause heating in a plug, because plugs and sockets are not always made to a very high standard.

First make sure the plug connections are good, and the plug pins are clean. If the plug pins are a dull colour you could clean themn up with metal polish or fine wire wool.

If after this it still gets hot, I would replace the plug and socket with ones of a reputable make like MK or Crabtree. The sprung contacts on the socket live and neutral can overheat and lose their spring so the contact is not good. An immersion heater usually takes a 13 amp fuse.

The water heater should be hard-wired flex , not connected with a plug. Still a 13A fuse.

You are observing "Pin Fizz".

When electrical wires and connectors get hot, this is a sign that something is not correct. The heat tells you that there is a resistance at this point and energy is being uselessly wasted.

Fix this issue and then put an amprobe on the circuit and check the current load, then fuse accordingly.

Chance is that you have poor contact or your plug in socket is getting burning out or you have a burnt out wire, these might result to high amp resulting to fuse burn out, i suggest you hire an experts to avoid further damage. Good luck, see link below