Immersion heater keeps tripping the fuse box

**Damien** · 31-12-2019, 07:59

Wondered if anyone had any ideas into an issue I am having. I don't know a lot about heating systems, pumps or how they all work so my terminology might be wrong.

In the airing cupboard, next to the big red hot water tank, there is a switch. I assume this switch is for the water pump? The water pressure is certainly almost non-existent with it off. However a quick Google suggests this switch is actually the immersion heater. The boiler also doesn't work with this switch on.

Anyway, as soon as this switch turns on it trips the fuse box. I am not even sure if this is an issue for an electrician or a plumber? Any ideas of what could be happening?

Thanks

heero_yuy · 31-12-2019, 08:27

The switch is likely to be the immersion heater. Just follow the flexible cable that emerges from the heater cover and it should go back to the switch.

If it trips the leakage breaker (Master switch) then the heater element or possibly the thermostat is likely to be faulty. (Short circuit to earth)

An electrician can verify which part is faulty. The thermostat is easy to change as it fits inside the element in a sheath. If the element needs changing then it is necessary to drain the hot water system. Both parts are relatively in-expensive.

This happened a few years ago in my mothers house and it turned out to be a fleck of rust shorting a connection under the cover. Worth a look.

**Damien** · 31-12-2019, 09:08

Cheers. Would that impact the water pressure? The switch seems to lower the general water pressure of the bathroom only, turn off the boiler and the thing that lets you turn on/off the hot water and heating downstairs.

**Mick** · 31-12-2019, 10:05

I don’t profess to be a plumber or Electrician, not my forte, however, I’ve spent many a times watching my dad fix his boiler, hot water systems, over many years when I used to live there.

By the sounds of it, you have a Conventional Boiler system, e.g not a Combi boiler that heats water instantly on hot tap flow.

The switch you mention is to power on the immersion heater. Immersion heater should only be used, as a fast source of heating water in the tank. A number of potential issues can occur, bad heating element, bad wiring, blocked or dead pump, which would affect water pressure. You could try turning thermostat down, see if that stops the tripping.

I’ve witnessed my dad over the years, strip whole water tank system down upstairs, replace pump, new heating element. Self repair is inexpensive if you know what you’re doing, parts can be obtained from screw fix, B&Q etc. Bear in the mind that it is illegal to tinker with the Boiler systems, by anyone not certified as Gas Safe Registered, what used to be classed as CORGI. But this issue you’re having, is more electrical than gas.

There is lots of arguments about either having a Conventional Boiler or Combi system, I have been used to both, the pros to conventional is there is a back up to having heated water, if boiler packs in. Back in the day, when I lived with my parents, their conventional boiler was about 40 years old and it had a few minor issues like air pockets forming, pump having to be replaced a few times.

I moved in to a new property in 2018 and the Combi boiler has broke down twice. First time it was an internal valve, £150 to fix, then two months ago, it was the PCB, the brains of the boiler, that needed to be replaced, that was another £250, though this is relatively cheap, I’ve seen £300 and upwatds, for that kind of job.

Taf · 31-12-2019, 11:43

The switch could be power for the changeover valve (switches water from the boiler between radiators and hot water tank). A photo would help!

But even that would not affect pressure, just where the boiler feed is going to.

**Damien** · 31-12-2019, 17:31

Quote:

Originally Posted by Mick

By the sounds of it, you have a Conventional Boiler system, e.g not a Combi boiler that heats water instantly on hot tap flow.

Yup, conventional boiler.

Quote:

The switch you mention is to power on the immersion heater. Immersion heater should only be used, as a fast source of heating water in the tank. A number of potential issues can occur, bad heating element, bad wiring, blocked or dead pump, which would affect water pressure. You could try turning thermostat down, see if that stops the tripping.

Nah, tried turning it all the way down. The fact it trips literally the moment I switch it on makes me think it must be quite close to the electrics rather than anything deeper inside the mechinisms themselves, there is no time for anything else to kick in.

Quote:

Self repair is inexpensive if you know what you’re doing, parts can be obtained from screw fix, B&Q etc. Bear in the mind that it is illegal to tinker with the Boiler systems, by anyone not certified as Gas Safe Registered, what used to be classed as CORGI. But this issue you’re having, is more electrical than gas.

Nah, I won't touch it unless it's very, very simple. The fact I don't actually know what the correct terms are or what anything is connected too proves I shouldn't be touching anything. I do want to understand the problem a bit better though so I am not taken for a ride by whomever I call in. I don't want this to be days of a plumber saying it's an electric problem and an electrician saying it's a plumbing problem. I have very bad luck with tradesmen. Central heating is an annoying hybrid of the two disciplines as well.

**Damien** · 31-12-2019, 17:38

Quote:

Originally Posted by Taf

The switch could be power for the changeover valve (switches water from the boiler between radiators and hot water tank). A photo would help!

But even that would not affect pressure, just where the boiler feed is going to.

The pressure is definitely down but only in the bathroom. Not the kitchen. I don't understand what could be stopping the heating system and the water pressure at the same time, hence why I thought it might be the pump.

Here is a picture:

SnoopZ · 31-12-2019, 17:49

My immersion heater is inside my tank with a switch like yours, the immersion heater in my house is ONLY to be switched on if my boiler is faulty, so it is always off.

I'm guessing you need a new element inside the tank and you should call a plumber in to find out.

You will probably get more help on a dedicated plumbing forum.

heero_yuy · 31-12-2019, 17:54

The cable coming out of the switch is certainly not man enough for an immersion heater. You need to trace where it goes.

**Damien** · 31-12-2019, 18:04

One of the cables going into a thermostat on the actual tank...

pip08456 · 31-12-2019, 18:18

Quote:

Originally Posted by SnoopZ

My immersion heater is inside my tank with a switch like yours, the immersion heater in my house is ONLY to be switched on if my boiler is faulty, so it is always off.

I'm guessing you need a new element inside the tank and you should call a plumber in to find out.

You will probably get more help on a dedicated plumbing forum.

New element is an electricians job.

**Hugh** · 31-12-2019, 18:34

Slight tangent - is your current accommodation rented or owned/mortgaged?

Might make a difference with optimal solution - when I replaced my old boiler with a combi boiler, my gas bill dropped by 30%;.

**Damien** · 31-12-2019, 18:38

Rented

heero_yuy · 31-12-2019, 18:49

Get the landlord to sort the issue. It's what you pay rent for.

Taf · 31-12-2019, 18:49

Quote:

Originally Posted by Damien

Rented

Ask your landlord to claim for a combi boiler upgrade. Often free, and many landlords don't know about the various schemes.

I take it your hot tank is fed from a header tank in the attic? Maybe that is not filling properly? And if it doesn't, the immersion element would overheat and trip very quickly.