Water heater tripping fuse breaker

[spikeyv81]

Hi, i've done a quick search but not found anything relevant...

I have a combi boiler that provides heating and hot water. I also have a immersion tank. I've had these both switched on for the last 6 odd months because with 3 adults using the power shower in the morning water runs out very quickly.

Everything has been working fine until last two weeks the immersion heater has started to trip the fuse switch (15amp) I can switch it back on and all is well for a few hours before it trips again.

From what I can tell the boiler/timer and immersion tank are all on the same circuit as it all goes out when the fuse trips.

I've no idea whether this is correct or the load is far too much that setup was present when we bought the house, but I do notice every now and then when I flick wall socket switch a tiny spark but we've not had a probably for over 4 years...

Any advice even ones that is going to cost me a fortune! is appreciated.

 

[JohnD]

A combi provides hot water to taps, at mains pressure, by heating the incoming water from the main instantly, without needing a cylinder. It is extremely unusual to have a combi with a hot water cylinder. Which hot taps are fed from the combi, and which from the cylinder?

If your cylinder is heated by the boiler, then there is no need to turn on the electric immersion heater. The heat from electricity costs about twice as much as heat from gas, and the boiler will have about ten times the power of the immersion heater.

If you think one of the appliances is causing the trip, turn it off for a few days and see if the fault stops happening. If not, turn off the other for a few days.

What letters and numbers are on the thing that trips? Does anything else stop working apart from the boiler and the immersion heater?

 

[spikeyv81]

Hi and thanks for your reply.... sorry my knowledge on these things is very limited as you've already guessed. I thought it was a combi because it provides hot water for taps and was as central heating. From what the plumber told me we have water tanks (plastic) in the loft that holds water and is used by the power shower.
So I might be completely wrong about it being a combi.
I understand the cost immersion tank heating water but unfortunately at the moment its that or cold showers.

i've turned off the immersion tank and the problem has disappeared so i think it is down to this but im baffled as to why it has worked for 6 odd months only recently started to trip the fuse.

on the fuse box it such says 'Heating' and 15amp... when the fuse trips the timer (where i can set the program for hot water & central heating) turns off too and from what I can tell the boiler too, they all seem to be on the same circuit.

thanks again

 

[TicklyT]

Immersion heaters do not last forever.

Two common failures are:-

Soft water - the slightly acidic water corrodes the element jacket, which pinholes, so the innards of the heater get damp enough to pop the breaker.

Hard water - limescale builds up, causing local overheating of the element jacket, which then cracks, and the innards get damp that way.

If either has happened, it's time for a new immersion heater.

Adding a timer, set up so it just works for an hour or so when it's needed instead of running 24/7 can help improve the heater's longevity and keep your leccy bills in check

 

[JohnD]

A modern boiler should heat a modern cylinder in 20 minutes. If yours doesn't, put a description and some photos on the Plumbing & CH section.

Also run your shower into a bucket, time it, and see how many litres per minute it delivers.

Measure the height and diameter of the cylinder. How is it insulated?

An immersion heater has a trivial heat output.

If you have a cold tank in the loft, and a hot cylinder, and a pumped power shower, then you have almost certainly not got a combi.

Does the thing that tripped look like this?

http://i.ebayimg.com/t/Wylex-B15-BS...Aw/$(KGrHqZHJ!wE-dd40O8ZBPu4Yz82iw~~60_12.JPG

or this?

http://i.ebayimg.com/t/15A-Plug-MCB...QEWk~$(KGrHqEOKiEEyV2hTMDRBMpIbIbcLg~~_12.JPG

 

[spikeyv81]

thanks John you are right it's not a combi cold water tank in the loft.

add fire the fire it is the one in the second picture.

 

[JohnD]

OK. You can turn the power off and search for any signs of a damaged flex, or water dripping onto a switch or connector, but very likely you need a new Immersion Heater element. Old ones can be very difficult to get out without damaging the cylinder, but an experienced plumber who's been around a bit should be able to do it. Ask friends and neighbours for a recommendation. He does not need to be Gas Safe certified as he is not touching the boiler. I am not a pro plumber and I would prefer not to try as it can be rather difficult.

Round here the Incalloy sheathed elements have a long working life, but it will depend what sort of water you have in your area. The local plumber should know. the lowest priced ones are unlikely to be the best.

BTW you appear to have a Wylex Standard fusebox. Probably a cream plastic one but it might be dark brown or grey metal. It is pretty old now and it is impractical to add RCD protection to it. See if you can find a well-recommended local electrician to take a look and advise. ask him which Competent Person scheme he is in, and check him on their website. If he is properly qualified he will be pleased to be asked. If not you don't want him.

 

[spikeyv81]

thanks for the advice and your patients. I'll get a plumber I've used before his pretty good and also get an electrician in to look at the fuse box I think it was put in by the council as it's ex council maintained property.

I'm just baffled why it cuts out after a few hours as I would expect it to happen straight ... anyway I'll get the professionals in

thanks John