Fuse keeps blowing

[coylesy]

Hi folks,

A 30 amp fuse on my consumer board keeps blowing when both the boiler (oil fired) and power shower are switched on at the same time. The fuse does not blow when the devices are used independently. Both the burner on the boiler and shower are newly fitted devices. Any suggestions?

 

[ban-all-sheds]

My suggestion is that the combined load is too high for a 30A fuse.

To confirm - when you say "power shower" do you mean a pump, or an instant-heat type?

Who fitted the appliances? What certificate(s) did you get?

 

[wingcoax]

Have you checked if both circuits are wired to the same fuse? may sound silly but i have come across jobs where these things are linked in a j b or fused spare. If both wired to same fuse do you have a spare fuseway in your consumer unit? if so move one cable to the spare and fit the correct rated fuse.Not forgetting to switch the mains switch off first.

 

[ricicle]

If both wired to same fuse do you have a spare fuseway in your consumer unit? if so move one cable to the spare and fit the correct rated fuse.Not forgetting to switch the mains switch off first.

An assessment of the circuit parameters for suitability of a protective device will be required and testing of the new circuit.

 

[ericmark]

Hi folks,

A 30 amp fuse on my consumer board keeps blowing when both the boiler (oil fired) and power shower are switched on at the same time. The fuse does not blow when the devices are used independently. Both the burner on the boiler and shower are newly fitted devices. Any suggestions?

Something wrong! Power shower around 5 amp and boiler around 3 amp and fuse 30 amp will take quite an overload to blow.

I am sure either it is not a power shower but an electrical heated shower or it's not a fuse but a RCBO if the later it will look like a switch with B32 marked or something similar and a test button.

Either you have a neutral earth fault if not fuse but RCBO controlling or it is not a power shower but standard electric shower and it is an over load.

There should be installation certificates for both and completion certificates and something on the shower to say what size it is. I would expect if power shower and boiler each will also have a fused connection unit which should have a fuse in. About 3A for boiler and around 5A for power shower although the latter may be 13A. Please come back with more information as it seems something is wrong with what you relate.

 

[maltaron]

Oil Boiler only takes less than an amp (normally 50watts) plus a bit for the CH pump, so I would assume that the two are on the same fuse and the shower is on the limit of the 30 amp fuse. In any case the boiler should be on its own FCU fused at 2amp.

 

[Chri5]

Bets are on

1-2 that it's a electric heated shower with pump


Could you confirm the model of the shower unit / pump or better still google it and confirm back the load (amps) that the unit uses.

 

[ban-all-sheds]

And start tracking down the twonk that installed them - you need to get him back to put right his mistakes.

 

[coylesy]

Thanks for the replies,

The shower is a power shower, not heated (Mira event XS non thermostatic).

Appliance power supply – 230–240 V, 50 Hz, fused at 3 Amps, via a double pole switched fused connection unit (not supplied) with a minimum 3 mm contact separation in each pole.

The boiler and shower wiring were all in place when the house was bought and the original units just replaced so no actual installation of cabling etc took place. The original units had been working fine for a while but then both packed in (after a long period of non use). This was noted by an electrician who was originally called because the fuse was blowing repeatedly. He said there were faults in both the shower and boiler, hence the replacements.

What is even stranger is that after switching the power off to change a light switch, upon turning the power back on the fuse in question blew (30 AMP FUSE, NOT LIGHT FUSE). I turned everything off, killed the power, replaced the fuse and turned it back on again. All are working with the exception of a double socket on the same circuit and the shower? This has further added to my confusion so I’ve called an electrician. I’m at a loss… All further suggestions are welcome!

 

[MTE]

All are working with the exception of a double socket on the same circuit and the shower?

Was there anything plugged into the sockets at the time? You don't want a socket on the same circuit as shower and boiler. It could be that an appliance fault in the sockets could be causing the fuse to blow. Extension leads are especially suceptible to this regular tripping.
May not be but definitely worth looking at.

 

[JohnD]

Looks like a wiring fault or error.

have you answered ...

Who fitted the appliances? What certificate(s) did you get?

 

[josh1e]

might be misleading. but from what i've read - if i understand you right.

the fuse tripped previously
both appliances were replaced at the recommendation of the sparky
the fuse still trips even after the spark replaced them

if that's the case then can you get a refund on the work done so far as there may have been no fault with them - prooven as the fault still exists.

also the fault maybe with a socket / spur or device taken from the wiring somewhere in the house, for example a loft light, socket in the loft for a tv aeriel amplifier, air conditioning unit in the loft / on the wall outside etc etc etc...

if the appliances have already been replaced & the fault hasn't cleared then i would be chasing the person who told me to replace them and chasing the cables on that circuit to see if the previous homeowner connected anything that maybe hidden / not obvious.

hth

 

[coylesy]

thanks folks,

no certificates a it was a mate (plumber/boiler engineer) who swapped the appliances. strange thing was that before they were switched the fuse was blowing everytime the power was switched on at the board. it only seems to blow now when both are on at the same time? electrician should be round by the end of tomorrow so it'll be interesting to hear what he reckons.

as for the sockets, there are at least three sockets on that circuit along with the shower, boiler, circulating pump and extractor fan. appliances plugged in are coffee maker, micro, toaster and washing machine. i read somewhere that fuses can deteriorate before blowing. do you think that maybe having to much stuff on the same 30a circuit is just too much and eventually the fuse is going bye bye?

anyways, i've said to the spark that whatever need done needs done. it's doing my head in and this last socket and shower problem is about to push me over the edge! i'll have to see what happens. thanks for the help!

 

[josh1e]

I'm not sure about regs for the circuits, but i've never known sockets to be on the same circuit / fuse as the shower. (except for sometimes the shower pump & fan)

are you sure they are on the same fuse / circuit?

it seems a huge load if the shower, boiler, washing machine, coffee maker & toaster are all on there. theyre all quite high usage appliances, not like a lamp or adsl modem etc..

I would speak to the spark & see if it's worth getting everything else removed from the circuit. sockets should be on there own trips, and it maybe opportunity to tidy it up for future problem solving...

i'm only a diy'er but to have all that on 1 circuit seems very unnatural mate. it might just be the trip is simply overloaded. have you tried unplugging everything & then running the shower / boiler? maybe the sockets were added after the original circuit installation?

 

[coylesy]

yeah, you're probably right. i think the house has been wired poorly. all that stuff is def on the same circuit rated at 30 amp(kitchen/bathroom/utility sockets plus boiler etc). another ciruit (30amp) for the living room sockets and a 30amp for the cooker which is prob a bit small for it? then a 15 or 20 for the immersion and two fives for the lights. i think some rewiring may be in order... anyone want to buy a house?!