my consumer unit keeps tripping

Postby dj1969 » Sun Jan 11, 2009 10:50 pm


im hoping someone here can give me some advice with the following. i moved into my 1 bed flat last summer and its all elec (no gas) so i invested in 2 'all singing all dancing' (so i thought) electric heaters, 1.2kw and 2kw to heat my lounge & bedroom. they simply plug in and run off a 13amp plug. not only have i found that they are very expensive to run and dont actually give out that much heat unless they are on all the time, when i actually use them, if my immersion tank goes on at the same time all my sockets trip.

obviously i can set the timer on my immersion to come on in the early hours of the morning (when the heaters are not on) but im wondering if this is ok and if its only on for 2 hours if the water will stay hot for use the following evening.

any advice would be much appreciated.

thanks :)
Posts: 3
Joined: Sun Jan 11, 2009 10:39 pm


Simply Build It

Postby ericmark » Mon Jan 12, 2009 11:19 am

A number of points.
1) Immersion heater should be on it's own circuit not on ring main.
2) Cisterns should be lagged so how long it needs to be on will depend on how much water is used.
3) 1.2 + 2 = 3.2Kw = 14 amp this is not that much power for immersion heater most likely 3kw = 13 amp to trip i.e. total of 27 amp seems odd as 32 amp is normal size to supply a ring main.
So I would want to further check what is going on. Maybe getting an electrician to look at it will find some other reason for tripping other than pure load?

Postby dj1969 » Mon Jan 12, 2009 3:23 pm

hi ericmark

thanks for the reply :)

it looks like the immersion is running off my main socket ring as this goes out when it trips and its the socket one that goes off. the fuses on my distribution board are as follows;
shower 32amp
hob 32amp
kitchen sockets 32amp
lights 6amp
sockets 20amp (which now makes sense if it trys to use 27amps per below)

i'll try to find an electrician locally who actually knows what they're talking about, as the guy who did some work for me recently, and supposedly checked everything out, obviously didn't !!

thanks again.
Posts: 3
Joined: Sun Jan 11, 2009 10:39 pm

Postby ericmark » Mon Jan 12, 2009 6:52 pm

Now with a little more info things start to make more sense.
You show hob and kitchen sockets on 32A MCB so maybe you can use either a socket built into hob or kitchen ring main for one of the heaters.
Pure maths
1.2Kw = 5.217391 Amp
2Kw = 8.695652 Amp
3Kw = 13.04348 Amp
So if any heater is powered off kitchen then likely it will not trip.
The other sockets are on a radial I should think and 20A will be correct.
Immersion should not really be on with sockets but cost of changing my be something you will not want to pay for.

Postby dj1969 » Mon Jan 12, 2009 8:48 pm

thank you so much Eric, its all starting to make sense to me now !

i can finally do the calculations between kw and amp and understand what my 'big' appliances actually need to run, and ensure they're on the right ring.

at least next time an electrician comes round i will have some idea of what needs to be done.

thanks again :)
Posts: 3
Joined: Sun Jan 11, 2009 10:39 pm

Postby ericmark » Tue Jan 13, 2009 12:43 pm

He may be able to fit a socket from kitchen ring that you can use else where for the heater with less fuss then new supply to immersion heater? Although the immersion should be on it's own circuit if this involves a lot of work then a little common sense and thought is required to find a method with low cost and disruption.
I am sure he can find a way

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