UK Gas Cooker conked and electrical cooker replacement

advicewelcom · Nov 5, 2021

Hi, quick posting - welcome any advice as new to this stuff...

Have a Howden HJA 0150 gas grill/oven with a broken thermostat that and can't get a replacement (grill igniting but no gas coming out of oven burners when on).

The Howden grill/oven is on a ring in the kitchen which has following appliances on it:
-microwave
-fridge freezer
-kettle
-toaster
-a Howden gas hob
-the busted Howden grill/oven
-couple of kitchen sockets generally not used

It all goes back to a RCD with a fuse that says - MTN132 b32 hanger fuse

There is an electrical wall connection for the grill/oven, with (I think) a 6mm wire for the ring (and not the thicker 10mm wires used for showers).

I may want to replace with just an electrical gill/oven. So some questions...

-Is there is max kilowatt oven that I could just wire into the current wall socket (which is used for the current grill/oven electrical ignition connection)?

-Would I need to replace the fuse in the RCD for the main? And is so with what?

-Would these things ensure the fuse would not trip if the oven was switched on?

-There are lots of electrical ovens but the instructions say they should be wired directly to the fuse box, so wondering if there is one which can just run from this ring main (if I upgrade the fuse)?

Would hate to buy an electrical oven and then its a nightmare and expense to fit it (the fuse box is currently full).

Welcome advice.

(attached pic of gas connection, and wall sockets for hob and grill/oven)

advicewelcom · Dec 17, 2021

Oh poo. RCD flipped off and is not switching back on. I can put things to what they were before and try it, but if RCD stays off, any ideas?

DPG · Dec 17, 2021

Are the 2 circuits fed from different RCDs?

advicewelcom · Dec 18, 2021

Pic of the one RCD with Boiler Radial and Kitchen circuit off.

RCD failed when removing the twin socket and re-connecting the kitchen circuit (pics in next posting). I don't think it would reset even when I turned the Boiler and Kitchen circuit off (but that could be me not pressing it hard enough to reset it).

advicewelcom · Dec 18, 2021

Before & after pics attached of wiring adjustments when RCD went off.

PIC 1. BEFORE circuit before changes
-Boiler radial circuit (pretty sure only boiler)
-Twin sockets on ring to HOB FCU and to other kitchen sockets
-Switched HOB FCU has supply, connections to HOB and back to ring (3 wires)
-Noted that the earths on Twin socket are on different ends
-Pretty sure this IS a kitchen ring as tested it

PIC 2. AFTER circuit changes
-Just connected the kitchen circuit ring up without twin sockets

Why did RCD go off?

If you connect the earths together does the RCD go pop? Just don't get it.

Avo Mk8 · Dec 18, 2021

advicewelcom said:
If you connect the earths together does the RCD go pop? Just don't get it.

I said I wouldn't

The twin socket presumably has the two earth terminals visibly strapped together?

I don't immediately see the electrical difference between the two configurations you show. I don't get it either!

You know the RCD will stay tripped if N & E somehow get connected together, even when the two MCB's you are using are off?

You might try lifting the N feed to the boiler (with it off!) just to make sure another fault hasn't appeared in the meantine, and see if you can reset the RCD.

And finally, you haven't connected the cooker in the meantime by any chance have you? If so that's another avenue!

advicewelcom · Dec 18, 2021

Avo Mk8 said:
I said I wouldn't

Was your idea to plug the washing machine to the twin socket, your on the hook at the moment ;-)

Avo Mk8 said:
The twin socket presumably has the two earth terminals visibly strapped together?

OK, well I think that means they are connected within the socket and defo not the source of the issue.

Avo Mk8 said:
I don't immediately see the electrical difference between the two configurations you show. I don't get it either! You know the RCD will stay tripped if N & E somehow get connected together, even when the two MCB's you are using are off?

Ah Ok, could be a short between N and E then eh? I could try taking off the twin socket only (not messing with the other sockets) and trying again with the terminal block connector and see if I get the same result. I only realised the RCD tripped when someone mentioned the upstairs sockets were off - so it wasn't really event driven by me turning something on - just seemed to quietly happen by itself.

Avo Mk8 said:
You might try lifting the N feed to the boiler (with it off!) just to make sure another fault hasn't appeared in the meantine, and see if you can reset the RCD.

I heard that lots of RCD un-correctable trips are due to boiler connections. It an old boiler so it could be something loose. You're saying to pull off the neutral on the boiler FCU connection and see if that stops tripping when using the terminal connection block to by-pass the twin sockets?

I did think I saw a 5v AC reading across the terminals of the boiler FCU even when everything was off (which was a bit weird) - pic attached.

Even if I got it working - I would have a twin socket into the boiler FCU, and would the current 3A fuse in the boiler FCU have to be replaced with a 13A fuse as it now has twin socket connected with a washing machine plugged in? Is that going to create an issue? That FCU fuse is pretty vital, it blows, no heating during winter.

Avo Mk8 said:
And finally, you haven't connected the cooker in the meantime by any chance have you? If so that's another avenue!

The oven is always connected and has never tripped anything else, The grill on it works fine and the issue is the gas thermostat knob, but I could switch it off from its wall FCU to rule it out when testing.

Avo Mk8 · Dec 18, 2021

advicewelcom said:
Ah Ok, could be a short between N and E then eh? I could try taking off the twin socket only (not messing with the other sockets) and trying again with the terminal block connector and see if I get the same result. I only realised the RCD tripped when someone mentioned the upstairs sockets were off - so it wasn't really event driven by me turning something on - just seemed to quietly happen by itself.

If you inadvertently touched N & E together while doing the changes, that would likely have tripped the RCD. That's normal behaviour and in itself nothing to worry about. But you give the impression you couldn't then reset the RCD, which implied there might be a further problem. If you can reset the RCD, and it stays reset, all should be all OK.

advicewelcom said:
You're saying to pull off the neutral on the boiler FCU connection and see if that stops tripping when using the terminal connection block to by-pass the twin sockets?"

yes

advicewelcom said:
I did think I saw a 5v AC reading across the terminals of the boiler FCU even when everything was off (which was a bit weird) - pic attached.

Probably a capacitatively coupled voltage from the house wiring, and since the meter is high impedance, it gives a reading. Once you put any sort of load on, it would disappear. You see this mentioned on this forum sometimes.

advicewelcom said:
Even if I got it working - I would have a twin socket into the boiler FCU, and would the current 3A fuse in the boiler FCU have to be replaced with a 13A fuse as it now has twin socket connected with a washing machine plugged in? Is that going to create an issue? That FCU fuse is pretty vital, it blows, no heating during winter.

You're confusing yourself! You have a 20A radial from the 'fuse board' which you should connect directly to both the twin socket and the input to the fcu. Do not connect the twin socket to the boiler side of the fcu!

You don't need to change the fuse, leave as is.

advicewelcom said:
The oven is always connected and has never tripped anything else, The grill on it works fine and the issue is the gas thermostat knob, but I could switch it off from its wall FCU to rule it out when testing.

Sorry I was meaning if you had bought a new electric oven and connected it. They occasionally cause this sort of problem. Ignore this.

Hope you sort it.

marconi · Dec 19, 2021

Good morning. MAy I ask some questions please?

1. Does the rcd trip when the washing machine is unplugged?

2. How, step by step, do you re-apply power? eg: all mcbs and RCD are on and i use the red main switch. Or. the main switch is on as are all the mcbs and I use the RCD. Or, the two mcbs in question are off and the RCD is off, the main switch is on and I then I turn on the RCD. Or, MAin switch is on, RCD and two mcbs are both off, and then I turn on the RCD and then the 20A mcb and then the 32A mcb?

3. Turn off red main switch and then CArefully remove lid of the consumer unit and take a photo of the wiring top and bottom of the RCD and then put the lid back on. DO NOT PUT YOUR FINGERS INSIDE!!!

4. With your multimeter set to the highest ac voltage range measure the voltages between:

a. earth of left hand FCU and the earth of the double socket to its right.

b. earth of the double socket and the securing screw of the FCU which switches the socket below for WM.

5. With Main Sswitch Off and your MM set to low ohms setting measure the resistance between:

b. earth of LH FCU and boiler pipes.

c. boiler pipes and a securing screw of the FCU which switches the socket for washing machine.

d. the securing screw of the FCU and a securing screw of the socket for the washing machine.

e. Between the pins of the plug of the washing machine L-N, L-E and N-E.

advicewelcom · Dec 19, 2021

marconi said:
Good morning. MAy I ask some questions please?

1. Does the rcd trip when the washing machine is unplugged?

Hi, yes, the washing machine was off and out of the twin socket when changing the wiring. I suspect this is me being careless with the N and E as mentioned before, but I have to go in with a testing approach (hopefully today) to try again.

marconi said:
2. How, step by step, do you re-apply power? eg: all mcbs and RCD are on and i use the red main switch. Or. the main switch is on as are all the mcbs and I use the RCD. Or, the two mcbs in question are off and the RCD is off, the main switch is on and I then I turn on the RCD. Or, MAin switch is on, RCD and two mcbs are both off, and then I turn on the RCD and then the 20A mcb and then the 32A mcb?

Will be mindful of this on the 2nd testing, but the last time

Main switch was on
RCD was on
Two circuits for boiler and kitchen ring were off

Did was wiring changes, then was told sockets were not working upstairs - went to check and found the RCD tripped and unable to reset until I changed the wiring back to what it was before.

marconi said:
3. Turn off red main switch and then CArefully remove lid of the consumer unit and take a photo of the wiring top and bottom of the RCD and then put the lid back on. DO NOT PUT YOUR FINGERS INSIDE!!!

Okay - should be able to do that, bit tricky to get the cover off, but can do it carefully, understand there is live connections via the tails (I think) so not touch anything inside.

With the below I assume u mean the securing screw of the wire inside and not the silver securing screws of the socket visible outside.

marconi said:
4. With your multimeter set to the highest ac voltage range measure the voltages between:

a. earth of left hand FCU and the earth of the double socket to its right.

OK - V's between Boiler FCU Earth to double socket Earth

marconi said:
b. earth of the double socket and the securing screw of the FCU which switches the socket below for WM.

*There isn't a FCU for the WM twin socket? - I think you mean Volts across Twin socket Earth to HOB FCU Earth (pic attached)

marconi said:
5. With Main Sswitch Off and your MM set to low ohms setting measure the resistance between:

b. earth of LH FCU and boiler pipes.

Ok - Ω's between Boiler FCU Earth to Boiler pipes

marconi said:
c. boiler pipes and a securing screw of the FCU which switches the socket for washing machine.

OK - Ω's between Boiler pipes and Twin socket Earth (I assume)

marconi said:
d. the securing screw of the FCU and a securing screw of the socket for the washing machine.

OK - Ω's between HOB FCU Earth and Twin Socket Earth

marconi said:
e. Between the pins of the plug of the washing machine L-N, L-E and N-E.

OK - Ω's between washing machine plug pins L-N, L-E, N-E

*Welcome to clarify the above.

Can add this approach to the general test strategy if I have the same problems when trying again with the wiring.

advicewelcom · Dec 19, 2021

Avo Mk8 said:
You're confusing yourself! You have a 20A radial from the 'fuse board' which you should connect directly to both the twin socket and the input to the fcu. Do not connect the twin socket to the boiler side of the fcu!

Just have to clarify this (PANIC STATIONS).

You are saying to connect from the Boiler FCU supply input to the TWIN SOCKET?

Think you're saying don't connect from the FCU output going to the boiler.

Attached a diagram of potential new wiring - is this correct? - wire from the Twin socket into the Boiler FCU Live, Neutral & Earth Supply connections??

And terminal block connect the incoming 32A ring supply to the HOB FCU??

DPG · Dec 19, 2021

This really does need an electrician getting in.

advicewelcom · Dec 19, 2021

DPG said:
This really does need an electrician getting in.

Try getting one, and then try dealing with the risks with virus in the household. I think I will have get elecy if it keeps tripping out. But will try the below first...

GENERAL TEST APPROACH
-Do wiring again and careful of N & E shorts
-Check the RCD
-If tripping lift Boiler FCU Neutral to boiler and see if can reset RCD

If still have tripping issues:
-Check whats going off and how in fuseboard
-Take photo of fuseboard circuit
-Do some MM testing with fuseboard

... seem ok?

marconi · Dec 19, 2021

OK - V's between Boiler FCU Earth to double socket Earth

The fact that you measure a voltage albeit small between the earth conductor of the boiler fcu and the earth conductor of the double socket on the right indicates a break in continuity of an earth conductor (more correctly circuit protective conductor cpc). This fault could be on the ring or on the radial to fcu or both. If the cpc between the fcu and the consumer unit and the cpcs of the ring back to the cu where complete and connected correctly then no voltage can exist between the boiler and double socket cpcs because they are effectively joined together. This state of affairs can cause an rcd to trip.

Time to call in a sparks with the right test equipment.

You can forget about taking the lid off the cu.

advicewelcom · Dec 19, 2021

marconi said:
OK - V's between Boiler FCU Earth to double socket Earth

The fact that you measure a voltage albeit small between the earth conductor of the boiler fcu and the earth conductor of the double socket on the right indicates a break in continuity of an earth conductor (more correctly circuit protective conductor cpc). This fault could be on the ring or on the radial to fcu or both. If the cpc between the fcu and the consumer unit and the cpcs of the ring back to the cu where complete and connected correctly then no voltage can exist between the boiler and double socket cpcs because they are effectively joined together. This state of affairs can cause an rcd to trip.

Haven't measured anything yet, assume this Earth to Earth V measurement test is to be done before any wiring changes to the Boiler radial and Kitchen Ring (seperate circuits) - and should come back with a 0v if there is no break in continuity.

Avo Mk8 · Dec 19, 2021

advicewelcom said:
Just have to clarify this (PANIC STATIONS).

You are saying to connect from the Boiler FCU supply input to the TWIN SOCKET?

Think you're saying don't connect from the FCU output going to the boiler.

Attached a diagram of potential new wiring - is this correct? - wire from the Twin socket into the Boiler FCU Live, Neutral & Earth Supply connections??

And terminal block connect the incoming 32A ring supply to the HOB FCU??

Yes. The 20A circuit is a 'radial', and you can feed multiple accessories (within reason) by daisy-chaining them. It's not the same as a ring.
So you connect the twin socket to the 2.5mm cable going into the boiler fcu, not the fused output of the fcu.
Live coming into fcu goes to live of twin socket, etc.

And then that fcu is left feeding the boiler exactly as it was before, same fuse, unchanged wiring on the output.

brianmoooore · Dec 19, 2021

Do we know if the boiler spur circuit is RCD protected?

advicewelcom · Dec 19, 2021

brianmoooore said:
Do we know if the boiler spur circuit is RCD protected?

Yes, RCD off and no supply goes to boiler.

DPG · Dec 19, 2021

advicewelcom said:
Yes, RCD off and no supply goes to boiler.

Are the circuits in question protected by an RCD though?

advicewelcom · Dec 19, 2021

If you have a bit of spare 3 core wiring in which the earth does not have a sleeve, is that okay to use to connect the twin socket to the boiler FCU?

westward10 · Dec 19, 2021

As already stated whilst forum is happy to help the DIYer it has to draw the line at step by step guidance. This task is way out of your comfort zone and the pic in #51 demonstrates this because the back box with the block connectors floating about in it is no longer earthed. Because you have interfered with the existing wiring you now have an rcd tripping with no idea as to why so I suggest you reinstate what you have altered and call an electrician.

advicewelcom · Dec 19, 2021

westward10 said:
As already stated whilst forum is happy to help the DIYer it has to draw the line at step by step guidance. This task is way out of your comfort zone and the pic in #51 demonstrates this because the back box with the block connectors floating about in it is no longer earthed. Because you have interfered with the existing wiring you now have an rcd tripping with no idea as to why so I suggest you reinstate what you have altered and call an electrician.

Needs must, there is a pandemic on and not allowed to bring others in, moreover its turkey time soon.

Not sure your analysis is on the mark as rewired it with a bit of 3core and RCD was fine. I suspect the Neutral and Earth were touched in first attempt (which I understand trips RCD).

(PIC ATTACHED) It don't look pretty, I assume I need a bit of neutral sleeving, perhaps wrap the terminal block up in insulation tape, and feed the connecting wire through the back box hole instead?

Just hoping its connected okay and experts on this group are happy with it - as have an oven to order. So very happy and thankful if its gets a thumbs up with any changes needed?

westward10 · Dec 20, 2021

That box is not earthed. It would be unwise to advise you further you need an electrician covid or not to assess your situation.

advicewelcom · Dec 20, 2021

westward10 said:
That box is not earthed. It would be unwise to advise you further you need an electrician covid or not to assess your situation.

Dying of Covid is nothing we can do about on this forum, dying from electrical shock is ;-) Good suggestion, I can fit a fly lead but looks like its been discussed quite a bit and seems not required by the regs as earthing happens through the lug for recessed back boxes (@ 2:22). Looks more applicable for surface mounted boxes.

telectrix · Dec 20, 2021

advicewelcom said:
Dying of Covid is nothing we can do about on this forum, dying from electrical shock is ;-) Good suggestion, I can fit a fly lead but looks like its been discussed quite a bit and seems not required by the regs as earthing happens through the lug for recessed back boxes (@ 2:22). Looks more applicable for surface mounted boxes.

earthing back boxes was made optional around 2005 under the 16th.however, most of us prefer to earth them for the simple reson that if the faceplate is removed for any reason, you lose the earth through the faceplate oins so the back box could become live if a fault developed.

westward10 · Dec 20, 2021

telectrix said:
earthing back boxes was made optional around 2005 under the 16th.however, most of us prefer to earth them for the simple reson that if the faceplate is removed for any reason, you lose the earth through the faceplate oins so the back box could become live if a fault developed.

It looks like it is going to be blanked hence it needs an earth. Many electrcians to the exact same thing.

UK Gas Cooker conked and electrical cooker replacement

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