Change to 32 RCD or leave it at 16 RCD

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have 6mm wire that used to feed my old cooker in the old kitchen that has become a utility room now. this was connected to 32 RCD at the CU. the cooker has been removed and i am using the circuit to feed the immersing element of DHW cylinder via 2.5mm flexi wire. the immersing element is 3kw and hence I replaced the 32 RCD with 16 RCD at the CU. now i am adding an electric oven next the DHW cylinder which will be fed from the 45amp wall plate that is currently feeding the immersing element. The oven is 3.6kw and will be connected via 6mm cable .
do i need to upgrade the RCD at the CU to 32 or just leave it at 16. in another words, can the 16 RCD at the CU feed both DHW cylinder and the oven?
 
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Think you need to sort out your terms.
I do not think you mean RCD. Probably you mean MCB? Or it could be an RCBO…
Does the 16/32 device have a test button??

Back to your query. The over current device in the consumer unit is there to protect the cable.
Your DHW element is 13amp so a 16AMP CPD will pop if you add a 16AMP oven to the same circuit.
Put the 32amp (whatever it is) back. You didn’t need to change it.

PS I would install a 13amp switched fused connection unit adjacent to the DHW heater. Needed for isolation.
 
Last edited:
many thanks for the speedy reply Tayler. yes i mean RCBO and it does have testing button.
the 6mm wire that is coming out of the 45amp wall plate is connected to the feed side of the switch with 13amp fuse. and 2.5mm flexi wire is connected from the load side of the switch to the DHW element.
what i am planning to do is to connect the e 6mm wire that is coming out of the 45amp wall plate to a junction box. Then this junction box will feed the DHW element switch via 2.5mm wire then the oven via 6mm wire. so it is better to put the 32 RCBO back, correct?
 
If you don’t put the 32amp RCBO back the 16AMP one will trip every time you have the DHW heater on and then switch on the oven.
You don’t want that to happen half way through cooking your roast chicken.

You shouldn’t need a junction box. Doesn’t the 6mm circuit terminate on a cooker wall plate?

I see you have a wall plate. So 2.5mm cable to the 13A FCU for the DHW.
The oven will probably come with a cable. Just connect that to the wall plate too. No additional junction box needed.
 
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If you don’t put the 32amp RCBO back the 16AMP one will trip every time you have the DHW heater on and then switch on the oven.
understood

You shouldn’t need a junction box. Doesn’t the 6mm circuit terminate on a cooker wall plate?
yes it does. but there is another 6mm cable coming out of the wall plate that used to feed the cooker. And this what i am using to feed both the oven and the DHW element as it is long enough and will be in-between the 2 appliances for convenience
 
OK.. Dont like junctions when they aren't necessary. Just make sure the junction is accessible and plenty big enough to terminate the 6mm plus the other two cables. Toolstation sell a 60A junction box that will do.

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