What size RCD for mainswitch

[nrg]

Hi

I recently visited a property who had an old style (Black with yellow button) RCD that was not functioning. It has an old re-wireable fuse board rated at 60amps for the main switch. I replaced the old RCD with a new one (customer didn't want a new CU) and tested to make sure it tripped as should an it did. My question is what size should I have installed (Ampage) when it has a 100amp 1361 Type II Service Head ?

Thanks

 

[Simonslimline]

What good is it asking after you have installed it anyway?

 

[nrg]

Because, as a conscientious electrician, I want to make sure that what I have done is correct. I thought this forum was here to help improve the quality of electrical installations in the UK. Sorry I must have got the wrong end of the stick !!!

 

[Octopus]

Did you complete an EIC?

 

[nrg]

Just doing it now which got me thinking .........

 

[Deleted member 26818]

You should use a device that is rated at or higher than the expected load.
You should have determined this value when you filled out the section in the EIC for supply characteristics.

 

[nrg]

Spin

Can you quantify that ? "You should use a device that is rated at or higher than the expected load."
So if I expect them to use no more than 45amps a 63amp RCD would sufficient ? What about the 100amp main fuse ? doesn't that come into it ?

 

[Silly Sausage]

What about the 100amp main fuse ? doesn't that come into it ?

Did you actually confirm it is a 100A fuse? :wink_smile:

 

[Deleted member 26818]

If there is a 100A main fuse, then it would suggest that the expected load is 100A.
However the fact that the service head has 100A on it does not necessarily indicate that the fuse within is 100A, that is just an indication of the maximum amperage the head is designed for.

 

[nrg]

Thanks guys

No didn't confirm that the head was actually 100amp but it was only installed about a month ago as part of a refresh program in our area. The property has minimal load, has gas central heating and only a single cooker & gas hob ! I have just spoken to Elecsa and they have advised that if it is a direct replacement then 63amps is fine if there was no sign over thermal damage. (which there wasn't) I am going back to do some other work for them on Friday so might just swap to 100amp and be done with it. Thanks again

 

[Deleted member 26818]

If the head was replaced recently, then the DNO should be able to inform you of the size of fuse installed.
One option would be to remove the fuse and have a look, though doing such is apparently frowned upon.
A bit surprised that the DNO did not offer a TN-C-S earth connection with the upgrade?

 

[Silly Sausage]

Another thought, what's the rating of the meter?
Mine's 80A and the guy put an 80A fuse in.

 

[Prat P]

Because, as a conscientious electrician, I want to make sure that what I have done is correct. I thought this forum was here to help improve the quality of electrical installations in the UK. Sorry I must have got the wrong end of the stick !!!

As a conscientious electrician you should have convinced them to change the rewirable board for an up to date version even just on economic principles,if the rcd had worn out through time it would be reasonable to assume the breakers,main switch and other control gear will be in a similar condition,for this reason I would have said Get a new board put in,its not going to cost that much extra anyway and imagine paying for a new rcd this week and then next week you need to replace the main switch.

 

[Silly Sausage]

As a conscientious electrician you should have convinced them to change the rewirable board for an up to date version..............................

Ey up, here we go again!!!

:smilielol5:

 

[Knobhead]

Another fully qualified rip off merchant.

If they didn’t want a new CU that is their choice, your choice is to do as you’re asked or walk away.

 

[Guest77]

Hi

I recently visited a property who had an old style (Black with yellow button) RCD that was not functioning. It has an old re-wireable fuse board rated at 60amps for the main switch. I replaced the old RCD with a new one (customer didn't want a new CU) and tested to make sure it tripped as should an it did. My question is what size should I have installed (Ampage) when it has a 100amp 1361 Type II Service Head ?

Thanks

That is called a voltage trip, there was never an RCD there, now you have installed one what is your next move ?

 

[Guest77]

Another fully qualified rip off merchant.

If they didn’t want a new CU that is their choice, your choice is to do as you’re asked or walk away.

Or take photos then walk away.

 

[Guest77]

Because, as a conscientious electrician, I want to make sure that what I have done is correct. I thought this forum was here to help improve the quality of electrical installations in the UK. Sorry I must have got the wrong end of the stick !!!

Fair enough and I don't intend to give you a hard time, in future do an assessment of the installation first though, you removed a voltage trip and stuck a 63 amp RCD in without really thinking about it, we all make mistakes, luckily this time it won't kill anyone.

 

[Silly Sausage]

There was never an RCD there, now you have installed one what is your next move ?

Post the Invoice?

 

[Prat P]

Another fully qualified rip off merchant.

If they didn’t want a new CU that is their choice, your choice is to do as you’re asked or walk away.

No I am not a rip off merchant I am simply being conscientious which was the point of my reply,I dont know what your job is but mine is a bit more complex than 'just do as your asked or walk away'..do customers know what is needed for their installation to be safe? No they do not,I only gave my legitimate opinion and I qualified my opinion with facts,i.e. Age of equipment,anticipated maintenance costs,additional labour..I think my decision to advise a new board is justifiable and I resent being referred to as a rip off merchant so kindly choose your words more appropriately or back your claim up.