Would you code a 60 amp main switch been fed from a 100 amp BS1361

[mpb]

I carried out a EICR and the main switch for the consumer unit is only rated at 60 amps and the main supply fuse is a BS1361 rated at 100 amps.

Im thinking this should be a C2, what are your thoughts please.

Many thanks

Martin

 

[nickblake]

How do you know it's 100 amps , very rare to get a domestic fuse at that rating normally 60 or 80 amps

 

[davesparks]

I carried out a EICR and the main switch for the consumer unit is only rated at 60 amps and the main supply fuse is a BS1361 rated at 100 amps.

Im thinking this should be a C2, what are your thoughts please.

Many thanks

Martin

What is the potential danger you have identified?

 

[mpb]

How do you know it's 100 amps , very rare to get a domestic fuse at that rating normally 60 or 80 amps

It's a shop and I had to pull the fuse to change the main board and this board is Economy 7.

 

[HandySparks]

It's a shop and I had to pull the fuse to change the main board and this board is Economy 7.

If it's E7, then it's likely to have a fixed load. What is the actual load?

 

[7029 dave]

If you have changed the board/ cu it will be 100amp anyway.?

 

[mpb]

What is the potential danger you have identified?

I was thinking the potential danger is the switching capacity isn't high enough in case of a fault.

 

[mpb]

If you have changed the board/ cu it will be 100amp anyway.?

Haven't changed this board. I want to change it but need to discuss it with the owner but he doesn't like spending money.

 

[davesparks]

I was thinking the potential danger is the switching capacity isn't high enough in case of a fault.

That's not a danger, that is a fact about the inadequacy of the equipment.
What situation can you imagine where the main switch will be required to break fault current?
What is the total load on the board? Is it a fixed load or variable?

 

[davesparks]

Haven't changed this board. I want to change it but need to discuss it with the owner but he doesn't like spending money.

You want to change it? I hope that is just a lapse of concentration and not a serious comment!

 

[mpb]

That's not a danger, that is a fact about the inadequacy of the equipment.
What situation can you imagine where the main switch will be required to break fault current?
What is the total load on the board? Is it a fixed load or variable?

There a four 3kw storage heaters on this board. So a load of 52 amps been drawn.

So the load is under the 60 amp rating of the main switch.

 

[7029 dave]

There are thousands of cu's out there with 60 amp dp switches backed by 100amp service fuse.

 

[telectrix]

you can't do anything till you've assessed the load on this CU. get the clamp meter out at midnight.

 

[mpb]

So I should code it as a C3 improvement recommended.

 

[davesparks]

There are thousands of cu's out there with 60 amp dp switches backed by 100amp service fuse.

That doesn't necessarily make it right though. There are thousands of 3036 CUs with a bit of 2.5 in place of the fusewire too.

 

[davesparks]

So I should code it as a C3 improvement recommended.

What is the improvement you recommend? How could you improve on a 60A switch being used for a fixed 52A load?

 

[telectrix]

There a four 3kw storage heaters on this board. So a load of 52 amps been drawn.

So the load is under the 60 amp rating of the main switch.

which heaters are thermostatically controlled, so the full 52A will only be seen when they first switch on. therefore, no code.

 

[7029 dave]

Yeah true, as stated if he is worried clamp the full load current, doubt if pulling more than 60amps.

 

[mpb]

I see your thinking now, so I won't code this.

Sometimes I need to stand back and look at what I'm seeing and thinking from a different angle.

Thank you for your advice.

Martin

 

[telectrix]

I see your thinking now, so I won't code this.

Sometimes I need to stand back and look at what I'm seeing and thinking from a different angle.

Thank you for your advice.

Martin

no problem. the consultancy invoice is in the post. :smilewinkgrin:

 

[Dave OCD]

There a four 3kw storage heaters on this board. So a load of 52 amps been drawn.

So the load is under the 60 amp rating of the main switch.

They'll most likely be 3.4Kw [or 2.55] so you're over 59 amps at 230volts if they're the larger heaters.

 

[davesparks]

I see your thinking now, so I won't code this.

Sometimes I need to stand back and look at what I'm seeing and thinking from a different angle.

Thank you for your advice.

Martin

Whether you code it or not is your decision.
When deciding on coding an observation you will find it helps to ask yourself the same questions I have done above. For C1 'what is the immediate danger here?', C2 'what is the potential danger?' for C3 'what improvement do I recommend/can this situation be improved?'

 

[davesparks]

They'll most likely be 3.4Kw [or 2.55] so you're over 59 amps at 230volts if they're the larger heaters.

But we don't have 230V supplies and the stated power of the heaters will be at 240V, the power dissipated will be less at 230V.

 

[Dave OCD]

Well 230v is the declared single phase voltage throughout the country now even though nothing has really changed [apart from the network becoming ever more stretched to the limit] so that's what we have to base calculations on, I see what you're saying about the heaters though.

 

[7029 dave]

I have never seen the voltage at 230v, and am measuring everyday, the lowest I have seen it is 235v. Never seen 216v, but 250v yes. 315v but that was ug fault lol

 

[davesparks]

Well 230v is the declared single phase voltage throughout the country now even though nothing has really changed [apart from the network becoming ever more stretched to the limit] so that's what we have to base calculations on, I see what you're saying about the heaters though.

That is not the declared voltage, it is the nominal voltage, something which some jobsworth in an office has written down and is impossible to implement. Nothing has changed because it cannot be changed, the whole country has substations with their output fixed at 250/433, there's nothing any jobsworth penpisher can do about that!
It doesn't change the basic physics though, If the stated power rating is at 240V you cannot just replace 240 with 230 in the calculation. The power dissipated will be less at 230V so the current which flows will be less.

 

[Risteard]

I have never seen the voltage at 230v, and am measuring everyday, the lowest I have seen it is 235v. Never seen 216v, but 250v yes. 315v but that was ug fault lol

Here I regularly measure bang on 230V.

 

[davesparks]

Here I regularly measure bang on 230V.

I thought I was measuring that kind of voltage around here a little while ago, my first reaction was to check the tester against another one, sure enough it had wandered off by around 10 volts and the actual voltage was >240

 

[Risteard]

Ironically the supply here was always 230V unlike the 220V in the south of Ireland and the 240V in Britain, and so harmonisation had no effect here!

 

[Dave OCD]

That is not the declared voltage, it is the nominal voltage, something which some jobsworth in an office has written down and is impossible to implement. Nothing has changed because it cannot be changed, the whole country has substations with their output fixed at 250/433, there's nothing any jobsworth penpisher can do about that!
It doesn't change the basic physics though, If the stated power rating is at 240V you cannot just replace 240 with 230 in the calculation. The power dissipated will be less at 230V so the current which flows will be less.

Yes DECLARED as the NOMINAL voltage, only because the distribution network is so stretched and it gives them more leeway, I often see low to mid 230s here in Cornwall. And what's a penpisher ? :wacko: