I work on a caravan site as the maintenance man. I need to wire in 5 more caravans. Need to put in another 100 amp fuse box. Not an issue installing etc, but my problem is there is a 100 amp breaker coming out of the generator at the start of the feed. A new feed is not an option. I need to make it fused at 200 amp at the start of the feed. Can not find standard 200 amp fuses so any help would be greatly appreciated. (Cable is 30mm armoured over 20m)
Fuse issue
- Thread starter James1985
- Start date
Help Support Talk Electrician Forum:
- Joined
- Nov 28, 2009
- Messages
- 14,661
- Reaction score
- 817
Have you heard about diversity? Just because you have a 100A rated consumer unit does NOT mean it WILL draw 100A and that 2 of them will draw 200A You need to look at how many circuits in total and what is the likely load taking into account diversity. What size mcb's feed each hookup point? What do you tell the site users is their allocated rating?
It must be some "generator" to be rated at 100A
It must be some "generator" to be rated at 100A
i suggest you get a sparky. you are way out of your depth with this. you cannot simply double the rating of the circuits OCPD just so you can pull double is design current, it will end up with needing a new cable once it goes bang
and you probably dont know what section 708 is either...
and you probably dont know what section 708 is either...
Last edited by a moderator:
The cable can handle 200 amp. Each caravan is on 20amp fuse. 5 caravans to a fuse box. It does trip on occasion so is near capacity of 100 amp most of the time. So need 200 amp
Yes it's a big generator smartass. 220 kva. 300 amps per phase
and what about volt drop once you double the load? what about Zs when you double the OCPD?
Welcome to the forum James.
Firstly, 30mm is not a standard cable size.
What size is, the existing cable?
The generator compensates for the load. She is nowhere near her limit yet. The cable is big enough for 200amp. Just need a bigger fuse than the 100amp mcb currently used on that run. Is this possible? Currently have 4 separate lines coming off the massive busbar. Each with 100amp mcbs running to fuse boxes powering 5 caravans each off 20amp fuses
Sorry. The size up from 25. We have been using 20mm and 25mm so thought next size up was 30
20mm doesnt exist either. 25mm does, however cable sizes area measured by their CSA, not their outer size, but of course you would already know that. wonder if youre from essex?
- Joined
- Nov 28, 2009
- Messages
- 14,661
- Reaction score
- 817
Just because each caravan has a 20A fuse (is it really a fuse or mcb) does not mean each caravan is drawing 20A all the time or the CU is at it's 100A capacity. You need to look up "diversity" And unless they are hooked up with 32a commando plugs, that's the wrong rating for a normal caravan 16A commando.
And we don't like bad language here thanks.
If you have a distribution board with a number of 100A mcb's and the generator can really supply the load, then the solution is not to bodge a fuse or mcb that's too high a rating for the board or the cable, but a completely new circuit from the main DB with a new cable of correct size to the additional consumer unit.
Last edited by a moderator:
I helped do the whole thing from start to finish. 90 mm coming from the generator to the busbar. 25mm to 1 of the fuse boxes (further away). 20mm to the other 2. The cable i am talking about is bigger than the 25mm. The sparky i helped said it's good enough to run another 5 at a later date. That date is now and my boss won't pay a sparky to do it. If your not going to help y are you commenting?
you could always try looking up electricity at work act. you are not competent to be doing the work. also look at 134.1.1 in 7671 (not that you will have a copy or even know what that is anyway)
They are wired straight into internal fuse box as 16amp jacks kept melting during winter.
I know it won't be drawing that all the time but a washing machine, kettle and fan puts it at the top end of that. This has been lumbered on me to sort out so I have got to do it. Instead of shooting me down at every opportunity u could help instead
- Joined
- Nov 28, 2009
- Messages
- 14,661
- Reaction score
- 817
So this is a residential park home site not a touring van site? So the site owner is the DNO and providing them a totally inadequate supply for their needs? Shall we even mention the re sale of electricity etc.
YOU do not want to get involved in this mess. Being an employee does not force you do do something that is dangerous or beyond your abilities. Flatly refuse and insist the site owner does it properly, which will probably cost him a lot of money.
We are not shooting you down, just advising you to refuse to do something dangerous and get your employer to face up to his responsibilities and do it properly.
YOU do not want to get involved in this mess. Being an employee does not force you do do something that is dangerous or beyond your abilities. Flatly refuse and insist the site owner does it properly, which will probably cost him a lot of money.
We are not shooting you down, just advising you to refuse to do something dangerous and get your employer to face up to his responsibilities and do it properly.
Last edited by a moderator:
looks like ESQCR might apply to him too then
the most 'help' you can expect is to be told you are way out of your depth and to get someone who knows what they are doing. unfortunately, when, not if, you courgette it up, it will be some innocent person who ends up dead and not you or your boss, although you might be room mates at one of HM hotels for a while
The sparky put a bigger cable in for this exact reason so I'm sure he had a plan of how to do it. My boss won't pay for him so I got to do it. I'm not a sparky by any means and I'm not pretending to be. I have basic knowledge and that's it.
So what I'm asking is it just as simple as a bigger fuse? And if not, why? And does anyone have an idea what the sparky's plan was if it wasn't to do that?
So what I'm asking is it just as simple as a bigger fuse? And if not, why? And does anyone have an idea what the sparky's plan was if it wasn't to do that?
have a read though all of 7671
- Joined
- Nov 28, 2009
- Messages
- 14,661
- Reaction score
- 817
Perhaps he thought these were all low power outlets and allowing for diversity it would be okay. But as it seems with melting 16A commando plugs the demand is actually a lot higher than you or he thought, so the whole installation needs a re think.
It's not so much that it was "designed" wrong but probably never designed at all and it has just evolved into what it is now.
If the demand is as high as you say (probably even higher than you may think now) then just a bigger fuse will only show up the next weakness when another bit of the install starts to melt. As I say, YOU don't want to be responsible WHEN that happens.
