busbar help

[Paul1985]

Hi im just after a bit of advice just in case im missing anything not had a lot to do with busbars. Basically iv got a 100a 3 phase supply 25mm tails it gose to a 60a isolator with rewirable fuses which is next to the meter. Then to a 100a busbar feeding 3 isolators which is next to the busbar. I want to up grade the rewirable fused isolator to a 100a with bs88 the volt drop to the other isolators is very low as they are next to the busbar. Am i missing anything cheers

 

[Pete999]

Hi im just after a bit of advice just in case im missing anything not had a lot to do with busbars. Basically iv got a 100a 3 phase supply 25mm tails it gose to a 60a isolator with rewirable fuses which is next to the meter. Then to a 100a busbar feeding 3 isolators which is next to the busbar. I want to up grade the rewirable fused isolator to a 100a with bs88 the volt drop to the other isolators is very low as they are next to the busbar. Am i missing anything cheers

Why are you wanting to swap the switched fused/Fused switch? what rating are the bus bars?

 

[Paul1985]

Busbars are 100a. I want to uprate it as iv got to change it as its rewirable fuse so whilst im at it may as well increase as in the future may want extra no point in paying out again for another fused isolator if i can fit one now With out to much trouble.

 

[Pete999]

Busbars are 100a. I want to uprate it as iv got to change it as its rewirable fuse so whilst im at it may as well increase as in the future may want extra no point in paying out again for another fused isolator if i can fit one now With out to much trouble.

Fair enough, but you are increasing the S/F from 60a to 100a are the bus bars rated for that increase?

 

[Paul1985]

They are 100a busbar.

 

[Bobster]

How do you know the bus bars are rated at 100A?

 

[Paul1985]

Original paperwork still stuck to it and its on it. Do think they could be changed?

 

[Bobster]

Just buy a fused isolate that will take 100A BS88 fuses then fit 60A fuses.

If they ever wish to upgrade, then look at replacing the bars, all you need to do with the fused isolator is up the fuse size.

No point in making a job more costly if it's not needed.

 

[Paul1985]

Its not the fuses that cost the money its the 100a isolator and as i wont be paying it dosnt effect me. totally agree stick 60a in but as i work here every day and if i want a supply for something i know i can get it from there as i will be able to. Is there chart for sizing of busbar so i can double check they are what i think. Thanks

 

[Knobhead]

If the supply is 100A and the busbars 100A why do you need uprate the bars? Just fit a 100A fused switch with 80A fuses, at least you’ll have a bit of discrimination.

 

[Darkwood]

How do you know your incoming DNO fuses are 100Amp?... remember just because the carrier says 100amp it doesn't mean the fuses inside are that rating.
I believe the DNO fuses are type III or IV anyway so fitting 100Amp BS88's -II would be fine, the fuses ratings between 60 - 100 amp are too close to give any real discrimination and at best only partial to a small percentage, as its a small supply by contrast discrimination will always be a problem between upstream and downstream devices. (regarding a short-circuit).

You will have overload discrimination as Tony says with 80amps as you may not have access to the DNO fuses to confirm they are Type III/IV

 

[Paul1985]

Thanks alot And some good points cheers.

 

[Flanders]

Busbars are 100a. I want to uprate it as iv got to change it as its rewirable fuse so whilst im at it may as well increase as in the future may want extra no point in paying out again for another fused isolator if i can fit one now With out to much trouble.

Dare a ask what is wrong with the rewirable fuses if not groke don't fix it

 

[Paul1985]

My work place is just trying to update things slowly.

 

[davesparks]

What make and model is the old switchfuse?

If it's MEM or BILL you can buy the bs88 fuseholder a which will fit in to the existing bases as a direct replacement.

 

[Knobhead]

That's handy to know. Cheers Dave.

 

[Darkwood]

What make and model is the old switchfuse?

If it's MEM or BILL you can buy the bs88 fuseholder a which will fit in to the existing bases as a direct replacement.

Even the new black holders replace the old cast rewirables best backwards compatability out there me thinks!

 

[davesparks]

I have found it is quicker and cheaper to get a new fuseholder with fuses than it is to try and track down 60/100 amp fuse wire these days

 

[Knobhead]

Always the practical one Dave.

I’ve got to admit I rarely came across rewirable fuses other than on the old DC systems.

 

[Rockingit]

I bought the last reel of 80A fuse wire that City's computers claimed to exist a while back, and no other wholesaler was listing either....certainly seems to be like hens teeth now.

 

[Bobster]

Think I've got a roll of 80A fuse wire in my garage somewhere.

 

[davesparks]

Always the practical one Dave.

I’ve got to admit I rarely came across rewirable fuses other than on the old DC systems.

Well you have to be practical once you leave the warm and fluffy domestic world!

Fix it within 24hrs or loose the client!

 

[Knobhead]

24Hrs? Dear god that would cost £1000’s per minute, I’d be hung off one off the nearest OH crane.

Even though we were still using switchgear from the 30/40’s all used HRC fuses. Definitely not to BS88.
For some reason the 220V DC system never used them, fortunately the 440/660V systems did. A rewireable fuse going at 220V is frightening enough.

We did have some rewireable 3.3KV oil filled fuses for capacitor banks. As far as I know we never had one blow. I wouldn’t like to be around if one did.

 

[davesparks]

24Hrs? Dear god that would cost £1000’s per minute, I’d be hung off one off the nearest OH crane.

Even though we were still using switchgear from the 30/40’s all used HRC fuses. Definitely not to BS88.
For some reason the 220V DC system never used them, fortunately the 440/660V systems did. A rewireable fuse going at 220V is frightening enough.

We did have some rewireable 3.3KV oil filled fuses for capacitor banks. As far as I know we never had one blow. I wouldn’t like to be around if one did.

In this instance I'm thinking of a local care home, different failures carry different levels of urgency.
In this case the fault affected the residents and had to be fixed within 24hours or else the CQC would have to be informed (care quality commission)
Other faults have to be fixed quicker, and other stuff just gets put in the book to be dealt with next time I visit.

Other places the downtime is measured in seconds, like the inflatable stage roof slowly collapsing as 5000 festival goers watch and the stage manager tried to evacuate the stage as the band try to carry on playing.
(The 3 minutes it took to get the site live again but it felt like forever)

 

[Engineer54]

Definitely not to BS88.

Why's that, BS 88 ''ARE'' HRC fuses with a breaking capacity range up to 120KA and above. Come in all shapes and sizes from circular to square.... Types may change but still conform to BS 88.