Fuse Types

neglected_goldfish · 22 Mar 2004

Hi

Could someone possibly tell me the difference between Type B and Type C fuses?

Many thanks,

Craig.

Big_Spark · 22 Mar 2004

neglected_goldfish said:
Hi

Could someone possibly tell me the difference between Type B and Type C fuses?

Craig, they are MCB's not fuses, however to stop being nitpicky and answer your question, it is all to do with reaction time of the device which is connected to loading.

Type B are fast reacting breakers, they will trip when subjected to about 1.2 times their rated current for more than abour 0.2 seconds.

Type C are similar, but will withstand up to 1.4 times rated current for up to 0.5 seconds

Type D, also known as Motor Rated, are similar to HRC fuses in the way they behave. For very short periods of time they can withstand, in some cases, up to five times their rated capacity, but this will be for very short periods, just enough to allow a motor to start and then drop back down to normal load. Usually this takes maybe no more that 0.5 to 1.3 seconds.

The above is certainly not a definitive answer, and without looking up the exact time figures I would not say they are 100% accurate, but the difference in operation is..if you see what I mean

neglected_goldfish · 22 Mar 2004

Fantastic!

Thanks for the fast response.

Type B it is for me.

Regards,

fish

PS. what happened to Type A?

Goofyish · 22 Mar 2004

According to BS EN 60898 the tripping characteristics are:

Type B: 3 to 5 x Rated Current
Type C: 5 to 10 x Reated Current
Type D: 10 to 14 x Rated Current

Big_Spark · 22 Mar 2004

Goofyish said:
According to BS EN 60898 the tripping characteristics are:

Type B: 3 to 5 x Rated Current
Type C: 5 to 10 x Reated Current
Type D: 10 to 14 x Rated Current

Thanks Goofy...saved me looking it up in a minute

ban-all-sheds · 22 Mar 2004

neglected_goldfish said:
Type B it is for me.

You may find that you get nuisance tripping on lighting circuits when bulbs blow. Depending on how long the lighting circuit is, and what size cable, you might like to consider a 10A rather than 6A MCB, or a Type C.

neglected_goldfish · 23 Mar 2004

Thanks for the advice.

Although it is only a small flat. There'll be 5 wall lights (40w each) and 4 ceiling lights (max 120w each). I'm using 1.5mm twin and earth and everythings all 1-way switching.

What would you recomend?

Regards,

fish

journeyman · 23 Mar 2004

Only 10A in a lighting circuit if there are no SES or SBC lampholders.

neglected_goldfish · 23 Mar 2004

Sorry to be a pain, but what are SES and SBC lampholders?

I'm pretty new to this and not too up on the abbreviations yet.

Regards,

fish

Big_Spark · 23 Mar 2004

journeyman said:
Only 10A in a lighting circuit if there are no SES or SBC lampholders.

Over the top.

and what the hell has it to do with rating if he were to have lamps with SES or SBC caps?

Goldfish, SES abd SBS are types of cap for a lamp, SES are Small Eddison Screw and the SBC are Small Bayonet Cap.

To answer your question, a 6A Type B MCB is sufficient for your needs, anything bigger is too big.

journeyman · 23 Mar 2004

SES: Small Edison Screw
SBC: Small Bayonet Cap
They are the smaller fittings for bulbs(lamps); as opposed to the standard or lager size fittings:

ES: Edison Screw
BC: Bayonet Cap

BC is the standard fitting for a ceiling rose pendant in the UK.

Also known as

ES: E27
BC: B22
SES: E14
SBC: B15

These are the four main fittings for lamps. You are allowed a mximum circuit breaker size of 6A for SES and SBC, and a maximum of 16A for ES and BC.

Big_Spark · 23 Mar 2004

journeyman said:
These are the four main fittings for lamps. You are allowed a mximum circuit breaker size of 6A for SES and SBC, and a maximum of 16A for ES and BC.

16A breaker on lighting!! What's your name Bodgit!!

Your talking rubbish journeyman, if someone has told you that then they were bulling you and it is crazy.

The cap on a lamp does not dictate the size of overcurrent protective device, and you would certainly never put a lighiting circuit on a 16A breaker.

journeyman · 23 Mar 2004

Over the top.

and what the hell has it to do with rating if he were to have lamps with SES or SBC cap.

I no longer have my copy of the wiring regulations and I cannot afford to replace it at the moment. I think my copy may have been fifteenth edition, it had a green cover.

In my copy there was a table which mentioned the maximum size of circuit breaker or fuse allowed for these types of lampholders. Maybe this regulation no longer exists. I stand to be corrected.

I do agree that only 6A should be used for domestic installations. However there is an issue of nuisance tripping associated with Type B circuit breakers. There has been debate about this on other forums and possibly this one.

pipme · 23 Mar 2004

Hi,

There is a table on p.126 of J Whitfield's 6th edition, Guide to Wiring regs BS7671. This taken, apparently, from table 558 of 16th edition of BS 7671 : 1992.

Refers to 'Overcurrent protection of lampholders' tabulated in max Amps.

It does not however, invite the use of this as a means of choosing the protection for the circuit involved.

I think you would need, as in all this sparkling stuff, to be cautious in the interpretation, and personally I would be (as a non spark) following FWL's advice.

Not being argumentative .... But the above part of the book in question, seems a bit iffy in this area.
Perhaps one of the engineers could comment on this. Please.

P.

journeyman · 23 Mar 2004

Maximum: greatest possible amount: the largest or greatest amount, number, extent, or degree possible or allowed

Encarta® World English Dictionary © & (P) 1999, 2000 Microsoft Corporation. All rights reserved. Developed for Microsoft by Bloomsbury Publishing Plc.

I did not say that a 16A breaker should be used. The point I was really making was that one has to be careful about using a 10A breaker in a domestic circuit; where SBC or SES lampholders could be used. It is not for a DIY person like myself to judge the regulations or whether they make sense or not. If the regulations exist and the table says 6A maximum for SES and SBC then it is 6A maximum. If the regulations say 16A maximum for BC and ES then it is 16A maximum, of course one could use 6A or 10A.

Please read the above definition of the word: maximum. Maximum does not mean must.

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