Appliance fuses

[endecotp]

I often use 2A vs 3A fuses in sensitive equipment like alarm panels

They aren't to BS 1362 though, so you're talking about a completely different type of fuse.

My understanding is that the current vs delay curves are specified only for 3A and 13A, so if you use another size you might theoretically need to worry about whether it is fast or slow-blow. Not an issue in practice, I suspect.

 

[stillp]

My understanding is that the current vs delay curves are specified only for 3A and 13A

Your understanding is not correct.

 

[endecotp]

My understanding is that the current vs delay curves are specified only for 3A and 13A

Your understanding is not correct.

Thanks for the correction; feel free to update the Wikipedia page for BS1363, which currently says:


BS 1362 specifies sand-filled ceramic-bodied cylindrical fuses, 1" (25.4 mm) in length, with two metallic end caps of 1/4" (6.3 mm) diameter and roughly 1/5" long. The standard specifies breaking time versus current characteristics only for 3 A or 13 A fuses.

• For 3 A fuses: 0.02–80 s at 9 A, < 0.1 s at 20 A and < 0.03 s at 30 A.
• For 13 A fuses: 1–400 s at 30 A, 0.1–20 s at 50 A and 0.01–0.2 s at 100 A.

 

[Ray Tay]

EFLImpudence, Are you ignoring the cooker question, then?

I clearly did not. "Some makers are pretty irresponsible."
And the regs are not tight enough.

What is the minimum sized cable size that will take 40A?

 

[EFLImpudence]

EFLImpudence, Are you ignoring the cooker question, then?

I clearly did not. "Some makers are pretty irresponsible."

Ah, ok. I did not think that referred to the cooker.
You should have said ALL makers.

And the regs are not tight enough.

Not for you.

What is the minimum sized cable size that will take 40A?

Well, our regs say 4mm² is maximum 37A but I suspect it would do.
Of course, another fault with cookers is they get hot so maybe 6mm² to be on the safe side.

 

[bernardgreen]

What is the minimum sized cable size that will take 40A?

Under what conditions ?. As you are being pedantic about fuse values you could put 40 amps along 2.5 mm² copper if the cable can disipate 60 watts of heat per metre without going above 20° C.

Or at -273° C there would be no limit to how much current could flow along 2.5 mm² copper.

[/pedentry]

 

[PBC_1966]

secondly, as for rate of rise heat detectors, I am presuming they monitor the ambient temperature and if the temperature starts to go up rapidly they send off the alarm

That's right. In our place we moved into last year we have just the usual complement of a couple of smoke detectors near the bedrooms, but I'm in the process of running a full system thoughout the house and workshop. Smoke detectors for the kitchen area are just a nuisance, but I have a rate-of-rise detector ready to go up. The particular Edwards unit I'm using triggers on an increase of more than 15 deg. F. per minute, and also includes a fixed heat detector set at 135 degrees. You just need to be careful not to locate them where a quick hot blast of air rising from opening an oven might cause false triggering.

Yes they are recognised. In the BS1362 complaint range of fuses, you get 1A, 2A, 3A, 5A, 7A, 10A, and 13A. Historicly 3A, 5A and 13A have been most common.

Although as I mentioned before, in the early days of BS1363 plugs the suggested fuses for most uses were 2, 5, 10 & 13A. But for anyone saying that these days nothing but the "preferred" 3 & 13A should be used, then what's the point of the BS1362 range still being manufactured with all the other values?

 

[Risteard]

the current vs delay curves are specified only for 3A and 13A

Precisely my point.

 

[Risteard]

But for anyone saying that these days nothing but the "preferred" 3 & 13A should be used, then what's the point of the BS1362 range still being manufactured with all the other values?

I wasn't suggesting that they shouldn't be used, but that manufacturer's data is required to confirm operation when using a non-standard rating as their characteristics are not covered within the Standard.

Also, RE: the 2A fuse I wasn't saying that these aren't BS 1362 - I assumed that a fuse for the intruder alarm panel was being referred to (which wouldn't be a BS 1362 fuse).

 

[PBC_1966]

I assumed that a fuse for the intruder alarm panel was being referred to (which wouldn't be a BS 1362 fuse).

I thought that reference was to a fuse for the supplying FCU ?

 

[Iggifer]

BS1362 2A Fuse

• eveares
• 30 Mar 2016

Could be round the back, but where is the ASTA mark on that fuse?

Also What fuse would you personally use then if you had a 5 Amp load over 0.75mm² flex then? 3A is to low for a 5A load, and 13 Amps through 0.75mm² flex in lengths over 2 Meters and when not used with a portable appliance is not allowed either.

Protection against excessive damage by a short circuit is still achieved even if the smaller cord sizes are inadvertently protected by a 13A fuse. In addition, it has been accepted in the UK that some marginal damage to small flexible cords is tolerable under short circuit conditions, for example where a 0.22mm² cord is used with a 13A BS 1362 fuse

Not saying I agree, but....

 

[eveares]

I thought that reference was to a fuse for the supplying FCU ?

Yes, quite so. I was not talking about the internal glass fuses in the alarm panel, the fuse in the FCU supplying the panel.

Also, RE: the 2A fuse I wasn't saying that these aren't BS 1362

I read it as BS1362 fuses only come in the 3 and 13 amp variates.

 

[eveares]

Could be round the back, but where is the ASTA mark on that fuse?

Yes the ASTA mark along with the Kitemark mark and the NIGLON branding are not shown in my photo as they are round the back.

 

[endecotp]

I thought that reference was to a fuse for the supplying FCU ?

Yes, quite so. I was not talking about the internal glass fuses in the alarm panel, the fuse in the FCU supplying the panel.

In that case, I think you should probably fit a larger diameter flex. At some point in the future the fuse may blow and be replaced with a larger one because "that is what they had in Tesco".

I'd suggest using fuses other than 3A and 13A only in not-user-servicable locations (e.g. inside appliances) - but in fact we tend to use fuses of different physical sizes there anyway.

 

[Iggifer]

Most panels (fire and intruder) that I've seen have glass fuses anyway. I'd just wire it in 1.25mm and be done with it.