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Posted By Topic: Ceramic Fuse Bases

Oct 21 2019 07:27

At what point should I be upgrading these to one of the new bases?

How do I tell when I need to do this and when it's safe to just insert a plug in straight into the existing ceramic base?

Or should I be upgrading these every time?


Oct 21 2019 10:08

When a serf is removed from a ceramic base there is a possibility of electric shock because of exposed terminals.

A new plastic base has covers over the terminals.

However, if they are lost then it’s back to square one.

Oct 21 2019 10:40

If the PSSC is above 1 kA, they are not fit for purpose. Replace with something else, as even a new SERF is only a 1kA rating.

Below 1kA; if they have significant deposits of copper and / or carbon, they should be replaced; as the deposits reduce the breaking capacity.
Technically can replace with a new SERF; but (much) better to replace with mcb.

for replacing base only, mostly you can't find bases that are a proper fit for older fuse styles. And chances are that the carrier is also degraded.

Oct 21 2019 10:45

So basically when doing any installation work on a circuit when you upgrade the SERF to a plug in (because SERFs can't protect any new work) you should do a PSSC test at the old base and replace according to the results/how degraded the base is?

Do I need to check the other bases or only what I've worked on?

Oct 21 2019 13:53

Correct we can't use a SERF to provide fasult, short circuit, or overload protection for any new work; so for these it's "upgrade regardless".
Generally a plug-in (3 kA) will be adequate for domestic; although I tend towards SE8s & similar if there's room. Partly because rail-mount mcbs are cheaper, and partly to provide for the next job and / or installing RCD

Whether it's worth keeping any old bases / carriers in good condition to be used as replacement parts is your choice (I don't).

And yes, regardless whether replacing for degradation, or for the "no-SERF" rule; whatever you fit as replacement has to be adequately rated. Which really means doing a PSSC calc / test if you want to be sure. Most EFLI meters give a PSSC result that's accurate enough for this purpose.

True ESR 59(3)(b) allows restoration to original condition. Which allows replace emnt of old SERF with new SERF - but only as ESR 113 allows a SERF to remain in service. And it won't if the PSSC has risen above the kA rating.


Oct 21 2019 16:25

Right so if I work on a circuit, swap to a plug in MCB, check the PSSC and find it's too high for the base then I must swap it out as it's no longer fit for purpose

Is it my responsibility to check the PSSC at the other bases (as I would assume it'd be pretty similar at them all) and to upgrade them as required? Or is it only my responsibility to check and upgrade the circuit I worked on?

Oct 22 2019 08:48

We're only ever responsible for 2 things WRT installations.
The first is what we work on: that what we do is safe and doesn't adversely affect the safety of any other part of the installation[ESR 13], and also compliant [ESRs 59, 60, etc].
The second is any "immediate danger to life or property" we discover while we're doing the work - and that responsibility is only to report [ESR 19].

So while checking that what you have done is (or what you intend to do will be) OK, if we find the PSSC has risen - eg because the network has been upgraded over the years - we only have to deal with the effects of that on our own work. We have no legal duty WRT the other circuits not worked on.
Same if we find that BTI has been added, so the protection rating(s) are no longer suitable for the cables. The protection we're working on has to be right, but we don't have to upgrade the rest.

Such deficiencies don't amount to "immediate danger"; so formal reporting is not required.

That said, as the hired experts we have a moral duty to advise our customer if we find such things - otherwise how would they know anything was less than 100% OK? Tell them what you've found WRT the circuit worked on, and ask whether they want you to check the other circuits.

They won't know it, but they have obligations also, and if any part of the installation no longer complies with original rules then ESR 113 says it is not allowed to remain in service. Not that I'd be using that to justify telling them they "must" upgrade, unless the problem was bad enough to be "electrically unsafe" - which is where ESR 15 kicks in.


Oct 22 2019 19:58

Thank you, that's really interesting and informative

I always wondered where the line was drawn with these things

So, am I right in saying that ESR 19 (2) says "If a person to whom this regulation applies has reasonable grounds to believe
that the works, installation, fitting, or appliance presents an immediate danger
to life or property, the person must, as soon as practicable, advise both of the
following people of the danger:
(a) the owner or occupier of the property where the danger exists:
(b) WorkSafe."

My question is what is deemed an immediate danger to life or property as it says?

ESR 5 says "electrically unsafe means, in relation to works, installations, fittings, applian-
ces, and associated equipment, that there is a significant risk that a person may
suffer serious harm, or that property may suffer significant damage, as a result
of dangers arising, directly or indirectly, from the use of, or passage of electri-
city through, the works, installations, fittings, appliances, or associated equip-

Would you say that something that is electrically unsafe meets the definition of immediate danger to life or property and it's those things they are referring too?

And if so is it just the things listed in ESR 20-24b that we have an obligation to act on WRT ESR 19?

Or do you believe immediate danger to life or property is much wider than that?

Apologies for the multiple questions, like I said, I'm just wanting to work out where my obligations start and where they finish and when certain regulations such as ESR 19 kick in


Oct 23 2019 09:09

Well off-topic now; time to start a new thread.

Oct 23 2019 09:12

Fair comment, I have a tendency to get carried away from the original topic as most will have noticed hah

Will ask this in a new thread when I have a moment

Oct 23 2019 10:11

already done