Slow fuse vs time lag fuse
larkim
fuses at Maplin.
Are they the same thing?
Cheers!
Matt
Tabby
IIRC slow blow have nodules on, time delay have a spring mechanism. T
fuse are slower, and can replace slow fuses no problem.
NT
fred
<ac249dcc-2fd0-4929...@w29g2000vba.googlegroups.com>,
larkim <matthew...@gmail.com> writes
>Need a slow fuse 2.5amp for my boiler but can only find' time delay'
>fuses at Maplin.
>Are they the same thing?
There are different flavours, one has what looks like a spring inside
and has the longest time delay function (commonly called anti-surge),
the other just had a blob in the middle of the fusewire (commonly called
time delay). I'd suggest you probably want the former and Maplin are
usually quite good at showing pictures so it should be clear. If in
doubt, post the Maplin code. Does the original have a spring?
--
fred
FIVE TV's superbright logo - not the DOG's, it's bollocks
larkim
> In article
> <ac249dcc-2fd0-4929-b00b-8aae1e5d7...@w29g2000vba.googlegroups.com>,
> larkim <matthew.lar...@gmail.com> writes
>
> >Need a slow fuse 2.5amp for my boiler but can only find' time delay'
> >fuses at Maplin.
> >Are they the same thing?
>
> There are different flavours, one has what looks like a spring inside
> and has the longest time delay function (commonly called anti-surge),
> the other just had a blob in the middle of the fusewire (commonly called
> time delay). I'd suggest you probably want the former and Maplin are
> usually quite good at showing pictures so it should be clear. If in
> doubt, post the Maplin code. Does the original have a spring?
> --
> fred
> FIVE TV's superbright logo - not the DOG's, it's bollocks
Thanks for that.
The original was in a ceramic case so I can't "see" into it. The
fuses that I bought were maplin ref GL63T (20mm Time Glass Delay (T))
I suspect the original was closer to this in terms of what it
physically looks like, don't know if there are any performance
differences:-
http://www.cle-electrical.co.uk/products/309/5x20-minature-ceramic-fuses-slow-blow-(pk10)
Cheers!
Matt
fred
<9691eb1d-8eec-4ea0...@p38g2000vbn.googlegroups.com>,
larkim <matthew...@gmail.com> writes
>On Jan 5, 11:11 am, fred <n...@for.mail> wrote:
>> In article
>> <ac249dcc-2fd0-4929-b00b-8aae1e5d7...@w29g2000vba.googlegroups.com>,
>> larkim <matthew.lar...@gmail.com> writes
>>
>> >Need a slow fuse 2.5amp for my boiler but can only find' time delay'
>> >fuses at Maplin.
>> >Are they the same thing?
>>
>> There are different flavours, one has what looks like a spring inside
>> and has the longest time delay function (commonly called anti-surge),
>> the other just had a blob in the middle of the fusewire (commonly called
>> time delay). I'd suggest you probably want the former and Maplin are
>> usually quite good at showing pictures so it should be clear. If in
>> doubt, post the Maplin code. Does the original have a spring?
>> --
>> fred
>> FIVE TV's superbright logo - not the DOG's, it's bollocks
>
>Thanks for that.
>
>The original was in a ceramic case so I can't "see" into it. The
>fuses that I bought were maplin ref GL63T (20mm Time Glass Delay (T))
>
tell you whether this is a light overload situation in which case the
fusewire will be largely intact but have a break or if it is a high
current fault in which case the fusewire will have vaporised.
The one you point to at Maplin has a spring so has the longer fusing
characteristic. Glass fuses have a lower breaking capacity but in your
in-case environment (where it is backed up by a BS fuse in the FCU
supplying the system) I'd be happy to use one.
Here's a short summary I just picked up on a search:
Fusing Speed
A quick-acting fuse is designed to react both to short and long term
overload conditions. They are very robust in construction and will
withstand shocks and vibration. But they do tend to have a higher
resistance and the voltage drop caused by this may be a problem in some
applications. This higher resistance also means that more heat is
produced and this must be effectively dissipated.
Time delay fuses will react to long term overload currents but will
withstand transient surges without harm; several types are available.
For example, one type has what looks like a spring inside the barrel and
these will stand up to surges of around ten times the normal rating for
75 milliseconds. Another type has a "blob" in the middle of the fuse
element and this type has a reduced surge capacity, typically ten times
rated current but only for 25 milliseconds. Time delay types have a very
low resistance and can be used in enclosed places as there is little
self-generated heat but they are only available in the lower current
ratings. Both the "spring" and the "blob" type are time delay fuses.
Copied from http://www.glodark.co.uk/fuses.htm
>I suspect the original was closer to this in terms of what it
>physically looks like, don't know if there are any performance
>differences:-
>http://www.cle-electrical.co.uk/products/309/5x20-minature-ceramic-fuses-slow-
>blow-(pk10)
>
Dunno.
Bob Eager
> Here's a short summary I just picked up on a search:
>
> Fusing Speed
>
> A quick-acting fuse is designed to react both to short and long term
> overload conditions. They are very robust in construction and will
> withstand shocks and vibration. But they do tend to have a higher
> resistance and the voltage drop caused by this may be a problem in some
> applications. This higher resistance also means that more heat is
> produced and this must be effectively dissipated.
>
> Time delay fuses will react to long term overload currents but will
> withstand transient surges without harm; several types are available.
> For example, one type has what looks like a spring inside the barrel and
> these will stand up to surges of around ten times the normal rating for
> 75 milliseconds. Another type has a "blob" in the middle of the fuse
> element and this type has a reduced surge capacity, typically ten times
> rated current but only for 25 milliseconds. Time delay types have a very
> low resistance and can be used in enclosed places as there is little
> self-generated heat but they are only available in the lower current
> ratings. Both the "spring" and the "blob" type are time delay fuses.
>
> Copied from http://www.glodark.co.uk/fuses.htm
I was inspired to see what Wikipedia had on the subject. The best bit?
A link to the DIY FAQ....
Did someone here write any of that WP stuff?
--
Use the BIG mirror service in the UK:
http://www.mirrorservice.org
*lightning protection* - a w_tom conductor
larkim
> On Wed, 05 Jan 2011 12:54:51 +0000, fred wrote:
> > Here's a short summary I just picked up on a search:
>
> > Fusing Speed
>
> > A quick-acting fuse is designed to react both to short and long term
> > overload conditions. They are very robust in construction and will
> > withstand shocks and vibration. But they do tend to have a higher
> > resistance and the voltage drop caused by this may be a problem in some
> > applications. This higher resistance also means that more heat is
> > produced and this must be effectively dissipated.
>
> > Time delay fuses will react to long term overload currents but will
> > withstand transient surges without harm; several types are available.
> > For example, one type has what looks like a spring inside the barrel and
> > these will stand up to surges of around ten times the normal rating for
> > 75 milliseconds. Another type has a "blob" in the middle of the fuse
> > element and this type has a reduced surge capacity, typically ten times
> > rated current but only for 25 milliseconds. Time delay types have a very
> > low resistance and can be used in enclosed places as there is little
> > self-generated heat but they are only available in the lower current
> > ratings. Both the "spring" and the "blob" type are time delay fuses.
>
>
> I was inspired to see what Wikipedia had on the subject. The best bit?
>
> A link to the DIY FAQ....
>
> Did someone here write any of that WP stuff?
> --
> Use the BIG mirror service in the UK:
> http://www.mirrorservice.org
>
> *lightning protection* - a w_tom conductor
Have to say Wikipedia was my first stop before I went and bought any
at Maplin. I "trusted" that the wiki entry which says "time delay
fuse (also known as anti-surge, or slow-blow)" to convince myself that
they were sufficiently close to warrant taking the risk!
Now, speaking cynically (!), I now have a service contract on the
boiler, so if the PCB should blow because the fuse I have used isn't
quite right, I'll simply stick back in the original blown fuse and
keep schtum. Unethical, unlawful perhaps. But I suspect just what
most people would do to ensure their insurance backed service contract
pays up!!
Matt
larkim
> In article
> larkim <matthew.lar...@gmail.com> writes
>
> >I suspect the original was closer to this in terms of what it
> >physically looks like, don't know if there are any performance
> >differences:-
> >blow-(pk10)
>
> Dunno.
> --
> fred
> FIVE TV's superbright logo - not the DOG's, it's bollocks
Thanks, very helpful. Interestingly I've spoken to a few people who
"should" know, and had different responses. Some say a "time delay"
isn't the same as a "slow" fuse, others say they are the same thing!
As you say, the whole device is protected by a "normal" 3A fuse, so
there isn't a particularly serious risk of having the wrong type in
the environment it is in.
Cheers!
Matt
larkim
>
> tell you whether this is a light overload situation in which case the
> fusewire will be largely intact but have a break or if it is a high
> current fault in which case the fusewire will have vaporised.
>
> The one you point to at Maplin has a spring so has the longer fusing
> characteristic. Glass fuses have a lower breaking capacity but in your
> in-case environment (where it is backed up by a BS fuse in the FCU
> supplying the system) I'd be happy to use one.
Just for my info / sanity, can you clarify this. "Hammer" and
"breaking capacity" imply physical impact. Is that the sort of
situation you are imagining?
Or am I missing the point?!? (Most likely!)
Matt
harry
I think he means bust the old one open and look inside (for a spring
if any) :-)
fred
<c9c29c6d-ac0f-4d1b...@fx12g2000vbb.googlegroups.com>,
larkim <matthew...@gmail.com> writes
Hammer is to break the tube on your existing blown fuse to open it for
examination and determine whether it is a single wire strand (with or
without blob) or a spring type, and to see whether the wire remains
solid with a single break (implying light overload) or vaporised
(implying some high current - short circuit - fault).
Breaking capacity is the capability of the fuse to interrupt a certain
level of fault current. In a high current fault, the fusewire may
vaporise and 1. the vapour could conduct for a period, extending the
duration of the fault current leading to further damage or 2. coat the
inside of a glass envelope fuse, leaving a conducting path behind which
could create a hazard.
High breaking capacity fuses generally have ceramic bodies and are sand
filled to extinguish any arc that may tend to be created by the fault.
Typical breaking capacities:
20 mm glass fuse - 35A or 10x rated current value
20 mm sand-filled ceramic - 1500A
BS1362 fuse, UK ring main plug - 6 kA
BS1361 fuse, UK distribution board - 16 kA
Andy Wade
> larkim <matthew...@gmail.com> writes
>> Need a slow fuse 2.5amp for my boiler but can only find' time delay'
>> fuses at Maplin.
>> Are they the same thing?
Yes.
> There are different flavours, one has what looks like a spring inside
> and has the longest time delay function (commonly called anti-surge),
> the other just had a blob in the middle of the fusewire (commonly called
> time delay).
That might be a red herring. Look at the marking on the endcaps:
- F2.5A is a 'fast' fuse
- T2.5A is the time delay type, aka anti-surge.
The characteristics are standardised in IEC 60127 and 'T' types can have
either the spring or blob construction, both meeting the same standard.
There are other types: FF is 'ultra-fast' for semiconductor protection
and some manufacturers have an 'M' type, intermediate between F and T.
These are far less common.
For a mains application you should always use an HBC (ceramic body) type
(T2.5AH).
--
Andy
larkim
> On 05/01/2011 11:11, fred wrote:
>
I think in summary it is very confusing!!!
- there are "T", "F", "M" and "FF" fuses
- however, various websites say that there are different "types" of
"T" fuses (notably "anti-surge" and "time delay")
- at least one source describes "anti-surge" and "time delay" as
having different capabilities
- some people (whose opinions I believe are genuine and based on
experience) disagree between themselves whether the different types of
"T" fuses are interchangeable
- all "T" fuses apparently meet the same industry standards
- it seems that having a ceramic body vs a glass body may create
different performance characteristics
- but my application (inside a boiler) doesn't ask for a specific body
type (in fact it asks for a "slow" fuse, which is differently named
again!)
- it is easier to get hold of glass bodied fuses than ceramic ones
(for "T" fuses at 2.5A) as you can get them from Maplin (and
interestingly Amazon and PTS sell glass bodied too)
However, my boiler seems to be working!!
Interesting in any event!!
Matt
Dave W
as being the most definitive and in agreement with my experience. The
names given can mean anything, there are indeed several types of delay
as depicted in the IEC graphs. We used glass 20mm delay fuses inside
equipment for mains input, but only ceramic fuses should be used for
general mains use, as fault current could be enormous for a short
circuit.
Dave W
Arfa Daily
"larkim" <matthew...@gmail.com> wrote in message
news:887444b6-b6ff-40d3...@j25g2000vbs.googlegroups.com...
For the purpose that you are looking at, either fuse type will provide
sufficient protection to your boiler circuitry. However, be aware that the
fusing characteristic is not the only parameter that you may need to take
into consideration. You say that the original fuse had a ceramic case. This
normally indicates that it is an 'HRC' or High Rupture Current type. The
case is ceramic rather than glass to prevent it from exploding under severe
overload conditions. These fuses are very typically used as the mains input
fuse on switch mode power supplies. I don't know if your boiler uses a
switcher or a linear type, but a lot of equipment these days does use
switchers, so there is a possibility your boiler might. If that is the case,
then the fuse should really be replaced with a ceramic one for safety's
sake, although a common 'T' rated type will still be fine. Look for a
conventional mains transformer. It may be an encapsulated PCB mounted type.
If it has one of these, then it is a linear supply, and you should be fine
with a 'T' rated glass type.
Arfa