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Fuse calculation
Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v |
Fuse calculation
Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v 1150/240=4.79 so theoretically a 5A fuse shoud do. -- Graham. %Profound_observation% |
Fuse calculation
On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave
wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v Assuming you mean at the BS1363 plug then the fuse should be sized to protect the cable. -- |
Fuse calculation
whisky-dave pretended :
Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v 5amp ought to cover it, but it is very tight. If it fails find a 10amp. |
Fuse calculation
On Monday, 19 March 2018 16:11:42 UTC, The Other Mike wrote:
On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v Assuming you mean at the BS1363 plug then the fuse should be sized to protect the cable. -- Nice, that's the sort of answer I'd expect :-) But this was a question given to students doing our science foundation course where they are expected to say 5 Amps. (a student has left their marked paper (mid semester test) in the lab so I thought I'd have a look). I have also been told that H&S state that consumers/users should only use either a 3A of 13 amp fuse in a plug and that is what we as technicians have been told to use, even though I have loads of fuses including 1A, 2A, 5A, 7A, 10A and 13A https://www.rospa.com/home-safety/uk...hoosing-fuses/ |
Fuse calculation
On 19/03/2018 16:15, Harry Bloomfield wrote:
whisky-dave pretended : Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v 5amp ought to cover it, but it is very tight. If it fails find a 10amp. It isn't *all* that tight in practice but the plug will run slightly warm. A nominal 5A fuse will take nearly 20A to blow in the first second and will probably support a current of 7A almost indefinitely. eg. https://docs-emea.rs-online.com/webd...6b8002b71e.pdf It would be much more challenging with a halogen light where there is a significant inrush current when the filament is cold. An electric fire is a relatively benign load with a decently high cold resistance. Nominally 13A fuses will support boiling two 3kW kettles for long enough to destroy the still coiled up extension cable they were plugged into. All our village hall extension cables now have thermal overload protection to save them from the church's tea ladies. -- Regards, Martin Brown |
Fuse calculation
In article ,
whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v If you're talking a plug fuse, the load is irrelevant. As it is to protect the flex etc. In other words, a table light with a 20 watt bulb would be fine with a 13 amp fuse if the cable was rated at 13 amps. -- *The closest I ever got to a 4.0 in school was my blood alcohol content* Dave Plowman London SW To e-mail, change noise into sound. |
Fuse calculation
In message
Martin Brown wrote: On 19/03/2018 16:15, Harry Bloomfield wrote: whisky-dave pretended : Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v 5amp ought to cover it, but it is very tight. If it fails find a 10amp. It isn't *all* that tight in practice but the plug will run slightly warm. A nominal 5A fuse will take nearly 20A to blow in the first second and will probably support a current of 7A almost indefinitely. eg. https://docs-emea.rs-online.com/webd...6b8002b71e.pdf It would be much more challenging with a halogen light where there is a significant inrush current when the filament is cold. An electric fire is a relatively benign load with a decently high cold resistance. Nominally 13A fuses will support boiling two 3kW kettles for long enough to destroy the still coiled up extension cable they were plugged into. This is due to induction heating not resistive heating by the load supplied. All our village hall extension cables now have thermal overload protection to save them from the church's tea ladies. -- John Bryan |
Fuse calculation
On 19/03/2018 16:53, Dave Plowman (News) wrote:
In article , whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v If you're talking a plug fuse, the load is irrelevant. As it is to protect the flex etc. In other words, a table light with a 20 watt bulb would be fine with a 13 amp fuse if the cable was rated at 13 amps. Won't all fuses less than 13a protect the cable then! |
Fuse calculation
On 19/03/18 15:27, whisky-dave wrote:
Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v well you could TRY a 5A. But my guess is that its pushing the limits. 13A. Remember the fuse is to protect the wiring that is downstream of it only. -- New Socialism consists essentially in being seen to have your heart in the right place whilst your head is in the clouds and your hand is in someone else's pocket. |
Fuse calculation
whisky-dave wrote:
Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v 10A . But 13A is fine. -- Roger Hayter |
Fuse calculation
On 19/03/2018 16:18, whisky-dave wrote:
On Monday, 19 March 2018 16:11:42 UTC, The Other Mike wrote: On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v Assuming you mean at the BS1363 plug then the fuse should be sized to protect the cable. -- Nice, that's the sort of answer I'd expect :-) But this was a question given to students doing our science foundation course where they are expected to say 5 Amps. (a student has left their marked paper (mid semester test) in the lab so I thought I'd have a look). I have also been told that H&S state that consumers/users should only use either a 3A of 13 amp fuse in a plug and that is what we as technicians have been told to use, even though I have loads of fuses including 1A, 2A, 5A, 7A, 10A and 13A https://www.rospa.com/home-safety/uk...hoosing-fuses/ I think some of that might be down to BS7671 only mentioning 3A and 13A fuses. Although I cannot find a reference to that ATM. -- Adam |
Fuse calculation
On Monday, 19 March 2018 16:18:39 UTC, whisky-dave wrote:
On Monday, 19 March 2018 16:11:42 UTC, The Other Mike wrote: On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v Assuming you mean at the BS1363 plug then the fuse should be sized to protect the cable. -- Nice, that's the sort of answer I'd expect :-) But this was a question given to students doing our science foundation course where they are expected to say 5 Amps. (a student has left their marked paper (mid semester test) in the lab so I thought I'd have a look). 5A is a better answer than 13. It would give added protection against a partial short of the heating element. Either is compliant with BS. TBH this is very basic stuff. I have also been told that H&S state that consumers/users should only use either a 3A of 13 amp fuse in a plug and that is what we as technicians have been told to use, even though I have loads of fuses including 1A, 2A, 5A, 7A, 10A and 13A complete cobblers of course. https://www.rospa.com/home-safety/uk...hoosing-fuses/ a useful rule of thumb for folks that need to be told which fuse because they have no idea. Such people normally only have 3 & 13A. That's all it is. NT |
Fuse calculation
On Monday, 19 March 2018 17:59:10 UTC, Sam wrote:
On 19/03/2018 16:53, Dave Plowman (News) wrote: In article , whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v If you're talking a plug fuse, the load is irrelevant. As it is to protect the flex etc. In other words, a table light with a 20 watt bulb would be fine with a 13 amp fuse if the cable was rated at 13 amps. Won't all fuses less than 13a protect the cable then! No, for 4 reasons. 1. Some appliances have old thin cables that come nowhere near being protected by a 10A fuse. 2. Some old appliances need low current mains fuses to give them basic safety protection. 3. Some new appliances have noncompliant CCS cables. 3. Some 13A fuses are in reality 13A or greater. This applies both to old pre-ASTM and new counterfeit fuses. NT |
Fuse calculation
On Monday, 19 March 2018 18:28:56 UTC, The Natural Philosopher wrote:
On 19/03/18 15:27, whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v well you could TRY a 5A. But my guess is that its pushing the limits. it's not, any more than a 13A load is pushing it with a 13A fuse. It's precisely what they're designed for. 13A. Remember the fuse is to protect the wiring that is downstream of it only. that garbage is much trotted out. NT |
Fuse calculation
On Monday, 19 March 2018 19:25:17 UTC, John Bryan wrote:
In message Martin Brown wrote: On 19/03/2018 16:15, Harry Bloomfield wrote: whisky-dave pretended : Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v 5amp ought to cover it, but it is very tight. If it fails find a 10amp. It isn't *all* that tight in practice but the plug will run slightly warm. A nominal 5A fuse will take nearly 20A to blow in the first second and will probably support a current of 7A almost indefinitely. eg. https://docs-emea.rs-online.com/webd...6b8002b71e.pdf It would be much more challenging with a halogen light where there is a significant inrush current when the filament is cold. An electric fire is a relatively benign load with a decently high cold resistance. Nominally 13A fuses will support boiling two 3kW kettles for long enough to destroy the still coiled up extension cable they were plugged into. This is due to induction heating not resistive heating by the load supplied. Since current is the same but opposite direction in L&N conductors there is no significant induction heating. NT |
Fuse calculation
wrote:
On Monday, 19 March 2018 16:18:39 UTC, whisky-dave wrote: On Monday, 19 March 2018 16:11:42 UTC, The Other Mike wrote: On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v Assuming you mean at the BS1363 plug then the fuse should be sized to protect the cable. -- Nice, that's the sort of answer I'd expect :-) But this was a question given to students doing our science foundation course where they are expected to say 5 Amps. (a student has left their marked paper (mid semester test) in the lab so I thought I'd have a look). 5A is a better answer than 13. It would give added protection against a partial short of the heating element. Either is compliant with BS. TBH this is very basic stuff. It depends on the heating elements temperature coefficient of resistivity and how hot it gets. Some 1.15kW heaters may draw much more than 5A for tens of seconds on starting. I have also been told that H&S state that consumers/users should only use either a 3A of 13 amp fuse in a plug and that is what we as technicians have been told to use, even though I have loads of fuses including 1A, 2A, 5A, 7A, 10A and 13A complete cobblers of course. https://www.rospa.com/home-safety/uk...icity/plugs-fu ses/choosing-fuses/ a useful rule of thumb for folks that need to be told which fuse because they have no idea. Such people normally only have 3 & 13A. That's all it is. NT -- Roger Hayter |
Fuse calculation
John Bryan wrote:
In message Martin Brown wrote: On 19/03/2018 16:15, Harry Bloomfield wrote: whisky-dave pretended : Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v 5amp ought to cover it, but it is very tight. If it fails find a 10amp. It isn't *all* that tight in practice but the plug will run slightly warm. A nominal 5A fuse will take nearly 20A to blow in the first second and will probably support a current of 7A almost indefinitely. eg. https://docs-emea.rs-online.com/webd...6b8002b71e.pdf It would be much more challenging with a halogen light where there is a significant inrush current when the filament is cold. An electric fire is a relatively benign load with a decently high cold resistance. Nominally 13A fuses will support boiling two 3kW kettles for long enough to destroy the still coiled up extension cable they were plugged into. This is due to induction heating not resistive heating by the load supplied. No it is due to resistive heating and poor heat dissipation by the coiled lead. All our village hall extension cables now have thermal overload protection to save them from the church's tea ladies. -- Roger Hayter |
Fuse calculation
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Fuse calculation
on 19/03/2018, John Bryan supposed :
This is due to induction heating not resistive heating by the load supplied. Rubbish, there will be no inductive heating effect. The current in live will match that in neutral and thus negate any induction. The only heating effect in a coiled lead on ac is that of resistive heating, which becomes a problem on a coiled up lead, because the heat produced is unable to escape. |
Fuse calculation
On 19/03/2018 19:55, Harry Bloomfield wrote:
on 19/03/2018, John Bryan supposed : This is due to induction heating not resistive heating by the load supplied. Rubbish, there will be no inductive heating effect. The current in live will match that in neutral and thus negate any induction. The only heating effect in a coiled lead on ac is that of resistive heating, which becomes a problem on a coiled up lead, because the heat produced is unable to escape. Could not have put it better! |
Fuse calculation
On 19/03/2018 19:48, GB wrote:
On 19/03/2018 19:28, wrote: On Monday, 19 March 2018 16:18:39 UTC, whisky-daveĀ* wrote: On Monday, 19 March 2018 16:11:42 UTC, The Other MikeĀ* wrote: On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v Assuming you mean at the BS1363 plug then the fuse should be sized to protect the cable. -- Nice, that's the sort of answer I'd expect :-) Does the BS require that the heating element should burn out before the cable does (say there's a voltage surge)? And does the BS require that the element will burn out safely without setting fire to something? I don't think that BS761 has an opinion on it. Overload is not relevant (the load is set by the heaters wattage) so in this case only fault current applies. If you have such a voltage surge then the least of your worries would be a 1.15kW heater! -- Adam |
Fuse calculation
John Bryan wrote:
All our village hall extension cables now have thermal overload protection to save them from the church's tea ladies. Hmm, a strict reading of the rules would suggest that your electrical installation is defective - not fit for purpose as you should have sockets available where the kettles need to go, rather than using extension leads. Of course, how to provide sockets in the middle of the floor for kettles which don't then become a trip hazard when the same area is used as a dance floor is an interesting challenge... Mike |
Fuse calculation
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Fuse calculation
On Monday, 19 March 2018 19:39:09 UTC, Roger Hayter wrote:
tabbypurr wrote: On Monday, 19 March 2018 16:18:39 UTC, whisky-dave wrote: On Monday, 19 March 2018 16:11:42 UTC, The Other Mike wrote: On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v Assuming you mean at the BS1363 plug then the fuse should be sized to protect the cable. -- Nice, that's the sort of answer I'd expect :-) But this was a question given to students doing our science foundation course where they are expected to say 5 Amps. (a student has left their marked paper (mid semester test) in the lab so I thought I'd have a look). 5A is a better answer than 13. It would give added protection against a partial short of the heating element. Either is compliant with BS. TBH this is very basic stuff. It depends on the heating elements temperature coefficient of resistivity and how hot it gets. Some 1.15kW heaters may draw much more than 5A for tens of seconds on starting. a) which ones? b) fuses are pretty tolerant of that. Look up the curves. NT |
Fuse calculation
On Mon, 19 Mar 2018 19:55:23 +0000, Harry Bloomfield wrote:
on 19/03/2018, John Bryan supposed : This is due to induction heating not resistive heating by the load supplied. Rubbish, there will be no inductive heating effect. The current in live will match that in neutral and thus negate any induction. The only heating effect in a coiled lead on ac is that of resistive heating, which becomes a problem on a coiled up lead, because the heat produced is unable to escape. +1 Nicely put. That saved me having to stick *my* oar in. :-) -- Johnny B Good |
Fuse calculation
On Mon, 19 Mar 2018 17:59:03 +0000, Sam wrote:
On 19/03/2018 16:53, Dave Plowman (News) wrote: In article , whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v If you're talking a plug fuse, the load is irrelevant. As it is to protect the flex etc. In other words, a table light with a 20 watt bulb would be fine with a 13 amp fuse if the cable was rated at 13 amps. Won't all fuses less than 13a protect the cable then! Yes. Provided the load doesn't demand the use of a higher fuse rating, the lower the better the protection. The only issue would that of the heating effect inside the plug when running close to the chosen fuse rating current limit[1]. With a table lamp, even a 1A fuse will be safe from this unless you fit a 250W GLS lamp (in which case, choose a 2 or 3 amp fuse. :-). [1] All fuses rely upon the heating effect to perform their function so the plug's fuse holder must be designed to cope with the circa 1 to 2 watt's worth of dissipation whenever the fuse is carrying its rated current. The lower the fuse rating, the lower the dissipation at the rated current. However, this isn't a linear variation since the thicker fuse wire inside a 13A fuse cartridge will conduct the heat away more rapidly via its end caps into the Live pin and the live wire termination than the thinner wire in a 1A fuse cartridge. -- Johnny B Good |
Fuse calculation
On 19/03/2018 15:27, whisky-dave wrote:
Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v 13A. Bill |
Fuse calculation
On 19/03/2018 21:34, Mike Humphrey wrote:
John Bryan wrote: All our village hall extension cables now have thermal overload protection to save them from the church's tea ladies. Hmm, a strict reading of the rules would suggest that your electrical installation is defective - not fit for purpose as you should have sockets available where the kettles need to go, rather than using There is power where the kettles should go, but the tea ladies sometimes do strange things to avoid walking about 3m to the kitchen bench. The extension was coiled up and being used essentially as a 2 way adaptor so they could plug in multiple kettles at once on a nearby table instead. extension leads. Of course, how to provide sockets in the middle of the floor for kettles which don't then become a trip hazard when the same area is used as a dance floor is an interesting challenge... I have concluded that you have to assume that people will do crazy things and defend against them. Rules only go so far and get ignored. -- Regards, Martin Brown |
Fuse calculation
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Fuse calculation
Unless there is a surge on start up which can happen on heaters.
I'm very surprised we do not get 7.5 amp fuses for this sort of thing. 13 amp ones go with a heck of a bang. You can get very slow blow fuses of course with a lot of that heat conducting stuff in them, but I'd guess a lot of fuses one sees in pound shops are dodgy in the extreme. Brian -- ----- - This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please! "Graham." wrote in message ... Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v 1150/240=4.79 so theoretically a 5A fuse shoud do. -- Graham. %Profound_observation% |
Fuse calculation
Yes most people who set questions in exams have not experienced the real
world very much has been my suspicion for a while now. They are steeped in the maths but know little about the real world. Brian -- ----- - This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please! "Bill Wright" wrote in message ... On 19/03/2018 15:27, whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v 13A. Bill |
Fuse calculation
In article ,
Johnny B Good wrote: Something less trivial than a 60W table lamp such as a mains powered radio or TV set will have its own safety fuse built in to protect against the risk of conflagration, And that is the correct way to protect the appliance if needed. Not using the plug fuse. In the appliance you can choose the most suitable type of fuse. Fast blow, anti-surge, etc. Hence there not being the same range of plug fuses as once was the case. Most won't understand the differences. So best to make things for a single one. -- *What happens if you get scared half to death twice? * Dave Plowman London SW To e-mail, change noise into sound. |
Fuse calculation
In article ,
Martin Brown wrote: There is power where the kettles should go, but the tea ladies sometimes do strange things to avoid walking about 3m to the kitchen bench. The extension was coiled up and being used essentially as a 2 way adaptor so they could plug in multiple kettles at once on a nearby table instead. I'd say you shouldn't make such an extension available in a public place. Use single outlet ones only. And not cable reels as they tend not to get fully unwound. -- *The sooner you fall behind, the more time you'll have to catch up * Dave Plowman London SW To e-mail, change noise into sound. |
Fuse calculation
In article ,
Brian Gaff wrote: Yes most people who set questions in exams have not experienced the real world very much has been my suspicion for a while now. They are steeped in the maths but know little about the real world. It is the real world which says no new appliance should require a less than 13 amp fuse in a plug. Because if a lower value blows, many will just replace it with what is to hand, so likely a 13 amp one. -- *Change is inevitable, except from a vending machine* Dave Plowman London SW To e-mail, change noise into sound. |
Fuse calculation
On Monday, 19 March 2018 17:02:42 UTC, Dave Plowman (News) wrote:
In article , whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v If you're talking a plug fuse, the load is irrelevant. As it is to protect the flex etc. In other words, a table light with a 20 watt bulb would be fine with a 13 amp fuse if the cable was rated at 13 amps. But that wasn't the question was it. This was a mid-term test, so you would got this question wrong. |
Fuse calculation
On Monday, 19 March 2018 18:38:42 UTC, Roger Hayter wrote:
whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v 10A . But 13A is fine. So we both got it wrong then because the answer is 5A. |
Fuse calculation
On Monday, 19 March 2018 19:28:09 UTC, wrote:
On Monday, 19 March 2018 16:18:39 UTC, whisky-dave wrote: On Monday, 19 March 2018 16:11:42 UTC, The Other Mike wrote: On Mon, 19 Mar 2018 08:27:31 -0700 (PDT), whisky-dave wrote: Which is the best fuse to use (3A, 5A or 13A) with a 1.15kW electric fire at a potential difference of 240v Assuming you mean at the BS1363 plug then the fuse should be sized to protect the cable. -- Nice, that's the sort of answer I'd expect :-) But this was a question given to students doing our science foundation course where they are expected to say 5 Amps. (a student has left their marked paper (mid semester test) in the lab so I thought I'd have a look). 5A is a better answer than 13. It would give added protection against a partial short of the heating element. Either is compliant with BS. TBH this is very basic stuff. Which is why it's a question in the science foundation course I supose. I have also been told that H&S state that consumers/users should only use either a 3A of 13 amp fuse in a plug and that is what we as technicians have been told to use, even though I have loads of fuses including 1A, 2A, 5A, 7A, 10A and 13A complete cobblers of course. https://www.rospa.com/home-safety/uk...hoosing-fuses/ a useful rule of thumb for folks that need to be told which fuse because they have no idea. Such people normally only have 3 & 13A. That's all it is. The same fuses our PAT tester person uses then. So it really depends on your job then and little to do with the applienace ? So as I would think not a very good quetion to ask. |
Fuse calculation
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Fuse calculation
On Tuesday, 20 March 2018 09:24:58 UTC, Brian Gaff wrote:
Yes most people who set questions in exams have not experienced the real world very much has been my suspicion for a while now. They are steeped in the maths but know little about the real world. Brian He is an Associate Lecturer late 60s early 70s. |
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