Hi im a bit of a DIY er and do some welding in my shed have done for years but few months ago had the fuse box in my hoouse replaced with these new MCB breakers up untill then had no probs with the fuses blowing when useing welder but now every time i try weld the breaker trips.My shed is wired from standard 13amp plug socket the cable to the shed is the old 210 and runs into into a fuse box n the shed i only ever run onething at a time in the shed as not to overload. my question is in the main box the MCB switch on the down ring which the shed is pluged into is a b20 nhxb20 MCB would it be ok to replace that breaker with a b40 nhxB40 MCD to deal with the inital surge the welder requires to start up thank you in advance for Any help
MCB breaker keeps tripping
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No, Although it might be possible (Zs permitting) to change it to a C20 (which will have the same magnetic trip as a B40), but it sounds like you need a proper supply putting into your shed.
I would expect its not a ring either (will not a complete one anyway) otherwise it would have been put on a B32
Doc Hudson
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The purpose of the overload protective device (fuse / MCB) is to protect the cable. You do not just go increasing fuse rating without ensuring the cable capacity is adequate. Didn't you discuss your requirements with who-ever replaced the fuse box? As these are very basic design considerations when selecting the appropriate cables & circuit breakers required for your expected loads. (of course some builders/DIY'ers/wannabe electricians sometimes just by a cheap pre-loaded consumer unit from B&Q, then try and fit whatever circuits are there onto the nearest value without doing any correct design calculations). A 'C' type breaker may be adequate but earth loop impedance would need to be verified. As a general rule of thumb upgrading a protective device is normally above the knowledge of the average DIY person as they lack correct test equipment.
Doc H.
Doc H.
Thank you Doc for your reply thats why i am asking i am no electricain but from a laymans view my line of thinking is that every thing was ok with the old fuse box and the cable to the shed has never been an issue no fuses were ever blown when useing the welder.I am trying to understand why it keeps tripping and again my line of thought is that the first draw of electric when the welder is first used is to strong for the breaker and it thinks circuit is being overloaded and therfore trips to protect the circuit but if i was to fit a stronger breaker it would not trip but no harm would be done to the circuit(cable) because it took the start up surge with the old fuse box in place.No did not discuss requirments was and still am in middle of cancer battle with the wife so was not on my mind at the time its not my house its owned by houseing association reason for the lead to the shed running from a plug is to make the supply temporay to the shed not a perminant supply and therefor fits in with there regulations
what welder do you have? buzz boxes are well known for tripping MCB's as they are more sensitive than fuses. small inverter welders are not normally such an issue
a welder is not a normal domestic appliance and as such is not usually allowed for unless specifically requested
I’m guessing your old fuseboard had rewireable fuses and as such these are less sensitive to loads than the modern MCB.
This suggests your welder was pulling more load through the rewireable fuse, but for not long enough to blow the fuse.
can you post the make and model number of your welder?
This suggests your welder was pulling more load through the rewireable fuse, but for not long enough to blow the fuse.
can you post the make and model number of your welder?
Grimmy , what did you mean by the cable being "the old 210 " The shed supply is plugged into a 13A socket so its a flex I presume , so the 13A fuse isn't blowing , its bypassing that and tripping the B20 which is faster to trip than a fuse .
Wondering if you could feed that original socket from a 32A in the board , perhaps the upstairs ring or fit one to suit .
Is there an RCD in the shed ?
Wondering if you could feed that original socket from a 32A in the board , perhaps the upstairs ring or fit one to suit .
Is there an RCD in the shed ?
thats T&E. it is not designed to be fitted into a plug or used for what you are doing with it
Not that replacing the cable will solve your problem! At the end of the day the initial inrush surge of your welder exceeds what the circuit breaker can sustain, so it doesn't work.
The whole circuit needs upgrading to have both adequate current capacity and conformity with recognised installation standards. The former so that it will work, and he second for your safety.
The only reason it worked before is down to the inadequacy of fuses in distribution boards which is why they have been superseded.
The whole circuit needs upgrading to have both adequate current capacity and conformity with recognised installation standards. The former so that it will work, and he second for your safety.
The only reason it worked before is down to the inadequacy of fuses in distribution boards which is why they have been superseded.
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I would ask why the circuit it is plugged into is only on a B20. That probably means it is a radial circuit so can't be any higher. I wonder what else is running from that circuit.
As above, get the shed rewired on a more substantial circuit better suited to the job.
As above, get the shed rewired on a more substantial circuit better suited to the job.
Doc Hudson
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The problem here is you are looking at your symptoms in relation to one particular characteristic of the item your are powering. (i.e. inrush currents from your welder). But you forget that ALL electrical circuits must be designed to fail-safe so that fuses or breakers will disconnect the power before either the circuit, the property, any people or animals will not be harmed or injured in the event of a fault.
So if there was an overload fault caused by someone cutting the cable or sticking a nail in it and shorting out Live & Neutral (or earth), The fuse must be the weakest link in the circuit NOT the cable. If you look up the current capacity of your cable you will find it is not designed to carry 40Amps. So a while a larger rated MCB may stop your in-rush problem, it would not protect the cable so it will not comply with BS7671 wiring regulations.
Just because something worked before did not mean it was safe or correctly wired. With the old fuse box you could have plugged in a washing machine wired between live and earth and it would have worked. The logic of it worked before so it must have been ok is a flawed concept. Just as I can use a car with bald tyres, no seatbelt, no airbags, worn break-pads, but as long as I get to my destination it must be ok? It is not, and it IS dangerous!
Doc H.
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Everyday is a school day
i am 63 and been doing this job for a very very long time and I have never heard it called that. The only other variant on 'twin' or 'twin and earth' I have ever heard was on here where someone called it something like 'twin and skin'....but I think that was something they had made up
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A jumbled memory on the part of the OP perhaps? Hearing it verbally as two-five and one-five, and then later thinking, what was the secondd number....ermmm....ten? without thinking too deeply into it :s
Rather like the Woman who goes to automotive parts counter and asks for a "710 cap"
210 cable . I was thinking , about time to pack up :C
One or two odd terms do turn up occasionally , I went to a firm in the '70s and noticed that "KoBo ", s were often referred to .
It was their name for Knockout Boxes.
They had the old idea of a stores & storeman at the office which had to be navigated with care . Before the days of Starrett cutters we all used the dreaded Enox cutters , a body with two tiny screws holding a circular , hardened ,3/4 in. hacksaw blade . The centre mandrill needed a separate 1/4" drill .
I asked for a 1/4" drill and half a dozen Eclipse hacksaw blades .
I was given a 5/16" drill , which won't fit and one (1) 10" hacksaw blade , flexible , unbreakable, manufacturer DingDong :C
I was put right by an older hand , he said the store guy says if you ask for a 1/4" drill you will get a 1/4" clearance drill which is 5/16" , he knows it won't fit the Enox .
And they will only give you one hacksaw blade at a time and its 10" unless you tell him its for cutting 6" trunking .
Storemen were like that . :C
One or two odd terms do turn up occasionally , I went to a firm in the '70s and noticed that "KoBo ", s were often referred to .
It was their name for Knockout Boxes.
They had the old idea of a stores & storeman at the office which had to be navigated with care . Before the days of Starrett cutters we all used the dreaded Enox cutters , a body with two tiny screws holding a circular , hardened ,3/4 in. hacksaw blade . The centre mandrill needed a separate 1/4" drill .
I asked for a 1/4" drill and half a dozen Eclipse hacksaw blades .
I was given a 5/16" drill , which won't fit and one (1) 10" hacksaw blade , flexible , unbreakable, manufacturer DingDong :C
I was put right by an older hand , he said the store guy says if you ask for a 1/4" drill you will get a 1/4" clearance drill which is 5/16" , he knows it won't fit the Enox .
And they will only give you one hacksaw blade at a time and its 10" unless you tell him its for cutting 6" trunking .
Storemen were like that . :C
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