I have recently found what I consider to be design faults on an electrical domestic appliance. It has the very real danger of a lethal voltage being present on the casing if no RCD protection were available & a second fault could lead to it being a fire hazard. Th manufacturers have not responded to my report & I cannot find any "body" to report it to using a google search. Does anyone have any ideas who the relevant body might be? Thanks.
Safety issue with domestic appliance
- Thread starter jj4091
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Trading Standards.
Surely the manufacturer would be interested.
What do you mean by a lethal voltage? Would the OPD not operate.
What do you mean by a lethal voltage? Would the OPD not operate.
AMDEA might also be interested.
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You could also try those bbc watchdog type programmes?
Do you mean that the case is not earthed? If it's not, then RCD protection would not help, but if it is earthed then the MCB/fuse ought to clear the fault if there's no RCD (assuming the installation uses a supplier-provided earth).
Kind Regards, John
It would not help as in prevent a voltage appearing on the case.
It ought to help as in making it less likely to be lethal.
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Risk assessment and perception.
I watched a very good U-tube video by PW on ELCB-v where he highlighted the problems with the old device, however I question the dangers of parallel paths as it still does not change the fact it will trip at less than 50 volt. Although the problems associated with voltage gradient are likely valid.
We try to work out risks in our head, rather than do an experiment, and as a result we can get it wrong in both directions.
I was told you can’t have earth electrodes with a TN system, which is correct, as they are extraneous conductive parts not electrodes it is just the label which is wrong, you can have a copper covered rod hammered into the ground. As to if this is a good idea is another question, I have seen where a fault on a TN-C-S supply has melted the bonding cables to extraneous conductive part which had a very good contact with earth, but an earth rod with a 40Ω resistance with a 230 volt supply will only carry 5.75 amp it is only when the rod is 4Ω where there is a problem and the cable needs to carry 57.5 amp.
I have both considered item to be safe when in fact there was a danger, and considered it to be dangerous when in fact safe. I did not see the danger of having an earth mat used for amateur radio connected to the DNO supplied earth with a TN-C-S system until I saw the melted cable.
However having a 80 volt to earth voltage on the aerial of a TV I saw as dangerous even though the manufacturer stated it could only deliver 3 mA so was considered safe, as I could foresee some aerial fitter letting go of the ladder when he got a shock, I however did not foresee the danger that if earthed to would be more likely to get a lighting strike. Cure is de-coupling capacitors, but I did not realise this until a lot latter.
I read report of “It has the very real danger of a lethal voltage being present on the casing if no RCD protection were available.” and my first thought is how does a RCD stop a lethal voltage being present? It an appliance is earthed then any voltage should open the protective device be it a fuse, MCB, RCBO, or RCD one of the devices should trip. If not earthed i.e. Class II then the RCD will not trip until after you get a shock which is really too late.
As to “a second fault could lead to it being a fire hazard.” That is likely true with many appliances, if the thermal fuse is faulty with a fan heater a second fault of the fan stalling will be a fire hazard, in fact highly unlikely it will not go on fire. However we consider the likely scenario of the thermal fuse failing closed circuit is very small.
So if your letter to the manufacturer was as vague as the post on here I would expect them to simply put it in the bin.
I personally think the 110 volt yellow brick transformers are a fire risk, the over load is normally on the input, so 13A at 230 volt = 54A at 55 volt which is more than a 1.5 mm² cable can take, so if a cable is short circuited more than 35 meters down it’s length likely nothing will trip until the cable melts and shorts closer to the transformer, I see this as a major design fault, however these yellow bricks are used in many building sites with surprisingly few fires. It has been assessed that the risk from electric shock of a 230 volt system is more than the risk of fire with a 55 – 0 – 55 volt system. And however much the safely officer disagrees with this does not matter, on a building site his hands are tied.
So before you write letters, how about detailing what is wrong with the equipment as it may be to correct would create a bigger danger.
I watched a very good U-tube video by PW on ELCB-v where he highlighted the problems with the old device, however I question the dangers of parallel paths as it still does not change the fact it will trip at less than 50 volt. Although the problems associated with voltage gradient are likely valid.
We try to work out risks in our head, rather than do an experiment, and as a result we can get it wrong in both directions.
I was told you can’t have earth electrodes with a TN system, which is correct, as they are extraneous conductive parts not electrodes it is just the label which is wrong, you can have a copper covered rod hammered into the ground. As to if this is a good idea is another question, I have seen where a fault on a TN-C-S supply has melted the bonding cables to extraneous conductive part which had a very good contact with earth, but an earth rod with a 40Ω resistance with a 230 volt supply will only carry 5.75 amp it is only when the rod is 4Ω where there is a problem and the cable needs to carry 57.5 amp.
I have both considered item to be safe when in fact there was a danger, and considered it to be dangerous when in fact safe. I did not see the danger of having an earth mat used for amateur radio connected to the DNO supplied earth with a TN-C-S system until I saw the melted cable.
However having a 80 volt to earth voltage on the aerial of a TV I saw as dangerous even though the manufacturer stated it could only deliver 3 mA so was considered safe, as I could foresee some aerial fitter letting go of the ladder when he got a shock, I however did not foresee the danger that if earthed to would be more likely to get a lighting strike. Cure is de-coupling capacitors, but I did not realise this until a lot latter.
I read report of “It has the very real danger of a lethal voltage being present on the casing if no RCD protection were available.” and my first thought is how does a RCD stop a lethal voltage being present? It an appliance is earthed then any voltage should open the protective device be it a fuse, MCB, RCBO, or RCD one of the devices should trip. If not earthed i.e. Class II then the RCD will not trip until after you get a shock which is really too late.
As to “a second fault could lead to it being a fire hazard.” That is likely true with many appliances, if the thermal fuse is faulty with a fan heater a second fault of the fan stalling will be a fire hazard, in fact highly unlikely it will not go on fire. However we consider the likely scenario of the thermal fuse failing closed circuit is very small.
So if your letter to the manufacturer was as vague as the post on here I would expect them to simply put it in the bin.
I personally think the 110 volt yellow brick transformers are a fire risk, the over load is normally on the input, so 13A at 230 volt = 54A at 55 volt which is more than a 1.5 mm² cable can take, so if a cable is short circuited more than 35 meters down it’s length likely nothing will trip until the cable melts and shorts closer to the transformer, I see this as a major design fault, however these yellow bricks are used in many building sites with surprisingly few fires. It has been assessed that the risk from electric shock of a 230 volt system is more than the risk of fire with a 55 – 0 – 55 volt system. And however much the safely officer disagrees with this does not matter, on a building site his hands are tied.
So before you write letters, how about detailing what is wrong with the equipment as it may be to correct would create a bigger danger.
Indeed. That was the OP's comment I was responding to ....
Again, indeed. If current flowed through a person from the appliance to something that was earthed, then an RCD would reduce the probability of the shock being lethal.
Kind Regards, John
If you want to play label/word games, you could say that it was a TT installation with the DNO's incoming CNE conductor being the extraneous-c-p !
Kind Regards, John
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My point is it is in the main down to our perception of risk rather than actually taking statics and working out real risk. And unless we lay out out assessment of risk very carefully many will ignore it.
If you say the washing machine went of fire and killed two people, then the manufacturer may take note, if you say it may catch fire if used to dry clothing with cooking oil on it, they will disregard it. And even if former, likely they will claim latter anyway.
If you say the washing machine went of fire and killed two people, then the manufacturer may take note, if you say it may catch fire if used to dry clothing with cooking oil on it, they will disregard it. And even if former, likely they will claim latter anyway.
Indeed so ... that's probably why RCDs have become 'essential', not to mention metal CUs!
Kind Regards, John[/QUOTE]
As I said in the first post a lack of an rcd in any circuit this appliance (an electric oven) was connected to would result in the casing becoming live because on overload device does not always cut the supply. The fault is that one of the internal components shorts to earth when the casing of the oven heats up but not when cool. Even when it does the current does not always seem to be high enough to trip an mcb ( or probably blow a fuse ) but I would guess it is high enough to kill someone, although I am no expert on what it takes to do that.
Given that ovens are often connected to 32 or 45 Amp radial circuits & the fact that this oven has no internal overload protection I think there is a possibility that when this component shorts to earth there is a possibility of the heating of the outer casing when the component heats up it makes it become a fire risk, although I am willing to admit the risk is probably extremely low.
Trading standards say it is not their area.
AMDEA might be worth a try, but they seem to be a consumer group looking at their website.
I can't imagine a tv programme being interested in one case, which is all I know about, but I suspect it happens often as the problem part is readily available on e-bay, which is unusual for parts unless they fail regularly.
Eric, I gave the manufacturers precise details, but unless you were familiar with the make & model of this oven I doubt it would mean much to you.
But to get back to my original question is there a "body" or association that issues safety certificates to manufacturers?
Given that ovens are often connected to 32 or 45 Amp radial circuits & the fact that this oven has no internal overload protection I think there is a possibility that when this component shorts to earth there is a possibility of the heating of the outer casing when the component heats up it makes it become a fire risk, although I am willing to admit the risk is probably extremely low.
Trading standards say it is not their area.
AMDEA might be worth a try, but they seem to be a consumer group looking at their website.
I can't imagine a tv programme being interested in one case, which is all I know about, but I suspect it happens often as the problem part is readily available on e-bay, which is unusual for parts unless they fail regularly.
Eric, I gave the manufacturers precise details, but unless you were familiar with the make & model of this oven I doubt it would mean much to you.
But to get back to my original question is there a "body" or association that issues safety certificates to manufacturers?
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Thanks for clarifying. I therefore assume you are implying that the case is earthed, but (assuming the installation is satisfactory) that it's not a 'dead short' ('negligible impedance') that is occurring, so that the fault current is not high enough to trip and MCB (or blow a fuse), but (presumably) would trip an RCD, if present.
However, I wonder what is making you believe that the case is 'live'? If the case IS satisfactorily earthed, and IF your installation has an earth provided by your electricity supplier {rather than your own earth rod} - do you know the answer to that?) then, even if the fault current is not high enough to trip an MCB, the earthing should limit the voltage on the oven's casing to a very low (and probably fairly 'safe') level. If you have a local earth rod (a 'TT' earthing system), then the oven's case could/would rise to a dangerous voltage, which is why it is essential to protect a TT installation with RCD(s).
The current which flows through a person if they simultaneously touch something live and something 'earthed' is determined by the voltage of the live part (relative to earth) and the resistance of their body, not the current flowing through the fault. We work on the assumption that the risk of death increases if that current is above 30mA (0.03A), which will happen if the voltage one touches is more than about 30-50V. Unless you have a TT installation, the earthing of the case should keep the voltage well below that figure, even if the MCB does not trip.
The case is unlikley to heat up significantly, but the wiring might. However, the circuit should be designed so that the MCB would trip before the cables became excessively hot or suffered any harm - so should prevent any fire risk. The actual short within the oven, if there is one, itself might produce local heating and present some fire risk.
Is this a direct import from the Far East? If so, such items are not uncommonly 'dangerous' and Trading Standards really should be interested, particularly if it bears an 'invalid' "CE mark".
Kind Regards, John
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