New Miele Oven causing main RCD to trip. :(

[mfarrow]

You wouldn't use diversity deciding which switch rating would be suitable but you would limit the load at the circuit design stage.

... to 6A. Then 5 years later the home owner replaces some single fittings with 'multispots' 12V halogens. The lights now trip every time they're turned on so the owner calls an electrician out who puts a B10 in.

Put it another way, you wouldn't put in a 63A fuse into a 32A TPN switch disconnector and say "well that was the only fuse I had in the van, but it'll be alright 'cos I've measures the load and it's only 30A, and besides which the cable's thick enough to take it", would you?

 

[1john]

You wouldn't use diversity deciding which switch rating would be suitable but you would limit the load at the circuit design stage.

... to 6A. Then 5 years later the home owner replaces some single fittings with 'multispots' 12V halogens. The lights now trip every time they're turned on so the owner calls an electrician out who puts a B10 in.

Put it another way, you wouldn't put in a 63A fuse into a 32A TPN switch disconnector and say "well that was the only fuse I had in the van, but it'll be alright 'cos I've measures the load and it's only 30A, and besides which the cable's thick enough to take it", would you?

thats quite a bizaare way of looking at it, and a little excessive. Someone would have to have 28 x 50W lamps on one switch to exceed the 6 Amp rating of the switch. The likelyhood of this happening is slim, i think i have seen 'multispot' fittings upto about 8, and they are usually 20W lamps on those fittings. Also if the homeowner is going to severely alter their installation then they should do a bit of research first. I don't think most sparks would uprate a MCB without some prior checking. In the case being discussed here it seems to be the electricians work that he has designed, and subsuquently altered.

 

[skenk]

You wouldn't use diversity deciding which switch rating would be suitable but you would limit the load at the circuit design stage.

... to 6A. Then 5 years later the home owner replaces some single fittings with 'multispots' 12V halogens. The lights now trip every time they're turned on so the owner calls an electrician out who puts a B10 in.

Or the homeowner uprates their 7kW shower on a '3036 & 6mm^2 cable to 10.5kw which probably wont even trip. . . When they uprate the lights they take responsibility for the extra load, you don't design & install on the basis that some DIYer may add an extra load at a later date

Put it another way, you wouldn't put in a 63A fuse into a 32A TPN switch disconnector and say "well that was the only fuse I had in the van, but it'll be alright 'cos I've measures the load and it's only 30A, and besides which the cable's thick enough to take it", would you?

Er sorry but how does that relate to my post?

 

[Stoday]

Getting back to the oven, the most likely explanation is the metal sheathed heating elements.

If damp gets into the mineral insulation of the metal sheathed elements used in ovens, you can get earth leakage. Running the element up to temperature will eliminate the moisture. Afterwards, the element will remain OK because it takes some time for moisture to creep through the seal.

Normally there would be no problem with a new oven, but this one had been sitting in a showroom for several months.

Can, of course, happen with any metal sheathed heating element, including immersion heaters. I suppose it could be regarded as a fault because it won't happen to every element, but it is so easily cured it's being a bit pernickity to call it a fault.

Of course this was not a problem before the 17th. No one would notice before RCDs and RCBOs were included in circuits feeding appliances with MS heating elements.

 

[newbieneedshelp]

Getting back to the oven, the most likely explanation is the metal sheathed heating elements.

If damp gets into the mineral insulation of the metal sheathed elements used in ovens, you can get earth leakage. Running the element up to temperature will eliminate the moisture. Afterwards, the element will remain OK because it takes some time for moisture to creep through the seal.

Normally there would be no problem with a new oven, but this one had been sitting in a showroom for several months.

Can, of course, happen with any metal sheathed heating element, including immersion heaters. I suppose it could be regarded as a fault because it won't happen to every element, but it is so easily cured it's being a bit pernickity to call it a fault.

Of course this was not a problem before the 17th. No one would notice before RCDs and RCBOs were included in circuits feeding appliances with MS heating elements.

Do you know what? From an amatuers point of view this feels like the right guess to my problem. The first time the RCD tripped was when the oven got to 32deg, then 90 deg and then 130 deg. It tripped the first three times then but has now been working well since! (Have I just jinxed it?!) Salmon on Tuesday, Chicken in breadcrumbs last night!

I'll post back if it plays up but it does seem solid now. Oh, and it was in the showroom for a year.

Thanks,

Lee

 

[JohnD]

... if the oven has not been used for a while, there is a possibility it is damp inside...try to warm the oven up again. If it is a bit damp, heating it up will dry it out... .