Blomberg MKN24001 Ceramic Hob Exploded, opinions appreciated.

[Twoten]

I was asked to report on the following for an letting agent that had the hob installed.

A tenant complained because a new (about a month old) Blomberg Ceramic Hob exploded.
The user said it was being used to cook 8 x flat breads which take about a minute each. Just as she’s finished the last one she noticed a bit of smoke coming from the control knobs so turned the control off (not the isolator), removed the pan and went out of the room. Very shortly after, there was a loud bang. She returned to the kitchen and found this!

There were pieces across the kitchen, some as far as 4′ to 5′.

The control unit is the bank of 4 selector switches not regulators. I opened the switch panel up and found a very slight smell of burning but no sign of smoke or heat damage. I tested the operation of the switches and element as far as possible and it appeared to work fine and switch off completely.
It looks like the worktop is scorched along the edge of the exposed element but I can’t be certain this wasn’t like it before this hob was installed however the heatproof tape on the end bracket/plate is also scorched.
The piece of glass that was bonded to the corner has separated, some of the bonding on the glass and on the bracket.
The element has 3 cracks in the insulated surround. When the hob shattered the glass as hot enough to scorch the worktop.

When the hob was installed, the installers only fitted one fixing clip in the centre at each end (these are the spring type). The spring clips at the front and back were not fitted. Looking at the picture, it looks as if there may not have been enough clearance so instead of enlarging the hole they left the clips off. Having said that, the unit was not a tight fit. I’m going to go back and measure the cut out.

The only other thing I can add is the bases of the pans used on this hob slightly convex so don’t sit flat though they didn’t cause a problem with the previous ceramic hob.

I have my own suspicion what might have caused this, but would be interested in other engineers thoughts before making a final decision.

[electrofix]

have you checked the aperture size it was fitted into. the front look butt up to the work surface if the back is the same then expansion may have done it

is the pan suitable for a ceramic hob ?

Dave

[Twoten]

electrofix wrote:have you checked the aperture size it was fitted into. the front look butt up to the work surface if the back is the same then expansion may have done it
Dave

The dimensions of the cut-out are 490 x 562 matching the installation requirements.

electrofix wrote:
is the pan suitable for a ceramic hob ?
Dave

The pan that “was in use at the time” looks like it’s ceramic hob compatible. The had another saucepan in the kitchen that wouldn’t be suitable as the base is convex.
If it was caused by an incorrect pan, would the glass have spread so far round the kitchen?

[electrofix]

don’t know but this has gone I think because the glass got hotter in one part than another. this will setup an internal stress in the glass so it went with a bang. the distance travelled is down to the release of this stress

problem here you will never find out what happened. Tennant said she was cooking flat bread, did the pan she said she was using look suitable for the purpose?

from the looks of the pictures it seems the worksurface has been burning. that would tend to indicate a pan was used that was too big and overhung the edge causing excess heat to get at the wood work

Dave

[Twoten]

Unfortunately, I don’t know if the burnt area of worktop adjacent to the ring was already burnt or not.

The user said she had removed the pan. I think this is likely otherwise the glass would not have scattered in all directions. I suspect the user left the ring on (although she denies this), this would account for the scorch marks on the worktop caused by the shards of glass. Had she turned the hob off before removing the pan, I doubt it would have been hot enough to scorch.

As you say, I’ll never find out what happened. Fortunately, I did explain to the agent there’s a good chance I wouldn’t be able say for sure or prove what had cause this and at best it would only be an opinion.

[Author]

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