As part of the long overdue kitchen revamp, we are looking at an
induction hob mounted on a granite worktop. It is a De Dietrich hob,
glass with no frame round it, and we would like to embed this into the
granite so that the glass hob surface is at the same level as the
granite.

I have been told that we would have to leave about a 5 - 10 mm gap
around the glass to allow for expansion; I do not believe this to be
true as glass does not expand very much and it is an induction hob
with small, localised hot spots. I would have thought a 1 - 2 mm gap
around the hob, probably filled with a black silicone compound would
have sufficed.

Does any one have any experience of this, or comments?

Thanks

Andy Bernard

Andy Bernard wrote:
As part of the long overdue kitchen revamp, we are looking at an
induction hob mounted on a granite worktop. It is a De Dietrich hob,
glass with no frame round it, and we would like to embed this into the
granite so that the glass hob surface is at the same level as the
granite.

I have been told that we would have to leave about a 5 - 10 mm gap
around the glass to allow for expansion; I do not believe this to be
true as glass does not expand very much and it is an induction hob
with small, localised hot spots. I would have thought a 1 - 2 mm gap
around the hob, probably filled with a black silicone compound would
have sufficed.

Does any one have any experience of this, or comments?

I don't have experience of fitting to granite, but I do have a
DeDietrich induction hob (it's like magic!), and it definitely doesn't
expand 10-20mm when in use (5mm gap all the way round = 10mm linear
expansion. I'd be amazed if it expans as much as 1mm. I'd say a gap of
2mm would be more than sufficient.

--
Grunff

"Grunff" wrote in message
...
Andy Bernard wrote:
As part of the long overdue kitchen revamp, we are looking at an
induction hob mounted on a granite worktop. It is a De Dietrich hob,
glass with no frame round it, and we would like to embed this into the
granite so that the glass hob surface is at the same level as the
granite.

I have been told that we would have to leave about a 5 - 10 mm gap
around the glass to allow for expansion; I do not believe this to be
true as glass does not expand very much and it is an induction hob
with small, localised hot spots. I would have thought a 1 - 2 mm gap
around the hob, probably filled with a black silicone compound would
have sufficed.

Does any one have any experience of this, or comments?

I don't have experience of fitting to granite, but I do have a
DeDietrich induction hob (it's like magic!), and it definitely doesn't
expand 10-20mm when in use (5mm gap all the way round = 10mm linear
expansion. I'd be amazed if it expans as much as 1mm. I'd say a gap of
2mm would be more than sufficient.

It might be worth asking De Dietrich.

As you say, only the area under a pan gets hot. The edge of hot plate does not
get hot, otherwise you would not be able to operate the touch controls. When
you think about it, there must be a temperature gradient across the ceramic
surface leading to internal expansion problems. Much worse on halogen hobs as
they get hotter.

I am also an induction hob fan. Excellent temperature control, but not as
indistructable as a stainless steal solid plate hob!

Michael Chare

On 12 Oct 2004 06:05:02 -0700, (Andy
Bernard) wrote:

As part of the long overdue kitchen revamp, we are looking at an
induction hob mounted on a granite worktop. It is a De Dietrich hob,
glass with no frame round it, and we would like to embed this into the
granite so that the glass hob surface is at the same level as the
granite.

I have been told that we would have to leave about a 5 - 10 mm gap
around the glass to allow for expansion; I do not believe this to be
true as glass does not expand very much and it is an induction hob
with small, localised hot spots. I would have thought a 1 - 2 mm gap
around the hob, probably filled with a black silicone compound would
have sufficed.

Hi,

If the granite isn't cut perfectly straight it will be a lot more
noticable with a 1mm seam than with a 5mm seam.

Also if the hob expands 1mm into a 2mm seam it will be more likely to
squash the sealant out than with a 5mm seam, plus the hob itself will
get much more compression stress.

Finally if you ever need to get the hob out you'll have a devil of a
job with a 1 or 2mm seam compared to a 5mm seam.

cheers,
Pete.

"Andy Bernard" wrote in message
om...
As part of the long overdue kitchen revamp, we are looking at an
induction hob mounted on a granite worktop. It is a De Dietrich hob,
glass with no frame round it, and we would like to embed this into the
granite so that the glass hob surface is at the same level as the
granite.

I have been told that we would have to leave about a 5 - 10 mm gap
around the glass to allow for expansion; I do not believe this to be
true as glass does not expand very much and it is an induction hob
with small, localised hot spots. I would have thought a 1 - 2 mm gap
around the hob, probably filled with a black silicone compound would
have sufficed.

Does any one have any experience of this, or comments?

According to my bible!! the coefficients of expansion (alpha) for the
following substances a
Granite = 8.3
Soft Glass (soda?) = 8.5
Borosilicate glass (pyrex) = 3
Fused Silica = 0.5
All these figures are multiplied by 10 to the power of -6.

It is likely that the so called ceramic surface probably has a coefficient
somewhere between 3 and 0.5
The equation to apply is probably?? Orig length * (1+alpha * T) = Final
length.
I would imagine that the ceramic surface would only gain heat from the
container being heated, one of the party tricks I believe, is to place a
piece of paper between the saucepan and the hob and to marvel at it's
unspoiled condition after extended boiling.
The induction coil itself generates some heat hence the need to allow
adequate air flow under the hob.
It's difficult to apply the info above as the change in temperatures is
known only to the manufacturers.
Hope this helps
Good luck
Tom (BTW, I'm hoping to install one in my kitchen when it's
refurbished next year)

"Tom" wrote in message ...

According to my bible!! the coefficients of expansion (alpha) for the
following substances a
Granite = 8.3
Soft Glass (soda?) = 8.5
Borosilicate glass (pyrex) = 3
Fused Silica = 0.5
All these figures are multiplied by 10 to the power of -6.

It is likely that the so called ceramic surface probably has a coefficient
somewhere between 3 and 0.5
The equation to apply is probably?? Orig length * (1+alpha * T) = Final
length.
I would imagine that the ceramic surface would only gain heat from the
container being heated, one of the party tricks I believe, is to place a
piece of paper between the saucepan and the hob and to marvel at it's
unspoiled condition after extended boiling.
The induction coil itself generates some heat hence the need to allow
adequate air flow under the hob.
It's difficult to apply the info above as the change in temperatures is
known only to the manufacturers.
Hope this helps
Good luck
Tom (BTW, I'm hoping to install one in my kitchen when it's
refurbished next year)


Hi

Many thanks for your postings - they confirm my initial thinkiang and
the question is now with De Dietrich to ensure that no warranties are
invalidated as a result.

Andy Bernrd

Hi

Many thanks for your postings - they confirm my initial thinkiang and
the question is now with De Dietrich to ensure that no warranties are
invalidated as a result.

Andy Bernrd
Andy
Insert lara to contact.
I would very much like to read the results of your investigations and
enquiries with De Dietrich ( French Manufacturer??).
I would be grateful if you can post again.
Regards
Tom )