I think I need a 4cm x 57cm* extractor fan arrangement to provide an
airflow above a built-in microwave. Without it, the microwave would be
in essentially a sealed box.

Any ideas if these are commercially available?

* that's the inside dimensions of a 60cm unit.
--
Roland Perry

Roland Perry wrote:

I think I need a 4cm x 57cm* extractor fan arrangement to provide an
airflow above a built-in microwave. Without it, the microwave would be
in essentially a sealed box.

Any ideas if these are commercially available?

* that's the inside dimensions of a 60cm unit.

If you have somewhere (false ceiling, top of cupboards?) to duct it away
and use a ducted fan you can get rectangular duct about 4cm in one
dimension, use stop end and cut out the side of the duct. All standard,
so cheaper; and gets rid of cooking smells/fat.

--

Roger Hayter

On 20/06/2020 10:08, Roland Perry wrote:
I think I need a 4cm x 57cm* extractor fan arrangement to provide an
airflow above a built-in microwave. Without it, the microwave would be
in essentially a sealed box.

Any ideas if these are commercially available?

* that's the inside dimensions of a 60cm unit.


Maybe you just need ventilation holes (and a covering grille plate) as
the fan inside the microwave itself will push the hot air out if the
holes are correctly positioned.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 20/06/2020 10:08, Roland Perry wrote:
I think I need a 4cm x 57cm* extractor fan arrangement to provide an
airflow above a built-in microwave. Without it, the microwave would be
in essentially a sealed box.

Any ideas if these are commercially available?

* that's the inside dimensions of a 60cm unit.
Had you considered putting a false back on the cupboard above and
effectively creating a chimney? If the cupboards stop short of the
ceiling then the hot air will vent easily, if not you'll need to duct it
through the top cupboard to a grill. Don't forget to provide an inlet.
Alternatively, could you adapt one of the standard microwave fixing kits
which have grills?

In message , at 10:25:02 on
Sat, 20 Jun 2020, Roger Hayter remarked:
Roland Perry wrote:

I think I need a 4cm x 57cm* extractor fan arrangement to provide an
airflow above a built-in microwave. Without it, the microwave would be
in essentially a sealed box.

Any ideas if these are commercially available?

* that's the inside dimensions of a 60cm unit.

If you have somewhere (false ceiling, top of cupboards?) to duct it away
and use a ducted fan you can get rectangular duct about 4cm in one
dimension, use stop end and cut out the side of the duct. All standard,
so cheaper; and gets rid of cooking smells/fat.

It's not practical to expel the air other than out the front. As for
smalls/fat, they shouldn't be any worse than a microwave on the
countertop, and people are happy with those.
--
Roland Perry

In message , at 10:31:31 on Sat, 20
Jun 2020, alan_m remarked:
On 20/06/2020 10:08, Roland Perry wrote:
I think I need a 4cm x 57cm* extractor fan arrangement to provide an
airflow above a built-in microwave. Without it, the microwave would be
in essentially a sealed box.
Any ideas if these are commercially available?
* that's the inside dimensions of a 60cm unit.

Maybe you just need ventilation holes (and a covering grille plate) as
the fan inside the microwave itself will push the hot air out if the
holes are correctly positioned.

At the moment there's a big hole with the dimensions I gave. But it has
to cope with air intake and outlet. So I was hoping for something with a
grille and fan, to assist the circulation from the microwave's internal
fan (to help stop that recirculating air back into the oven's intake
inside the wall unit)
--
Roland Perry

In message , at 11:06:29 on Sat, 20
Jun 2020, remarked:
On 20/06/2020 10:08, Roland Perry wrote:
I think I need a 4cm x 57cm* extractor fan arrangement to provide an
airflow above a built-in microwave. Without it, the microwave would be
in essentially a sealed box.
Any ideas if these are commercially available?
* that's the inside dimensions of a 60cm unit.
Had you considered putting a false back on the cupboard above and
effectively creating a chimney? If the cupboards stop short of the
ceiling then the hot air will vent easily, if not you'll need to duct
it through the top cupboard to a grill. Don't forget to provide an inlet.

That's a possibility, but I was trying to avoid all those new holes.

Alternatively, could you adapt one of the standard microwave fixing
kits which have grills?

I suspect this one (I have the bezel) once had a grill, but it's been
misplaced. If I'm fitting a new one, it'd be handy if it had fan assist.
--
Roland Perry

Roland Perry brought next idea :
At the moment there's a big hole with the dimensions I gave. But it has to
cope with air intake and outlet.

Could you not manage to add a partition so the intake and outlet are
separated, to ensure there is some flow rather than recirculation of
the same air?

On 20/06/2020 12:40, Roland Perry wrote:

I suspect this one (I have the bezel) once had a grill, but it's been
misplaced. If I'm fitting a new one, it'd be handy if it had fan assist.


I'm lost. Wouldn't you be buying a microwave designed for building in?
That'll have ducts built into the microwave.

I don't know how much it matters if there's no ventilation, assuming
it's say an 800w microwave, used for a couple of minutes at a time?

In message , at 14:37:05 on Sat, 20 Jun
2020, Harry Bloomfield remarked:
Roland Perry brought next idea :
At the moment there's a big hole with the dimensions I gave. But it
has to cope with air intake and outlet.

Could you not manage to add a partition so the intake and outlet are
separated, to ensure there is some flow rather than recirculation of
the same air?

I'd still need a grille at the front for the airflow.

The intake is at the rear of the RHS, and there are two outlets: one at
the front of the RHS for the electronics, and another in the top for the
cooking chamber.

Unfortunately, the RHS of the oven is against a brick wall.

I might be able to run some trunking from the rear LH corner (where I
could stick a vent to the room), along the back, and round the corner to
the inlet. Plan view:

==========================#
vent ------trunking -----+ #
| mmmmmmmmmmmmmmmmmmmmmm+ #
| m + #
| m - # wall
| m m #
| m m #
| m #
| m #
| mmmmmmmmmmmmmmmmmmmmmm #
___ door ____#

facing room

inlets
outlets (side and top)
To the left is free space.
--
Roland Perry

In message , at 15:53:30 on Sat, 20 Jun
2020, GB remarked:
On 20/06/2020 12:40, Roland Perry wrote:

I suspect this one (I have the bezel) once had a grill, but it's been
misplaced. If I'm fitting a new one, it'd be handy if it had fan
assist.

I'm lost. Wouldn't you be buying a microwave designed for building in?
That'll have ducts built into the microwave.

I've got one that works OK already (1000w), even if designed for
countertop.

I don't know how much it matters if there's no ventilation, assuming
it's say an 800w microwave, used for a couple of minutes at a time?

Given that we've had no kitchen since before lockdown we've been
exploring the various settings, one of which is a conventional oven.

Also things like Combination/Jacket Potatoes etc have the thing on for
half an hour.
--
Roland Perry

Roland Perry submitted this idea :
I might be able to run some trunking from the rear LH corner (where I
could stick a vent to the room), along the back, and round the corner to
the inlet. Plan view:

A passive system is a better bet than an active one, if it can be
arranged. You only need to duct one - the intake or the outlet, the
other will find its own route.

In message , at 18:57:38 on Sat, 20 Jun
2020, Harry Bloomfield remarked:
Roland Perry submitted this idea :
I might be able to run some trunking from the rear LH corner (where I
could stick a vent to the room), along the back, and round the corner to
the inlet. Plan view:

A passive system is a better bet than an active one, if it can be
arranged. You only need to duct one - the intake or the outlet, the
other will find its own route.

As there's one inlet and two outlets...

Still need a grille for the front though.
--
Roland Perry

On 20/06/2020 16:21, Roland Perry wrote:

Given that we've had no kitchen since before lockdown we've been
exploring the various settings, one of which is a conventional oven.

Also things like Combination/Jacket Potatoes etc have the thing on for
half an hour.

I can see why you're concerned.


I know it would be usual to vent the warm air upwards, but as this is a
fan duct, you could also take it downwards or sideways if that works
better. If the air is just hot, not moist, it may not matter much where
it ends up - behind the plinth at the bottom of the units, for example.

Put mesh over it though or nasty insects come in.
Brian

--
----- --
This newsgroup posting comes to you directly from...
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Note this Signature is meaningless.!
"Roger Hayter" wrote in message
...
Roland Perry wrote:

I think I need a 4cm x 57cm* extractor fan arrangement to provide an
airflow above a built-in microwave. Without it, the microwave would be
in essentially a sealed box.

Any ideas if these are commercially available?

* that's the inside dimensions of a 60cm unit.

If you have somewhere (false ceiling, top of cupboards?) to duct it away
and use a ducted fan you can get rectangular duct about 4cm in one
dimension, use stop end and cut out the side of the duct. All standard,
so cheaper; and gets rid of cooking smells/fat.

--

Roger Hayter

In message , at 22:36:50 on Sat, 20 Jun
2020, GB remarked:
On 20/06/2020 16:21, Roland Perry wrote:

Given that we've had no kitchen since before lockdown we've been
exploring the various settings, one of which is a conventional oven.
Also things like Combination/Jacket Potatoes etc have the thing on
for half an hour.

I can see why you're concerned.

Because there are items in the same set of units which need to be kept
at room temperature.

I know it would be usual to vent the warm air upwards, but as this is a
fan duct,

I was proposing an intake duct, the outlet straight into the room. But I
need something to fill the 4x57cm slot, and was thinking something with
fan assist might be helpful.

you could also take it downwards

The main hot air exhaust is at the op of the microwave, so "down" is
difficult.

or sideways if that works better.

That's a possibility. See my earlier diagram, maybe an outlet on the LHS
as well. I could probably fit a fan scavenged from a computer PSU on the
inside. Now, if it was possible to power that off the same supply as the
interior light, we could have a solution.

If the air is just hot, not moist, it may not matter much where it ends
up - behind the plinth at the bottom of the units, for example.

That area's pretty airtight.
--
Roland Perry