Recirculating hob - seal MDF or not?

[dormermike]

Hello

Not sure if this is the right section.

In process of having new kitchen with island hob and it's an induction recirculating hob. The picture shows what I'm working with and I'm currently putting some ducting in to direct the airflow to the bottom of the units. It won't be a fully sealed tight fit, just trying to get it as good as possible. It's a Bora hob, requires 25mm clearance at back which we've got. I'm concerned about the exposed MDF and chipboard though. Would it be prudent to seal these?

Thanks

 

[foxhole]

Very little info , photo of a piece of wood not helpful.

 

[opps]

As above, your post is somewhat vague... however, I think you are concerned that the steam sucked into the ducting might leak into the void. If so, I see nothing to lose from applying a dilute coat of oil based varnish over the interior faces of the chipboard and MDF.

EDIT- one of my customers has one (externally vented- IIRC). Nice bit of kit

 

[dormermike]

As above, your post is somewhat vague... however, I think you are concerned that the steam sucked into the ducting might leak into the void. If so, I see nothing to lose from applying a dilute coat of oil based varnish over the interior faces of the chipboard and MDF.

EDIT- one of my customers has one (externally vented- IIRC). Nice bit of kit

That's exactly it, thank you. Sorry my original post was vague. The hob is basically designed to vent into the voids. I'm making a duct as best I can, but I'm thinking any exposed MDF could be best protected.

So an oil based varnish. When you say dilute, not with water presumably? Why dilute and not just neat, for my understanding.

Thanks

 

[foxhole]

I would be concerned about venting into room under units the moisture will rot the units.

 

[dormermike]

I would be concerned about venting into room under units the moisture will rot the units.

Yeah, apparently it's designed for that, but I do know what you mean. I'm concerned about it too. I'll be fitting secondary extraction. I did not like the idea of underfloor ducting as it would congeal fat, same difference I suppose.

Bora supposed to be best for recirc extraction so I'm trying to give it the best shot.

 

[opps]

If you dilute the oil based varnish with a little bit of white spirit, it will help the varnish to soak in. The end grain of the chipboard would benefit from additional full fat coats of varnish.

Personally, I would be concerned about the steam potentially being trapped in the cavity under the units. Bora don't seem to address those issues on the following page ( https://www.bora.com/gb/gb/service/kitchen-exhaust-air-recirculating-air/ ). It might be prudent to fit grills on both sides of the island. Given how expensive they are, why not email them and ask them for tips. You might, for example be able to use plywood/etc to restrict the space under the units that the steam can potentially occupy.

Let us know how you get on.

 

[dormermike]

Thanks. I did email them. The classic is what's shown in your link. I have the M Pure, and it can be placed almost flush against a back panel, provided there is 25mm clearance and 500cm2 at the bottom, that's all that is needed. See photo below.

My original photo shows 40mm clearance, and the right hand side (green) panel is where the extractor will blow onto. I'm making up a duct to direct it down as much as possible, but it seems inevitable to me that eventually the MDF will absorb moisture. Maybe in Germany they make their kitchens out of solid timber.

As to the moisture the manufacturer (Bora) said:

Regarding your concern because of moisture:

When you work with the recirculation system, it is physically normal that the relative air humidity in the room increases when cooking with recirculating air. Especially when there is a large temperature difference, e.g. when warm air meets cold tiles. This can be compared to a foggy mirror in the bathroom after a shower. This is especially the case during the cold season.

To avoid an increase of air humidity, the following measures are recommended:

Activation of the automatic after run function (starts automatically when you end your cooking process)

With the automatic after run, the BORA system is prepared for the next cooking process. The piping and the recirculation unit are freed from residual liquid and dried. To ensure optimal filter performance, we recommend to observe the filter service indicator and to replace the activated charcoal filter regularly.

Observance of a normal living space climate

Regular ventilation balances the general room climate and also prevents mould formation. Mould forms only in damp, stagnant air. With the recirculated air version, the air is always in motion. The relative humidity is about 40-60%.

If the predefined minimum dimensions are respected and the air circulates in the living space, mould formation is excluded when using BORA recirculation or exhaust air systems. Wooden and kitchen components as well as other constructional elements are not affected by that.

 

[opps]

A foggy mirror has airflow though, and the water drips off...

I still think that a vent the front and back will help the steam to escape more effectively - cross currents and all that..

Their response is a bit word salad, but they are expensive and seem to have many happy (affluent) customers.

 

[dormermike]

A foggy mirror has airflow though, and the water drips off...

I still think that a vent the front and back will help the steam to escape more effectively - cross currents and all that..

Their response is a bit word salad, but they are expensive and seem to have many happy (affluent) customers.

Vent front and back, at floor level ? That's what I'm planning to do, double up the 500cm2 basically. Also I was thinking an extractor in the base unit might not be a bad idea, I have power in the island, in fact I may be able to piggy back it off the hob fan. But that's just belt and braces. I'm going to varnish exposed panels too.

Thanks for all the help.

 

[chirpychippy]

Nope you don't have to seal anything, the ducting will direct the moisture to the underside of your cabinets which are sealed and through the two vents you need to cut into your plinths.

 

[Murdochcat]

Sounds VERY naff if you ask me

 

[dormermike]

Sounds VERY naff if you ask me

In what way?

 

[^woody^]

Surely a recirculating hood is just as good as no hood at all?

TBH, I would suspect that the through-flow of air will just mean that the significant part of the moisture just gets pushed through the duct and back out into the kitchen, so no need for any coatings in the enclosure.