Oven Heat

[Thurlestone]

I have a Knaus Sun Ti 650 and have found when we use the oven that the area around it gets very hot and the cutlery drawer is so hot that the metal cutlery is too hot to use. Has anyone had a similar problem with their motorhome and has anyone been able to resolve the matter. I have thought of fitting either a fan behind it or a vent to the exterior. I don't know if either action will create any other problem.

[globebuster]

Something's not right there for sure.

 

Stating the obvious - Either the oven is producing excessive heat, or more likely insuffecient isolation/ventilation, so not dissapating heat from the surrounding structure.

 

Are there heat shields to deflect the heat from the drawer?

[tonyishuk]

We made a heat shield from aluminum foil and spread it over the top of the oven. Improved it slightly.

 

Plastic silver bubble wrap would melt.

 

We tried 2 sheets of ali foil with some fiberglass innards, but that split when laid and we did not like the thought of fiber glass particles in the air.

 

Plan C. 4 layers of ali foil, the two outer left flat, the twoinner cores were scrunched to give an air gap between the sheets. Improved the situation slightly,we just make sure the drawer is pulled open when the cooker is left on for a time.

 

Rgds

[PJay]

tonyishuk - 2013-05-10 9:09 PM

 

We made a heat shield from aluminum foil and spread it over the top of the oven. Improved it slightly.

 

Plastic silver bubble wrap would melt.

 

We tried 2 sheets of ali foil with some fiberglass innards, but that split when laid and we did not like the thought of fiber glass particles in the air.

 

Plan C. 4 layers of ali foil, the two outer left flat, the twoinner cores were scrunched to give an air gap between the sheets. Improved the situation slightly,we just make sure the drawer is pulled open when the cooker is left on for a time.

 

Rgds

 

You can buy pads that go behind radiators,(to stop heat going out the walls) which may be better for you

Also maybe the silver sun shields thatyou get for puttimg over windscreens, can sometimes get them in the £ shops

[gocro]

The oven should have sufficient insulation to retain the heat to cook your food. These ovens are either poorly installed or designed. You can buy rocksill, mineral wool sheets to beef up the insulation or more likely the isolation from the rest of the habitation.

As ever where gas is concerned be very cautious not to impede the air supply.

Radiator foil and sunscreens are likely to have a polystyrene core and would probably be a mite dangerous.

[Derek Uzzell]

This advert is for a similar Knaus motorhome http://tinyurl.com/c2zfovp

 

The 4th, 5th and 6th photos show the kitchen arrangement, with a largish (probably SMEV-made) gas-oven beneath an under-worktop drawer.

 

The oven's installation instructions are likely to have included recommendations about the amount of space that should be left above the oven but, with a drawer that's visibly close to the oven's top surface, it's inevitable that the drawer and its contents will get hot if the oven is used for a long period.

 

As globebuster suggests, fitting a shield between the top of the oven and the bottom of the drawer (assuming this is practicable) should help to reduce heat transfer to the drawer.

 

You've considered fitting a vent to dissipate the oven's heat outside the motorhome and this approach (normally using a fridge ventilation grille) is reasonably commonplace. It's possibly your best bet, though - if your Knaus has an unusual bodywork colour - finding a grille that doesn't look unsightly might prove tricky. Adding a fan should be less visually intrusive, although you'd still need to arrange for the hot air to be exhausted outside the vehicle (through the floor?)

[Thurlestone]

Thanks Derek

 

My van is exactly as the one shown bar it being right hand drive. The oven is the same style and location and as the drawer has a plastic inner I am concerned damage will be done. I think the previous owner did not use the oven very much. I am going to seek a black vent cover to match the fridge one on the other side. In this way it should look ok and won't let a lot of damp in from below. I was really surprised when I took the oven out of its location that it does not appear to have any insulation material around it but did not want to fit this without having ventilation. I am really pleased with your suggestion and will undertake it to enable both reduced heat and a clear route of ventilation.

 

David

[gocro]

If your oven has NO insulation it will find it impossible to attain heat levels high enough to cook with, it will in effect just warm food, some insulation is required to hold the heat in otherwise you will just be warming the van,

[Brian Kirby]

Thurlestone - 2013-05-11 11:43 AM

 

Thanks Derek

 

My van is exactly as the one shown bar it being right hand drive. The oven is the same style and location and as the drawer has a plastic inner I am concerned damage will be done. I think the previous owner did not use the oven very much. I am going to seek a black vent cover to match the fridge one on the other side. In this way it should look ok and won't let a lot of damp in from below. I was really surprised when I took the oven out of its location that it does not appear to have any insulation material around it but did not want to fit this without having ventilation. I am really pleased with your suggestion and will undertake it to enable both reduced heat and a clear route of ventilation.

 

David

SMEV is now owned by Dometic (isn't everything?), so have you tried contacting them for a copy of the installation instructions? This may be more productive, and possibly safer, than DIY solutions. What you describe sounds worryingly hot, especially just below a plastic drawer base. As with fridges, it may be that required safety/performance features have not been supplied/installed. I assume there may be water and drainage pipes, plus electric wiring, in the vicinity, that are all getting gently cooked as well?

[Derek Uzzell]

Installation and operating manuals for the current range of SMEV ovens/grills can be downloaded from here:

 

http://www.my-caravanning.com/en/products/kitchen/ovens/Dometic-SMEV-FO311GT/46944

 

The photo of the oven in the 2008 French Knaus motorhome suggests that David’s oven will be an earlier version of the FO311GT model. Some SMEV appliances can accept a ‘chimney’ (led to the leisure-vehicle’s roof) but not, I believe, this one.

 

There are exploded views of SMEV ovens here:

 

http://www.leisurespares.co.uk/files/ovens.pdf

 

There will be no external insulation fitted to these appliances. The oven (as David has discovered) is visually just a plain ‘cube’ made of sheet metal. What insulation there is will be fitted (out of sight) behind that sheet metal.

[Guest pelmetman]

Derek Uzzell - 2013-05-11 6:54 PM

 

There will be no external insulation fitted to these appliances. The oven (as David has discovered) is visually just a plain ‘cube’ made of sheet metal. What insulation there is will be fitted (out of sight) behind that sheet metal.

 

Which is as our 23 year old cooker is, works fine, roast dinners the lot ;-).......................It gets hot......so I turn of the fire in winter......or open the windows and door in summer :D

[Derek Uzzell]

David has said he has found "...when we use the oven that the area around it gets very hot and the cutlery drawer is so hot that the metal cutlery is too hot to use."

 

The normal expectation would be for the oven to be completely surrounded by vertical 'furniture boad' on each of its sides, by a horizontal sheet of board above and below, and by the motorhome's bodywork wall at the rear. It should be anticipated that, with this arrangement, the furniture board will heat up when the oven is being used.

 

In the (perhaps unlikely) event that there's no horizontal sheet of board above the oven, or there's any gap in that board, the bottom of the cutlery drawer above the oven will inevitably get hot.

 

Assuming there is an above-oven board (if not, one needs to be fitted), before choosing the ventilation-grille route, I'd explore the possibility of adding another board above (or below) the original with an air-gap between the two. I'd also look at insulating the underside of the drawer (with thin polystyrene sheet?). Adding a ventilation-grille should cure the present problem, but cutting holes in motorhome bodywork is best avoided if there's an altenative.

 

If a vent can't be found to exactly match the fridge vents on the other side of David's Knaus, MPK-branded black vents are widely marketed (see foot of this webpage)

 

http://www.rainbowconversions.co.uk/equipment/Fridges/fridges.htm

 

either surface-fitting or recessed-fitting, with a 'winter cover' being available for the latter type. Presumably these vents are OK regarding weather protection.

[Brian Kirby]

Derek Uzzell - 2013-05-12 7:57 AM

..........The normal expectation would be for the oven to be completely surrounded by vertical 'furniture boad' on each of its sides, by a horizontal sheet of board above and below, and by the motorhome's bodywork wall at the rear. It should be anticipated that, with this arrangement, the furniture board will heat up when the oven is being used.

 

In the (perhaps unlikely) event that there's no horizontal sheet of board above the oven, or there's any gap in that board, the bottom of the cutlery drawer above the oven will inevitably get hot.

 

Assuming there is an above-oven board (if not, one needs to be fitted), before choosing the ventilation-grille route, I'd explore the possibility of adding another board above (or below) the original with an air-gap between the two.

 

I agree with this. Looking at the installation instructions and comparing them to the photographs of the oven in Derek's excellent links, it seems unlikely the specified clearance of 170mm from the top of the oven to the underside of the top board of the appliance housing will have been met. It looks a bit as though Knaus have assumed that the drawer can be included within a greater clearance which, if true, I think questionable. Perhaps a sheet of Marinite or similar non-combustible board could be installed tight beneath the drawer without reducing the clearance below the specified 170mm? Larger DIY places often sell cut pieces of this type of product alongside their cut pieces of ply.

 

The main problem I can foresee in adding the vent grille without sealing off the cabinet below the drawer, is the perennial one of draughts into the van in winter. Even if the cabinet is sealed as suggested, I would think there would still be some draught into the van through the grilles top and bottom of the oven door. I know these are intended to vent the space between the oven insulation and the outer casing but, from the illustrations, it seems that outer casing is some way from being hermetically sealed!

 

I'd also look at insulating the underside of the drawer (with thin polystyrene sheet?). Adding a ventilation-grille should cure the present problem, but cutting holes in motorhome bodywork is best avoided if there's an altenative..........

 

I agree that trying the seal off the cabinet is preferable to installing a grille, but I'm rather wary of the idea insulating the floor of the drawer as suggested. First, the (presumably) expanded polystyrene is generally flammable, and second it has to be fixed in place in a way that would resist the temperatures above the oven. That, to me, would discount any kind of adhesive since, were it to drop off, one would not know this had happened until the heat of the oven got to work on it - via nasty smells and/or smoke! So mechanical fixings I think would be a must. But, if the cabinet cannot be closed below the drawer, leaving as the only solution insulation of the drawer, and if to achieve this securely mechanical fixings must be used, why not use something incombustible to externally case the drawer? Maybe a board similar to that suggested above could be used at sides, rear and underside. It would make the drawer a bit heavier, but not that much so in the overall scheme of things, it would shield the flammable materials from immediate exposure, and it should have the effect of shielding the drawer contents from the worst of the oven heat. Since the drawer can (presumably) fairly readily be removed, this should be a reasonably easy solution to achieve though not, IMO, as good as sealing the oven cabinet below the drawer.

[BIFFO]

We had a similar problem with the oven in our Hymer. Having used the oven we too found the utensil drawer extremely hot. Having spotted a similar van on site I wandered over to see if they were having the same problem. They were...........until they discovered a pull out tray at the top of the oven which dispersed the heat away from the drawer,it looked like part of the oven so unless you knew what to look for it can be easily missed.

Hope this is of use.

[Derek Uzzell]

bgrobbins@hotmail.co - 2013-05-12 4:01 PM

 

We had a similar problem with the oven in our Hymer. Having used the oven we too found the utensil drawer extremely hot. Having spotted a similar van on site I wandered over to see if they were having the same problem. They were...........until they discovered a pull out tray at the top of the oven which dispersed the heat away from the drawer,it looked like part of the oven so unless you knew what to look for it can be easily missed.

Hope this is of use.

 

There's a pull-out 'tray' in the FIG.6 (Page 130) diagram in the SMEV installation and operating manual .

 

http://www.waeco.com/tmp/DOM_FO_VN_EB_12S_02.pdf

 

The Page 19 reference to the diagram says:

 

"WHEN USING THE GRILL THE DOOR MUST BE KEPT OPEN AND WITH THE HEAT GUARD FULLY EXTRACTED (FIG. 6 - PG. 130)."

 

There's no information about the purpose of the "heat guard", but (as it's clearly linked to the operation of the grill) I don't think it's there to protect what's above the oven when the oven is being operated normally with its door closed and the grill off.

 

Perhaps what you are referring to is something different (have a look at the diagram), or perhaps you are suggesting that David's oven might be missing its heat guard?

[pepe63xnotuse]

If there's enough clearance, then I'd be installing something like a Vermiculite board....

 

http://shop.vitcas.com/vermiculite-fire-board---fire-proof-insulation-72-p.asp

 

 

[Derek Uzzell]

This advert is for a 2005 Hobby T-600FC like mine

 

http://www.blackcountrycaravans.co.uk/stocklist/997/2005-hobby-t600-fc-motorhome

 

The advert's 3rd photo showsthe kitchen with a SMEV oven of a similar size to David's set beneath the cutlery drawer. It should be obvious that the clearance between the top of the oven and the bottom of the drawer will be small.

 

My Hobby has no oven. Instead there is a storage cupboard with twin curved doors that is separated from the drawer by a horizontal piece of furniture board. The oven was standard on RHD UK-specification Transit-based Hobbys sold through Brownhills, but I don't know what modifications were made to allow it to be installed. I note that there's a curved piece of chromed metal in front of the oven's base, and there may (or may not) be something similar above the oven to protect the drawer from the oven's heat. If there's nothing above the oven to provide heat-protection for the drawer, the drawer will get very warm indeed.

 

In the Hobby's case it would be possible to insulate the drawer by attaching a thin sheet of metal to its underside. Alternatively, as the drawer has a moulded liner for the cutlery, it would be possible to introduce a thin sheet of insulating material beneath the liner. A thicker sheet of insulation could be employed if the original liner were removed and replaced by a shallower DIY-made liner.

 

It's pretty much impossible to advise what's the 'best' approach to David's problem without seeing his motorhome. However, when the oven is being used, if the temperature of the metal utensils in the cutlery drawer can be lowered to a point where they are not uncomfortably hot, and this can be done without performing surgery on the motorhome's bodywork, that should really be good enough.

[pepe63xnotuse]

As it doesn't look like they'd be room for the 25mm vermiculite,I'd probably be looking a lining the top of the oven casing with some thinner Masterboard..

http://www.building-supplies-online.co.uk/promat-masterboard-fire-protection-board-6mm-5840-p.asp

 

(..it's what used behind/around Agas,woodburning stoves etc).

[Brian Kirby]

Afraid that'd be unwise Pepe, is the installation instructions for the oven call for 170mm clearance above the top of the oven. So the oven top must be left unadorned.

 

It will require either of a sheet such as you cite installed 170mm above the oven, if the drawer permits, or a protective layer applied to the base of the drawer and casing its sides and back.

 

Actually, Vermiculite board might work very well used in that way. The boards can be obtained down to 10mm thickness, it is non-flammable, reasonably light, and it provides some insulation. My only reservation is that it is brittle, and of relatively low strength. The plastic base of that drawer has to be expected to flex in use, so there is a judgement around whether the thin board has sufficient flexibility to absorb the movement or whether the thicker boards would have the strength to resist it. But, I think it could work well. Could easily be attached using a few through bolts and washers. Good shout!

[Thurlestone]

Dear gocro

 

I am of course aware that the facts of physics means that heat has to be contained but in my caravans it had external insulation which is absent in the motorhome. The Smev oven lacks any visible lining in any of the surrounding cupboard etc.

[Thurlestone]

Hi Brian

 

I have waited to view the oven and cabinet and thoroughly digest all the advise given before posting a reply. First of all I would like to say it is a SMEV oven but it does not a number or specification easily viewed. The oven is held in place by 4 screws on the front surface and sits on a timber internal bar at the rear and another on the front of the cabinet. Below is a pan cupboard directly open to the oven metal base. Above the oven it is open with 40mm to the underneath of the plastic drawer and 170mm to the top of underneath of the work surface. With the drawer closed, there is only 40mm air space between it and the oven. I like the idea of insulating the drawer and think it may be possible to do this with the thin insulation board. The only ventilation I can assume is through the pan cupboard allowing access to air but the hot air rising must either exit via the grid around the oven or through the space around the cutlery drawer as there are no ventilation holes on the work surface or cabinet work. What do you think, please?

 

David

[Brian Kirby]

What you say bears out my suspicion that Knaus have placed the drawer into the overall clearance as recommended by SMEV. Whether that was their assumption, or was supported by SMEV, is open to conjecture, but won't help either way as you are where you are. Clearly you need the drawer, so the solution has to accept its retention.

 

My thought is that the drawer front is probably a fairly leaky fit to the cabinet as will be the front of the pan drawer below. So, air can reasonably circulate up and around the oven casing and, so the drawer will be likely to be opened during the process of cooking, serving and eating the meal, the venting of the cabinet is probably adequately catered for to the extent that no serious safety risk is created.

 

If that is a reasonable assumption, then what you have is a convenience issue that the oven heats the drawer and its contents to an uncomfortable degree.

 

I would therefore try to find a stockist/supplier of vermiculite boards in your area, and see what you can get hold of. You won't need a lot as the drawer is not that large. Before deciding what thickness to go for, I think it would be wise to assess how much the drawer base flexes, bearing in mind the effects of driving over uneven roads, and to try to see and handle some of the board. If the thinner vermiculite flexes slightly and can be expected to flex with the drawer, I'd go for that.

 

It is odd stuff, quite light, easy to work with woodworking tools, fire resistant, a moderate thermal insulant, but not hugely strong and it is brittle. It is commonly available under the trade name Vicuclad, although I note their thinnest is 20mm. Manufaturer Promat Ltd. They should be a ble to advise stockists/suppliers.

 

I think I'd case the drawer sides, base and rear, and I think I'd just fix it in place by putting countersunk machine screws through the plastic and the board, and drilling an oversized hole about 5mm into the board, so that the a washer and fixing nut can be recessed flush. That way, the fixings wouldn't project beyond the board faces to catch on anything. It will be necessary to tighten with care so as not to crack the board, but sufficiently to stop them working loose. Maybe incorporate an AV washer. If you talk to Promat they may have a better, more flexible product to offer. Alternatively if you can find a nearby stockist so may they.

 

I'd try that for openers since, as Derek suggests, cutting holes in the side walls of vans should be the last resort. I think you will have the potential for howling gales from the kitchen block if you have to go that route. That bit of extra insulation should suffice to keep the drawer and its contents cooler when the oven is used. It will still get warm, but not nearly as warm as at present. How warm will depend largely on how long you have the oven running. After all, insulants only resist the transmission of heat, they don't eliminate it.

[Brambles]

I think you are all missing a few fundamental points here. The oven is gas and so the oven needs a flow of air through it as well as around it.

The oven 'exhaust' is via the grill/slots at the top and this should not be impeded in any way. The pictures linked earlier show the drawer front is positioned just above the slots. This is not as per the installation instructions and creates a problem along with other possible issues.

 

The air rising within the cabinet should exit the cabinet somewhere, and this is achieved in most enclosures by venting through a gap between the oven top and the front mounting frame pieces. Just below that are the grid of slots for the oven exhaust gases. Now, if you, say, were to have a gap somewhere else inside the cabinet at the top, be it around the drawer area and into other cupboards or a designed slot, it is possible to create a situation where the exhaust gasses actually get sucked back into the slot around the frame and into the upper part of the cabinet below the draw. One big issue is the drawer front being so low as this restricts the exhaust flow of gasses and actually will help direct some of the very hot air back into the cabinet and hence heat the drawer up.

 

So 1st thing is to modify the draw front so it does not impede the flow. This could possibly be done by chamfering it but may be easier said than done. Another option is to make a new veneered/foiled 'wood' surround and mount the oven further forward so the front of the oven is flush with the drawer front, leaving just a clearance gap between the draw front and the top edge of the new surround piece.

Next step is to test if the upper slot around the frame has hot air flowing out or in. If in then the thermal movement of air inside the cabinet needs to be addressed. Either a lot more ventilation is required to exhaust all the hot air from the cabinet and drawer area, the suggestion of external fridge type grills is one method but should not be necessary.

The best solution is probably a second non combustible sheet just below the drawer, maintaining the clearances stated in the instructions and to seal of the top of the housing below the drawer. Once this is carried out all the heat should come out of the slots at the top of the oven drawing cool air in at the bottom.

This air exhausted is very hot and will warm up anything above it which impedes its flow upwards, hence the drawer must not stick out and the work top has to be something like 150mm above the slots.

This is clearly a bad installation not to the specified installation methods, and also not so unsual as many installers just flaunt the guidance which must be followed but of course the motorhome builder always thinks he knows better!

 

I am not suggesting what I have said above is all correct, but serious food for thought. Take it or leave it as I am not an expert in thermal management of ovens like this but in my world of electronics sometimes things get hot when they should not and every cabinet housing an array of heat generating equipment had to be tested and often modified, sometimes by some very simple modification to cure an issue. e.g. a very small defector plate on the back of some hot component just to send the rising air flow in a slightly different direction.

However I think in this oven case it is just the very hot air flow is being allowed to reach the drawer unit rather than escaping where it should. Maybe even the plate at the back of the oven for a chimney option has been left off, or there is an excessive gap around where the optional oven lamp can be fitted so all this has to be checked as well.

 

The summary of all this is to make sure the installation guidelines ARE followed, they are there for a reason. Tut tut Knaus!

 

Sorry it is a tome - got a bit carried away.

 

[Keithl]

Simple solution...

 

Take the drawer out when using the oven!

 

That way you get the required 170 mm clearance above the oven and the cutlery stays cool!

 

Sorted. Next...

 

Keith.,

[Derek Uzzell]

Brambles - 2013-05-14 1:44 AM

 

...The summary of all this is to make sure the installation guidelines ARE followed, they are there for a reason. Tut tut Knaus!

 

Irrespective of the SMEV installation guidelines, having a cutlery-drawer close to the top of this type of large-size gas-oven is commonplace on motorhomes - in fact, I'd go as far as saying it's the norm. The photos in the Hobby advert I provided a link to to show exactly the same arrangement as on David's Knaus and, unless something has been done to the Hobby to insulate the drawer's contents from the heat produced by the oven, with the same inevitable consequences. Here's another example of a large oven like David's with drawers directly above:

 

http://www.friendlyhippo.co.uk/hymerdirect/ovens.htm

 

David's complaint is that the metal utensils in his cutlery-drawer get too hot to handle. While this is indeed pretty warm, it's not the level of heat where furniture board starts to char!

 

Different ploys to combat the problem have been suggested and both of David's original ideas - an exterior vent or fan-ventilation (or both) - should be effective. These approaches have their obvious drawbacks and (as I've suggested earlier) if it's possible to reduce the heat in the drawer to a point where the utensils remain handleable, and to do this easily and without cutting the motorhome about, that will be the KISS solution.

 

David has not said what (if anything) is beneath the drawer - whether, if the drawer is removed, there is a void or any sort of 'shield'.

 

FIG. 1 of the SMEV installation instructions advise a 100mm gap at the oven's sides and a 170mm gap above the oven. But neither of these recommendations are likely to be practical when an oven is positioned in the manner commonly seen in motorhomes.

 

There's nothing in the SMEV instructions to suggest that the enclosure into which this oven-model is fitted must be vented. Even if the oven were installed as shown in FIG. 1 with 170mm of space above it, the surface above the oven would still get hot unless a shield of some kind were between the oven and the upper surface. In David's Knaus, if there were no cutlery-drawer in the way, the worktop above the oven would just get hot instead.

 

This advert http://tinyurl.com/bus534e is for a Chausson 2006 Welcome 74. Image 10/14 shows a largish gas-oven set above the fridge-freezer. There is a reasonable distance between the oven's top and the ceiling because a) there can be and b) if the oven were higher it would become even more dangerous to use. But the significant thing is (as will be seen from Images 1 & 2) that Chausson has fitted an extra grille to ventilate the oven's otherwise-sealed enclosure.

 

So, if it proves impossible to reduce the heat in the drawer to an acceptable level by straightforward non-surgical methods, an exterior vent is the next simplest approach. Fan-assisted ventilation would require electrical power, either provided automatically when the oven were switched on, or via a manual or heat-sensing switch. It's an option (and should be easy enough to implement) but an exterior vent is simpler and insulating the drawer simpler still.