Gas oven Temperature profile

[Hysteresis]

Mrs Hysteresis has bought a new Belling All Gas Range cooker to replace an ageing Leisure Ringmaster oven. The reason for change was spares availability.
We have been very pleased with the Leisure cooker and thought a replacement unit would be pretty much the same after all it is a gas heated box.
Initial trials of this new unit was disappointing in that the oven seamed rather cooler than the Leisure of at the same Gas Mark setting. we played around with it and found that the cooking on the top shelf was near that which we would expect from a particular Gas Mark Setting but on lower shelves the results were totally different suggesting a much lower gas Mark Temperature. Certainly totally different characteristics to the Leisure Unit.
This resulted in me doing some tests on the oven to try and determine what the problem was or indeed if there was a problem.
I used a high temperature digital thermometer to determine the oven temperature. I used a Gas Mark Setting of 7 , which equates to 220'C. I allowed the oven temperature 10 minutes to stabilise with the temperature probe on the shelf near the top of the oven. I returned a temp of 238'C which sound about right as it was high in the oven. I then repeated the test with the probe 5 inches lower and after a 10 minute stabilisation period the temperature indicated 188'C equivalent to Gas Mark 4 (Wow!!! 50'C difference in only 5 inches). I thought that must be wrong so I repeated the tests twice more and returned similar results.
I did yet another test with the probe in the base of the oven at 3 inches below the test on the low position shelf, this returned a temperature of 168'C equivalent to Gas Mark 3.
Obviously the lower the position in the oven then the lower the temperature but a 50'C reduction in only 5 inches change in height seems rather excessive.
The new Belling ovens are fitted with fans so I would have expected a very much more unified temperature, but the temperature gradient I am measuring makes these ovens virtually un-useable. It would suggest to me maybe a door seal problem but, Hey, this is a brand new oven.
I do not profess to be a Gas Oven expert by any stretch of the imagination, but would anyone who knows considerably more then me comment on what I consider to be a grossly unacceptable temperature gradient.
Maybe my expectation based on our Leisure cooker experience is unreasonable and would welcome your advice before I take the performance back to the Manufacturers Belling

 

[gasbanni]

Spares availability for your Leisure Rangemaster was/is good if you know where to go.
True that they may not be available from Rangemaster not necessarily true they're not available.

Too many variable factors to really comment on your findings .......how long are you leaving the probe between the door openings for the temperature to stabilise, how are you mounting the probe in the oven ? Is it touching the shelves. etc etc

 

[Hysteresis]

To late to refer to Leisure Rangemaster Spares I am afraid. The oven has been removed and presumably destroyed.
With respect to the the tests I have done.
There are not many variables involved here. Just setting the oven to Gas MarK 7 and measuring the temperature attained at three different level.
The probe is being left in position for in excess of 10 minutes so that the temperature indicator is stable and not changing. The probe is laid on the grid shelves such that the tip is NOT touching the metal of the grid and as such is measuring air temperature. The point is that in repeatable l tests I am getting a temperature gradient of around 10'C per inch, This seems to be very very excessive. The only thing I can suggest is that the gas oven is furnished with Fans. In an electric oven the fans simply circulate the heated air in the oven. If in the case of a gas oven, the fans may be inducing air to the oven for the purpose of oxygen injection to ensure efficient gas combustion. If this is the case the fans may be introducing cold external air to the oven and in doing so causing a cool air stream into the oven as such cooling the lower section of the oven disproportionately. !!!!!!!!!

 

[sxturbo]

The middle of the oven should be the temperature specified for the gas mark. If it is not then something is wrong.

Have you tried turning it to gas mark 8 and 6 and measuring the same as with gas mark 7?

 

[ETAF]

I'm no expert
But i would not expect that much difference , I use a 4 temp probe IBT 4X ( Mainly Purchased for a BBQ Smoker ) But often use on my electric fan oven when cooking a large joint of meat.
And don't see that much difference between top and bottom.

I would suggest calling Belling Tech line
https://www.belling.co.uk/contact-old/
Although you probably will have to deal with the company who sold the unit to you for any exchange/repair etc.
https://www.which.co.uk/consumer-rights/advice/what-do-i-do-if-i-have-a-faulty-product

 

[Hysteresis]

Thanks sxturbo, I haven't tried Gas Mark 8 and 6 but will today. I have temp tested the top of the oven with Gas mark 9 and I do get 255'C that being 10'C over the specified temperature for Gas Mark 9.
Thanks also to eta, I will telephone Belling today after a few more repeat tests. It may be all to do with there being a fan in the ovens, I have never used a gas oven with a fan before but may be legislation is different these days and a forced draught fan is required to ensure complete combustion, the external air flow may be effecting the temperature distribution, but I would have thought the fan would even out the temperature distribution as in an electric oven, this is having the opposite effect.

 

[sxturbo]

We have a belling, was there when we moved in and we aren't fans, it's an older model without the fan,it's taken us a little while to get used to it but now know the "tricks".

When we replace it, it won't be with another belling.

I fear your cooker is indeed faulty and might be to do with the temp sensor thingywthingy modulates the flame.

But should try the other settings as comparison, it might just be the way the valve is designed mark 7 isn't optimal for it, although this would be an odd thing to do as mark 7 is probably the most used and therefore should be the most accurate

 

[Hysteresis]

Thanks for your input sxturbo, i don't think it will be the sensor because the top shelf of the oven gets to 10'C above the Gas Mark setting, the problem is heat distribution, there is a 50'C variation in only a 5 inch level change, that just can't be right. So its not ultimate temperature it is distribution and not knowing the details of the mechanical design, I cannot contemplate what the problem is. I will discuss it with Belling but on other occasions I get to talk to a Customer Services employee who are not technical and they then discuss it with their Technical guys but without my input to the conversation.
Oh! What Joy

 

[sxturbo]

What happened to the days of buying something and it worked as it should straight out the box

 

[ericmark]

When were those days? In our first house we did not have a full width oven, so to be able to fit a turkey in the oven we got what was then the new Belling fan oven and because the element was at the back we had the width we needed, we had never used a fan oven before, and found it burnt the food, and we had the set the temperature well below what the books said to get good results, we did get use to it, but took some time.

On moving house we again had a Belling fan oven, but full width, and it was only then we realised all those years the old oven must have had a faulty thermostat, it was nothing to do with being a fan oven it was simply faulty from new.

The whole idea of the gas mark system was there was no thermostat as such, it was simply flame height, because the gas burnt in the oven there was always a through exchange of gases, the solid fuel oven however had a void around the oven where the combustion gases circulated, they did not (it was hoped) get into the oven its self, and by using dampers you could change how the oven was heated.

To fit a fan in a gas oven one would expect they would have to follow the solid fuel example and not have the flame in the oven so also no gas exchange in the oven so would need a thermostat, from what you say I would say there is some thing wrong, either in the design or a faulty component. A baffle missed out, or some thing else.

There may be a clue with the instructions, with the old solid fuel ovens which shelf changed temperature so you could cook at the same time items needing different temperatures, and the cooking instructions told you how to set dampers for even heat or varying heat through the oven, the fan oven made a big thing of being able to fill the oven with cakes and they would all cook at same rate.

So get out the cook book that came with the oven, and see what it says.

 

[Hysteresis]

Hi ericmark, interesting comments. This gas oven is not as you suggest, there is a fan, but what it is for I have no idea. The fan starts up after the oven has warmed up. As it does not run on first ignition I assume the fan was to stabilise the oven temperature over the full heigh of the oven. Clearly this oven does not do that so just what the fan function remains a mystery. I rang Belling to see what their comments are. They thought the same as me in that such a temperature gradient seemed excessive but could not make any comments as to the cause. I am already getting a service man to call about another issue relating to the programmer not operating and Belling are advising the service guy to have a lookout this temperature gradient issue whilst he is here. It seems every one I speak to agrees the temperature gradient appears excessive. I will see what the service man comes up with. I am expecting to get a reply of "That it is within expectations" which I will contest but in absence of a specification I will have little hope of an acceptable resolution. I will then get back to Belling as they seem to agree with my complaint.
In so far as a cookbook coming with the oven. I consider myself lucky I got an instruction booklet let alone a cookbook. The instructions leaflet makes no reference to Temperature gradient specification, but this oven does not operate anywhere near as well as the Leisure cooker it was purchased to replace.