3 Oven Gas Technical Page

3 Oven Gas Technical Page

The 3 & 5 oven gas or oil cookers and essentially the same cooker, just a different burner, and can be changed over if you change fuel type.

The gas can be Natural, LPG (bottled) or G25 ( Holland and Belgium), it is just a small adjustment to change over.

To operate the Thornhill Range Gas 3-Oven Range Cooker, simply turn the cooker on to the oven temperature you require in the main oven. It can be set with a time clock to come on and off as required.

It then takes 15 minutes to bring the hot plate to 180 C and 30 minutes for the oven to get to 180 C. If the oven is already on at, for example, 100 C, it only takes about 20 minutes to bring it up to 180 C.

If the main oven is at 180 C then the second oven will be 30-40 degree less than that, 140-150 C and the bottom oven 30-40 degrees less that that 100-120 C.

To use as a room heater, you simply set up the clock to the desired times,( usually the same as your central heating clock). Then leave the oven on at a set temperature. Roughly:

With the oven set at 100 C, you get around  1 kW to the room, 150 C- 2 kW and 200 C -3 kW (same as an AGA range cooker), so you set it according to how cold it is outside. In the summer because of the fast heat up you just turn it on and off a required for cooking.


We sell direct from the factory except in a few circumstances. This mean the price can be reduced by 20-25% as there are no middle men. We have a showroom in Canterbury where we can demonstrate the different fuels, but often existing customers near you will show you their cooker, but I only can do this if you are seriously interested in buying a cooker.

There is also a small amount of preparation to get done before we bring your cooker to your kitchen and install it in place.

1st_ Do you have a suitable place for an oil fired cooker, the width of the cooker is 1,000mm wide and the depth, please look at Cooker Dimensioned Side View .

2nd– Do you have a suitable chimney there. You can use a brick built or masonry chimney or have a ‘chimney’ constructed out of ‘twin wall’ flue pipe, (click for and example supplier. Best in the UK to got to HETAS where you can enter your post code and get a list of chimney technician in your area. They will be happy to to advise and quotes to line an existing or supply and fit  a twin wall system. The internal diameter of the flue is 5 inches or 125 mm, and it must be able to with stand 300 C. We always specify a Multi-fuel 316 flexible liner.


With a Thornhill 3 oven gas you can have a ‘balanced/low level discharge’ flue, where the exhaust goes straight out the back instead of up a chimney. This means the cooker has to be against an outside wall.

3rd– Floor. The cooker should stand on a non-flammable base. If you have a wooden floor you can lay a slab of stone, tiles or concrete, it should be over 3/4 inch  or 20 mm.

4th-Electrics. You will need a 3 amp supply, via a time clock to run the cooker.

5th-Oil. You will need a 10mm oil line laid in ready to connect to the cooker. In the UK go to www.gassafe.co.uk where you can enter your post code and get a full list of registered oil technicians in your area.

Its as simple as that, but if you have any problems or questions email us at info@trcookers.co.uk , we can answer questions and send further diagrams and links if required.

Size: 100cm or 149cm wide, 91cm high and 71cm deep see Cooker side view dimensions

Gas fired 3-5 oven cooker- Installation & Instruction Manual

Installation Advise Notes Gas

Doc J Building regs. for flue position for oil, gas or wood fuel.

Chimney Connection beside a wall


Now the very difficult bit WHAT COLOUR?. There is a very large choice, but if you email us your name and postal address we can send you 3 or 4 sample swatches as in the pictures. They are cast iron so quite heavy and I ask you to keep them till we deliver your cooker and then we collect them back.



















The cooker come in one piece, factory tested weighing about 650 Kg. So please advise any potential delivery problems, eg. flights of steps, tight corners or very narrow doors.

Size: 100cm or 149cm wide, 91cm high and 71cm deep see Cooker side view dimensions

Doc J Building regs. for flue position for oil, gas or wood fuel.

Running costs Based on 4p/kW.
The hot plate will heat up to boiling in 4-5 minutes, whilst the oven takes 25 minutes to get to 180C from cold. A timer can be used with the ovens, and the cooker used as an efficient room heater by leaving the cooker thermostat on, say, 100C, and timing it to come on with the central heating. In colder weather the oven temperature is set higher.  A radiator in most kitchens is not then required. The cooker will also be ready to use. However, in the summer and on warm days, the cooker can just be turned on when required, saving a lot of expensive fuel.

Under £240.00 of gas for cooking & heating your kitchen!
We’ve calculated that, based on our typical usage values, your oil-fired cooker could cost under £240 to run a year for all your cooking requirements, plus heating your kitchen.

Under £140 a year for cooking only!
Based on our typical usage values, your gas-fired cooker could cost under £140 to run a year for all your cooking requirements.

Cooking usage based on:
2kW/hour warm up + 3kW/hour cooking
2 hours cooking per day = 8kW/day @4p/kW NG that’s just 32p/day!
300 days (allowing for  holidays and summer) = @ 4p/kW just £ 96.00 a year.

Cost Comparisons
We could use electricity to heat the ovens, like an Aga range cooker Total Control, an ESSE EC4I or any of the Everhot range,  but as electricity is mostly made in the UK from gas & nuclear , it is a lot more expensive @ 16p/kW. So an electric iron range cooker will cost 16p x 8kW x 300 days to run. This gives a total cost of £ 384 per annum, and considerably more if a lot of cooking is done and the cooker used as a room heater. Click here to see Aga range cooker Total Control figures.

If the range cooker is used as a room heater in the place of a central heating radiator at the rate of 3kW/hour and used for three hours in the morning, two at lunchtime and from three – ten in the evening, 12 hours per day for say 210 days a year, the electric cooker would cost a staggering £1,210 a year, but the gas fired Thornhill Range Cooker just £302! A lot of the time a warm cooker in the kitchen and a wood stove in the sitting room is sufficient to heat the whole house.

Boiler cookers.

The concept of a cooker/boiler that heated water or did full central heating was popular 50 years ago with many thousand of coal fired ranges being manufactured, the most famous being Rayburns. These we converted to oil or gas as the new fuels became cheaper and more popular, but the lack of control over cooking and heating with just one power source meant they started to get expensive to run and wasted a lot of fuel. In the 80’s Stanley redesigned the concept using two burners and 2 sets of controls, one for the cooker and one for the boiler. Rayburn soon followed (they were not owned but the same American Cooperation then). This concept worked well, with similar models being manufactured by ESSE & Stovax. But the requirement from around the year 2000 for more efficiency and cleaner burning meant condensing boilers had to be fitted, so you are trying to cram more and more in an already small space. Its a bit like putting your washing machine and dishwasher in the same cabinet, when one breaks down so does the other and only specialist technicians will service and repair these cookers. There is no connection between the cooker and boiler in a twin burner cooker/boiler. There is NO fuel saving.

Advantages of a boiler cooker:

You save the space of a gas boiler, about 500 mm

Now The Disadvantages:

More (lot more?) expensive to buy than a separate cooker and boiler.

Difficult/more expensive to install

More expensive to service and repair.

Only 1 & 1/2 ovens

Not one penny in fuel saving.

Any Gas Safe technician can service a standard condensing oil boiler or a Thornhill gas fired cooker. They have the same type of burners.

If one breaks down, you always have a second heat source, a lot of people find that with an gas cooker in the kitchen and a good wood stove in the sitting room, they only have the central heating on for the very coldest days.

Another myth is ‘hot water’. We use very little of this these days, we shower and don’t have large daily baths, we have cold fill washing machines, we have cold fill dishwasher, incredibly efficient and only using a minimal amount of water heated to the exact temperature required. Modern controls on oil fired system means you only heat the water you need to the temperature you need. The running costs of an gas boiler for hot water are probably less that £60 per annum. Not worth investing £1,000 for ‘back boilers’ etc .

Size: 100cm or 149cm wide, 91cm high and 71cm deep see Cooker side view dimensions

Gas fired 3-5 oven cooker- Installation & Instruction Manual

Installation Advise Notes Gas

Doc J Building regs. for flue position for oil, gas or wood fuel.



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