Oven Narcosi - Tunnel Oven Build - UK

[david s]

4. It is important to insulate both under and over the oven to prevent heat loss. As the flue gallery and outer arch are connected to the oven, they can act as a heat sink drawing heat out of the inner oven chamber. An expansion gap reduces heat flow by conduction as well as reducing pressure on the cooler outer oven parts thereby reducing propensity to cracking. Some builders do add an expansion joint/heat break, some don’t.

9. The outer arch can be either cast or laid with brick

11. Standard house bricks should be fine, as the outer arch doesn’t get really hot.

14. If you want, but they invariably fail eventually. Most folk don’t rely on them after using their oven lots. Their placement will give you different readings depending on where you place them. There are many ways to gauge the temperature without the use of thermocouples.

[narcosi]

4. It is important to insulate both under and over the oven to prevent heat loss. As the flue gallery and outer arch are connected to the oven, they can act as a heat sink drawing heat out of the inner oven chamber. An expansion gap reduces heat flow by conduction as well as reducing pressure on the cooler outer oven parts thereby reducing propensity to cracking. Some builders do add an expansion joint/heat break, some don’t.

Thanks - if you leave a gap - what would you recommend filling it with?

[narcosi]

9. The outer arch can be either cast or laid with brick

I was meaning in inner tunner? the first message includes links to precast arches for the tunnel.

[narcosi]

11. Standard house bricks should be fine, as the outer arch doesn’t get really hot.

14. If you want, but they invariably fail eventually. Most folk don’t rely on them after using their oven lots. Their placement will give you different readings depending on where you place them. There are many ways to gauge the temperature without the use of thermocouples.

Thanks David really appreciate your input - 2 more questions knocked off

[david s]

Thanks - if you leave a gap - what would you recommend filling it with?

Some use ceramic rope or 5:1 vermicrete or ceramic fibre blanket or air. The gap on my design is between the outer arch and the flue gallery because the flue gallery is only 10 kg cast refractory and it’s insulated so is not much of a heat sink. I fill the gap between the floor and arch with ceramic fibre blanket sealed at the top with 5:1 vermicrete. At the top of the arch is just 5:1 vermicrete and I leave the sides as just an air gap.
Search for “thermal break” to see what others have done, or someone else may chime in with other ideas.

[david s]

I was meaning in inner tunner? the first message includes links to precast arches for the tunnel.

Sorry, I was forgetting you’re doing a barrel arch. They can be brick or cast. If you cast or brick, be sure to place wedges under the former so when they’re removed it will drop and you can slide it out. Wedges at the back of the former may need to have rope attachments because they’re hard to access. As you are in UK the uk wood fired oven forum may be of some use.