Inbuilt Vulcan Wall Furnace Flue Kit

[WartookMan]

I have purchased a Vulcan Wall Furnace for my (renovated) house. It is an inbuilt version so the flue goes up through the wall and directly through the roof above. I purchased the Universal Installation Kit similar to the following reference: http://www.tradelink.com.au/resources/attachments/GasCatalogue/06 HEATING JAN07.pdf (search for "Kit Installation Wall Furnace Universal"). It includes a twin-skin rectangular adapter which fits onto the top of the heater, and attaches to the single-skin tubular flue extension.

My question is, should the tubular flue be double/twin-skinned? Or is a single-skin sufficient? I have heard of the term DV (Direct Vent) but I'm not sure what this means. I have added a triple skin around the rectangular section about 500mm high - so that I can butt the insulation up against the heater within the roof cavity, without any problem from any fire.

Pete.

[mat]

I have two of these in my house and both have single skin flues where it changes from rectangular to round. They are in free space and only come into contact with the tile roof/flashing where it penetrates through the roof.

[Dave50]

yep I got one, same as Mat's, single skin until it enters the ceiling

[malb]

Our Braemar upright is double skinned rectangular through ceiling transitioning to a single round in the roof cavity. Heater has free air intake behind the grille for the outer jacket just above the heat exchanger. Air enters this from a combintion of venturi effect from the flue gas rising where the two paths meet at the transition, and the free air heating due to contact with the flue skin. Combined gas flow above the transition should be cooler than flue gas, and outer skin of the rectangular section significantly cooler than the inner skin.