It's very important only to use an approved pellet stove vent pipe for your chimney vent installation. Pellet stoves burn hotter than most other types of stove. Vent pipe is double walled to help keep the outside cool. The walls are separated by an air gap. The inner pipe is made from stainless steel to guard against high temperature corrosion from salts in the exhaust gases. The outer casing is galvanised steel to protect it against rusting.
Pipe joints generally push and twist to lock together. These joints must also be sealed with high temperature silicone to prevent any leaks. A pellet stove vent system is under pressure from the fans that run air into and out of the stove.
Three inch pipe can only be used for runs of less than ten feet. A 45 degree turn will add 20% to the calculated run of the pipe, a 90 degree elbow will add 30%. In general it's better to stay with four inch pipe which will cost little more for a short run anyway. See 3 or 4 inch venting?
Pellet stove vent pipe should always run more than three inches away from any combustible materials.
Any horizontal run should have a rise of 1/4 of an inch for every foot.
Pellet stove pipe, or PL vent is specially made for pellet stoves and is specified by most manufacturers in their installation instructions. Pellet pipe comes in internal diameters of either three or four inches.
The actual diameter of the pipe will be larger than this depending on the size of the air gap between the inner and the outer walls favoured by the manufacturer.
Pipe with a larger air space between the walls often has a better rating for clearance to combustibles which is normally three inches but can be as little as one inch.
If you are considering using pellet stove pipe with an enhanced combustible clearance rating, check your local building codes to make sure that you will be able to use the enhanced performance.
Different manufacturers use various methods of making the joints between sections of pipe airtight. This is important because the venting system is pressurized by the combustion blower and if the joints are not airtight, smoke and fumes might enter the living space.
Most PL vent sections lock together with a screw action, but this is not enough by itself. Some systems incorporate a silicone 'O' ring, a ceramic fiber gasket, or a manual application of high temperature silicone to each joint.
American Metal Products produce 'Amerivent'
BDM make 'Bio Vent'
ICC produce 'Excel' pellet vent
Lennox Hearth Products offer 'Security Chimneys'
Metal-Fab inc. make 'Biomass Chimney'
Selkirk (click for product details), produce pellet stove pipe under the names MetalBest, SuperPro, SuperVent and Energy Vent
Simpson Dura-Vent make PelletVent and PelletVentPro
Venting materials and products that MUST NOT BE USED TO VENT PELLET APPLIANCES include:
Dryer vent, Gas appliance (Type B) vent, PVC (plastic) pipe, Single wall stove pipe (unless clearly approved by the installation manual and local codes)"
The air gap helps to stop the exhaust gases cooling and condensing water vapor in the flue. The water contained in the exhaust combines with the flue gases from burning to form a corrosive acid which can rot the inner flue. This is even more likely if corn is being burned. For this reason, it's best to keep the run of the pellet stove venting inside the building where the flue will not become chilled.
If you are considering burning corn either by itself or mixed with wood pellets, it's best to go for a multi-fuel vent pipe with increased corrosion resistance.
An additional benefit is that this insulation keeps the outer pipe cool and allows it to run closer to combustibles than a single wall flue. In the UK, building regulations still require a pellet stove to be vented with the same type of flue as a woodburning stove.
PL vent inner pipe is made from stainless steel of varying grades to combat this corrosion. The outer tube is made from galvanized steel, aluminized steel, or painted with high temperature paint. The pipe is tested to 300¡C. / 570¡F.
A system of PL vent pipe is available which uses the air gap between the inner and outer walls to introduce outside air to the stove. On the face of it, this is a neat solution and avoids having a separate outside air pipe. The downside is that chilled air from outside the building will chill the inner vent pipe and may cause unwanted condensation.