Dunkirk XEB II Series, Installation, Operation & Maintenance Manual

16

8. 

Joining and Sealing the Vent Pipe:                                               

The vent pipe needs to be both watertight and gas 

tight. Seal all joints and seams as follows:

A. For Z-Flex Z-Vent stainless steel vent pipe use 

a high temperature silicone sealant rated for 

550°F. The outside of the male end and inside 

of the female end of the pipe must be cleaned 

with brake cleaner before applying silicone bead.                                                                                                   

For 3” vent pipe runs begin with the male end 

of the vent pipe over the boilers induced draft 

blower outlet. For 4” vent pipe runs begin with a 

6” length of 3” Z-Vent  over the boiler’s induced 

draft blower outlet, to which an even bead of high 

temperature silicone sealant should be applied. 

Then connect the 3” Z-Vent to a Z-Vent 3” to 4” 

reducer. Then continue the 4” Z-Vent pipe run by 

connecting the 4” male end of the Z-Vent to the 

reducer. (A locking band may be used around this 

joint for additional support.) Then following the 

sealing instructions, push the 4” male end of the 

Z-Vent over the 4” increaser 

fi

 tting. When using 

the Tjernlund VH-1 vent hood, the female end 

(

fl

 ared end) of the vent pipe will be connected to 

the termination hood. The male end of the vent 

hood must be crimped before pushing the Z-Vent 

over the vent hood’s connecting pipe. Before the 

pipes are joined, apply a ¼” bead of silicone one 

inch from the end of the male end. Then push the 

pipes together as far as they will go making sure 

any seams are aligned and oriented upward. Now 

apply another bead of silicone around this joint and 

smooth out. Then use a Z-Flex locking band around 

the center of the joint.
1.  Apply the high temperature silicone 

approximately one inch from the end, around 

the male end of the pipe in an even ¼” bead.

2.  Pipes can now be pushed together as far as they 

will go. The seams on pipe should be aligned 

and oriented upward in all horizontal appliances. 

Apply another bead of silicone around this joint 

and smooth out.

3.  Slide locking band over center of joint and 

tighten gear clamps. Make sure locking band is 

centered on joint.

4.  Check all joints and seams for gas tightness.
5.  Horizontal venting shall have slope not less 

than ¼” every 12 inches (21mm/m) downward 

away from the boiler to prevent collection of 

condensate throughout the assembly.

6.  Allow sealant to cure for 24 hours before 

operating appliance.

B.  For Heat-Fab Saf-T-Vent stainless steel vent pipe 

use a high temperature silicone sealant rated for 

550°F The outside of the male end and inside 

of the female end of the pipe must be cleaned 

before applying the silicone bead. For 3” vent 

pipe runs, the male end of the vent pipe which 

goes over the outlet of the boiler’s induced draft 

blower must be crimped. The vent pipe should be 

crimped as minimal as possible to provide a tight 

fi

 t over the outlet. After crimping is completed fol-

low the instructions for applying silicone sealant.                                                                                       

For 4” vent pipe runs, begin with a Saf-T-Vent 3” 

to 4” increaser 

fi

 tting over the boiler’s induced 

draft blower outlet, to which an even bead of high 

temperature silicone sealant should be applied. 

Then continue the 4” Saf-T-Vent pipe run by con-

necting the 4” male end of the Saf-T-Vent to the 

increaser. (A locking band may be used around this 

joint for additional support.) The vent 

fl

 ow must be 

in the direction indicated on the vent pipe.  When 

using the Tjernlund VH-1 vent hood, the female 

end (

fl

 ared end) of the vent pipe will be connected 

to the termination hood. Apply high temperature 

silicone in an even ¼” bead approximately ¼” to 

⅜

” from the end of the vent hood’s connecting 

vent pipe.  Also, run a similar size bead of silicone 

sealant down the seam weld of the vent pipe. Then 

push the female end over the vent hood’s connect-

ing vent pipe.
1.  Apply the high temperature silicone around 

the male end of the pipe (without the tabs) 

in an even ¼” bead. Silicone bead should be 

approximately ¼” to 

⅜

” from the end of the 

male end. Also, run a similar size bead of 

silicone sealant down the seam weld at the end 

of each joint.

2.  Pipes can now be pushed together as far as they 

will go. The seams on the vent pipe should be 

aligned and oriented upward in all horizontal 

appliances. With a moistened 

fi

 nger or 

fl

 at tool, 

spread any sealant that squeezes out around the 

circumference of the joint.

3.  Attach the sections together with the locking 

rings and tabs (except at the blower outlet 

where no  locking ring exists.)  Inspect the 

joint to ensure that 

fl

 ue gases will not leak. If 

necessary apply additional sealant around the 

joint.

4.  Horizontal venting shall have a slope not less 

than ¼” every 12 inches (21mm/m) downward 

away from the boiler to prevent collection of 

condensate throughout the assembly.

5.  Allow the sealant to cure for 24 hours before 

operating the appliance.

HORIZONTAL VENTING INSTRUCTIONS