White Mountain Hearth DVTL27FP90N-1 Installation Instructions And Owner's Manual page 18

Vent Runs
In planning the installation for the fireplace, it is necessary to install
certain components before the appliance is completely positioned
and installed. These include the direct vent system, gas piping for
the appliance and the electrical wiring.
The appliance can be mounted on any of the following surfaces:
1. A flat, hard surface
2. A raised wooden platform
3. Four corner supports (Example: Four concrete masonry blocks.)
These supports must be positioned adequate is made with
bottom standoffs). See local codes.
Note For Horizontal Vent Runs (Figure 25):
A specific wall thimble (see parts list page 55) must be used
for horizontal vent installations through combustible wall.
Page 18
INSTALLATION (continued)
Figure 25
VERTICAL, 90° ELBOW WITH HORIZONTAL TERMINATION
(12 inches minimum vertical rise shown)
Figure 26
33740-7-0515