Chase Area Minimum; Recessed Ledge Detail - ORTAL 98 Series Installation And Operation Manual

Chase Area Minimum

To ensure the convective heat within the chase passively moves to the heat release at an optimal rate, all parts of the interior of the
chase must at least the same size as the fireplace heat release (see "Heat Release" section on page 16 to determine your model's
required heat release size) at size at any given point. To determine if your chase meets this requirement, use the following equation
at the narrowest part of the chase.
Area of the Pipe:
5"x8" venting = 50.27 in
*
3"x5" venting = 19.63 in
*Used for Power Venting only
If the heat release is split into 25/75 portions due to an oversized ledge, the chase only needs to be the size of 75% of the heat
release because 25% of the heat is already being released at the ledge (see "Recessed Ledge Detail" section below for details).

Recessed Ledge Detail

A ledge over the top of a fireplace that is less than 24 inches from the top of the fireplace viewing area must maintain a minimum
of 12 inches from the top of the viewing area to the top of the framing. Entire structure must be non-combustible
(framing and finish).
Oversized Ledge
If ledge surface area exceeds 580 sq. in., the heat release must be divided between the ledge and the chase ceiling: 25% at
the ledge and 75% at the chase ceiling.
NOTE: Chase area minimum requirements must be met throughout the entire fireplace chase. See "Chase Area
Minimum" section above for details.
Chase Area = (Chase Length x Chase Depth) – (Area of the Pipe)
2
2
Ledge Size: A x B ≤ 580 sq. in.
A = ledge depth, B= ledge width (Top View)
Fireplace Chase (Top View)
23