Martin VENT-FREE FIREPLACE SYSTEMS 33ISDG Installation And Operating Instructions Manual page 10

GENERAL INSTALLATION INFORMATION
The following formula can be used to determine the maximum heater rating per the definition of unconfined space:
Consider two connecting rooms with an open area between, with the following dimensions:
If there were a door between the two rooms the calculation would be based only on the room with the heater.
If the area in which the heater may be operated is smaller than that defi ned as an
unconfi ned space or if the building is of unusually tight construction, provide adequate
combustion and ventilation air by one of the methods described in the National Fuel
Gas Code, ANSI Z223.1/NFPA54, Section 5.3 or applicable local codes.
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Figure 4 - Example of a Large Room with 1/2 Wall Divider
(L + L
1
BTU/Hr =
1
L = 15 / Ft., L
1 2
1
(15
BTU/Hr =
(15
BTU/Hr =
Counter
) Ft x (W) Ft x (H) Ft
2
50
= 12 Ft., W = 12 Ft., H = 8 Ft.
2
/ + 12) x (12) x (8)
2
50
1
/ ) x (12) x (8)
2
x 1000 = 29760 BTU/Hr
50
Fireplace
H
W
x 1000
x 1000 = 52800 BTU/Hr
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