Monessen Hearth HVFL18 Installation And Operating Instructions Manual page 9

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 defined as an
unconfined 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/NFPA 54, Section 5.3 or applicable local codes.
59D1015
Figure 1 - Example of a Large Room with 1/2 Wall Divider
BTU/Hr = (L
1
L = 15 / Ft., L
1 2
BTU/Hr = (15
BTU/Hr = (15
GENERAL INSTALLATION INFORMATION
Counter
+ L ) Ft x (W) Ft x (H) Ft
1 2
50
= 12 Ft., W = 12 Ft., H = 8 Ft.
2
1
/ + 12) x (12) x (8)
2
50
1
/ ) x (12) x (8)
2
50
Fireplace
H
W
x 1000
x 1000 = 52800 BTU/Hr
x 1000 = 29760 BTU/Hr
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