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Air openings to combustion area must not be
obstructed. Follow the chart below to obtain
and maintain adequate combustion air.
OUTSiDE
COmBUSTiON AiR
1 iN
2
(pARAGRApH 2)(SQ iN)
BTU/HR iNpUT
315,000
385,000
420,000
490,000
560,000
630,000
770,000
945,000
1,155,000
1,540,000
1,925,000
2,310,000
2,695,000
3,080,000
* Unconfined area: A space whose volume is not less than 50 cubic feet per 1000 BTU per hour of all appli-
ances installed in that space (cubic feet of space = height x width x length).
** Confined area: A space whose volume is less than 50 cubic feet per 1000 BTU per hour of all appliances in-
stalled in that space (cubic feet of space = height x width x length).
1. When a boiler is located in an unconfined
space in a building of conventional
construction frame, masonry or metal,
infiltration normally is adequate to
provide air for combustion and ventilation.
However, in any building which has
been altered to conserve energy or to
minimize infiltration, the boiler area
should be considered as a CONFiNED
SpACE. If there is any doubt, install air
supply provisions for combustion and
ventilation in accordance with section 5.3,
Air for Combustion and Ventilation, of the
latest revision of the NFPA 54 code, the
recommendations that follow, or applicable
provisions of the local building codes.
VENTILATION & COMBUSTION AIR
WARNING
COmBUSTiON AiR REQUiREmENTS
(miNimUm OpENiNG iN SQUARE iNCHES)
*
UNCONFiNED AREA
/5000BTU
63
77
84
98
112
126
154
189
231
308
385
462
539
616
iNSiDE
COmBUSTiON AiR
1 iN
/1000 BTU
2
(miN 100iN
) (FiG 4)
2
(SQ iN)
315
385
420
490
560
630
770
945
1155
1540
1925
2310
2695
3080
2. When a boiler is installed in an unconfined
space, in a building of unusually tight
construction, air for combustion and room
ventilation must be obtained from outdoors
or from spaces freely communicating with
the outdoors. A permanent opening or
openings having a total free area of not less
than 1 square inch per 5,000 BTU per hour
of total input rating of all appliances shall
be provided. Ducts may be used to convey
make-up air from the outdoors and shall have
the same cross-sectional area of the openings
to which they are connected.
8
**
CONFiNED AREA
OUTSiDE
COmBUSTiON AiR
1 iN
/4000
1 iN
2
BTU
(FiG 3)(SQ iN)
(FiG 3)(SQ iN)
78.75
96.25
105
123
140
158
193
237
289
385
482
578
675
770
/2000
2
BTU
158
193
210
245
280
315
385
473
578
770
963
1155
1348
1540
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