Boiler Sizing Replacement Guide

10
8. Convert the total square feet of radiation to
BTU/Hr. Each square foot of steam radiation
is based on a heat emission of 240 BTU/Hr.
with standard 70°F air temperature and 215°F
steam temperature in the radiator.
9. Size the replacement steam boiler by
selecting a unit with a AHRI NET Steam rating
equal to or greater than the BTU/Hr. capacity
of the radiation.
EXAMPLE:
Figure 7 is a tube type radiator,
20” high by 7” wide. There are 4
tubes per section and 8 sections.
Table F shows this size tube type
radiator has 2 ¼ square feet of
radiation per section. 2 ¼ times
8 (the number of sections) equals 18 square feet
of direct radiation. 18 times 240 (BTU/Hr.) equals
4,320 BTU/Hr. for this radiator.
8
7
6
5
4
3
2
1
7"
20"
FIGURE 7
TABLE F: SQUARE FEET OF RADIATION PER RADIATOR SECTION
OLD STYLE COLUMN RADIATORS
NO. OF TUBES OR COLUMNS
1 2 3 4 5 6
WIDTH
(IN.) 4½ 7⅜ 9 11½ 12½ 12½
HEIGHT
(IN.)
45 3½ 5 6 10 – –
38 3 4 5 8 10 –
32 2½ 3⅓ 4½ 6½ 8½ –
26 2 2⅔ 3¾ 5 7 7
23 1⅔ 2⅓ 3¼ 4½ – –
22 1⅔ 2¼ 3 4 6 6
20 1½ 2 2¾ 3½ 5 5
18 1⅓ 1¾ 2¼ 3 5 4⅓
17 – – – – – 4
16 – – – – 4 3¾
15 – 1½ – – – –
14 – – – – 4 3
13 – – – – 3 3
TUBE TYPE RADIATORS
NO. OF TUBES
3 4 5 6 7
WIDTH
(IN.) 5 7 8¾ 9¾ 12½
HEIGHT
(IN.)
38 3½ 4¼ 5 6 –
36 3½ 4¼ 5 6 7
32 3 3½ 4⅓ 5 6
26 2⅓ 2¾ 3½ 4 5
23 2 2½ 3 3½ 4½
22 – – – – 4½
20 1¾ 2¼ 2⅔ 3 3⅔
18 – – – – 3½
17 – – – – 3
16 – – – – 3
14 – – – – 2½
THIN TUBE RADIATORS
NO. OF TUBES
2 3 4 5 6
WIDTH
(IN.) 3½ 4 4¾ 6 7⅞
HEIGHT
(IN.)
38 2½ 2⅔ – – –
32 2 2⅓ – – 3⅔
26 – – 2⅓ 3 3
25 1½ 1⅔ 2 – 3
23 – – – 2 –
22 1⅓ 1⅓ 1 – –
20 – – 1 – 2⅓
19 1 1¼ 1⅔ – 2⅓
17 – – – 2 –
WALL TYPE RADIATORS
SIZE
SQ. FT. PER
RADIATOR
13½" x 17" x 3" 5
13½" x 21" x 3" 6
13½" x 22" x 3" 7
13½" x 29" x 3" 9
SECTIONAL WALL TYPE
RADIATORS
HEIGHT (IN.)
SQ. FT.
RADIATION
PER SECTION
37 2½
26½ 1
21½ 1½
15 1
13⅞ ¾
CAST IRON BASEBOARD
HEIGHT (IN.)
SQ. FT.
RADIATION
7 2.40
9 3.35