Boiler Sizing Replacement Guide

6
TABLE C: DESIGN TEMPERATURE CORRECTION FACTORS
(For other than 70° Design Temperature Dierence)
Note: Conversion factor for “in between” temperatures can be determined by interpolation between the closest tabulated values. Example: the
outdoor design temperature in Philadelphia, PA is 14°F. Indoor minus outdoor temperature equals 56°F. Interpolated factor equals 0.79 (rounded).
TABLE D: CEILING CORRECTION FACTORS
(For first floor heat loss in two story structure)
DESIGN TEMP.
DIFFERENCE FACTOR
DESIGN TEMP.
DIFFERENCE FACTOR
DESIGN TEMP.
DIFFERENCE FACTOR
25°F .35 55°F .78 90°F 1.29
30°F .42 60°F .85 95°F 1.36
35°F .50 65°F .92 100°F 1.43
40°F .57 75°F 1.07 105°F 1.50
45°F .64 80°F 1.15 110°F 1.57
50°F .71 85°F 1.20 115°F 1.64
CONSTRUCTION
DESIGN NO. FACTOR
CONSTRUCTION
DESIGN NO. FACTOR
CONSTRUCTION
DESIGN NO. FACTOR
CONSTRUCTION
DESIGN NO. FACTOR
1 .82 7 .88 13 .94 19 .82
2 .79 8 .86 14 .83 20 .89
3 .88 9 .91 15 .80 21 .88
4 .86 10 .94 16 .88 22 -
5 .83 11 .86 17 .87 23 -
6 .82 12 .91 18 .84
STEP 3: SELECT THE BOILER
The size of the replacement boiler will be based
on the Total Heat Loss of the building calculated
in Step 2. The boiler should be selected based on
its AHRI NET Rating in BTU/Hr. For example, if
the Total Heat Loss of the house is 85,000 BTU/
Hr. then the AHRI NET Rating of the replacement
boiler must be at least 85,000. It can be more-
but never less.
For convenience, Table E (opposite page) shows
the Net AHRI NET water ratings for current Weil-
McLain gas and oil boilers for homes and small
commercial buildings.
STEP 4: DETERMINE THE BID PRICE
Figure 3 (opposite page) is a general checklist of
the materials which may be required for a boiler
replacement job (also part of the Weil-McLain
Boiler Replacement Worksheet). This list can be
used to figure the cost of all materials as well as
labor, overhead, and profit.