Boiler Sizing Replacement Guide

2
BOILER REPLACEMENT GUIDE
INTRODUCTION
This booklet is designed to give the quality-
conscious hydronic heating contractor a step-
by-step procedure for properly sizing hot water
and steam replacement boilers. It is intended
primarily for use in sizing boilers for homes,
but in many cases can also be used for small
commercial buildings.
All too often replacement boilers are sized
simply by matching the rating of the old boiler.
This can result in an oversized boiler which
wastes fuel—or an undersized unit which will not
heat the building.
By following the procedures in this booklet, the
heating contractor will be able to accurately size
replacement boilers, sell more replacement jobs,
assure energy-ecient installations, and render
better service for customers.
SIZING HOT WATER BOILERS – Page 3
There is only one accepted method for
determining the proper size of a replacement
hot water boiler: THE HEAT LOSS OF THE
BUILDING MUST BE CALCULATED. By following
the steps in this booklet, the total heat loss of
the average house can be calculated in five
or ten minutes. In most cases it should not be
necessary to make a detailed calculation but,
if it is required for any reason, use or the latest
ASHRAE Handbook.
SIZING STEAM BOILERS – Page 9
To properly size a replacement steam boiler
DETERMINE THE TOTAL BTU CAPACITY OF
THE CONNECTED RADIATION. This method is
necessary in order to assure adequate steam
pressure to fill all parts of the system.
INDEX TO FIGURES & TABLES
PAGE PAGE
Figure 1 Job Survey Form 3 Figure 3 Material List 7
Figure 2 Heat Loss Calculation Form 4 Figure 4 Job Survey Form-Example 8
Table A Construction Characteristics 4 Figure 5 Heat Loss Calculation Form–
Example
9
Table B Heat Loss Table 5 Figure 6 Radiator Styles 9
Table C Design Temperature
Correction Factors
6 Figure 7 Radiator Example 10
Table D Ceiling Correction Factors 6 Table F Radiator Ratings 10
Table E Net Ratings of Weil-McLain Boilers 7