BOILER REPLACEMENT GUIDE Step-by-step procedures for properly sizing hot water and steam replacement boilers for homes and small commercial buildings
BOILER REPLACEMENT GUIDE INTRODUCTION SIZING HOT WATER BOILERS – Page 3 This booklet is designed to give the qualityconscious hydronic heating contractor a stepby-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.
SECTION 1 PROCEDURE FOR SIZING HOT WATER BOILERS STEP 1: COMPLETE A JOB SURVEY FORM Certain key information is required for each boiler replacement job in order to calculate the heat loss, select the proper boiler and determine the selling price. Figure 1 is a Job Survey Form (part of a Weil-McLain Boiler Replacement Worksheet) to aid in recording the required information. It will serve as a checklist of the basic data for the existing installation and a permanent record for your job file.
STEP 2: CALCULATE TOTAL HEAT LOSS The form shown in Figure 2 (Part of the WeilMcLain Boiler Replacement Worksheet) can be used for calculating total heat loss by following these steps. in heat loss for basements which are not to be heated; ignore crawl spaces which are open to basement areas. 4. If the Outdoor Design Temperature of the city is unknown, refer to back page.
TABLE B: HEAT LOSS TABLE (in BTU/Hr.) (Calculated at 70°F Design Temperature Difference FLOOR AREA SQ. FT.
TABLE C: DESIGN TEMPERATURE CORRECTION FACTORS (For other than 70° Design Temperature Difference) 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.
TABLE E: AHRI NET RATINGS IN BTU/HR. FOR WEIL-McLAIN BOILERS NOTE: Always consult product manual for details EVERGREEN MODEL EVG 220 EVG 299 EVG 399 ULTRA WM97+ WATER RATING AFUE MODEL 179,000 243,000 333,000 95.0% 95.0% 96.5%* ULT ULT ULT ULT ULT ULT ECO 80 105 155 230 299 399 WATER RATING 62,000 81,000 123,000 183,000 234,000 317,000 93.5% 94.0% 94.0% 94.1% 92.5% 91.7%* GV90+ WATER RATING AFUE MODEL WATER RATING ECO 70 ECO 110 ECO 155 57,000 88,000 124,000 95.2% 95.0% 95.
SAMPLE PROBLEM STEP 1: COMPLETE A JOB SURVEY FORM A properly completed Job Survey Form is shown in Figure 4. The Key Information: • 80°F design temperature difference. • Two story house with unheated basement-816 sq. ft. of floor space each level. • Type of Radiation: convector baseboard. • Type of System: series loop. • Owner wants to replace his old boiler with a new high efficiency gas fired water boiler. Owner wants night set-back thermostat.
STEP 2: CALCULATE TOTAL HEAT LOSS Correction Factor for Construction Number 17 of .87. Therefore, the total adjusted heat loss for the first floor is 33,450 BTU/Hr. (38,450 x .87 rounded). The Total Heat Loss for the example is calculated on the form shown in Figure 5 based on the following steps: 6. The total heat loss for the two levels is 71,900 BTU/Hr. 1. The construction of the house matches Construction Design Number 17 in Table A (page 4). STEP 3: SELECT THE BOILER 2.
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. FIGURE 7 EXAMPLE: 7" Figure 7 is a tube type radiator, 20” high by 7” wide. There are 4 tubes per section and 8 sections.
APPENDIX OTHER CONSIDERATIONS IN BOILER REPLACEMENT 1. INSTALLATION INSTRUCTIONS 4. CLEANING STEAM BOILERS In order for the warranty on a new boiler to be honored, the boiler must be installed in strict accordance with the manufacturer’s installation instructions. It is imperative that the heating contractor follows the instructions furnished with the equipment. If questions arise, the heating contractor should contact the distributor.
OUTDOOR DESIGN TEMPERATURES FOR SELECTED CITIES ALABAMA Anniston. . . . . . . . . . . . . . . . . 22 Birmingham. . . . . . . . . . . . . . . 21 Mobile. . . . . . . . . . . . . . . . . . . 29 Montgomery . . . . . . . . . . . . . 25 ALASKA Anchorage. . . . . . . . . . . . . . . -18 Fairbanks . . . . . . . . . . . . . . . -47 Juneau. . . . . . . . . . . . . . . . . . . . . 1 Nome. . . . . . . . . . . . . . . . . . . -27 ARIZONA Flagstaff. . . . . . . . . . . . . . . . . . 4 Phoenix. . . . . . . . . .
