WATER HEATER SIZING GUIDE FOR ENGINEERS

1 PVI Industries, LLC Fort Worth, Texas WATER HEATER SIZING GUIDE FOR ENGINEERS commercial INSTITUTIONAL INDUSTRIAL SIZING GUARANTEE PVI SIZING methods are guaranteed to be correct when used in accordance with the instructions as printed, as long as PVI equipment, with its unique performance characteristics, is used. If an installation should not have an adequate amount of hot WATER after proper use of the GUIDE , PVI will, at its cost, correct the installation to the engineer s satisfaction. COMMON FACTORS All calculated loads are converted to GPH (Gallons per Hour) 40 F to 140 F, or an 100 F rise. Appropriate conversion factors will be found near each formula. All BTU output calculations are based on RD (Recovery Demand) Requirement.

2 All SR (Storage Requirements) are a percentage of the RD. CODES Some city, municipal, state and/or federal regulations may require different SIZING methods; they take precedence. SCALD WARNING Because the danger of accidental scalding, the use of a thermostatically controlled temperature regulator is mandatory in installations such as rest homes, homes for the mentally handicapped, children s homes, schools, churches and hospitals. Such regulators should be set no higher than 110 F. Never should a WATER HEATER be used to control a maximum outlet temperature suitable for body comfort. WATER HEATER SIZING GUIDE FOR ENGINEERS commercial INSTITUTIONAL INDUSTRIAL Contents Page I Apartment Houses, Hotels, Motels.

3 2-4 II Dormitories, Fraternity and Sorority Houses .. 5-6 III Hospitals, Rest Homes, Nursing Homes, Orphanages, Convents .. 7-8 IV Schools and Churches .. 9 V Laundries: commercial & Institutional, Coin Operated .. 10-11 VI Food Service .. 12-14 VII Showers: Schools, Correctional Facilities, Stadiums, Industrial Plants, Foundries, Mines and Churches .. 15 VIII Office Buildings .. 16 IX Swimming Pools .. 17 X Instantaneous Steam SIZING (Hunter s Curves) 18-19 Section 1 2 Calculations in this section cover all hot WATER demands for the individual living units. Additional demands, for centralized food service, coin-operated laundries, etc., may be calculated by referring to other sections of this GUIDE specified in the discussion below.

4 Diversity Factors C are a function of the number of living units served, and are provided in this section. As the number of units increases, C decreases because the likelihood of all living units using hot WATER at the same time decreases. The major hot WATER load in a living unit is shower head consumption. If shower head consumption is provided for, lavatories and sinks will be well served. However, dishwashers and clothes washers in the living units impose large additional loads, and these are provided for in the table of Adjustment Factors AF on page 3. Section I. APARTMENT HOUSES, HOTELS AND MOTELS If the hotel or motel has central food service, calculate the additional load using Section VI, Food Service.

5 If it has central laundry facilities, calculate the additional load using Section V, Laundries. Add these to the basic load. The type of hotel or motel can have a strong impact on real hot WATER demand. Ask the architect about any of the following considerations and include the basis of your assumptions in your SIZING proposal. HOTELS AND MOTELS: SPECIAL CONSIDERATIONS 1. Hotels designed primarily to accommodate conventions and other regimented groups of people tend to create peak demand periods. We recommend NOT using the Diversity Factor. 2. Some convention-type hotels are being designed to accommodate three or four people per room, using roll-away beds. In such cases, in addition to eliminating the Diversity Factor, we recommend increasing the Adjustment Factor by multiplying the Recovery Demand by 3.

6 Hotels designed primarily for commercial trade rather than tourism will also see a regimented hot WATER demand, especially at wake-up time. We recommend NOT using the Diversity Factor. FORMULAS Formula Legend: RD = Recovery Demand 40 F to 140 F TU = Total number of living units FR = Flow rate of shower heads in gallons per minute AF = Unit / Time Adjustment Factor C = Diversity Factor SR = Storage Requirement Formula I (Apartments, Hotels and Motels designed for family or transient living) RD = TU x FR x AF x C x SR = RD x .25 (for minimum) Formula II (Convention-type Hotels and Motels) RD = TU x FR x AF x SR = RD x .33 (for minimum) NOTE: PVI strongly recommends insulating all hot WATER lines, and all calculations in this GUIDE are based on insulated lines.

7 For systems with non-insulated lines, multiply Recovery Demand RD by 3 ADJUSTMENT FACTORS CLASSIFICATION ADJUSTMENT FACTOR AF APARTMENT HOUSES 1 Bath 1 Bath and Dishwasher 1 Bath and Clothes Washer 1 Bath, Dish and Clothes Washer 2 Baths 2 Baths and Dishwasher 2 Baths and Clothes Washer 2 Baths, Dish and Clothes Washer 1 Bath 2 Baths HOTELS AND MOTELS DIVERSITY FACTORS NUMBER UNITS* TU DIVERSITY FACTOR C 1-20 .98 21-40 .96 41-60 .94 61-80 .92 81-100 .89 101-120 .85 121-140 .84 141-160 .81 161-180 .79 181-200 .75 201-260 .70 261-310 .67 311-370 .64 371-440 .63 441-520 .60 521-600 .56 601-680 .54 681-760 .53 761-840 .52 841-920 .51 921-1000.

8 50 *If some units have one bath and some have two baths, use the Diversity Factor for the total number of units. (Continues with examples on page 4.) 4 EXAMPLE Select WATER heating equipment for a 200-room convention-type motel. The flow rate of each shower head will be 2 GPM. The laundry will have three 50-lb washers. There will be no food service. The owners request one central system. First, calculate the rooms load: RD = TU x FR x AF x RD = 200 x 2 x 5 x RD = 1600 SR = RD x .33 SR = 528 Then, calculate the laundry load (Section V): RD = TW x PC x GC x RD = 3 x 50 x 3 x RD = 540 SR = RD x .4 SR = 216 Then add the loads: Total RD = 1600 Rooms RD + 540 Laundry RD 2140 gph 40 F to 140 F Total SR = 528 Rooms SR + 216 Laundry SR 744 Gallons Storage Select two WATER heaters with a combined minimum recovery of 2140 GPH of 40 F to 140 F, and a combined minimum storage of 744 gallons.

9 The Trade-Off Between Recovery Demand and Storage Requirements Reducing recovery demand necessitates a large increase in storage requirements and it is occasionally desirable. For example, if the energy source is gas, it may be desirable to reduce the gas line size or vent size. If the energy source is electricity , it may be economical to reduce the building s transformer size to reduce the demand factor applied by the utility. Or if steam or hot WATER are used, it may be desirable to reduce control and piping sizes and demands on the boilers. In any case, the following factors must be applied: First multiply the original calculated RD (recovery demand) by the factor in the above chart to determine the new RD.

10 Then multiply the original calculated SR (storage requirement) by the corresponding factor to determine the new SR. Use of these factors will ensure adequate recovery and storage capacity to maintain tenant satisfaction. RD Multiplier (percent reduction in RD) SR Multiplier .75 .50 .25 Section I. APARTMENT HOUSES, HOTELS AND MOTELS continued 5 Hot WATER demand for dormitory-type living is based on total number of students and a diversity factor for this number, which is directly related to the flow rate of the shower heads installed. When the total demand is calculated, there will be sufficient hot WATER available for all general purpose applications, such as lavatories, showers, tubs, general cleanup and small hand laundering.