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Introduction To Commercial Water Heating Pages

Parameters ....................................................................................................................................

2-3

What is Hot Water? ........................................................................................................................

3-4

Evaluating Water ............................................................................................................................

ll. Principles of Sizing

Hot Water Demand ........................................................................................................................

Profiles of Operation ......................................................................................................................

5-6

lll. Equipment Performance

Recovery Capacity Tables ..............................................................................................................

6-7

Storage Capacity And Tank Efficiency ............................................................................................

Gas and Oil - Fired Tank Type Heaters ..........................................................................................

Electric Tank Type Heaters .............................................................................................................

Auxiliary Tank (Unfired) ...................................................................................................................

Heater Recovery Plus Storage Tank Equals Demand ..................................................................

Heater Recovery And Storage Tank Performance Comparison ...................................................

When Using Electricity to Heat Water ............................................................................................

Estimating Water Heating Costs ...................................................................................................

lV. System Types And Application

Design Objectives ..........................................................................................................................

System Types .................................................................................................................................

Tank Type Water Heater Systems Using Gas, Oil and Electricity .................................................. 11-12
Creating The Successful System ..................................................................................................

Sizing Without Prepared Information ............................................................................................. 13-14
One Temperature System ..............................................................................................................

Two Temperature System ..............................................................................................................

Field Assistance .............................................................................................................................

This guide is different than most produced by the water heating industry. Instead of just referring you
to prepared sizing information the guide shows you how it’s done. Then, when new model heaters are

Index

Foreword

introduced or applications are different, you will have the information necessary to proceed on
your own with confidence.

You will learn how to evaluate water characteristics which could affect system life and
performance, develop a profile of system operation to establish demand and recovery periods,
size energy and storage requirements to meet system demands and, all told, create a
successful commercial water heating system.

Introduction to Commercial Water heating

Parameters

A water heater is an appliance for supplying hot water for residential or commercial use other than
space heating. The maximum outlet water temperature for a water heater is 210°F ( 98.5°C).

Water heaters are sometimes called boilers and may be so labeled. This is because the gallon
capacity of the tank and/or the energy input is above a level for which some codes require ASME
(American Society of Mechanical Engineers) construction. Essentially the requirement applies
when the water-containing capacity is in excess of 120 gallons or the heat input is above 200,000
Btuh (58.6 kw). Caution, some local inspectors interpret the code to mean including 120 gallons
and 200,000 Btuh. The “boiler” requirement can cause cost escalation or system rejection if not
taken into consideration by the system designer. One way that more expensive heater costs are
often avoided is by combining several “smaller” heaters into a system instead of one large unit.

The term water heater and water heating system is used interchangeably in this technical guide.
The water heating system may consist of one or more water heaters installed individually at
points-of-use or manifolded together to form a central system. Some systems are comprised of
water heater(s), with or without storage, hot water storage tanks, circulating pump, related piping
and controls.