State Industries 317913-000 User Manual

A TECHNICAL GUIDE TO

DESIGNING ENERGY-EFFICIENT

COMMERCIAL WATER HEATER

SYSTEMS

Printed in the U.S.A. 0210 317913-000

12345678901

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

12345678901

234567890

234567890

234567890

234567890

234567890

234567890

234567890

Index

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

Foreword

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

I. Introduction to Commercial Water heating

l. Introduction To Commercial Water Heating Pages

Parameters .................................................................................................................................... 2-3

What is Hot Water? ........................................................................................................................ 3-4

Evaluating Water ............................................................................................................................ 4

ll. Principles of Sizing

Hot Water Demand ........................................................................................................................ 5

Profiles of Operation ...................................................................................................................... 5-6

lll. Equipment Performance

Recovery Capacity Tables.............................................................................................................. 6-7

Storage Capacity And Tank Efficiency............................................................................................7

Gas and Oil - Fired Tank Type Heaters.......................................................................................... 8

Electric Tank Type Heaters............................................................................................................. 8

Auxiliary Tank (Unfired)................................................................................................................... 8

Heater Recovery Plus Storage Tank Equals Demand .................................................................. 8

Heater Recovery And Storage Tank Performance Comparison ................................................... 9

When Using Electricity to Heat Water ............................................................................................10

Estimating Water Heating Costs ................................................................................................... 10

lV. System T ypes And Application

Design Objectives .......................................................................................................................... 11

System Types ................................................................................................................................. 11

Tank Type Water Heater Systems Using Gas, Oil and Electricity.................................................. 11-12

Creating The Successful System ..................................................................................................13

Sizing Without Prepared Information ............................................................................................. 13-14

One Temperature System .............................................................................................................. 14

Two Temperature System .............................................................................................................. 15

Field Assistance ............................................................................................................................. 15

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

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.

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.

2

12345678901

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

12345678901

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

QUANTITY

TEMPERATURE

TIME & SPACE

The major objective of this presentation is to promote the design of energy-efficient commercial water
heating systems through proper sizing, equipment recommendations and system selection. Properly
designed commercial and industrial water heating systems are essential to the health and well being of
the community . Some activities would have to suspend operations or risk serious health and comfort
problems if they do not have the quantity of hot water at the temperature needed during the time it is
required.

Therefore, the key to proper water
heating system design is to identify

quantity, temperature and time

the
characteristics of the hot water
requirement. Also,

space available

for equipment should be noted.
But first, a knowledge of water and

its characteristics is necessary in
order to effectively design a water
heating system.

SYSTEM CONCEPTS

What is Hot Water?

Hot water is water to which heat energy has been added . . .as more heat is added the water becomes
hotter. This water temperature guide shows typical water heating system design temperatures.

In practice, the system designer will establish the temperature or temperatures of hot water needed
for the various activities through consultation with the user or their representative. It is also necessary
for the system designer to know the coldest entering water temperature in order to determine temperature
rise.

* The average temperature of the hot and cold water mixture applied to the body.
The hot water being normally obtained from the commercial water heating system at 140°F.

3

12345678901

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

12345678901

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

SUPPLY WATER

TEMPERATURE

PRESSURE
HARDNESS

Evaluating Water

The coldest water inlet temperature experienced during the year should be the base from which
the maximum system temperature rise is established. Your water supplier can provide this
information. Surface water sources such as lakes and rivers tend to fluctuate as the seasons
change. Well water remains relatively constant in temperature year round. A water heating
system supplied with varying incoming water temperatures will only provide adequate hot water if
the lowest cold water temperature encountered is used in the temperature rise calculation.

Other characteristics of the water supply which should be determined and evaluated by the system
designer include supply pressure, water hardness and the presence of silt. These facts may be
obtained by contacting your water supplier.

High water supply pressure (above the rated working pressure of the heater) should be reduced
by a water pressure reducing valve set to about 50 psig. This will also reduce water consumption
but, more important, will bring the water pressure well within the working pressure range of the
heater. It is then possible to provide proper relief valve protection on the heater.

It is also necessary to provide water pressure reducing valves on the 180°F rinse lines of
dishwashers.

Hardness is the term applied to the compounds of calcium and magnesium present in hard
water. So common are these two minerals in water that practically no supply can be found that
does not contain at least 1 or 2 grains per gallon. Hardness is also stated in parts per million.
One grain of hardness is equal to 17.1 parts per million. Water containing less than 1 grain per
gallon of dissolved calcium and magnesium hardness minerals is considered soft water.

The significance of hardness is that the heat transfer surfaces of the water heater will become
coated or blocked with the mineral deposits. Depending upon the type of heater, less hot water ,
noisy operation, increased energy costs and premature equipment failure are some of the
problems which may result from “hard” water. The system designer should select water heating
equipment which is capable of being delimed or repaired when used in hard water areas.

If the water supply contains silt or sediment, the water heating equipment should be capable of
being flushed (and have sediment risers installed in horizontal storage tanks) to extend heater
life and minimize energy expense.

The effects of hard water and silt upon the heating equipment can be minimized by lowering
water temperature, controlling flow, leakage and waste. For example, fixture and shower head
flow controls are a must to minimize hot water consumption and regulate the flow to system
design.

Energy saving fixtures benefit the user by reducing water and sewerage charges, energy and
maintenance costs. Reducing consumption through flow control is the one way
operating costs and the space to be occupied by a new water heating system can be dramatically
reduced.

4

initial cost,

12345678901

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

12345678901

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

234567890

II. Principles of Sizing

Hot Water Demand

The major determination in sizing and the basis of all computations is establishing the probable demand
for hot water. In addition, any

unusual conditions which might relate to hot water consumption must

also be recognized and planned for. Unusual conditions will be described under Profiles of Operation.
Sources of hot water demand information include the ASHRAE (American Society of Heating,

Refrigerating and Air Conditioning Engineers) Guide, and hot water using equipment manufacturers
such as dishwasher and washing machine makers. Government agencies may also require demand
criteria be met.

Profiles of Operation

The system designer should draw a profile of the proposed system hot water usage demand period.
The profile will also include the recovery period available before the next demand.

Demand and

recovery periods can be measured in seconds, minutes or hours.
Any

unusual needs for hot water during the demand or recovery periods are identified in order to
provide additional tank and/or recovery capacity . An unusual need could be a lesser, but significant
hot water requirement appearing just after the demand period. For example, a motel could have a
laundry operation which begins in mid-morning, after the guest shower load is over. If not taken into
consideration there many be no hot water available for the washing machines.

An oversimplification of system design is to say that systems are either for

intermittent use or continuous

use as shown in the following profiles.

Intermittent Use Profile

.

This example shows two demand and recovery periods within a day.

• A combination of heater recovery and hot water storage capacity should be selected to handle the

demands.

• The demands are separated by an 8 and a 12 hour recovery period.

• The heater recovery capacity of the shortest recovery period must be sufficient to heat all the water

in storage.

• Short demands usually mean placing emphasis on tank size. Heater recovery capacity is emphasized

on longer demands.

• The dividing line between long and short demands is about 3 to 4 hours.

• In this example storage is most important.

-The purpose of the storage tank is to permit relatively low heater recovery capacity while still
maintaining adequate hot water supply during the demand period.

5