Propane Tankless Water Heating in Commercial Building

Propane Tankless Water Heating in Commercial Building Applications

Efficiency and Performance Benefits

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Water heating is a major energy end-use in commercial buildings, and is verysignificant in certain commercial building types. Many commercial building owners andoperators have a critical need for water heating systems which are reliable, able tomeet varying levels of demand, energy efficient, and able to fit within a building’sspace constraints in order to maintain their business operations. Propane tanklesswater heaters are a flexible and energy efficient technology which provides theseattributes in many commercial applications. This course will explore how commercialbuildings use energy and the potential application of propane tankless systems toprovide a solution for water heating needs.

Course Description

Participants will:

Define commercial building market segments, identify key energy use trends, and understand the significance of water heating energy in this market.1

Assess the energy efficiency advantages of propane tankless water heaters in commercial building applications.3

Identify key operational and installation benefits of propane tankless water heaters in commercial building applications.2

Understand propane supply considerations when tankless water heating systems utilize propane4

Learning Objectives

U.S. Commercial Buildings: Market Composition and Energy Use

Overview of Commercial Buildings• A commercial building is any

structure that is neither residential, manufacturing or industrial, nor agricultural.

• Most common types include• Office: 18%• Warehouse and storage: 14%• Service: 11%• Mercantile: 11%

Source: US EIA CBECS 2012, Table 1

Office 18%

Warehouse and storage

14%

Service 11%

Mercantile 11%

Religious worship 8%

Education7%

Food service 7%

Public assembly 6%

Vacant 5%

Health care 3%

Lodging 3%

Other 7%

Commercial Building Types

Trends in Commercial Building Energy Use• Total energy per square foot

has decreased since 2003.• Absolute electricity and natural

gas use has increased since 2003 by 7%.

• 14% increase in the number of commercial buildings.

• 22% increase in floor space.

• Commercial sector energy use increase limited by:

• Codes & standards.• Less energy intensive activities.• More buildings in temperate

regions.Source: US EIA CBECS 2012, Table 1

Total Energy Use per Square Foot in Commercial Buildings

(kBtu/square foot)

Commercial Building Energy Use Projections• Annual Energy Outlook projections

out to 2050 show steady growth in commercial sector energy use.

• Electricity consumption growth.• Driven by more floor space.• Moderated by efficiency gains and

more rooftop solar.• Natural gas consumption growth.

• Reflects end uses like space heating and water heating.

• Also indicates growth in CHP systems.

Source: US EIA 2018 Annual Energy Outlook.

0

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1980 1990 2000 2010 2020 2030 2040 2050

2017history projections

electricity natural gas petroleum and other liquids other

Commercial Sector Energy ConsumptionQuadrillion British thermal units

Energy Consumption by End Use• Space heating is the highest

energy end use.• Next tier of end uses:

• Lighting• Ventilation• Refrigeration• Cooling• Cooking• Water heating

• Water heating is about 7% of total commercial building energy consumption.

• Much higher in some categories such as lodging, where water heating is about ¼ of total energy use.


1,756

656 668507

724

517670

172

405

889

0

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400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

Spaceheating

Cooling Ventilation Waterheating

Lighting Cooking Refrigeration Officeequipment

Computing Other

Major Fuel Consumption by End Use for Commercial Buildings (trillion Btu)

• Water heating energy varies significantly by building type.

• Six largest commercial hot water energy use building types:

• Lodging• Health Care (inpatient is the major

user compared to outpatient)• Mercantile• Education• Food Service• Office

• Collectively this group represents:• 85% of commercial building water

heating energy use.• 6% of all commercial building

energy use.

Water Heating Energy Use in Commercial Buildings


Lodging, 136

Health Care, 82

Mercantile, 66

Education, 68

Food Service, 43

Office, 35

Other, 66

Water Heating Energy Consumption by Building Type (trillion Btu)

Emerging Building Types for Tankless• Breweries• Fitness Clubs• Cannabis Growing• Restaurants• Health Care / Senior Living• Others…

Water Heating Energy by Fuel Type• Natural gas water heating systems

are the primary energy source in commercial buildings with high water heating loads.

• Electric water heating is generally < 10% of water heating energy use for a given building type.

• Propane water heating:• Not captured in this data set.• Can satisfy large hot water loads

just like natural gas systems.• Viable option in buildings without

natural gas access, compared to electric water heating or fuel oil systems.

Source: US EIA CBECS 2012

113

61 58 5440

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58

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1 73

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Lodging Health care Mercantile Education Food service Office Other

Ener

gy C

onsu

med

(Tril

lion

BTU

)

Water Heating Energy by Fuel Type

Other

Electric

Natural Gas

Water Heating Energy Use by Building Age• Most water heating energy

use occurs in older commercial buildings.

• Nearly 80% of water heating energy use occurs in pre-2000 buildings.

• Most water heating systems are older and system replacements offer:

• Better performance• Less energy use• Lower energy costs 0

20

40

60

80

100

120

Before1920

1920 to1945

1946 to1959

1960 to1969

1970 to1979

1980 to1989

1990 to1999

2000 to2003

2004 to2007

2008 to2012

Water Heating Energy Use by Year of Building Construction (trillion Btu)


Tankless Water Heating in Commercial Buildings

How Tankless Systems Work• Hot water demand (i.e. a shower) initiates

cold water flow into tankless unit.• Combustion begins within the tankless unit

(natural gas or propane).• Incoming water may be pre-heated using

combustion exhaust.• Water brought to temperature set point in

main heat exchanger.• Combustion modulates to match flow.• Tankless unit turns off once hot water

demand ends. Hot Water Outlet

Cold Water Inlet

Gas/Propane Inlet

Source: Rinnai

• Modular configuration by using individual tankless units as building blocks.

• Capacities from 199,000 Btu/hr. up to millions of Btus.

• Flow rates of several hundred GPM.• Systems ramp up to meet load as

needed.• Avoid standby losses which occur in

storage type systems.• Controllers spread out the run time

across the entire bank of tankless units.

Source: Noritz

Low demand

Increasing demand met by

increased output

High demand fires 2nd

tankless unit to

share load

Commercial Tankless Benefits – Flexible Capacity & Sizing

Generating Hot Water based on Demand Saves Energy Costs

Source: Rinnai

81 Room Hotel• 85% occupied• 90 lb. laundry

Flow Rate (GPM) Duration (%)0 – 5 87%

5 – 10 9%10 – 15 3%15 – 20 < 1%20 – 25 < 0.02%

Source: Intellihot

Hot Water Demand in Commercial Buildings – Example Data

Project Example: Hot Water Retrofit in a Hotel• Ruby’s Inn, near Bryce Canyon

National Park in Utah.• Up to 4,000 guests daily during peak

season.• Tour bus arrivals mean high peak hot

water demand.• Pre-Retrofit System:

• Five high efficiency, 199 kBtu/hr., 100-gallon tank water heaters.

• Inadequate hot water supply despite hundreds of gallons of stored water.

Project Example: Hot Water Retrofit in a Hotel (cont.)New High Performance System:• Banks of propane-fired tankless units

for all buildings.• Modular design• Cascading operation to share the load

• Serving hot water for ~700 guest rooms, restaurants, laundry, and other applications.

Benefits:• 30% energy savings.• $6,000 / month in fuel savings.• Avoiding $60,000 annually in room

refunds due to cold showers. Source: Rinnai

• Milligan College’s Sutton Hall —Tennessee.

• 64 dorms, 120 residents.• High peak demands for hot water.• Pre-Retrofit System:

• One 80-gallon, 199 kBtu/hr. tank water heater + two 100-gallon storage tanks.

• Inadequate hot water supply.• Frequent leaks.• Inefficient operation. Source: Intellihot

Project Example: Hot Water Retrofit in a College Residence Hall

New System:• Three tankless units.• Total capacity: 750 kBtu/hr.• Zero gallons of water

storage.• 96% thermal efficiency.• System meets design load.• No standby losses.• Reliable operation.• Cascading operation.

Source: Intellihot

Old Water Heater & Storage Tanks

3-Unit Tankless Array

Project Example: Hot Water Retrofit in a College Residence Hall (cont.)

Commercial Tankless Benefits – Space Savings & Compact Design

• Commercial building square footage is critical for maximizing key functions.

• Water heater size is also critical for installation, access, and maintenance.

• Tankless systems offer major space savings compared to tank water heaters and boilers.

• Options include free standing systems, wall mounted, and corner designs.

Image Source: Rinnai

Project Example: Space Savings in a Hotel Renovation• Residence Inn by Marriott,

Florence, AL.• 130-room hotel

• Original renovation specs:• Two 750-gallon, 750,000 Btu/hr.

boilers• Boiler footprint: 5’ x 12’

• Available Space:• Mechanical room could hold both

units, but with just a few inches of clearance between units and from the unit to the wall.

Source: Noritz

“…. we could make it work — barely. But if one unit ever needed servicing, both

would need to be pulled from the space, because there simply wasn’t enough

room to work. That, in turn, would mean the entire hotel would have to go

without hot water until maintenance was finished.”

–Project’s plumbing distributor

Project Example: Space Savings in a Hotel Renovation (cont.)

Project Example: Space Savings in a Hotel Renovation (cont.)• Tankless Solution• Multi-unit system with 17 tankless units at 199,900 Btu/hr. per unit.

• 12 tankless units supply the 130 guest rooms.• Five tankless units handle the dining area and hotel laundry.• 93% thermal efficiency.

• Wall hung layout saves space and fit within mechanical room.• Readily accessible for maintenance.• No interruptions in hot water service during maintenance.

• System Output: as little as 11,000 Btu/hr. up to 3.4 million Btu/hr. total capacity.• Allows the array to meet both peak demand and part-load conditions.• Avoids the space needs and energy losses of storing 1,500 gallons of hot water.

Image Source: Intellihot

Project Example: Space Savings in New Hotel Construction• Fairfield Inn & Suites, East Syracuse,

New York.• 108 guest rooms.• Original Design:

• Two storage tank water heaters.• Did not fit within mechanical room. • Over budget.

• Tankless Design:• Two 750 kBtu/hr. units for

guest rooms.• One 250 kBtu/hr. unit for

laundry boost.


Project Example: Space Savings in a Restaurant Upgrade• Tomato House Restaurant in Senoia, Georgia.• Existing storage tank water heater.

• Could not supply enough water at a high enough temperature.

• Health code compliance requires high water temps.• 30-minute time to boil for cooking.

• No room for a larger tank water heater in the restaurant. • Tankless Replacement System.

• 199 kBtu/hr. capacity with a 96% thermal efficiency.• Provides ample 140 degrees Fahrenheit hot water to

meet sanitation and cooking needs.• 10-minute time to boil for cooking.

• Space Savings.• Installing tankless unit in the ceiling actually created more space.

Commercial Tankless Benefits – Venting Options• Venting is needed to exhaust combustion

gases from tankless water heaters.• In some cases venting also brings in

combustion air from outdoors.• Venting details can impact:

• Installation cost and complexity.• Mechanical room layout and space needs.• Space needs for routing vents.• Building penetrations.• Building aesthetics.


Commercial Tankless Benefits – Venting Options (cont.)• Tankless water heater venting

innovations:• Common venting of multiple

tankless units to outdoors.• Reduces space needs.• Reduces labor and materials.• Reduces building penetrations.

Source: Rinnai

Commercial Tankless Benefits – Venting Options (cont.)• Residence Inn by Marriott, Florence, AL• Seventeen tankless units installed.

• Seventeen individual vents would not fit.

• Fan-assisted common vent used for two tankless banks + one unit vented individually.

• Three penetrations instead of 17.

Source: Noritz

Commercial Tankless Benefits – Venting Options (cont.)Tankless water heating venting innovations:• Concentric venting for combustion exhaust +

combustion supply air.• Eliminates the need for separate supply

and exhaust pipes.• Reduces building penetrations by ½.

Source: Rinnai

• Common combustion air header for direct vent tankless units.

Commercial Tankless Benefits – Energy Efficiency• Tankless systems achieve high

thermal efficiency.• No standby losses.• Match hot water output with hot

water demand.• Condensing operation to

extract additional thermal energy.

Commercial• > 200,000 Btu/hr. input

• ≥ 0.94 Thermal Efficiency

Residential• < 200,000 Btu/hr. input

• ≥ 0.90 Energy Factor

Commercial Tankless Benefits – Energy Efficiency- Energy Star Water Heaters

Project Example: Restaurant Retrofit“More and more restaurants are moving to tankless water heaters.”1

• Drago’s Restaurant, Metairie, Louisiana. • 10,000 square feet. • Old System: 150-gallon storage tank unit. • Replacement System: three tankless water heaters.

• Benefits:• Greater Hot Water Supply: could now refill the 80, 60, and 40 gallon kettles with

160 degree Fahrenheit water.• Space Savings: removed the old tank and installed the tankless outdoors.• Reliability: two tanks manifolded together for overall facility water needs and

redundancy if one unit fails. The third tankless unit is dedicated to the kettles.

1. ENERGY STAR Commercial Water Heaters website:https://www.energystar.gov/products/water_heaters/commercial_water_heaters; 10/2018

Project Example: Water Heater Retrofit at Large Casino Resort• Major resort with dozens

of propane-powered applications.

• Located about 60 miles north of San Diego in the Palomar Mountain area, on rural tribal lands.

• Natural gas access cost prohibitive.

• Electric water heating not viable.

• Water heating load• Demand charges

Source: www.buildwithpropane.com

Pala Casino Spa & Resort

“Propane is the least expensive versus electric…. We've got a lot of water we're heating. I couldn't imagine the size of an electric water heater that we would be using.” Bob Halstead, Facilities Director

Project Example: Water Heater Retrofit at Large Casino Resort (cont.)

• Pre-retrofit system:• Three tank-style propane water

heaters.

• New system:• 19-unit propane tankless array.• Serves casino’s potable hot water

needs (besides guest rooms).

• Tankless systems improves reliability.

• Sized to meet peak demands.• Shared duty cycles.• Provides redundancy / reliability.

• Lower energy costs. Source: www.buildwithpropane.com

An array of 19 propane-powered tankless water heaters replaced a set of three aging tank water heaters.

Commercial Propane Tankless Units — AvailabilityAHRI Directory• Lists > 100 commercial tankless

models with thermal efficiency ≥ 0.94.

• Highest rated models have thermal efficiency of 0.98, from four different manufacturers.

• https://www.ahridirectory.org

Propane Compatibility • Most/all natural gas tankless water

heaters can be easily configured for propane use.

• AHRI directory lists many tankless models as “both propane and natural gas”.

• Broad availability of propane-powered commercial tankless units.

• Manufacturers provide conversion info, such as:o https://www.intellihot.com/resources/intellihotu

Propane Tankless Water Heaters —Contributions Towards LEED Certification

LEED v4 for Building Design and Construction (July 2018 update)• Covers several commercial building types.• Includes schools, hospitality, and health care.

• Significant hot water loads in these building types.

• Minimum Energy Performance Prerequisite. • Three different compliance options.

• Option 2: Prescriptive Compliance with the ASHRAE 50% Advanced Energy Design Guides. Meet the service water heating efficiency requirements listed in ASHRAE’s 50% Guides.

Tankless Systems and LEED Certification

LEED School Example• Meeting Minimum Energy

Performance Prerequisite means following the service water heating provisions in the ASHRAE’s 50% Advanced Energy Design Guide for K–12 school buildings.

• Gas Water Heaterso ≥ 95% Efficiency

• AHRI Directoryo> 125 tankless models using natural

gas / propane meet this spec

Tankless Systems and LEED Certification (cont.)

Using Option 1 to Meet Minimum Energy Performance• “Whole Building Energy Simulation”

option.• Must show 5% improvement relative

to the baseline building, based on ASHRAE 90.1-2010, for new construction.

• Tankless water heaters can contribute to the savings goal.oBaseline building will be modeled

with tankless, but at 80% thermal efficiency.

oPropane/natural gas tankless models are widely available from 90% up to 98%.

Tankless Systems and LEED Certification (cont.)

Propane Supply for Commercial Buildings

Considerations for Adding Propane • Many projects involving tankless will not

involve adding propane to a commercial building.

• Scenarios when propane may be added to a building:

• New construction projects.• Replacing electric water heating with

propane tankless.• Replacing heating oil water heating with

propane tankless.• Build with Propane Commercial Guide.• Energy supplier technical support.

Additional Resources• AHRI Directory:

• www.ahridirectory.org

• Commercial case studies of natural gas/propane tankless applications:• www.intellihot.com/resources/case-studies• www.noritz.com/case-studies/• www.rinnai.us/commercial-water-heater/services/resources

• ENERGY STAR Commercial Water Heaters• www.energystar.gov/products/water_heaters/commercial_water_heaters

This concludes the learning portion of this unit.

For more information visit:

www.propane.com

PERC: Cinch Munson, [email protected]

Thank You for Your Time

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Propane Tankless Water Heating in Commercial Building