Presented by: Terry Stohs Viessmann Manufacturing Company Inc.

Presented by:Terry StohsViessmann Manufacturing Company Inc.

Design Challenges in Commercial Building.

Efficiency

Regulations

Mechanical Room Space

Customer Comfort

Installation Cost

System Design

Operational Cost

System Longevity

System Integration(BMS)

Initial Investment

Return On Investment

What makes a Condensing Boiler Condense?

Nov 2005 Foil 4

ENERGY CONTENT OF NATURAL GAS

SENSIBLE HEAT89.8%

Heat that can be measured or felt by a change in temperature

LATENT HEAT10.2%

Latent – Definition:Latin for “hidden”

Simplified Chemical Combustion Formula:

CH4 + 2 O2 CO2 +2 H2O

HEAT RECOVERY FROM FLUE GASES

How do we capture the latent heat?

Water vapor (steam) containing latent heat

MARKETING AND REALITY

99.8%

THE MOST EFFICIENT BOILER

98

% E

FFIC

IEN

T

….can reach efficiencies of 98% - and more…..

Thermal efficiency

Combustion

Efficie

ncy

AFUE

What Are The Test??

Condensate measured for condensing boilers test

Heat Exchanger

Constant Load∆T=100°FBTS-2000

Air Input

Fuel Input

180oF

80oF

COMBUSTION EFFICIENCY TESTINGFor condensing gas commercial boilers >300 MBH

Efficiency is manually calculated using formulas in BTS-2000 or CSA B140.7 - 05Efficiency is manually calculated using formulas in BTS-2000 or CSA B140.7 - 05

THERMAL EFFICIENCY TESTINGFor commercial gas or oil boilers >300 MBH

QIN

Heat Input, btu/h

Boiler TIN – Fixed water temp (35-80oF)

Condensate measured for condensing boilers

TOUT

W= Mass of water (lb)

∆T≥100°F

BTS-2000NOTE:In some appliances the combustion and thermal efficiencies are so close that the thermal efficiency can actually be measured higher than combustion efficiency. This can be due to a very well insulated jacket (low standby losses), the testing environment (space warmer than Return Water Temperature) and small errors in the test results.

ANSI Z21.13 / CSA 4.9-2007

Condensing boiler

Sensible heat

CondensationLatentheat

Total heatingvalue

Useableheat

Heatingsystem

MORE USABLE HEAT THROUGH CONDENSATION

What influences the rate of condensation?

Do All Condensing Boilers Perform Equally?

Remember, efficiency depends on the rate of condensate formation!

Heatingsystem

Govtregula-

tion

Fuel Burnertype

Returnwater temp

Effective use of

condensing

technology

Pipinglayout

FACTORS INFLUENCING EFFECTIVENESS OF CONDENSING

TECHNOLOGY

Govtregula-

tion

Effective use of

condensing

technology

FACTORS INFLUENCING EFFECTIVENESS OF CONDENSING

TECHNOLOGY

Heatingsystem

Returnwater temp

Effective use of

condensing

technology

FACTORS INFLUENCING EFFECTIVENESS OF CONDENSING

TECHNOLOGY

Foil 15

80

82

84

86

88

90

92

94

96

2001801601401201008060

Dew Point of Natural Gas

Condensingmode

Non-Condensingmode

Ste

ad

y s

tate

boiler

effi

cie

ncy %

Boiler return water temp of

98

SIMPLIFIED CONDENSING BOILER OPERATION

133

How do we get the most from a Condensing Boiler???

• Condensing Technology.• Rein in the energy savings.

Flue gas condensingIn contact with the Boiler’s heat exchanger

BoilerHeat exchanger

Flue gas

Latent energytransferredinto heating system

Make It RAIN!!!

Boiler return water temperature determines condensing operation

RETURN WATER TEMPERATURE

2. Efficiency Eliminate overheating Three to one rule Lower standby losses

Why use it?

1. Comfort Slow space temperature changes Constant heat output Keep up vs Catch up

Outdoor Reset Control

2272

86

104

158

176

195oF

133

117

167B

oiler

Wate

r Te

mp

era

ture

Dew pointNatural gas

Traditional boilers must be kept hot140o

F

Boiler water temperature modulated

oF+65 +50 32 +14 -4

Outside Temperature

On/off control

Boiler water temperature maintained

HYDRONIC WATER TEMPERATURES

IMPACT OF SYSTEM TEMPERATURES ON CONDENSATIONSupply/return temperature:

167/140oF

59 50 41 32 23 14 5 oF

167oF

140oFDewpoint temp 133oF

Condensation range

11.3oF

Syste

m w

ate

r te

mp

era

ture

68

86

104

122

140

158

oF

176

194

Outside temperature68

FanRadiators

SYSTEM WATER TEMPERATURE DROP

Typical system 20oF Temperature drop

160oF

160oF

What about a higher temperature drop?30oF……40oF?

140oF

Air flow

160OF

140°F

Fan Coils For Condensing Boilers

TraditionalFan Coil Sizing

150°F

Air flow

170OF

130°F

Fan Coils For Condensing Boilers

Fan Coil Sizing

150°F

INFLUENCING THE RETURN WATER TEMPERATURE

Let’s get creative

Hybrid SystemSystem Return

System Supply

Condensing boilerNon-Condensing boiler

CondensingBoiler

Burner

type

Effective use of

condensing

technology

FACTORS INFLUENCING EFFECTIVENESS OF CONDENSING

TECHNOLOGY

Natural Gas Combustion

1 part gas 10 parts air

+Excess air

More excess air = Lower CO2%Lower C02% = Lower dew point temperatureLower dew point temp. = Less condensation

What happens as we increase excess oxygen to achieve better flame quality?

What Methods are Available?

Does it Change Efficiency?

Turn Down

Higher CO2

=Higher Dew point=More Condensation

Dew

poin

t w

ate

r vap

or

77

86

95

104

113

122

131

140

oF

2 3 4 5 6 7 8 9 10 11 12

Natural Gas (95% CH4)

Lower CO2

=Lower Dew point=Less Condensation

Water vapor condenses below the dew point temperature

Turn Down Methods

Single unit multiple gas valves and burners

Low Mass High turndown

Multiple Gas valves single burner

Multiple boilersHigh Mass boiler

Effective use of

condensing

technology

Pipinglayout

FACTORS INFLUENCING EFFECTIVENESS OF CONDENSING TECHNOLOGY

USE OF MIXING VALVES WITH CONDENSING BOILERS

3-way mixing valve

Lower boiler return water temperature.

CORRECT

4-way mixing valve

Boiler return water temperature elevation

INCORRECT

CONDENSING BOILERS IN TWO TEMPERATURE SYSTEMS

Lowtempsystem

High temp system

COMBINATION OF BOILERS

LAG BOILER LEAD BOILER

System Return

System Supply

Condensing boilerCondensing boiler

Boiler

Integrated solutions for all your hydronic heating and DHW needs

DHW

Small Boilers

LargeBoiler

DHW

Thermal Solar

Thank You!!!

Terry StohsViessmann Manufacturing Company Inc.