ASHRAEMarch 24, 2015

Condensing Boilers and System Performance

Optimization

Boiler Efficiency Comparisons

• Standard Efficiency (80%)

– Atmospheric (no fan)

• Mid Efficiency (83-87%)

– Fan Assist or Forced Draft Fan (Sealed Combustion)

• High Efficiency / Condensing (87% and Above)

– Fan Assist or Forced Draft Fan (Sealed Combustion)

Part Load Efficiency

Combustion StoichiometeryCombustion Stoichiometery

• O2 (G) + ½ CH4 (G) � ½ CO2 (G) + H2O (G)

• An Interesting Thing Happens at about 130 deg. F.

• The H2O begins to Condense – Water + Carbon = Carbonic Acid

– Latent Heat of Vaporization

– High Efficiency

• Condensing Boilers Operating Above 130 deg. F Return Water

Are Not Condensing

Notice the difference between a typical and a

Condensing outdoor air reset schedule

110

100

90

150

140

130

120

3510 1570 30

200190

180

170

160

80

600 5 40 45 50 5520 25

Typical Reset

Condensing Reset Curve

Avg % % % T BIN to Range TOT J F M A M J J A S O N D TOT CUM LOAD

63 62 64 296 15 36 47 23 27 50 52 25 15 6 4.82 4.8 3.0

61 60 62 313 6 32 46 40 26 49 38 45 17 14 5.09 9.9 6.1

59 58 60 168 10 13 21 14 12 20 21 41 10 6 2.73 12.6 9.1

57 56 58 282 16 35 75 19 7 20 44 44 12 10 4.59 17.2 12.1

55 54 56 412 2 24 45 96 25 9 27 84 38 51 11 6.70 23.9 15.2

53 52 54 277 3 4 26 27 46 28 5 12 26 52 31 17 4.51 28.4 18.2

51 50 52 293 7 3 37 44 34 16 8 16 25 55 42 6 4.77 33.2 21.2

49 48 50 215 6 10 20 29 28 5 8 24 58 25 2 3.50 36.7 24.2

47 46 48 228 11 13 25 44 27 6 3 8 50 37 4 3.71 40.4 27.3

45 44 46 225 26 19 28 39 21 2 1 5 51 32 1 3.66 44.1 30.3

43 42 44 236 17 17 28 53 14 7 37 51 12 3.84 47.9 33.3

41 40 42 135 5 7 25 26 6 8 28 17 13 2.20 50.1 36.4

39 38 40 296 28 26 34 82 13 8 36 50 19 4.82 54.9 39.4

37 36 38 417 66 68 42 72 15 1 13 84 56 6.79 61.7 42.4

35 34 36 404 49 77 55 32 5 9 81 96 6.57 68.3 45.5

33 32 34 324 65 51 49 20 7 43 89 5.27 73.6 48.5

31 30 32 279 61 18 42 11 8 37 102 4.54 78.1 51.5

29 28 30 202 35 35 41 5 1 29 56 3.29 81.4 54.5

27 26 28 222 50 40 52 17 63 3.61 85.0 57.6

25 24 26 185 31 51 41 13 49 3.01 88.0 60.6

23 22 24 104 16 36 39 1 12 1.69 89.7 63.6

21 20 22 154 30 51 30 43 2.51 92.2 66.7

19 18 20 147 64 33 32 18 2.39 94.6 69.7

17 16 18 83 42 24 7 10 1.35 96.0 72.7

15 14 16 66 35 22 9 1.07 97.0 75.8

13 12 14 66 32 28 6 1.07 98.1 78.8

11 10 12 28 6 10 12 0.46 98.6 81.8

9 8 10 21 14 5 2 0.34 98.9 84.8

7 6 8 11 6 5 0.18 99.1 87.9

5 4 6 15 10 5 0.24 99.3 90.9

3 2 4 20 14 6 0.33 99.7 93.9

1 0 2 21 15 6 0.34 100.0 97.0

-1 -2 0 0.00 100.0 100.0

Cleveland, Ohio

Condensing Boilers

1. Complete corrosion resistant material

2. Epoxy coating to withstand temperature and condensate

3. Hybrid design protecting a portion of the surface area

4. Design Considerations

1. Corrosion Resistant Material

• Stainless Steel

Primary/secondary

Variable flow

• Aluminum

Giannoni Heat Exchanger

• 316 (Titanium) Stainless Steel

Heat Exchanger

• Fully modulating pre-mix

burner – neg reg valve

• Three rows of hydraulically

assembled (non welded)

tubes

Heat Exchanger

Stainless Steel Water Tube

2. Epoxy Coating

• Difficult to Implement

• Organic and Inorganic Materials

– Toxicity, adhesion, and life have been barriers to

wide scale adoption of this method.

3. Hybrid Design

Secondary Heat Exchanger

4. Design Considerations

ASHRAE

Metal

Temperature

Thermal

Conductivity

- t - - k -

(oF) (Btu/(hr oF ft))

Aluminum 68 118

Carbon Steel 68 21 - 31

Cast Iron, gray 70 27 - 46

Copper, pure 68 223

Cupronickel 68 17

Stainless Steel 68 6 - 26

Primary Secondary Pumped System

Parallel Piping: Boilers in Primary

Flow Meter

T-3 T

1,000,000 BTU’s/Hr Total Load

33 GPM 33 GPM33 GPM

100 GPM

Optimal Flow

= 50 GPM ?

500,000 BTUH

Optimal Flow

= 50 GPM ?

Optimal Flow

= 50 GPM ?Optimal Flow

= 50 GPM ?

500,000 BTUH500,000 BTUH

BOILERBOILER BOILER

Speed = 100% to System

Flow Corresponds to 30 ∆T

∆T 20 Deg F

Variable Volume Flow

Gas Control

• Natural gas or propane

– Orifice plate included

– Change pilot orifice

• Full input with 2” W.C.

– 3” W. C. FOR KN-30

• Operation @ 1.5” W.C

• Precise Dungs valve

The design uses a gas following method such that a changein airflow causes an instantaneous change in gas flow,which maintains the air/fuel ratio precisely.

Air/Fuel Coupling

gasvalve

gas PG= PA

PA

PG

airVFD

premixair/gas

1 to 1ratio

High Turndown Boilers

Venting and Combustion Air

All manufacturers have different requirements

• Maximum equivalent lengths

• Minimum lengths

• Elbow equivalent lengths

• Intake cap configurations

• Vent cap configurations

• Combined intake limitations-if at all

• Combined vents limitations-if at all

Control Strategy-Multi Function

Boiler Management System

How We Control Set-Point

• Boiler to Boiler Communication – HeatNet

• Multiple Heat Bands

• Add Boiler Delay Timing

• Adaptive Modulation – prevents short cycling

• Modulate Delay Time (Low Fire Hold)

• Mod Max – ‘till last boiler fire’

• Promote True Rotation (Sequencing)

Prevention & Compatibility

• Min/max vfd – load match (low fire, parallel operation)

• Log entry – troubleshoot and diagnostic tool

– Records major activity of boiler operation (history)

• Monitor min return temp – copper fin

• Heat exchanger delta T (limits to half fire)

• Firmware loading – flash drive or USB cable

• Fail safe mode – member boilers

• First boiler ON – venting

• Min boiler off time

PRIORITY 1Fusion boilers (condensing)

PRIORITY 2Futera III boilers (non-condensing)

>FIRING PRIORITY :1 BTU IN 500,000 CONDENSING YES MASS LOW

>MODE MIXED MIN RUNTIME: 10HRs MIN OFF TIME: 0s PREDICT START: YES

FIRING MODE menu(master boiler only)

BOILER TYPE menu(all boilers in set)

>FIRING PRIORITY :2 BTU IN 1250,000 CONDENSING NO MASS LOW

BOILER TYPE menu(all boilers in set)

START PRIORITY 1

>SET : FIRST

STOP PRIORITY 1

SET : LAST

START PRIORITY 1

>SET : FIRST

STOP PRIORITY 1

SET : OAT < 15°°°°F

Master Only

>BOILER TYPE LOAD FIRMWARE OPTION: BASE LOAD

>BASE LOAD BOILERS:1 START>MOD 95 STOP FIRST DELAY TIME 10mins

BASE LOADING menu(master boiler only)

SYSTEM menu( )master boiler only

MasterFIII/Fusion

BaseloadDominator

>BOILER TYPE LOAD FIRMWARE OPTION: BASE LOAD

>BASE LOAD BOILERS:1 START>MOD 95 STOP FIRST DELAY TIME 10mins

BASE LOADING menu(master boiler only)

SYSTEM menu( )master boiler only

MasterFIII/Fusion

BaseloadFII

Building Dashboard

System Dashboard

Boiler Status

Trending

Water Treatment

Corrosion & scale attack

Pipe wall corrosion

Thank You