White Paper76 800

76-800 May, 2012 THE TECHNIC L TIMES High Efficiency Boiler Retrofi ts and Terminal Equipment As the market moves towards higher efficiency boilers, an area that sometimes goes overlooked is existing terminal equipment. This doesn’t come up in every situation, but when an existing boiler is replaced with a new condensing model, supply water temperature generally decreases significantly, to around 140°F. This drop in entering water t emperature (EWT) to the terminal equipment comes with a significant performance penalty (42% when compared to 200°F EWT!) and may require either additional terminal equipment or replacement of existing terminal equipment with larger capacity models. Another important consideration is that the Final Air Temperature leaving the units will be significantly lower when low EWTs are used, which may result in occupant complaints. Shown below are tables for Horizontal Unit heaters and Cabinet Unit heaters with BTU outputs for both 200°F and 140°F EWT. As an example, if a space currently has an HSB-63 and 200°F EWT, the new output will be 26,038 BTU, down from 45,600 BTU! Meeting the heating requirements of the space now means either adding another HSB-63 or replacing the existing unit with an HSB-108. Table 1.1 – Hot Water Unit Heater Data Model Size BTU/hr Output 200°F Water 140°F Water HSB/HC-18 12,600 7,195 HSB/HC-24 16,200 9,250 HSB/HC-33 21,700 12,391 HSB/HC-47 30,900 17,644 HSB/HC-63 45,600 26,038 HSB/HC-86 60,200 34,374 HSB/HC-108 83,700 47,793 HSB/HC-121 93,000 53,103 HSB/HC-165 130,900 74,744 HSB/HC-193 143,000 81,653 HSB/HC-258 201,900 115,285 HSB/HC-290 228,600 130,531 HSB/HC-340 271,100 154,798 Table 1.2 – Cabinet Unit Heater Data Model Size BTU/hr Output 200°F Water 140°F Water 2 12,400 7,080 3 22,400 12,790 4 28,400 16,216 6 44,800 25,581 8 49,000 27,979 10 55,900 31,919 12 72,400 41,340 14 79,500 45,395 * All ratings are for 20° WTD, high fan speed , single row coil (CUH), and 60°F EAT * 140°F Water Correction Factor is 0.571.

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Transcript of White Paper76 800

8/10/2019 White Paper76 800

http://slidepdf.com/reader/full/white-paper76-800 1/2

76-80May, 201

THE TECHNIC L TIMES

High Efficiency Boi ler Retrofi ts and Terminal Equipment

As the market moves towards higher efficiency boilers, an area that sometimes goes

overlooked is existing terminal equipment. This doesn’t come up in every situation, but when an

existing boiler is replaced with a new condensing model, supply water temperature generally

decreases significantly, to around 140°F. This drop in entering water temperature (EWT) to the

terminal equipment comes with a significant performance penalty (42% when compared to 200°F

EWT!) and may require either additional terminal equipment or replacement of existing terminal

equipment with larger capacity models. Another important consideration is that the Final AirTemperature leaving the units will be significantly lower when low EWTs are used, which may

result in occupant complaints.

Shown below are tables for Horizontal Unit heaters and Cabinet Unit heaters with BTU

outputs for both 200°F and 140°F EWT. As an example, if a space currently has an HSB-63 and

200°F EWT, the new output will be 26,038 BTU, down from 45,600 BTU! Meeting the heating

requirements of the space now means either adding another HSB-63 or replacing the existing unit

with an HSB-108.

Table 1.1 – Hot Water Unit Heater Data

Model SizeBTU/hr Output

200°F Water 140°F Water

HSB/HC-18 12,600 7,195

HSB/HC-24 16,200 9,250

HSB/HC-33 21,700 12,391

HSB/HC-47 30,900 17,644

HSB/HC-63 45,600 26,038

HSB/HC-86 60,200 34,374

HSB/HC-108 83,700 47,793

HSB/HC-121 93,000 53,103

HSB/HC-165 130,900 74,744

HSB/HC-193 143,000 81,653

HSB/HC-258 201,900 115,285

HSB/HC-290 228,600 130,531

HSB/HC-340 271,100 154,798

Table 1.2 – Cabinet Unit Heater Data

Model SizeBTU/hr Output

200°F Water 140°F Water

2 12,400 7,080

3 22,400 12,790

4 28,400 16,216

6 44,800 25,581

8 49,000 27,979

10 55,900 31,91912 72,400 41,340

14 79,500 45,395

* All ratings are for 20° WTD, high fan speed , single row coil(CUH), and 60°F EAT

* 140°F Water Correction Factor is 0.571.

8/10/2019 White Paper76 800

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Commercial Products Group Modine Manufacturing Company 1500 DeKoven Avenue Racine, WI USA 53403-2552

Phone: 1.866.823.1631 www.modinehvac.com

The tables below show Final Air Temperatures (FAT) for the models described above.

The FAT is calculated by using the formula shown below:

1.085

Table 2.1 – Hot Water Unit Heater Data

Model SizeFinal Air Temperature (°F)

200°F Water 140°F Water

HSB/HC-18 93 79

HSB/HC-24 100 83

HSB/HC-33 91 78

HSB/HC-47 98 82

HSB/HC-63 97 81

HSB/HC-86 101 83

HSB/HC-108 98 82

HSB/HC-121 107 87HSB/HC-165 96 81

HSB/HC-193 105 86

HSB/HC-258 100 83

HSB/HC-290 105 86

HSB/HC-340 108 87

Table 2.2 – Cabinet Unit Heater Data

Model SizeFinal Ai r Temperature (°F)

200°F Water 140°F Water

2 106 86

3 123 96

4 118 93

6 127 98

8 114 91

10 109 88

12 114 91

14 111 89

* All ratings are for 20° WTD, high fan speed , single row coil(CUH), and 60°F EAT

Stepping back to take a complete view of the system will identify any spaces where the terminal

units will not provide enough heat and allow for proper sizing of the new boiler if additional

heaters are required. This “big picture” approach will prevent any surprises at installation andcommissioning, and will ensure happy customers and space occupants.