Carrier 50HQ User Manual download pdf (Page 12)

For example, using the Corrected Heat of Rejection

from the last step:

If the units selected are not within 10% of the load

calculations, review what effect changing the GPM,

water temperature and/or airflow will have on the

corrected capacities. If the desired capacity cannot

be achieved, select the next larger or smaller unit

and repeat Steps I through VI.

VIII AHRI/ISO/ASHRAE 13256-1 Conversion

Performance standard AHRI/ISO/ASHRAE

13256-1 became effective on January 1, 2000 and

replaced the existing AHRI Standards 320 Water-

Loop Heat Pumps (WLHP), 325 Ground-Water

Heat Pumps (GWHP), and 330 Ground-Loop Heat

Pumps (GLHP).

The AHRI/ISO Standard incorporates a consistent

rating methodology for including fan and pump

energy for calculating cooling capacity, heating

capacity, and energy efficiency ratios (EER). This

simplifies the use of rating data for heat pump per-

formance modeling in seasonal energy analysis cal-

culations, and allows for direct rating comparisons

across applications.

a) ISO Capacity and Efficiency Equations

The following equations are used to calculate and

correct cooling capacity, heating capacity, and re-

spective EER:

ISO Cooling Capacity = (Cooling Capacity in

Btuh) + (Fan Power Correction in Watts x 3.412)

ISO Cooling EER = (ISO Cooling Capacity in

Btuh/3.412)/(Power Input in watts – fan power

correction in watts + pump power correction in

watts) = Watts/Watts

ISO Heating Capacity = (Heating Capacity in

Btuh) – (Fan Power Correction in Watts x 3.412)

ISO Heating COP = (ISO Heating Capacity in

Btuh/3.412)/(Power Input in watts – fan power

correction in watts + pump power correction in

watts) = Watts/Watts

b) Identify the design conditions corrected for air and

water conditions.

Airflow Cfm = 2400 Cfm

Water Flow (based upon 11.4 F rise in temp) =

15.0 GPM

External Static Pressure = 0.5 in. wg

Water Pressure Drop = 4.3 ft of head

Cooling Power Input = 5,960 watts

Cooling Capacity = 64,365 Btuh

Heating Power Input = 5,500 watts

Heating Capacity = 86,000 Btuh

c) Perform Fan Power Correction Adjustment

Use the following formula to calculate Fan Power

Correction:

Fan Power

Correction = (Cfm x 0.472) x (External Static

Pressure x 249)/300 = Watts

= (2400 x 0.472) x (0.5 x 249)/300

= 470 Watts

d) Perform Pump Power Correction Adjustment

Use the following formula to calculate Pump Pow-

er Correction:

Pump Power

Correction = (GPM x 0.0631) x (Pressure Drop

x 2,990)/300

= Watts

= (15.0 x 0.0631) x

(4.3 x 2,990)/300

= 41 Watts

e) Perform Cooling Capacity Calculation

Use the following formula to calculate cooling

capacity:

ISO Cooling

Capacity = (Cooling Capacity) + (Fan Power

Correction x 3.412)

= 64,365 + (470 x 3.412)

= 65,969 Btuh

f) Perform Cooling EER Calculation

ISO EER = (ISO Cooling Capacity/3.412)/

(Cooling Power Input – Fan Power

Correction + Pump Power

Correction)

= Watts/Watts

= (65,969/3.412)/(5,960 – 470 + 41)

= 3.50 Watts/Watt

= 11.9 Btuh/Watt

g) Perform Heating Capacity Calculation

Use the following formula to calculate heating

capacity:

ISO Heating

Capacity = (Heating Capacity) – (Fan Power

Correction x 3.412)

= 86,000 – (470 x 3.412)

= 84,396 Btuh

h) Perform Heating COP Calculation

ISO EER = (ISO Heating Capacity/3.412)/

(Heating Power Input – Fan Power

Correction + Pump Power

Correction)

= Watts/Watts

= (86,000/3.412)/(5,500 – 470 + 41)

= 4.97 Watts/Watt

= 17.0 Btuh/Watt

Actual Temperature

Rise

85,619

= 11.4 F

15.0 x 500

Selection procedure (cont)

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Carrier 50HQ User Manual Page 12

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