Heat Controller HEV-HEH SEriES Design Guide
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Heat Controller, LLC HEV/H SERIES Engineering Design Guide
Step 1 Determine the actual heating and cooling loads at the
desired dry bulb and wet bulb conditions.
Step 2 Obtain the following design parameters: Entering water
temperature, water ow rate in GPM, air ow in CFM,
water ow pressure drop and design wet and dry bulb
temperatures. Air ow CFM should be between 300 and
450 CFM per ton. Unit water pressure drop should be
kept as close as possible to each other to make water
balancing easier. Go to the appropriate tables and nd
the proper indicated water ow and water temperature.
Step 3 Select a unit based on total and sensible cooling condi-
tions. Select a unit which is closest to, but no larger
than, the actual cooling load.
Step 4 Enter tables at the design water ow and water tem-
perature. Read the total and sensible cooling capacities
(Note: interpolation is permissible, extrapolation is not).
Step 5 Read the heating capacity. If it exceeds the design
criteria it is acceptable. It is quite normal for Water-
Source Heat Pumps to be selected on cooling capacity
only since the heating output is usually greater than the
cooling capacity.
Step 6 Determine the correction factors associated with the
variable factors of dry bulb and wet bulb.
Corrected Total Cooling =
tabulated total cooling x wet bulb correction.
Corrected Sensible Cooling =
tabulated sensible cooling x wet/dry bulb correction.
Step 7 Compare the corrected capacities to the load require-
ments. Normally if the capacities are within 10% of the
loads, the equipment is acceptable. It is better to under-
size than oversize, as undersizing improves humidity
control, reduces sound levels and extends the life of the
equipment.
Step 8 When completed, calculate water temperature rise
and assess the selection. If the units selected are not
within 10% of the load calculations, then review what
effect changing the GPM, water temperature and/or air
ow and air temperature would have on the corrected
capacities. If the desired capacity cannot be achieved,
select the next larger or smaller unit and repeat the pro-
cedure. Remember, when in doubt, undersize slightly
for best performance.
Example Equipment Selection For Cooling
Step 1 Load Determination:
Assume we have determined that the appropriate cooling load
at the desired dry bulb 80°F and wet bulb 65°F condi-
tions is as follows:
Total Cooling .............................................. 22,100 BTUH
Sensible Cooling......................................... 16,500 BTUH
Entering Air Temp ....................................... 80°F Dry Bulb /
65°F Wet Bulb
Step 2 Design Conditions:
Similarly, we have also obtained the following design parameters:
Entering Water Temp.......................................... 90°F
Water Flow (Based upon 10°F rise in temp.) ..... 6.0 GPM
Air Flow .............................................................. 730 CFM
Step 3, 4 & 5 HEV/H Selection:
After making our preliminary selection (HEH026 - Full Load), we
enter the tables at design water ow and water temper-
ature and read Total Cooling, Sens. Cooling and Heat of
Rej. capacities:
Total Cooling....................................................24,200 BTUH
Sensible Cooling..............................................16,300 BTUH
Heat of Rejection.............................................29,900 BTUH
Step 6 & 7 Entering Air and Airow Corrections:
Next, we determine our correction factors.
Table Ent Air Air Flow Corrected
Corrected Total Cooling = 24,200 x 0.975 x 0.978 = 23,076
Corrected Sens Cooling = 16,300 x 1.096 x 0.926 = 16,543
Corrected Heat of Reject = 29,900 x 0.979 x 0.978 = 28,628
Step 8 Water Temperature Rise Calculation & Assessment:
Actual Temperature Rise ................................. 9.5°F
When we compare the Corrected Total Cooling and Corrected
Sensible Cooling gures with our load requirements
stated in Step 1, we discover that our selection is within
+/- 10% of our sensible load requirement. Furthermore,
we see that our Corrected Total Cooling gure is within
1,000 Btuh the actual indicated load.
Selection Procedure
