Specifications

TRM
5
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THE SMART SOLUTION FOR ENERGY EFFICIENCY
Tranquility Vertical Stack (TRM) Series
Rev.: 05/23/07D
Selection Procedure
Step 1 Determine the actual heating and cooling loads at the
desired dry bulb and wet bulb conditions.
Step 2 Obtain the following de sign parameters: Entering
water temperature, water fl ow rate in GPM, air fl ow
in CFM, water fl ow pressure drop and design wet
and dry bulb temperatures. Air fl 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
ap pro pri ate tables and fi nd the proper indicated water
fl ow and water tem per a ture.
Step 3 Select a unit based on total and sensible cooling
conditions. Select a unit which is closest to, but no
larger than, the actual cooling load.
Step 4 Enter tables at the design water fl ow and water
temperature. Read the total and sensible cooling
capacities (Note: interpolation is per mis si ble,
ex trap o la tion 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 (page 14).
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
re quire ments. Normally if the capacities are within 10%
of the loads, the equipment is ac cept able. It is better
to undersize than oversize, as undersizing improves
humidity control, reduces sound levels and extends the
life of the equip ment.
Step 8 When completed, calculate water temperature rise
and assess the selection. If the units selected are not
within 10% of the load cal cu la tions, then review what
effect chang ing the GPM, water temperature and/or air
fl ow and air tem per a ture would have on the corrected
capacities. If the desired capacity cannot be achieved,
select the next larger or smaller unit and repeat the
procedure. Remember, when in doubt, undersize
slightly for best performance.
Example Equipment Selection For Cool ing
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 con di tions is
as follows:
Total Cooling ...........................................15,100 BTUH
Sensible Cooling ......................................10,500 BTUH
Entering Air Temp ........ 80°F Dry Bulb / 65°F Wet Bulb
Step 2 Design Conditions:
Similarly, we have also obtained the following design pa ram e ters:
Entering Water Temp ............................................90°F
Water Flow (Based upon 10°F rise in temp.) 4.5 GPM
Air Flow .........................................................515 CFM
Step 3, 4 & 5 HP Selection:
After making our preliminary selection (TRM18), we enter the
tables at design water fl ow and water tem per a ture and read Total
Cooling, Sens. Cooling and Heat of Rej. ca pac i ties:
Total Cooling ............................................16,800 BTUH
Sensible Cooling ......................................12,500 BTUH
Heat of Rejection .....................................21,300 BTUH
Step 6 & 7 Entering Air and Airfl ow Corrections:
Next, we determine our correction factors.
Table Ent Air Air Flow Cor rect ed
Corrected Total Cooling = 16,800 x 0.957 x 0.934 = 15,016
Corrected Sens Cooling = 12,500 x 1.093 x 0.833 = 11,381
Corrected Heat of Reject = 21,300 x 0.970 x 0.952 = 19,669
Step 8 Water Temperature Rise Calculation & As sess ment:
Actual Temperature Rise 8.9°F
When we compare the Corrected Total Cooling and Corrected
Sensible Cooling fi gures with our load re quire ments stated in Step
1, we discover that our selection is within +/- 10% of our sensible
load requirement. Fur ther more, we see that our Cor rect ed Total
Cooling fi gure is slightly undersized as recommended, when
compared to the actual in di cat ed load.