Carrier 48TFD008-014 User Manual download pdf (Page 19)

VII Select net heating capacity of unit to meet

design condition requirements.

Enter the Heating Capacities and Efficiencies rating

table. The 48TFD006 unit will provide 59,200 Btuh

of heating.

Enter the 62AQ060 Heating rating table at 450 cfm.

At 70 F and 0° F find the heating value for the

Energy$Recycler to be 15.2 MBtuh.

The customer heat requirement is 60,000 Btuh.

Rooftop Heat Capacity 59,200 Btuh

Rooftop fan heat from Step II 4,884 Btuh

Energy$Recycler Heat Capacity 15,200 Btuh

add Energy$Recycler optional

supply fan heat if supplied 0 Btuh

Total Unit heat with Energy$Recycler 79,284 Btuh

The required heating capacity is 60,000 Btuh. The

total unit net heating capacity is 79,284 Btuh. The

48TFD006 unit is sufficient.

VIII Determine net cooling capacity.

Cooling capacities are gross capacities and do not in-

clude indoor (evaporator) or optional Energy$Recycler

supply fan heat.

Determine net cooling capacity using the following

formula:

Net Capacity = (Gross Capacity Rooftop Unit +

Energy$Recycler) – (Indoor [evaporator] fan motor

[IFM] Heat + Optional Energy$Recycler Supply Fan

Motor Heat)

Gross Total Cooling

Rooftop unit 58,400 Btuh

Energy$Recycler 13,000 Btuh

Total 71,400 Btuh

Less

IFM heat (from Step II) <4,884> Btuh

Opt. Energy$Recycler Supply

Fan Motor Heat none

Net Total Capacity 66,516 Btuh

Gross Sensible Cooling

Rooftop unit 51,400 Btuh

Energy$Recycler 10,090 Btuh

Total 61,490 Btuh

Less

IFM heat (from Step II) <4,884> Btuh

Opt. Energy$Recycler Supply

Fan Motor Heat none

Net Sensible Capacity 56,606 Btuh

IX Determine the operating watts of the rooftop

unit and Energy$Recycler unit.

Cooling with Energy$Recycler in operation:

a) Rooftop unit:

Using the 48TF006 cooling capacity table and the

calculations described in Step VI of this procedure,

determine:

compressor watts 5,690 watts

Indoor fan motor from Step II 1,431 watts

Outdoor fan motor from Physical Data table find

hp†

Assume OD motor efficiency is 0.75.

Watts = (746 x hp)/(motor Eff)

= (746 x

)/(0.75)

= 249 watts

†Dual circuit units will have two outdoor fans, dou-

ble values.

b) Energy$Recycler:

Compressor watts from 62AQ060

Cooling Ratings table 1,060 watts

Optional supply fan from

fan curves none selected

Exhaust fan operating watts from 62AQ060

Exhaust Fan Performance Curve at 230-v,

450 cfm, 0.2 in. wg, Static = 110 watts

Total watts for the unit in operation

at design conditions 8,540 watts

X Electrical data RLA, FLA, LRA, MCA and

MOCP.

Separate Power Supply:

If the 62AQ is wired for separate power see the Elec-

trical Data table.

Single Power Supply with Unit:

The unit is 230 v-3-60 Hz, so from the 48TF Electri-

cal Data table, find unit electrical data. For the rooftop

unit with alternate indoor fan motor the data is MCA

= 27.3 amps, MOCP = 35 amps, Min Unit Discon-

nect Size FLA = 27, and LRA = 128.

For this example follow the steps outlined in the

Application Data section of the Energy$Recycler

Product Data for single power supply for all rooftop

units except size 014 (230-v) and 62AQ on 460-v

power supply. For other size and voltage conditions

follow corresponding steps also outlined in the

Energy$Recycler Product Data Application data

section.

From the Single Power Supply table (Electrical Data,

Energy$Recycler Product Data) find 230 v, for

62AQ060300, “X” = 8.1 amps and “Y” = 9.3 amps.

Add “X” amps to the MCA and MOCP and add “Y”

amps to the minimum disconnect size.

(MOCP calculation is 43.1. Round the value down to

40. 40 is greater than the MCA of 35.4, therefore 40

is the correct MOCP.)

The wiring to the unit must be suitable for the MCA

calculated above.

The overcurrent protective device for the combination

load is equal to 40, thus a single disconnect may be

used for BOTH the MAIN UNIT and the 62AQ pro-

vided that the wire supplying the 62AQ is sized for a

minimum of 33% of the maximum overcurrent pro-

tection device value (i.e., 40 x .33 = 14 Amps). No

further subfusing is required.

In this example a 40-amp disconnect would be used

for the combined load of the 48TF006 and the

62AQ060 Energy$Recycler unit.

MCA MOCP FLA LRA

48TF 27.3 35 27 128

62AQ 8.1

8.1 9.3 31.7

Total 35.4 43.1 36.3 159.7

1 ... 18 19 20 ... 80

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Carrier 48TFD008-014 User Manual Page 19

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