Marvair AVPA60 Manuel d'utilisateur télécharger pdf (Page 3)

3 AVPA & HVEA PDS 4/2012 rev.2

Savings with an Economizer

The following table shows the annual electrical cost of cooling a 10 ft. x 20 ft. x 9 ft. (3m x 6m x 2.7m)

shelter in nine cities in the US. Costs are shown for an air conditioner without an economizer (ComPac I

units), for an air conditioner with an economizer (ComPac II units) and the savings. The savings do not

include any demand charges. The savings are based on the electrical usage of a five ton air conditioner and

an electric rate of $.10 per kilowatt-hour, the approximate average commercial rate in the US.

Hours of Operation Atlanta, GA Boston, MA Chicago, IL Dallas, TX Denver, CO Houston, TX

Annual Compressor & Condenser Motor Run Time

without Economizer (Hrs.)

6,531 6,348 6,361 6,628 6,472 6,655

Annual Compressor & Condenser Motor Run Time

with Economizer (Hrs.)

3,841 2,153 2,424 3,798 750 4,970

Run Time Savings with the Economimizer (Hrs.) 2,690 4,195 3,937 2,830 5,722 1,685

Annual Costs Saving ($) of 9.0 EER unit with an Economizer (ComPac II)

Annual Operating Cost 9.0 EER Unit without

Economizer ($)

$4,100.00 $3,985.00 $4,792.00 $4,161.00 $3,657.00 $4,178.00

Annual Operating Cost 9.0 EER with Economizer $2,685.00 $1,784.00 $2,315.00 $2,671.00 $940.00 $3,291.00

Annual Savings using 9.0 EER Unit with

Economizer

$1,415.00 $2,201.00 $2,477.00 $1,490.00 $2,717.00 $887.00

Hours of Operation Los Angeles, CA Miami, FL Phoenix, AZ Pittsburgh, PA Seattle, WA St. Louis, MO

Annual Compressor & Condenser Motor Run

Time without Economizer (Hrs.)

6,467 6,779 6,765 6,386 6,465 6,472

Annual Compressor & Condenser Motor Run

Time with Economizer (Hrs.)

3,862 6,391 3,106 1,929 1,654 2,716

Run Time Savings with the Economimizer (Hrs.) 2,605 388 3,659 4,457 4,811 3,756

Annual Costs Saving ($) of 9.0 EER unit with an Economizer (ComPac II)

Annual Operating Cost 9.0 EER Unit without

Economizer ($)

$4,060.00 $4,255.00 $4,247.00 $4,009.00 $3,653.00 $4,063.00

Annual Operating Cost 9.0 EER with Economizer $2,686.00 $4,051.00 $2,315.00 $1,667.00 $1,368.00 $2,090.00

Annual Savings using 9.0 EER Unit with

Economizer

$1,374.00 $204.00 $1,932.00 $2,342.00 $2,285.00 $1,973.00

Shelter Metrics:

•10’x20’x9’building

•Internalheatgain(electronicsload):12,000watts.

•Buildingsurfacearea(excludingfloorarea):740ft²

•R-Valueofwallsandceiling:R-12

•Internalsheltertemperature(Thermostatsetpoint):75ºF

Air Conditioner Metrics:

•ComPacIIEconomizersetting:57ºF(wetbulb)

•A/Cunitcapacity:60,000BTUH(5tons)with1-stagecompres-

sor

•NominalEER(unitefficiency):9.0(modelsAVPA)

•Costofpower:$.10perKWH

Operation of the 2-Stage Compressor Air Conditioners with a

CommStat 4™ Lead/Lag Thermostat Controller

Marvair’s HVESA air conditioners have 2-stage compressors. These units can provide substantial energy

savings and better control of temperature and humidity by matching the cooling requirement with the

performance of the air conditioner. First stage is typically 65% of the total (2-stage) capacity of the air

conditioner. When operated from power supplied by a generator, starting the air conditioner in 1-stage means

lower start-up amps.

When two, 2-stage air conditioners are controlled by a CommStat 4 lead/lag controller in a redundant

application, one of the air conditioners is the lead unit and the second is the lag unit. On a call for cooling,

the lead unit starts operation in the 1-stage (low capacity). If the temperature in the building continues to

rise above the set point temperature, the 1-stage (low capacity) of the lag unit will be initiated. When the

temperature in the building drops to the set point, the air conditioners will turn off. On a subsequent call for

cooling the process will repeat.

If the set point temperature is not reached with 1-stage capacity operation of both air conditioners after

approximately six minutes (this time period is field adjustable), the lead air conditioner will commence

operation in 2-stage (full capacity). If the temperature in the building continues to rise past the setpoint, the

lag unit will switch to 2-stage cooling approximately six minutes (field adjustable) after it began operation. At

that time, both air conditioners are operating in maximum capacity.

When the temperature in the building is satisfied, both units will turn off.

If the units have economizers (ComPac II air conditioners), the enthalpy sensor determines whether to use

outside air or use mechanical cooling. When the economizer is used, the compressors do not operate.

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Marvair AVPA60 Manuel d'utilisateur Page 3

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