Emerson AE4-1395 User Manual

8

© 2012 Emerson Climate Technologies, Inc.

Printed in the U.S.A.

Application Engineering

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hot-gas-bypass for capacity control are also ideal units 

for a digital scroll retrofit.
Retrofit Applications To Avoid

equipment modifications.
The success of the retrofit will depend on the amount

of  planning  and  evaluation  done  before  the  retrofit.

Applications such as clean rooms for manufacturing 

sensitive components, laboratories, hospital operating 

and recovery rooms, and equipment rooms that require 

constant cooling are all applications that would benefit

from a modulating digital scroll. Many of these are 

critical cooling applications and require equipment that 

is  designed  specifically  for  these  applications.  Don’t

attempt  to  retrofit  a  non-modulating  HVAC  unit,  in  a

critical application, to one with a digital scroll in an attempt 

to make the unit perform well beyond its intended use.

Applications that have complex refrigeration circuits 

(modulating reheat, heat recovery for water heating, 

etc.) should not be considered for a digital scroll retrofit.

 

predictions.
Successful digital scroll retrofit projects, and resultant

energy savings, have been documented by several 

industry energy groups. Predicting the energy usage 

and calculating a return on investment before the 

project is undertaken is not trivial and is best done by 

experienced companies that use advanced software 

programs  to  predict  energy  use.  Before  large  retrofit

projects are considered, as much front-end analysis 

as possible should be done to better predict how much 

energy might be saved. Tabular performance data and 

the ten coefficients for the AHRI polynomial equation for

performance at 50% and 100% load are available for 

modeling purposes in the Online Product Information 

(OPI) section at www.EmersonClimate.com.

 

Before  beginning  the  retrofit,  the  system  should  be

operable and system operating conditions should be 

logged for future reference. The compressor suction 

& discharge pressures, suction superheat, subcooling, 

volts, amps, evaporator air flow and leaving temperature,

and system charge should all be measured and recorded 

prior to any system modifications.

The replacement digital scroll compressor should be 

compared to the non-modulating compressor in at least 

these three areas:

1.  Performance – the full load capacity of the digital 

scroll should be approximately equal to the capacity 

of the compressor being replaced. In some cases 

in might make sense to “right size” the compressor 

capacity for the load if the compressor is grossly 

oversized.

2.  Electrical – the digital scroll compressor RLA and 

LRA should be compared to the compressor being 

replaced. Contactor, wire, breaker/fuse, and run 

capacitor sizes should be evaluated.

3.  Mechanical – in most cases the compressor 

mounting will be identical for the non-modulating 

and the digital scroll. There could be minor 

difference in the suction and discharge tubing 

locations, as well as the height of the compressor. 

The following steps should be followed to remove the 

non-modulating compressor from the system. 

1.  Using an EPA approved refrigerant recovery 

machine, recover the system refrigerant charge 

from the low and high sides of the system.

2.  Disconnect and lockout the power supply. 

Confirm that all voltage sources have been 

disconnected by using a voltmeter. Disconnect the 

conduits and wiring to the compressor and move 

them out of the way as much as possible.

3.  By using manifold gauges, verify that the system 

refrigerant charge is completely recovered from 

the system. Suction and discharge pressures must 

be 0 psig.

4.  Using a tubing cutter, cut the suction and discharge 

lines close to the compressor.

5.  Remove the compressor mounting bolts.
6.  Plug the compressor suction and discharge 

connections to prevent the spillage of oil from the 

compressor when removing it from the system.