Staging active cooling start-up

Patent metadata

Field	Value
Publication number	US-9534822-B2
Application number	US-201414322534-A
Country	US
Kind code	B2
Filing date	Jul 2, 2014
Priority date	Jul 2, 2013
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

A novel process for activating available compressors in multiple compressor air conditioning systems, using an Optimum Stage-Up Process. This process is programmed into a controller as an algorithm, to provide a process for fast compressor start. This process shortens the time to initiate operation of compressors in a multi-compressor air conditioning system required to meet the demand call under any load condition, and hence shortens the time required for the actual sensed interior region air temperature to reach the interior region temperature set point. The Optimum Stage-up Algorithm estimates the number of compressor stages or steps that must be initiated, based on sensed or measured values, to meet the demand at any load condition. These measured values include the sensed temperature of the interior region being cooled, which is compared to the temperature set point of this interior region as well as measured mixed air temperature and supply air temperature.

First claim

The invention claimed is:

1. A process for sequentially starting compressors using a controller in a multi-compressor system to rapidly equalize a sensed interior temperature of a region and an interior temperature set point of the region, comprising the steps of:
providing a multiple compressor cooling system;
providing a controller;
measuring the interior region temperature and providing a signal indicative of the measured interior region temperature to the controller;
comparing the measured interior region temperature to the interior region set point temperature, the controller determining whether a call for cooling is required based on correspondence between the measured temperature and the set point temperature;
entering an active cooling mode when the difference in the measured temperature and the set point temperature exceeds a predetermined amount by first calculating a step number based on a mixed air temperature, a measured supply air temperature, a supply fan speed setting, and a constant determined by a refrigerant capacity of the multi-compressor system; then
determining a compressor staging cycle;
enabling a predetermined fast start sequence by the controller initiating the staging cycle by starting a first preselected compressor in the fast start sequence of the multi-compressor system by the controller;
after a predetermined amount of time, continuing staging by starting a second compressor in the multi-compressor system by the controller and repeating this step until all of the compressors in the fast start sequence are brought on line, completing the staging cycle.

2. The process of claim 1 wherein the step of measuring the interior region temperature includes providing at least one sensor for measuring at least one of the interior region temperature and a return air temperature.

3. The process of claim 2 wherein the step of entering an active cooling mode includes utilizing a fixed supply fan speed setting, wherein the fixed supply fan speed setting is 100% or 1.

4. The process of claim 2 wherein the step of entering an active cooling mode includes utilizing a variable supply fan speed setting, wherein the variable supply fan speed setting is a value greater than 0 to 100% or a fractional value greater than 0 to 1.

5. The process of claim 2 further including an initial step of activating a user selectable option for a fast compressor start operation before entering the active cooling mode.

6. The process of claim 2 further including a step of determining the type of refrigerant installed in the system and providing a signal to the controller indicative of a refrigerant type installed in the system.

7. The process of claim 5 further including the additional steps of:
first providing a controller with a plurality of fast compressor start programs,
then activating the user selectable option for a fast compressor start operation,
then, determining the type of refrigerant installed in the system and providing a signal to the controller indicative of the refrigerant type installed in the system, the controller selecting one of the plurality of fast compressor start programs based on the installed refrigerant type before entering the active cooling mode.

8. The process of claim 2 further including the additional steps of:
providing an economizer;
providing a sensor to monitor an outdoor environmental condition and communicating a signal to the controller indicative of outdoor environmental conditions, the controller determining whether outdoor environmental conditions are suitable for economizer operation contributing to satisfying a cooling demand; and
the controller activating the economizer when outdoor environmental conditions are suitable for economizer operation contributing to satisfying the cooling demand.

9. The process of claim 2 wherein mixed air temperature is a calculated temperature based on at least one of interior region temperature and return air temperature combined with the supply air temperature.

10. The process of claim 8 wherein mixed air temperature is a calculated temperature based on at least one of interior region temperature and return air temperature combined with a sensed outdoor temperature when the controller determines outdoor environmental conditions are suitable for economizer operation.

11. The process of claim 2 wherein the predetermined amount of time before continuing staging by starting a second compressor is a time sufficient to avoid electrical overload resulting from compressor start up.

12. The process of claim 11 wherein the time sufficient to avoid electrical overload resulting from compressor start up is 5-20 seconds.

13. The process of claim 1 wherein after each compressor is brought on line, the controller monitors its on-cycle for a period of time longer than one minute before compressor shutdown.

14. The process of claim 1 wherein after each compressor is brought on line, the controller monitors its on-cycle for a period of time shorter than 10 minutes after which the compressor is shut down.

15. The process of claim 2 wherein the step of providing a multiple compressor cooling system having one or more modulating compressors.

16. The process of claim 15 wherein the step number for entering the active cooling mode is calculated by the controller, the step number calculated by the controller first estimating a START STAGE, wherein
START STAGE={[(MAT−SATSP)*VFDSP]/STEP DELTA}− N

where N=−1, 0, 1, 2, 3 . . .
where
START STAGE is the initial compressor staging at start,
MAT is the calculated Mixed Air Temperature (° F.);
SATSP is the programmed Supply Air Temperature Set Point (° F.);
VFDSP is the VFD Speed programmed into the controller,
STEP DELTA=Temperature drop associated with the system (° F.) and programmed into the controller, based on the number of compressors in the system and the system capacity of the compressors;
determining the START STAGE; and
obtaining the compressor staging cycle corresponding to the step number correlated to the START STAGE programmed into the controller; and
enabling the fast start sequence based on the step number.

17. The process of claim 16 wherein the step of determining the START STAGE further includes
rounding the START STAGE to the nearest whole number to obtain the step number, the step number correlated to the START STAGE programmed into the controller before obtaining the compressor staging cycle corresponding to the step number programmed into the controller.

18. The process of claim 16 wherein the step of obtaining the compressor staging cycle further includes
obtaining the compressor staging cycle corresponding to the step numbers correlated to the two nearest START STAGE whole numbers programmed into the controller;
interpolating the value of the step number between the two whole numbers for START STAGE based on the value of the START STAGE; to obtain a step number;
obtaining the compressor staging cycle corresponding to the nearest step number correlated to the START STAGE programmed into the controller and interpolating operation of one of the modulating compressors to match the value of the interpolated step number; and
enabling the fast start sequence based on the step number and the interpolated value for operation of one of the modulating compressors.

19. The process of claim 1 wherein the step number for entering the active cooling mode is calculated by the controller, the step number calculating by the controller first determining the required capacity, wherein

Assignees

• Johnson Controls Tech Co

Inventors

• Karkhanis Rajiv
• Caskey Curtis Wayne

Classifications

• F25B2400/06

  Several compression cycles arranged in parallel · CPC title

• F25B2500/26

  characterised by the startup of the refrigeration cycle · CPC title

• F25B49/022 Primary

  Compressor control arrangements · CPC title

• F25B2700/2104

  of an indoor room or compartment · CPC title

• F25B2400/13

  Economisers · CPC title