The Hybrid Valve
September 7, 2009
In recent years the supermarket industry has been undergoing a gradual shift in thinking regarding the preferred method for controlling evaporator discharge temperature.
While mechanical evaporator pressure regulators (EPRs) continue to have a strong following, more attention is being given to electric suction line pressure regulator valves, which are commonly referred to as electric evaporator pressure regulators (EEPRs).
EPR valves are normally closed, and may require several pounds of pressure drop to open the main piston. That is, a pressure drop that translates into lower common suction pressure requirements. By contrast, the EEPR is a regulator that is installed in the suction line and utilizes an electric step motor to drive the piston open or closed.
In an existing supermarket, converting from mechanical EPR to EEPR suction line control typically requires the removal of existing EPR valves and brazing new EEPR valves in their place. In addition, the necessary energy management system (EMS) interface boards and accompanying wiring will be required to complete the installation. The electrical/electronic upgrades can be done prior to the day of conversion.
Replacing valves can be expensive and could require considerable downtime to accomplish. However, Parker Hannifin’s Sporlan Division has a kit that converts its mechanical EPR valve, (S)ORIT, into a hybrid EEPR valve, CDS. This conversion is accomplished by removing the pilot assembly and piston from the (S)ORIT valve and replacing it with a CDS operator that is designed to mate with the (S)ORIT body. The conversion is completed with the addition of the required EMS interface board and wiring, and entering the required setting parameters, which allow the CDS to be controlled. This solution reduces material costs and a good portion of the labor required for a retrofit.
A TESTIn 2007 a supermarket chain conducted a conversion feasibility study. The goal of the test was stated as follows: “The purpose of the (S)ORIT to CDS conversion is to test and validate the energy savings and case temperature improvements associated with the use of the new conversion kit.”
The following potential benefits were outlined:
• The opportunity to incorporate this technology into upcoming store remodels for the purpose of reducing energy expenditures;
• Reduce the possibility of refrigerant leaks as the hybrid valve has one leak path (no pilot operator, pilot lines, flare nuts, etc.);
• Provide consistent evaporator discharge air temperature, increasing product integrity and reducing product shrinkage; and
• Achieve consistent suction pressure, which will allow more efficient compressor cycling.
The following priority list was developed, setting into motion the test:
1. Determine an appropriate store site for the test.
2. Install equipment to track temperature, pressure, and energy consumption.
3. Order the materials necessary for the conversion.
4. Familiarize the refrigeration contractor with the scope of the test.
5. Begin data logging to establish a baseline for comparison.
6. Install necessary EMS interface boards, wiring, etc.
7. Install (S)ORIT to CDS conversion kits.
8. Continue data logging after conversion.
9. Complete test, evaluate data, and document result.
In order to form an unbiased decision, the following parameters were monitored:
• Case control temperatures for the control rack;
• Suction pressure for the test rack;
• The ability to maintain defined set points;
• Energy consumption (kW/kWh);
• Compressor cycling;
• Failures or problems related to conversion kits and/or performance;
• Labor cost for installation;
• Energy cost savings; and
• Costs associated with installation.
THE RESULTSThe results were positive, according to Phillip Pittman, service supervisor for T.O. Refrigeration of Shreveport, La. “I have been very impressed with the improvement in performance at the store with the limited changeout that we have done so far. With only the remote header converted to CDS, we are seeing the low-temp side of rack B floating and cycling compressors. We never saw that before.
“I think we will most likely see some substantial energy consumption improvement in this store. Additionally, store management has noticed improved product quality.”
For more information, visit www.parker.com.
Publication date: 09/07/2009