An evaporator pressure regulating (EPR) valve is installed in a suction line to maintain a set pressure in one or more evaporators.
Mechanical EPRs are widely used, but in circuits where very tight temperature control is desired, as in fresh meat cases, electronically controlled stepper motor EPRs or EEPRs, have become more commonplace. EEPRs require a dedicated electronic controller or connection to a host rack controller or EMS.
Installing an EPR that will give correct, reliable, and long-lasting service isn't difficult as long as the manufacturer's specifications, instructions, and warnings are observed and respected.
Talk to the site manager as you would on any service call. Find out what is wrong or needed from his viewpoint. Then evaluate the site, the system, and the particular circuit or circuits at issue. Use the trade's best practices. Observe normal care in isolating the problem, sizing the valve, cutting, and brazing.
As usual, observe EPA regulations and proper safety measures. Make certain that inert gas is flowing through the valve before brazing.
Evaluate the system. Use the compressor data sheets to verify that the compressor runs within its normal application envelope under all operating conditions.
Size the valve. Check the evaporator data plate or manufacturer's specifications for the fixture. The valve is sized to the line set and evaporator capacity using the EPR manufacturers guidelines and tables.
Orient the valve properly. Valves have a direction-of-flow indication on the label or cast into the body of the valve.
Wet wrap the valve. Take this step just as you would for a TXV. A heat-damaged EPR may not operate, or it may function erratically, leaving the system and its owner no better off than before the call.
Before soldering, remove Schrader valve cores. This is done to allow inert gas to escape.
Secure the valve to prevent vibration. Vibration stresses joints and leads to leaks. Secure the valve on both inlet and outlet sides, as close to the connections as practical.
Adjust correctly. Use the specific valve manufacturer's instructions. If the EPR is being installed for frost protection, adjust the valve with the system under minimum load.
Tim Morgan is application engineering laboratory manager, and Max Robinson is principal technical writer at Danfoss in Baltimore. They can be reached at 410/931-8250. danfoss.com