Original message
| Rookietech
 |  "Pilot Operated EPR Valve"
, posted Sat 24 Sep 13:15  
How do these things work. They use high pressure gas to pilot the normally open valve. ok. There are three pressures.... High side Pressure, Evaporator Inlet Pressure, and Spring Pressure..
How in the heck does this thing work to throttle refrigerant and maintain a constant evaporator pressure? If hot gass was constantly allowed to press against the spring then it would always remain closed. So I'm guessing the pilot of the evaporator inlet pressure has something to do with regulating the high pressure gas.. or something.
Has anyone ever worked on any of these things before? IF SO. could u please explain to me how they work.. because I'm completely lost.
THANKS.
ROOK
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Replies:
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| Xenos
| "Re(1):Pilot Operated EPR Valve" , posted Sat 24 Sep 13:30:
And EPR valve is an inlet pressure regulating valve. It controls it’s inlet pressure above set point. Therefore it opens whenever it’s inlet pressure exceeds the Spring set point. On a piloted version it’s the pilot line that is the inlet pressure. Now what is the inlet pressure to an EPR ? it’s the outlet pressure of the evaporator. So if we look at it this way it’s controlling the outlet pressure of the evaporator above set point. This scenario is used when ever there are multiple evaporators and we are controlling the system based on the coldest evaporator. When controlling this way all the evaporators would be cold unless we controlled the pressure in the coils we wanted to be warmer, like a fridge and freezer application.
P.S There is no high pressure side involved unless used to cotrol head pressure.
Xenos.
The best way to escape a problem is to solve it.
[this message was edited by Xenos on Sat 24 Sep 13:35] |
| | Rookietech
| "Re(2):Pilot Operated EPR Valve" , posted Sat 24 Sep 14:10
Here is what my book says.
"When larger Btu capacities are called for as in supermarket installations, a larger EPR valve, or pilot EPR valves must be chosen. Some piloted EPR valves use high-pressure gas to pilot a normally open valve. These valves are held open by a spring and are forced closed by high-side gas pressure. There are actually three pressures that control the modulation of the main valve piston. They include the high-pressure source, the evaporator pressure, and spring pressure. A pilot port that is controlled by a pilot regulator valve indirectly controls the operation of the main regulating valve. These valves include a solenoid stop feature when hot gas defrost is used. A solenoid valve in the EPR valve will be de-energized, shutting off the suction inlet pressure. This allows the internal pilot spring to force the EPR valve closed."
And that's all it says in my book
ROOK
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| | Xenos
| "Re(3):Pilot Operated EPR Valve" , posted Sat 24 Sep 14:47
OOPS..In this case high pressure gas is used as the closing force on the valve. It’s not controlling it, it’s just that the inlet pressure sends a signal to the regulator and the regulator uses this high pressure gas to force the valve closed.
Xenos.
The best way to escape a problem is to solve it.
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| | Xenos
| "Re(4):Pilot Operated EPR Valve" , posted Sat 24 Sep 15:36
Or should I say the high pressure gas is used as the closing force to regulate the valve based on the valves inlet pressure witch is the evaporator out let pressure.
Xenos.
The best way to escape a problem is to solve it.
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| | freezone12
| "Re(5):Pilot Operated EPR Valve" , posted Mon 26 Sep 18:27
this page might help you better understand EPR's.
http://www.climaticcontrol.com/info/jjzgate/Infotec/Info-Tecs11-20/Infotec_11(rev1).htm
cut and paste it
_______________________________________
If it don't fit force it.
If it breaks it needed to be replaced anyways.
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