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Originally Posted by Phase Loss

If you are using an EEPR and your suction pressure is swinging 10#...your EMS programming is wrong for that valve.

Yea, but the micro was in learning mode. We locked the evaporator eepr 100% open while checking each superheat. I was explained the way this unit operates is the eepr maintains case temp. Opens when it is above set point and closes when it is satisfied. So when this is running normally it probably maintains a fairly consistant suction pressure. Not even sure if this thing has liquid line solenoid valves. I’ll check a unit tomorrow. The compressors cycle to maintain the suction pressure set point which is probably also set by the micro. When we were done adjusting all the superheats, we put the micro in learning mode again so it can “learn” when all cases are running.
This is my first experience with electronic epr’s. I’ve adjusted many manual ones in my years. On manual eprs you set them to the design suction and then adjust the superheat. My thinking on this type of system is get the suction consistent and then adjust the superheat. Should work.

Thanks,

C

If you are using an EEPR and your suction pressure is swinging 10#...your EMS programming is wrong for that valve.

Darn. I thought someone had tried method of adjusting superheat. Oh well.

c

Maybe I am not explaining myself fully. I am not worried about the eepr. When we are done with checking superheat, we put the eepr in auto mode. The eepr along with the microprocessor will maintain case temp. I am only concerned about checking and adjusting the superheat. These medium temp cases are empty so I have minimium load. The suction pressure is fluctuating 10#s. Not only is the suction pressure constantly changing so is the suction temperature. This makes checking and adjusting superheat difficult at best.
A guess at the worst.
Seems to me there has to be a better way.

c

Sporlan bulletin 90-21-1 describes it will.

"When adjusting both evaporator pressure regulating valves and thermostatic expansion valves, the following procedure is recommended.

With the expansion valve at the Sporlan factory setting, or at a manufacturer's predetermined setpoint, and under the actual minimum load condition, the evaporator pressure regulating valve should be adjusted to the desired setting.

If necessary, the thermostatic expansion valve or valves can be adjusted to the desired superheat setting while under the normal operating load condition"

I would let the epr do its job. Txv needs steady loading to stabilize it will maintain superheat setting w/ a modulating epr. Just make sure tstat call for cooling is constant.

New Install Superheat

I helped starting up a new supermarket installation which I helped install. Was told to check and adjust all superheats to 6 degrees. Was instructed to adjust exactly as Nanotech described in this post with several additional steps.
http://http://hvac-talk.com/vbb/show....php?t=848682\

We locked the eepr to 100% and made sure the case temp was at design temp.

I noticed the suction pressure was always fluctuating, due to other circuits, which I imagine made the txv hunt all over the place.
Seems to me there may be a better method. Do whatever you have to do to make the suction pressure remain constant, as in turn off some compressors, valve off some cases, etc… Once you get that adjust the superheat. The txv shouldn’t be hunting all over the place and the superheat should be relative constant. Open or close the valve as needed.

So will this work? If not, why.

Regards,

Cipher