Setting EPR and TXV

[kengineering]

Hello,
As customers are requesting higher evap temps I am trying to determine the BTUH of our MT display cases at those requested temps. i.e 20°f, 22°f, 24°f etc. I have a Coriolus flow meter and all the software working well and have baseline information at a 20°f evap. To simulate different rack temps I've installed a simple Sporlan ORIT, EPR valve. Raising the EPR presure from 20 to 22°, psi converted, the Superheat changes and we have a cat and mouse game to get the system balanced again and SH always winds up high even when TXV is wide open.
My question; What am I missing.

[seanf]

What type of expansion valve are you using?

How does the rest of the system look? Subcooling, liquid line sight glass, filters and strainers clean?

[RANGER1]

Are you calculating superheat on the evaporator pressure, upstream of EPR valve?

[kengineering]

What type of expansion valve are you using?

How does the rest of the system look? Subcooling, liquid line sight glass, filters and strainers clean?

Using a sporlan SBVE-AA TXV. which has worked for us for many years @20°f evap temp. The condensing unit is one we pair with this case set-up all the time with TXV factory preset SH .
Full charge, all components are new so filters and strainers are clean.

[kengineering]

SH calculated at the access port at the TXV sensing bulb.

[seanf]

Using a sporlan SBVE-AA TXV. which has worked for us for many years @20°f evap temp. The condensing unit is one we pair with this case set-up all the time with TXV factory preset SH .
Full charge, all components are new so filters and strainers are clean.

Is the sizing of the EPR ok?
Do you have a sight glass you can use to check you have a constant solid liquid supply to the TXV?

[RANGER1]

https://www.parker.com/content/dam/P...-090/90-20.pdf

Do you have any flow through EPR when TX valve fully open & what is pressure upstream & downstream at that point.
Instruction suggest 30 minutes settling period.
Air on/off temperatures also gives good information on how it is working or not.
You could treak pressure setting down a little to see if flow etc comes back as a test.

[al]

Fitting an EPR will mess with TXV as you are putting a false restriction on the suction line, the EPR will open / close to maintain its setting irrespective of the TXV. I only come across EPR on rack type systems to allow higher suction pressures on display cases.

[kengineering]

Thanks for all the idea sharing. Seems we just needed to make very small adjustments and be patient. One of the difficulties I face is working from home and trusting that my guidence to the Lab Guys is understood and executed.

Thanks again, Ken