Help Needed Internal vs External=valve

[Royal241]

I have a 1/5 ton external equalizing valve that needs to be replaced. Not available for the next 3 weeks. Can I use a internal equalizing valve? what is the difference? it's running of a 2 7hp rack, r22. this a small open showcase. i just dont understand the diff between internal and external, please shed some light. thank you!

[mad fridgie]

The difference or I should say the requirement , depends upon the pressure drop between the expansion valve outlet and the evap outlet (TEV bulb position)
If the evap has distributor, then you have a large pressure drop, you then need an external, no distributor more than likely to be OK with an internal valve.

[aramis]

External equalization should always be used if the pressure drop in the evap is greater than a corresponding 2K change in saturation temperature.

If your evaporator is compact, it would mosl likely need external equalization.

If you install an internal eq when you have high thermal loads, the valve will think you have high superheat because of the high pressure drop and close, starving the evaporator.

Read this: http://www.danfoss.com/NR/rdonlyres/CA5E4257-4F6B-4F41-A268-8CB4FE6874DD/0/PFA00A102.pdf

[Royal241]

Got it, well explained, thank you.