DDR VALVE

[NANOTECH]

Can I replace the DDR valve with a OLDR valve on a Margaux rack? If so, what are the deciding factors wether to use an OLDR or a LDR? It seems to me a few years back I heard that you had to come back in with a DDR on a Margaux rack!!

[icemeister]

In order to get the condensed defrost gas back to the liquid header on a HG defrost rack we need to establish a pressure difference between the hot gas (or Kool Gas) and the liquid header.

There are two basic methods to accomplish this. One is the discharge method where you have a differential regulator (DDR) after the tee for the HG header. The other is the liquid method where you install a differential regulator (OLDR) in the liquid line upstream of of the liquid header.

They both accomplish the same thing, although the liquid method is probably a bit more energy efficient because the discharge method increases the compressor discharge pressure above that of the condenser. The liquid method however will cause a loss of apparent subcooling due to the pressure drop in the liquid feed, so its probably best you have a mechanical subcooler when using the liquid method.

Otherwise, the difference is the DDR energizes to fully open and the OLDR de-energizes to open.

http://sporlanonline.com/90-50.pdf

[crackertech]

In order to get the condensed defrost gas back to the liquid header on a HG defrost rack we need to establish a pressure difference between the hot gas (or Kool Gas) and the liquid header.

There are two basic methods to accomplish this. One is the discharge method where you have a differential regulator (DDR) after the tee for the HG header. The other is the liquid method where you install a differential regulator (OLDR) in the liquid line upstream of of the liquid header.

They both accomplish the same thing, although the liquid method is probably a bit more energy efficient because the discharge method increases the compressor discharge pressure above that of the condenser. The liquid method however will cause a loss of apparent subcooling due to the pressure drop in the liquid feed, so its probably best you have a mechanical subcooler when using the liquid method.

Otherwise, the difference is the DDR energizes to fully open and the OLDR de-energizes to open.

http://sporlanonline.com/90-50.pdf

Or in plain English DDR's are de energized during defrost and OLDRs are energized during defrost.

[icemeister]

Or in plain English DDR's are de energized during defrost and OLDRs are energized during defrost.

You have a knack of cutting through my mumbo-jumbo.

[crackertech]

You have a knack of cutting through my mumbo-jumbo.

[legend]

Only if the return gas fron the liquid line does not return to the discharge line. I have seen a lot of margaux racks return to the discharge line (Food Lion). If you have tees and check valves on all your liquid lines attached to another header use a DDR.

[icemeister]

Only if the return gas fron the liquid line does not return to the discharge line. I have seen a lot of margaux racks return to the discharge line (Food Lion). If you have tees and check valves on all your liquid lines attached to another header use a DDR.

This may well be what NANOTECH is concerned about.

Good info!

I've never run across a rack set up like that, but it would certainly work...as long as you have a DDR.