Rawal device

[MAragorn]

I stumbled upon this device a while ago. I wondered if anyone here is familiar with this DX control device.

"The APR Control provides capacity modulation for all sizes and configurations of air conditioning systems. By matching system capacity to continuously changing load conditions, the APR Control enhanced system is able to maintain better comfort conditions, as well as, provide a number of unique solutions that standard air conditioning systems (below 50 tons) are unable to achieve."

http://www.rawal.com/index.htm

 

[HVACctrl]

I haven't heard anything about it, but it does sound interesting. On the flip side, I would think that I might have heard about it if it were a generally accepted and functional device.

I don't know. But it is interesting. Hopefully someone has used one and can comment.

Ed

http://www.engineerboards.com

 

[Yorkman]

Sounds like a combination evap.pressure regulator and hot gas bypass, to me.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[ClydeMule]

It is a hot gas bypass valve and a desuperheating expansion valve connected toghether via a "desuperheating chamber."

You could do the same thing with installing the parts separately. I think it is marketed to HVAC applications because in a refrigeration system there is a good chance the system will have an accumulator. ON a cooling only DX system there will probably not be an accumulator, therefore the the desuperheating chamber comes into play.

Never used one, I have just bought the parts separately from Sporlan.

 

[MAragorn]

So

Being as dumb as I am about DX, what do these devices either put together as in this one unit, or seperately do for a system?

 

[ClydeMule]

A hot gas bypass valve (regulator) is a pressure actuated valve that is connected to the discharge of the compressor (valve inlet) and to the suction side of the system. It can be hooked directly to the suction or in between the expansion valve and DX distributor. There are special distributors made with a side inlet to accept a hot gas connection. For a chiller you can just put a tee in between the TEV outlet and evap inlet.

WIth this method, you get a good mixing of hot and cool gas and you don't drop the refrigerant velocity through the evap at low load.

If you are in a situation where you can't put the hot gas directly into the evaporator, you pipe the outlet directly to the suction side of the compressor. The downside to this is that you run the possibility of directly dump hot (<100F) refrigerant directly into the compressor. At the same time, if you are at 100% bypass, there is no refrigerant flowing through the evap and oil will just sit there.

In this case you should use a desuperheating expansion valve. The DEV has a sensing bulb that is strapped to the suction line of the compressor. The vavlve acts based on temperature. As the suction temperature rises, this valve will open to admit liquid to the suction line to the keep the return gas under control.

If there is no accumulator, this must be done far enough upstream are piped in such away that the liquid fully mixes and vaporizes before entering the compressor. If your system has an accumulator the connection is made before it.

The second method is often what you are stuck with in a retrofit application. I think that is the is the "schtick" to the Rawal, it can be added later on and it acts as one device.