Condensor Positioned below Parralell System

[allanbaker]

I have a debate that i wonder if any one can solve, if there is a real solution?

System: 2 Bitzer 4j13.2 194800 btu/hr with a 321000btu/hr THR Condensor 12deg TD running at -12C/45C.

From the plant the pipes go up into the roof (2 m) and run in the roof for 20Meters then down past the level of the compressors for a further 2meters ( Condensor 2m below Plant).

The plant has been running fine since 2000 and now there are queries about the position of the condensor.
I have installed certain components and i would like to find out what are the correct components and are risers and pipe size changes or additional components nessesary?

I have a check valve on the outlet of the oil sep and on the outlet of the condensor.

Who knows the answer??

[The MG Pony]

Any pictures? Or could you outline the system in question in far more detail?

Thanks

Pony

[Billy Ray]

Hi Allanbaker,

you should not have any real problems with the installation as you describe.

You should ideally (I assume you have) have the liquid receiver below the condenser to allow natural drainage. Its not advisable to have the receiver adjacent to your compressors in this instance.

I'm not sure what the NRV on the condenser outlet is achieving!! shouldn't be required, although some one may correct me. If anything, this may be detrimental as it produces a pressure drop between condenser & receiver, which you dont really want.

Hope this is off help.

Billy Ray

[allanbaker]

I'm not sure what the NRV on the condenser outlet is achieving!! shouldn't be required, although some one may correct me. If anything, this may be detrimental as it produces a pressure drop between condenser & receiver, which you dont really want.
Billy Ray

Hi Billy the reason that we installed the NRV on the outlet is for the possibility of the liquid migration to the condensor on the off cycle or power failure which we have a lot of in south africa.

Pony what kind of details would you like?

I am not quering whether the system is under capacity or not, because it works, my query is what is the common practice for installing an aircooled condensor below the parralel rack. which for Billy's info has the liquid reciever at the compressor rack (above the condensor). I need to find out, does one need to reduce pipe sizes on the return pipes (rizers ) which is one of the complaint that we have received or any additional problems that might arise! Can there be substaintial presure drops that i have overlooked.
Thersupermarket has been sold and the new owner has another company come in to asses the plant and they want to move the condensor possible replace it, which i believe is not nessesary.

[nike123]

Maybe you find something in this book:
http://www.mediafire.com/?9w3lxecx1b0

Also this:
http://www.mediafire.com/?5nam2dyzaxz

[Springbok]

Hey Allan Baker...I'm from South Africa and used to work for a company where we did work for Shoprite/Checkers.We had a similiar incident on a few systems where the compressor was upstairs in the plantroom, and they had moved the condensor only(reciever at compressor) downstairs (outside) because of heat in the plantroom.Although it was more than 2 meters below the plantroom,it still worked.Although when we did move the condensors firstly,we did not change the rizers' pipe sizes.

Myself personally was concerned about the drainage abililty since the reciever was above the condensor,but we did install pressure reading valves on the high side to monitor pressure drops and subcooling during seasons.I left the company a while later.Hope this helps,buddy,otherwise,the links given are helpfull....cheers

[allanbaker]

Thanks Nike123 i love to read ......not thats why im a techy

[Gary]

Lifting a column of liquid 2 meters requires a pressure difference of roughly 3 psi between the condenser and the receiver.

The receiver being in a warm equipment room with the condenser outdoors, I would be more concerned about the difference between indoor and outdoor temperatures.

The pressure in the receiver will tend to correspond to the temperature of its surroundings, as will the pressure in the condenser.

If the temperature surrounding the receiver is higher than the outdoor temperature, it is possible that the pressure in the receiver will be higher than the pressure in the condenser, which will stop the flow of liquid.

Head pressure (fan) controls must maintain a condenser pressure that is at least 3 psi higher than the highest expected receiver pressure.

[allanbaker]

Thanks Gary thats the stuff that we are looking for. We have plant room cooling controlling the temp to 20Deg C, so that is not a concern. Also i think that coming from outside ambient 32Deg (South Africa) we should be ok. Althought it can get cold in winter (dont laugh) 0 Deg will be the coldestlike for one or two days. The Condesing pressure is controlled by guardian as i said before. I think that we are fine with the presure drop of 3 psi. Any other problem you can see?

Wheres Marc he normally has words of wisdom on this sort and he is from these parts.
I personnaly think there is no real problems with the design. Iam just looking for potential shortcomings

[allanbaker]

Hey Nike 123 the stuff you gave me to read .....which i did very quickly has nothing about piping condensors below compressors and recievers for that matter....As one can see i dont ask too many questions...... hoping they are not dumb ones. I have tried to research this myself. All the literature i have doesn't give me the correct answer as i need to explain my installation to my opposition, who happens to be a friend of mine. He also doesn't have the nessessary literature but i was hoping i would be able to hammer him with documentation, but i cannot find supporting document for or against the application.

[Gary]

Thanks Gary thats the stuff that we are looking for. We have plant room cooling controlling the temp to 20Deg C, so that is not a concern. Also i think that coming from outside ambient 32Deg (South Africa) we should be ok. Althought it can get cold in winter (dont laugh) 0 Deg will be the coldestlike for one or two days. The Condesing pressure is controlled by guardian as i said before. I think that we are fine with the presure drop of 3 psi. Any other problem you can see?

Wheres Marc he normally has words of wisdom on this sort and he is from these parts.
I personnaly think there is no real problems with the design. Iam just looking for potential shortcomings

Sounds a lot like Florida weather.

I'm thinking Marc has been banished to the netherworld. Stranger yet, all of his posts have disappeared, making for a great many one sided threads.

Marc puts me in mind of a popular TV show we have here called "House", about a brilliant doctor (Gregory House) with a very abrasive bedside manner.

[nike123]

Hey Nike 123 the stuff you gave me to read .....which i did very quickly has nothing about piping condensors below compressors and recievers for that matter....As one can see i dont ask too many questions...... hoping they are not dumb ones. I have tried to research this myself. All the literature i have doesn't give me the correct answer as i need to explain my installation to my opposition, who happens to be a friend of mine. He also doesn't have the nessessary literature but i was hoping i would be able to hammer him with documentation, but i cannot find supporting document for or against the application.

That is why I said "maybe".
Thats are guidelines for piping layout, and I post them as possible helping tool to resolve your (and other peoples) piping layout problems.

[Billy Ray]

Hi AllanBaker,

you may of misinterpreted by post. I was sugessting the reciever should be below the condenser outside (directly below & short drainage pipe to the receiver).

My point was if the receiver was adjacent to the compressors, the liquid would have to flow back uphill through the same route as the discharge pipe (as Gary's comment for raising a head of liquid).

Regarding pipe sizing or special pipe arangements, i dont see any need for this. Select pipe work as per normal.

Billy Ray

[750 Valve]

Personally I would never pipe a system as you have described, there are too many variables to say it DEFINITELY won't be an issue, I like good condenser drain lines with absolutely NO traps in the return line, makes for a very consistent receiver liquid level and less chance of logging liquid in low ambients. On the occasion that we have to install a condenser lower than the reciever we move the receiver to be underneath the condenser (good drainage and sits in the same ambient conditions as the condenser). I have seen instances from other contractors where lines have been installed between the vapour part of the reciever (top) and the discharge header of the condenser (to ensure equal pressures and no ability to vapour lock the receiver), a couple have used NRVs in this line and a few have not (I imagine a VERY small PD across the NRV would be required), operation of both I have found to be pretty similar.

[SteinarN]

I have installed several comercial systems with the condenser several metres below the compressor and receiver and the condenser outlet line routed forming several so called "traps". No problem at all. The net effect is that the condenser outlet pressure will be higher than the receiver pressure, to overcome the static pressure of the liquid raising from the condenser to the receiver as Gary notes above. The liqiud subcooling at condenser outlet will also be higher by an amount coresponding to the static pressure of the liquid column.

I have not experienced any problems with lowering the condensing temperature below the plant room temperature in winter. The condenser outlet subcooling will maybe increase slightly to allow for some heat flow into the receiver in the warm plant room. The system may require slightly more refrigerant quantity in that case.