In Parallel Rack do you separate tubes for each Evaporator?

[georgedvf]

Hello!

When using a Parallel Compressor Rack (*****), do you use (1) cooper tube for each Evaporator from the Manifold or do you use a single bigger tube and connect it to several Evaporatos?

I've seen both but can't get a reason to use one or other.

Thanks!

[cool runings]

Hello!

When using a Parallel Compressor Rack (*****), do you use (1) cooper tube for each Evaporator from the Manifold or do you use a single bigger tube and connect it to several Evaporatos?

I've seen both but can't get a reason to use one or other.

Thanks!

Both..

Where I'm from the one tube is called a ring main (one liquid suplying many evaps).

The other is the stub type.

One suply for each individual section.

The one pipe (ring main) is the most popular nowadays and has replaced the individual stub system.

Cost will be the biggest reason.
To run the single pipe (ring main) it uses less copper tubing
so will be cheaper to install.

All the best

coolrunnings

.

[georgedvf]

Thanks coolrunnings.

And if I use the "ring main" solution, how do I design correctly the pipe diameter considering that each Evaporator has solenoid valve to stop when temperature is achieved or to defrost individually?

I forgot, Do you use this solution in suction line too?

Thanks!

[lawrence1]

georgedvf,
With freezers here i use stubs from each evaporator to the rack where i fit Sporlan Sorit valves for temp control and shutdown for defrosting,the liquid solenoid is only for defrost,temp control by the sorit(pressure)Lawrie

[georgedvf]

Thanks Lawrence1, Do you only use stubs on freezers? Is there a technical reason to do that?

Thanks!

[lawrence1]

georgedvf,
No we use stubs on all racks (low temp and medium temp)

[georgedvf]

Is there a technical reason for you to not use a ring mains?

Thanks!

[Aik]

Hello!

When using a Parallel Compressor Rack (*****), do you use (1) cooper tube for each Evaporator from the Manifold or do you use a single bigger tube and connect it to several Evaporatos?

I've seen both but can't get a reason to use one or other.

Thanks!

I use one liquid tube and one suction tube. But if there are many evaporators (big capacity) than some times I prefer to divide suction tube on two tubes, because diameter of one tube too big and it cost more expensive than two smaller...

[750 Valve]

I'd look to find a happy medium, basically you need to assess the total load - lets say its 150kw MT load

I would look at what the maximum I could put on one 2 and 1/8 ring main - to do this you really need to map out the pipework on a drawing and have some idea of distances and pipe routing, you should be able to squeeze somewhere around 40kw of MT load on to each main without too much pressure drop - I like to work off 1 to 1.5k Maximum. This would mean you will be looking at 4 x 2-1/8" ring main suction lines on that 150kw load, but you really need to assess each bit of pipework for pressure drop.

It is far cheaper to run ring mains however low load scenarios need to be taken into account especially when sizing vertical lines (risers), installation time is cut by about 25 to 30% on ring mains as it is physically less sets of pipes but a lot more care and attention needs to go into sizing and installation practices.

[georgedvf]

Thanks 750 Valve!

And what about liquid lines, is there a special consideration to design diameters when using ring mains? When low load scenario the velocity drops enormously, this is critical in liquid lines? Ashrae books only says that liquid lines should have 1.5m/s or less (how much less???).

Thanks!

[750 Valve]

Low velocity is not usually an issue in liquid lines, and I would be looking at cond drain lines in the vicinity of 0.5m/s max = nice big drain line

[Aik]

Thanks 750 Valve!
Ashrae books only says that liquid lines should have 1.5m/s or less (how much less???).

According to Braidert recomendations, velocity in liquid pipe should be in interval of 0.3-1.2 m/s.
In condencer drain line velosity should be less than 0.5 m/s (like 750 Valve said).