Help !! NRV requirement in a KTK chiller.

[Mark@Equine]

Hi all, this is my first post so be kind (and helpfull please).

We have some KTK chillers and are being told by the supplier that there needs to be a modification to fit non return valves in the compressor discharge lines before the common header. They are saying this will solve reliability issues and is a production mistake.

Does this make sense and will it help reliability? Your thoughts please.

Ta, Mark.

[stufus]

Make's perfect sense .
The lack of NRV's on the compressor discharge means even if a compressor is not running it will still be subject to full discharge pressure generated by the other compressors.
This can cause a lot of expensive problems on start up!!!
Cheers
Stu

[install monkey]

even more expense if theyre fitted the wrong way!!!

Make's perfect sense .
The lack of NRV's on the compressor discharge means even if a compressor is not running it will still be subject to full discharge pressure generated by the other compressors.
This can cause a lot of expensive problems on start up!!!
Cheers
Stu

[Brian_UK]

Also, if it is recommended by the manufacturers then it would make sense to have the modification carried out.

[Grizzly]

Hi Mark and welcome to the forum.
Yours is not a new dilemma.
Stufus and Brian make good points! (As usual)

The need for a non return valve seems to have become more necessary as the use of smaller multiple compressors has become more prevalent.
Basically earlier versions of scroll type compressors had weak internal non return / discharge valves.
Which would struggle to cope with the amounts of condensed vapour / liquid.
That could collect in the discharge pipe between the condenser and compressor.
Resulting in effectively a "Head of Liquid" sitting on top of the compressors upon start-up.
With the modern highly compact chiller (Not sure of your particular design?)
The need for a non return valve is even more relevant, particularly with the newer Condensers using "free cooling " options.
Add the fact that many chillers have condenser coils that are designed for use in more countries (read hotter climates).
You have larger than necessary condensers acting in some instances like receivers, were is the condensed liquid going to sit?

Long winded I know but hopefully you get the gist of what I mean?
Cheers Grizzly

[Sumit]

Hi,

NRVs are used not in multiple compressor chillers but also in the single compressor chillers.York single compressor chillers have NRVs at their discharge.

As Grizzly mentioned, " free cooling " options.What does it mean, I have never heard about this term.Can anyone please explain it ??

Cheers

Sumit.

[stufus]

READ THIS
http://en.wikipedia.org/wiki/Free_cooling
(http://en.wikipedia.org/wiki/Free_cooling)
Cheers
Stu


Hi,

NRVs are used not in multiple compressor chillers but also in the single compressor chillers.York single compressor chillers have NRVs at their discharge.

As Grizzly mentioned, " free cooling " options.What does it mean, I have never heard about this term.Can anyone please explain it ??

Cheers

Sumit.

[Sumit]

Hi Stufus ,

Its very well explained there.But can you please briefly explain the method " Refrigeration Migration " of free cooling.I have some confusion regarding this, not able to understand it completely.


Cheers

Sumit

[stufus]

Refrigerant will always move (migrate) to the coldest part of the system ,it eliminates the need for compressor operation as the fans and heat diff with the water in the hydraulic circuit and cooling tower provide the heat gain and rejection the maintain changes in state(vapour to liquid and liquid to vapour) effectively providing free cooling.
Cheers
Stu

[chemi-cool]

You have larger than necessary condensers acting in some instances like receivers, were is the condensed liquid going to sit?
Cheers Grizzly

The bottom third of the condenser is designed for the liquid.
If liquid returns to the compressor head from the top of the condenser, you are way over charged.

In general, when there is more then 1 compressor or the condenser above the compressor, a NRV should be installed.
Do not forget a crankcase heater. protecting the compressor from liquid.