refnet or T ?

[cruzeiros]

this is the question. i'm really confused...what is the advantage of using refnet joints instead of ordinary T ?
in other thread on the forum i understand that frank has a video material about this... ( if you please send it to me : proiectare@climteh.ro ) and peter...i understand that you do it for mitshu (use t instead of refnet) but with their permission ???
what is so special after all about this refnet joints ?
thanks in advance

[frank]

File sent. Its 23mb though.

A straight tee piece will add more resistance to the circuit.

The refnet joint allows for a choice of different pipe sizes to be brazed in without having to use reducers.

[frank]

Details of the refnet and their use attached

[rbartlett]

Funnily enough Marc and I were discussing this very thing due to Daikin uk inability to source R22 refnets.

I spoke space air who started saying "oh you can't use a 410a refnet on a 22 system. we need the index to select the correct ones"

Hmm...wasn't convinced.


cheers

richard

I'd like a copy too if poss ;-))

[frank]

the basic refnets are similar but you do need the selection charts to make sure the correct ones are used. As pipe sizes are generally smaller with R410A it would be quite easy to use the wrong one by using the selection chart for R22 on an R410A system.

If you want I can try and post the charts for both gases but as they don't give physical sizes it wouldn't be much use.

[frank]

I'm trying to send the movie file but as it's a large file it is taking hell of a long time - I think NTL has a maximum file upload size of 10mb so I may have to wait until Monday and send it from the office

It's failed sending once to Cruz

[chillin out]

Hi Frank,

Upload the file free of charge to ...
http://www.megaupload.com

Then every person that wants it can get it there.


Chillin

[frank]

Chillin

you nearly beat me to it.

Down load here http://rapidshare.de/users/8QBLT

Password is refnet

By the way, as it's japanese there is no sound.

What it is trying to tell you is that it's OK to install the refnet up to 30deg from horizontal - over that the flow is affected

[rbartlett]

the basic refnets are similar but you do need the selection charts to make sure the correct ones are used. As pipe sizes are generally smaller with R410A it would be quite easy to use the wrong one by using the selection chart for R22 on an R410A system.

If you want I can try and post the charts for both gases but as they don't give physical sizes it wouldn't be much use.

most refnets are multi sized so this is a mute point..when all is said and done it's a joint. pure and simple.

from peter1

We never install the Refnet joints in VRF's (Mitsubishi), always simple T' s and that's because 1. The Belgium importer gave us permission for this after many field tests 2. they are real techs and understand that a VRF is not more then some sort of a pack with many evaporators connected to it.

We did at least 15 VRf's like this.

cheers

richard

[rbartlett]

I'm glad you've managed to get recognition.. if only from yourself..but hey it's better than nothing

cheers

richard

[slingblade]

He he, damn I am a genius. Not just a genius but THE genius. Just watched the movie.

Everyone who has ever asked me why it was important to mount refnet's in a horizontal plane was given the answer "because at lower loads the liguid refrigerant flow beggins to represent sewer flow with vapour on the top and liquid on the bottom, the liquid will follow the path of least resistance as assisted by gravity".

Damn I'm good, real good !!

Yet more positive proof that you are indeed barking mad. LOL.

[Peter_1]

He he, damn I am a genius. Not just a genius but THE genius. Just watched the movie.

Everyone who has ever asked me why it was important to mount refnet's in a horizontal plane was given the answer "because at lower loads the liguid refrigerant flow beggins to represent sewer flow with vapour on the top and liquid on the bottom, the liquid will follow the path of least resistance as assisted by gravity".

Damn I'm good, real good !!

Yes, we mount T's with the permission of Mitsubishi and why not.
Let's face it like I said before, a VRF or VRf is a pre-engineered pack, nothing more, nothing less.
Saw never Refnet's in a sueprmarket and it works very well.
As long as you follow the basic rules, sloped liquid and suction lines the right way, T downwards for liquid intersection and upwards for a suction-T.

Do you know that there exists Whit product Refnet's?

The reason for horizontal mounting is almost the same reason as for a simple distributor in an evaporator and in every course Mitsubishi or Daikin is giving, they give you also the reason why (which seems for me very basic)

[Temprite]

You could always use a Y piece.Surely that would cause less restriction to flow.

The refnets just look like glorified Y pieces anyway.

[Peter_1]

I meant VRF or VRV instead of VRf

http://www.mir.be/NL/catalogue.php?cid=12
White products refnets

Anyone re-calculated already the speeds in the lines if Daikin or Mitsubishi gives you the copper you have to install for a VRV or VRF?
Almost speed of sound to be sure that oil always returns, if along upward sloped suction lines

[cruzeiros]

thanks to all for your answers....so it's more or less something to take more money from you (the producer)..and also the refnet headers or distribution kit that i see on the accesory lists.
and the lessons about installing them..i think every refrigeration guy knows how the T must be put on the suction or liquid...and it had nothing to do either it's a refnet or a T
..and another question...i see that on this systems..they say that no oil trap is necesary ?!?! how come ?

[Peter_1]

See 3th alinea post 19

[cruzeiros]

Almost speed of sound to be sure that oil always returns, if along upward sloped suction lines

i thought this was a joke.. so that's the big secret? small size pipes ? but other problems can occur... is'n'it ?

[Peter_1]

Me..joking???
Other things that can happen...sure, 4way valves that break due to passing Mach 1
Well their speed isn't of course not that high but it's very high compared to the normal values used in common refrigeration systems and used to let run the system economically.

Indeed, most of the refrigeration techs know how to make a T - at least, that should belong to their basics - but not all airco techs are refrigeration techs.
And even then....

We once had to replace a counter at Carrefour because there was a problem with not reaching t's temperature.
They had replaced probes, TEV's, orifices , dryers...

At least they came to the result that there was something wrong with the counter and installed a new one. The tech who took that decision was already 15 to 20 years a Refr . tech.
They also never realized that it was the farthest counter on the copper .
Same problem with the new counter of course so BESC5240 and I had to go on site to look what was happening.
Two faults: they had made a T upwards the liquid line and liquid line sloped upwards very heavy.
They installed a new liquid line and problem was solved.

BTW, how do you install the copper in supermarkets?
Normally, we hang up trenches (ladders, not the completely closed types) on the ceilings above the counters and they are played horizontally for the sight, or sloped downwards towards the compressors for the oil return but are then inverse sloped for the liquid line
Best way I think is collecting some counters to some common suction and liquid headers and run then the bigger lines from there on to the machine room.

Do you use fixtures for the copper in the trenches or do you lay them simply in the trenches or hang them under the trenches?

Correct me: I'm laying a cable right now and I layed/laid/... it yesterday

[frank]

Peter

In English it is LAID. There is no such word as LAYED.

See here http://dictionary.reference.com/search?q=layed

Type in LAID for definition

[cruzeiros]

.. is it best to have the arriving flows in at A and B and so the combined leaving at C? Then with diverging flows, is it best for the arriving flow to enter at C and leave at A and B?

a) if is the suction line is ok in this position, the condensate line when collect 2 condensers also ok ,discharge line - definitely not ok and if is the liquid line and C is leading to an evaporator it's a useless split but.. it works.

b)suction - not good even if C is a header
condensate - no way ; discharge line - no.. and for liquid line definitely reverse or on horizontal is the right way.

i don't explain why because.."it's better to keep your mouth shut..than to remove all doubt" .. but if you want you can choose one or some of the answers and debate over them to make the posts shorter.

i also have a question..for the discharge line..oil traps are needed ? also explain your answers

[cruzeiros]

i have found a recent thread about oil trap in discharge line..forget it
sorry..next time i'll be more careful.

[Peter_1]

[QUOTE=Marc O'Brien]Dynamic (and static) pressure drops are proportional to velocity squared which is to say the relationship between pressure drop and velocity is exponential. [QUOTE]

Static pressure proportional to velocity squared??
Dynamic Ok but static...?
We also have a 2 phase flow
http://www.surrey.ac.uk/eng/cpe/UKJapan/07Wangetal.pdf

[cruzeiros]

Mr O'brien..i see that you "speak" about duct but what can you tell us about fluid (***** in this case - not air) dynamic through pipes ? my guess is that the data is changing a little because of the oil perhaps ?!?! or does not have anything to do with the material ? i don't think you use copper for the duct fittings.. or have you done a study about smaller dimensions..(much smaller then 100 mm) like the ones most used in the refrigeration systems ?

[cruzeiros]

Mr O'Brien...sorry for that.

no, i think not..i hope i get some ideas from you...

Thanks..and forgive me if my questions are foolish.

[Peter_1]

You can see that while there is a huge difference between the duct length static pressure loss's on account of the different air_volume/wall_surface ratios the fitting dynamic losses are almost much more similar or much less different.

Interesting Marc. Will have a closer look if I find some spare time (when I'm retired I think)

BTW, I should have gone on to mention that these fitting dynamic pressure losses are only different on account of their different construction. I used my windows ductualator which is written to take into consideration that the smaller 100mm diam fitting will be pressed while the larger will be segmented. If they were both pressed or both segmented then for a given velocity their static losses would be identical on account of their identical dynamically lost static pressures

That's what I thought and reason for my first confused question.
But your first line in this quote'...these fitting dynamic pressure...' does this not has to be '...static losses...'

Cruzeiros question: will the effects even not much bigger with liquid refrigerant (instead of air) due to the higher mass flow and viscosity?



"Does this not has to be" this sentence is not correct, correct it for me please.

[frank]

Now, we all know that when installing a twin split you have to keep the pipe lengths fairly even so that the system operates in balance.

A question though - What do you do if the indoor units are not an eqaul distance from the outdoor unit?

Answers on a postcard please

[Andy]

Now, we all know that when installing a twin split you have to keep the pipe lengths fairly even so that the system operates in balance.

A question though - What do you do if the indoor units are not an eqaul distance from the outdoor unit?

Answers on a postcard please

Did you do this Frank

Surely a tee in the middle would have been possible and one set of pipes only


What did people do before the outdoors came with multiple connections Fit a tee thats what happens when plumbers are let loose on A/C

Kind Regards Andy

[frank]

Did you do this Frank

NO!

If you look carefully, about 2m from the condensing unit is a refnet splitter - right on top of the pipe support. Seems like the installer has been well trained in the art of system design