my first post: pipe run question

[omodos]

Sorry to ask such a low level question, but I want to know what is correct before the engineer comes to install 9000btu split system, so at least I can have a go at him.

Outside unit will be more or less on the same level as the inside unit with just the thickness of the wall separating the two, so maximum 1 metre. Does the copper piping provided in a 3m roll need cutting down to length? And if so do any sort of traps with the shortened piping need to be created? Or can it just be a straight run to the compressor….any reply will be greatly appreciated

[exotiic]

I believe most units require a minimum of 3m pipe run so if the unit is to be installed at the same heigh of the indoor unit the pipe will have to be coiled behind the unit without restricting airflow. If the pipe run is cut to 1m, you may encounter heating issues within the unit.

[omodos]

ta for reply, here is where it gets confusing, i did some research and yes systems come pre-charged and they mention minimum pipe length, so when the engineer comes and does cut the extra piping, he uses the vac to compensate for the reduction in piping length by reducing the coolant in the system accordingly,not sure what best practice is......

[monkey spanners]

You can either reduce the charge( x grams per meter) or increase the pipe run to the minimum requirements of the system.

[Peter_1]

@Exotiic If the pipe run is cut to 1m, you may encounter heating issues within the unit.

Can you explain this once for me, I should say just the opposite.

@Omodos he uses the vac to compensate for the reduction in piping length
We vac to remove moisture and non-condensables, never heard you could use this to correct pipe length

@monkey spanners, you gave in my opinion the only 2 good answers

[Grizzly]

Can you please explain How these units are installed?
So that I can have a go at the installation Engineer!

Not from me anyway.
Now if you have already had a system that you think could have issues.
Then fair enough, but you don't even have the grace to list your occupation.
Sorry but there is terminology you have used that as an engineer I find offencive!
Grizzly

[omodos]

To anyone who is offended, there are just as many cowboys in Cyprus as there are in all line so of work, I wanted to know what the facts are regarding minimum pipe run length etc so I can challenge anything stupid the installation engineer may do IF he does ...no offense meant to all of those out there who do know what they are doing,

[omodos]

Peter ta for reply,what is the truth?if you decrease pipe length to less than minimum will it imapct the compressor in a negative way?or is it best to just leave it coiled up and not reduce charge in system, or just reduce charge after cutting piping to under the min 3m recommended?thnx

[omodos]

Can you please explain How these units are installed?
So that I can have a go at the installation Engineer!

Not from me anyway.
Now if you have already had a system that you think could have issues.
Then fair enough, but you don't even have the grace to list your occupation.
Sorry but there is terminology you have used that as an engineer I find offencive!
Grizzly

Ok mr Grizzly, I am not here to question doubt your abilities or any other engineer abilities and i never asked for your opinion specifically, thanks and happy plumbing...

[omodos]

so can the coiled pipe be left coiled rather than be cut if compressor is at same height as indoor unit?cheers

[monkey spanners]

Yes it can be left coiled, or you can put the condenser further away or adjust the charge in the system to suit the now shorter circuit. If you run it with a shorter than designed piperun there is a risk of liquid returning to the compressor with oil dilution problems, or if the system runs with a low suction superheat due to this you can get a corresponding low discharge superheat and a lower air off temperature than would otherwise be the case in heating mode.
How bad will this be? How long is a piece of string?

In your original post you asked for information "so at least I can have a go at him", i can understand why some if not all members here wouldn't want to assist in you giving someone a hard time. Maybe it would be worth wording your questions differently if you don't want to give people the wrong impression.

Jon :)

[omodos]

ta Jon, I wanted to know coil or not to coil so as to be able to discuss with an engineer armed with the info i know now from everyone who has posted here, example of why is something I know was done that shouldn't have been done was installation of a 12,000btu splt unit for a room under 27 cubic meters...and the room is not in full day say either...thanks for your reply

[exotiic]

[quote=Peter_1;201750]@Exotiic If the pipe run is cut to 1m, you may encounter heating issues within the unit.

Can you explain this once for me, I should say just the opposite.

Monkey spanners beat me to it in post: "If you run it with a shorter than designed piperun there is a risk of liquid returning to the compressor with oil dilution problems, or if the system runs with a low suction superheat due to this you can get a corresponding low discharge superheat and a lower air off temperature than would otherwise be the case in heating mode.
How bad will this be? How long is a piece of string?"

What do you mean where you should say the opposite?

In Australia, if the unit does not meet the minimum pipe lengths some of the brands have refused warranty.

[Peter_1]

Peter ta for reply,what is the truth?if you decrease pipe length to less than minimum will it imapct the compressor in a negative way?or is it best to just leave it coiled up and not reduce charge in system, or just reduce charge after cutting piping to under the min 3m recommended?thnx

It doesn't look very nice if you see a coil behind or besides the unit. The advice of MonkeySpanners is the same way we do it, we reduce a little bit the refrigerant charge with the amount which is in 2 m lines. (23 gr/m for 1/4 and 53 gr/m for 3/8 R410a liquid line) This will not impact it in a negative way.

We have literally more than 50 units where we have 0.5 m. pipe length.(outdoor unit just on the back of the indoor)

[nike123]

It is enough to follow instalation instruction which comes with every unit. Some single split units have minimum pipe lengths requirement and most of them don't have.
Example from Fujitsu:
http://i51.tinypic.com/2v2h20h.jpg

[back2space]

If the pipe run is cut to 1m, you may encounter heating issues within the unit.

Hi there

What kind of heating issues could you encounter?

Just wondering as one of my units on my multi split is only 2metres pipe run.

Manufacturer specify 5mtr minimum on my outdoor unit.

[nike123]

Manufacturer specify 5mtr minimum on my outdoor unit.

For each circuit or combined?

[omodos]

thanks for all the responses,there was a guide on the side of the compressor telling you what to do in case you reduced or increased the pipe length, there also seems to be a minimum pipe length but if the piping is less than this min, reducing the charge as stated by the experts on this forum should be ok if you think about it//

[back2space]

For each circuit or combined?

For each circuit.

[nike123]

Refrigerant quantity does not need to be adjusted if combined length of pipes is not shorter than min. For example: If that is 4 indoor unit system and min. for each circuit is 5 m, than if combined length is not shorter of 20 m,than there is no need to adjust charge.
Some noise could be issue if individual pipes are shorter than stated in manual. In that case muffler could be installed in that circuit.

[omodos]

ta for all replies on this subject