Daikin Refnet Position

[puddleboy3]

Has anyone any experiance with daikin refnets that have been installed incorrectlly. How does the system perform etc? and what problems if any can i expect. Ive seen the Daikin video clip with the water going through the refnet but im not convinced! How are mitsi able to use T connections instead of refnets?

[ikke]

Has anyone any experiance with daikin refnets that have been installed incorrectlly. How does the system perform etc? and what problems if any can i expect. Ive seen the Daikin video clip with the water going through the refnet but im not convinced! How are mitsi able to use T connections instead of refnets?
Because Mitsi's system is much better. The design engineer of Mitsubishi Electric have done a good job in their fantastic development.

[puddleboy3]

Wouldnt go that far, i find the PURY unit to be very un-reliable. Oh there goes another inverter compressor and to top it all the unit has no emergency backup. You then speak to mitsi technical and they always recommend to change all inverter components. Money making scheme!!!!!!. As for the Daikin refnet problem i have checked a site with the refnets installed incorrect and all i can say is the system operates ok in a heating mode but as soon as the system goes to cooling, you start getting fan coils that cant maintain correct superheat!

[Jase]

If the refnets are installed incorrectly, then the system(s) have not been correctly commissioned from day one. Surely this sort of thing should be picked up from the start and personally speaking, I would not commission a site if I suspect any wrong doing!!

Jase

[puddleboy3]

Totally agree with you on that one, but i think gone are the days of having a seperate install engineer and a commissioning engineer. These days you install it, switch it on and who cares if it works or not as long as you get paid! Anybody else any comments on this!

[frank]

These days you install it, switch it on and who cares if it works or not as long as you get paid!

Those of us that work for ourselves have to care if it works otherwise we don't get paid ;)
It also stops the customer looking for someone else to do the next job as well. :)

I agree though that there is a lot of the "don't care" attitude amoung the younger generation of "engineers"

[puddleboy3]

I totally agree with you frank, but i am a young engineer and i have been to alot of problem sites, that so called experianced engineers have installed/commissioned/repaired to a very low standard and i must add that most of the jobs have been south of Scotland. I myself think the problem lies with training and some how preventing plumbers from installing A/C. Nice picture by the way :D

[RDY357]

Guys,
Mitsu and Daikin approach the system differently.
Daikin has gone to market by using Rep firms that know what they are doing. Mitsu typically goes through a supply house.
Daikin supplies training every month to contractors, engineers and their rep firms....free of charge
Daikin supplies a service advisor for start ups on the first couple of systems.
They also supply onsite help for people when requested.
Refnets reduce velocity loss and that is all they do.
By using a t fitting, you slow down the R410A and it cannot do its job.
Also, on the compressor issue, if installed correctly the system just works and you should not have any problems. If installed incorrectly, you will have constant callbacks.



Has anyone any experiance with daikin refnets that have been installed incorrectlly. How does the system perform etc? and what problems if any can i expect. Ive seen the Daikin video clip with the water going through the refnet but im not convinced! How are mitsi able to use T connections instead of refnets?

[cool#9]

Hi everyone
With a wrong position you may have noise, problem of oil back and also turbulences at the EXV so that create superheat problem in cooling mode...
This occurs especialy when you divide in two main branchs from the outdoor unit to supply a lot of power per branch...
Anyway the main problem is if you need inspection by Daikin's engineer....really need to have a good installation !
Regards
cool#9

[Thermatech]

Mitsubishi Electric have always included substantial sub coolers in City Multi heat pump & heat recovery systems.Subcooler improves performance but for us engineers it has a much more important impact on system performance. Subcooler eliminates bubbles.
Mitsi can have any tee configeration because there are no bubbles because bubbles have been eliminated from the liquid by the subcooler.
Daikin cannot remove all bubbles because indoor units units in heating mode dump warm liquid into common liquid line without subcooling so there will be bubbles which in turn will affect refrigerant flow at other refnet joints futher down the liquid line( see diakin video with water & bubbles flowing through refnet)
Even on Mitsi heat recovery R2 system warm liquid returning from any unit in heat mode first goes back to the B/C box & through the sub cooler circuit( bubbles eliminated) before going to any unit in cooling mode. Because there are no bubbles in liquid LEV valve performance is ideal.
Fair play to Daikin because they have given more attention to Subcooling in recient years, but they still have a long way to catch up on Mitsubishi on subcooler design & control.

[cool#9]

Hi Thermatech
What a relevant remark...!
Sub cooling is one of the best kept secret for these manufacturers but let's say i think daikin do the same in their bs boxes since the M heat recovery series, as i know...but they don't like T branch, maybe for commercial reasons.
On 2 pipes series M and P the sub cooling is done with an auxiliary heat exchanger through an exv.
Anyway i'm very interesting of mitsi system maybe you could link me to a web site to download some service manual.
Thankx in advance
cool#9

[Pol]

The Melco subcooling story sounds very nice, but you also need to think thermodynamics. a T (90° curve) causes a bigger pressure drop than a (45° curves) refnet joint. A T is cheaper, but decreases performance.

[RAKUMARADU]

Nothing like that for refnet position defnitely the installation engineer will be doing checklist and confirming that there is no problem

[nicolacozma]

However Daikin can reach 1000 meter total pipe length instead of 300 meter for Melco. Maybe because they are using optimized refnet joints or because they use subcooling technologies and some improved types of compressors.

[techguy]

I worked on Mitsu equipment for 16 years and used to carry out Mitsu's warranty work under contract in Ireland for them before they had a Tech Manager in Ireland.

To say " MItsu's equipment is the best so there" is a stupid statement. Mitsu's engineers did not sit down and design a system that can operate with T peices. The decision not to use refnets was taken as a purely cost saving excercise.

I was around in the early 90's when this was decided. So anyone telling you any differant is Bull****ting u.


I have serviced many systems with T peices installed the indoor units are noisy (refrigerant noise) refrigerant flow through the coils is erratic and therefore the actual duty the unit supplies is not usually what is on the badge.

It is possible to design a system correctly with T peices. But this in the real world this is never done.

This is purly a commercial issue. Tosh Sanyo Diakin Panasonic all recommend refnets. Mitsu used to in the early days.

At the end of the day you can't blame the installer he just does what he's told. The commissioning engineer does what he is told and the client suffers for it.

We are Like Diakin and offer the same services as should all manufacturers. Personally I think refnets are essential for a system to operate correctly but
I wouldn't blame any Mitsu giuys for not using them . Their trapped now as Mitsu don't suppy refnets anymore In the UK and Ireland and they do not have the option of using them.


T

[El Padre]

Have come across several systems that have had refnets installed incorrectly, the first sympton has always been one evaporator starved of refrigerant, as a pre-expansion fault, thermatech as always is correct in stating that ensuring that the liquid refrigerant is subcooled is a way of preventing this, I was under the impression that a tee should always be installed horizontally anyway in any type of refrigeration system, just as good working practice. I may be mistaken though.

Cheers