Precharged system, 1 meter run?

[craigix]

I'm currently installing a daikin inverter unit and when I bought it I was told it was precharged for up to 7 meters, when I told them the run was 1 meter they suggested I'd have to remove some of the precharged gas.

Is this correct? I remember ecoair telling me that was not the case when I installed one of their units.

Just looking for some clarification.

[brunstar]

depending on the model number but the outdoor units are usually pre charged to 10 meters anything in excess of 10 meters will require additional charge.
In relation to the pipe run, make sure that you mave a min pie run of 3 meters.
You do not remove charge from these systems.

You will find it is the LG split systems that are or use to be pre charged to 7 or 7.5 meters.

you will need to specify which model you are installing.

[monkey spanners]

Yes you will need to take some out, they have a minimum length also with the factory charge.

[brunstar]

by taking the gas out you will change the composition of the refrigerant. You will separate the R32 and the R125.
Any refrigerant work must be carried out in the liquid state..

[DEVIL]

Com one people it's a daikin and even if it wouldn't be, don't take any refrigerant out of the system, the person who told u to take out refrigerant is not rely a refrigeration technician, it has a liquid accumulator for storing refrigerant that might be in surplus

[les72]

Most of these little inverters now by Daikin, Mitsi, Hitachi etc have a MINIMUM pipe run of 3 metres, and usually pre-charged to 10/15 metres. You don't need to let any gas out - and whoever told you that needs shooting !

[monkey spanners]

Most of these little inverters now by Daikin, Mitsi, Hitachi etc have a MINIMUM pipe run of 3 metres, and usually pre-charged to 10/15 metres. You don't need to let any gas out - and whoever told you that needs shooting !

Agghhh, someones shooting at me!

Been told on two different manufacturers training courses this needs doing if pipework is under minimum length...

MS

[mad fridgie]

The minimum pipe run ia a relativily new issue. This came about due to excessive compressor failures on AC units in Asia ( mainly where out door units were underslung from the balconay above, literally no pipe run at all) The oil was being diluted, thus doing in the bearing!
So each machine now has a minimum pipe run (gernerally the longer the pre-charge, longer the min run) So you have to install the min run or remove some refrigerant. (To remove acturatly, I would say you have to be good to measure such a small amount and do not forget the weight in the gauge lines)
So my idvice for the smaller size units install minimum pipe run, for larger ones remove refrigerant (easier to measure)

[DEVIL]

Really i can't believe we really have this discussion.

mad fridgie > Way would the oil be diluted ?

But the problem is like this in some manuals you might find a minimum length but way ?, because they recommend for sound and vibrations because it's to close to the compressor and the refrigerant might make some sounds, and it's less then 3 m , for some it's just a minimum of 1,5-2 m

BUT again DON'T REMOVE REFRIGERANT FROM THE SYSTEM

[mad fridgie]

Really i can't believe we really have this discussion.

mad fridgie > Way would the oil be diluted ?

But the problem is like this in some manuals you might find a minimum length but way ?, because they recommend for sound and vibrations because it's to close to the compressor and the refrigerant might make some sounds, and it's less then 3 m , for some it's just a minimum of 1,5-2 m

BUT again DON'T REMOVE REFRIGERANT FROM THE SYSTEM

This information was obtained from Toshiba Corparation. As with any refrigeration system and overcharge this can cause very low suction superheat/wet suction or excessive discharge pressures. A wet suction can dilute the the oil. Diluted oil looses some of it lubrication properties. Poor lubrication causes overheating of bearings, Overheat of bearings causes excessive wear and/or copper plating. which causes the bearing to sieze over a period.
As far as minimum goes on some machines it is as little 0.6meters (each machine has its own set of rules)
One of type machines we used had a minimum pipe run of 7.5meter (5/8 and 3/8), try to hide all this pipe, is a bit un-sitely, (never mind the cost) On this size we would remove 400grams. Easy enough to measure correctly.
A small system with 3meter minimum (1/2 & 1/4) a simple coil behind the outdoor unit, is all that is required!

[craigix]

Hello everyone, thanks for the replies, the unit in question is a Daikin Inverter RXS35E2V1B (manufactured 2008).

I also already have a RXS25E2V1B (2006) running on a 2.5meter run, so I'm a little worried now. I've read and re-read the manual and it does not mention a minimum run anywhere, just a maximum.

[brunstar]

Hello everyone, thanks for the replies, the unit in question is a Daikin Inverter RXS35E2V1B (manufactured 2008).

I also already have a RXS25E2V1B (2006) running on a 2.5meter run, so I'm a little worried now. I've read and re-read the manual and it does not mention a minimum run anywhere, just a maximum.

If it is a high wall indoor unit connected to the RXS25E2V1B the min pipe run will be 1.5m on that model but if the indoor is an FVXS you will be looking at a minimum of 2.5m so a 3 meter rule will be safe.

[DEVIL]

Sorry i replayed and don't know what happened but it didn't save, so here's again:

I googled around and found some docs that stated that about Toshiba with the minim pipe length, but as i could say that doesn't say good stuff about Toshiba (the engineer that designed the unit didn't size the components as it should ).

As we say about Daikin the minimum run for pipes is 1.5 or 2, but only for the sound (of refrigerant) and vibrations, that comes from the outdoor unit, and it's not always specified in the manuals because the unit is not having a problem because refrigerant, and the outdoor unit is having a liquid receiver (heat pump) that is mainly for storing excess refrigerant because the amount of refrigerant in the receiver is fluctuating based on temperatures.

And, removing refrigerant from a system is a delicate problem, u have to remove it all with a recovery unit and charge only the amount u want (because it's a blended refrigerant).

So my opinion, NEVER remove refrigerant from a DAIKIN, or Mitsubishi , no mater what the pipe length is, and in this case it's a DAIKIN

[Imp]

Most manufacturers have a minimum length. Accumulator is designed to hold refrigerant over this minimum pipe run. Could also cause issues with operation. Was a major issue with LG some years back.

[yangchenchen]

So little over-charged refrigerant will have effects on the refrigeration system? It is impossible , even if there is no such as accumulator or gas-liquid separator in the refrigeration, there will be no harm.

[DEVIL]

Most manufacturers have a minimum length. Accumulator is designed to hold refrigerant over this minimum pipe run. Could also cause issues with operation. Was a major issue with LG some years back.

the accumulator is not designed for that, it is designed to coup with the differences in size of the outdoor - indoor heat exchanges and big outdoor temperature differences, and in the last place is the pipe length

[Imp]

This was in context to what LG officially stated for pipe runs less than 7 metres - that their accumulator was not big enough. As per your quote - the last place is the pipe length - this is about 1 metre pipe runs!!!!!!

[VRVIII]

Sorry i replayed and don't know what happened but it didn't save, so here's again:

I googled around and found some docs that stated that about Toshiba with the minim pipe length, but as i could say that doesn't say good stuff about Toshiba (the engineer that designed the unit didn't size the components as it should ).

As we say about Daikin the minimum run for pipes is 1.5 or 2, but only for the sound (of refrigerant) and vibrations, that comes from the outdoor unit, and it's not always specified in the manuals because the unit is not having a problem because refrigerant, and the outdoor unit is having a liquid receiver (heat pump) that is mainly for storing excess refrigerant because the amount of refrigerant in the receiver is fluctuating based on temperatures.

And, removing refrigerant from a system is a delicate problem, u have to remove it all with a recovery unit and charge only the amount u want (because it's a blended refrigerant).

So my opinion, NEVER remove refrigerant from a DAIKIN, or Mitsubishi , no mater what the pipe length is, and in this case it's a DAIKIN

The porpose of an accumulator is to ensure only gas enters the compressor preventing liquid pumping.

The Daikin installation manuals specify the following;

Split systems (RXS / RKS25~35F) minimum pipe run length of 1.5m or 2.5m when a FVXS indoor is connected.

Sky Air systems (RZQ(S) 71~140C) minimum pipe run length of 5m this can be reduced to 3m by removing 1kg of refrigerant.

[DEVIL]

The porpose of an accumulator is to ensure only gas enters the compressor preventing liquid pumping.

The Daikin installation manuals specify the following;

Split systems (RXS / RKS25~35F) minimum pipe run length of 1.5m or 2.5m when a FVXS indoor is connected.

Sky Air systems (RZQ(S) 71~140C) minimum pipe run length of 5m this can be reduced to 3m by removing 1kg of refrigerant.

Yeah one is the suction accumulator and one is liquid receiver they are not the same and have oposit behaver search on the forum and document yourself .

And to end the non sens i attached 2 manuals one for SKY daikin, and one for split , search in the document, there is no minimum pipe length and NOWHERE written that u should EVER remove refrigerant from system.

only in the RX manual it is written like this :
"Min. allowable length 1.5m
The suggested shortest pipe length is 1.5m, in order to avoid
noise from the outdoor unit and vibration.
(Mechanical noise and vibration may occur depending on how
the unit is installed and the environment in which it is "used.)

If someone has another opinion add documents to prove your opinion

[DEVIL]

sorry forgot the attachments, and actually couldn't attach them so i uploaded them to my site
http://www.fidelitas.ro/refrigeration-engineer/

[VRVIII]

Yeah one is the suction accumulator and one is liquid receiver they are not the same and have oposit behaver search on the forum and document yourself .

And to end the non sens i attached 2 manuals one for SKY daikin, and one for split , search in the document, there is no minimum pipe length and NOWHERE written that u should EVER remove refrigerant from system.

only in the RX manual it is written like this :
"Min. allowable length 1.5m
The suggested shortest pipe length is 1.5m, in order to avoid
noise from the outdoor unit and vibration.
(Mechanical noise and vibration may occur depending on how
the unit is installed and the environment in which it is "used.)

If someone has another opinion add documents to prove your opinion

Please see attached screen grab from RZQ71~140 installation manual, which also gives details on total refigerant charges with pipe run length less 5m. This has also been is clearly explained on Daikin Sky Air training courses for the last 2 years.RZQ Ref Charge.pdf

Also RXS / RKS / RXG units do not have a liquid line receiver they only have a suction accumlator installed.

[DEVIL]

Please see attached screen grab from RZQ71~140 installation manual, which also gives details on total refigerant charges with pipe run length less 5m. This has also been is clearly explained on Daikin Sky Air training courses for the last 2 years.RZQ Ref Charge.pdf

Also RXS / RKS / RXG units do not have a liquid line receiver they only have a suction accumlator installed.

Yes . right, but u might also see in your "screen grab" that the amount for 3-5 m , is the same as for 5-10 m, ain't it ??, way is that ?

And i know there is a recommended limit for sky for 5 m, because you might get confusing errors , but it is not a sky in the original discussion.

and to the second , RXS do have a liquid receiver here is my screen grab rxs.jpg
this is for 50 class, the smaller classes have a muffler that takes as a secondary effect the liquid receiver, of course the accumulator is important to

[paul_h]

Nearly all split systems have a minimum recommended pipe run. (it's ~1.5m for small splits, ~3m for larger wall splits). It's mainly for noise and on heat cycle though.
The accumalator will stop anything bad happening on cool mode with a 1m pipe run. You'll just have inefficient and noisy heat modes as the indoor unit will run hotter (requiring more defrosts and outdoor fan cycling)
Never take any refrigerant out though, either live with it, move the outdoor further away, or loop some piping around behind the unit.

Nearly every unit installed in australia is below the minimum piping length and works OK, not at it's most efficient, but OK.
I'm sick of installers fitting units 6m up the wall on a 2 story house just to save them the costs of 2 m of pipe and pipe ducting! They often only have 0.5m of piping down here.

[VRVIII]

Yes . right, but u might also see in your "screen grab" that the amount for 3-5 m , is the same as for 5-10 m, ain't it ??, way is that ?

And i know there is a recommended limit for sky for 5 m, because you might get confusing errors , but it is not a sky in the original discussion.

and to the second , RXS do have a liquid receiver here is my screen grab rxs.jpg
this is for 50 class, the smaller classes have a muffler that takes as a secondary effect the liquid receiver, of course the accumulator is important to

Devil,

If you had taken the time to look at the RZQ charge attachement you would have noticed the charge from 3~10m is 1kg less than the factory charge as I said previously 1kg must be removed with run legths less 5m. Obviously the factory charge is ideal for run length of 10~30m, with a run length of 5~10 the unit is overchaged but the receiver is big enough to handle this. However with run lengths less 5m the total refrigerant charge must be reduced in accordance with previously attached table from RZQ71~140 install manual.

As you say the RXS 50, 60 & 71 does have a receiver but these are completely different unit from the RXS35E in question. As I said the RXS/RKS/RXG20,25&35 do not have a receiver.

[DEVIL]

Yes but as i stated , it has a muffler in it's place, that as a side effect behaves like a liquid receiver.
And those are not completely different, they are just larger , and with the small needed modifications because of the larger thing.

and as for sky, don't remove refrigerant, just add the extra length to have the recommended 5 m, and at sky's u don't have less then that for the majority of the cases.

[VRVIII]

Yes but as i stated , it has a muffler in it's place, that as a side effect behaves like a liquid receiver.
And those are not completely different, they are just larger , and with the small needed modifications because of the larger thing.

and as for sky, don't remove refrigerant, just add the extra length to have the recommended 5 m, and at sky's u don't have less then that for the majority of the cases.

Devil,

We could go on about this weeks but trust me this infomation is 100% correct for Daikin units.
1. A suction muffler is never used to store refrigerant and is only used to reduce noise and absorb compressor pulses.
2. A suction accumularor is not used to store refigerant this is used to prevent liquid pumping during unstable conditions at start up/defrost/mode change. During normal operation the accumultor should only contain gas.
This RXS35 has no receiver and this obviously why the correct charge is important; unit factory charge 10m max run length then 20g per meter must be added there after.

With regard to the RZQ71~140C; section (a) at the bottom of the previously attached table clearly shows that a run lemgth of 3m is possible with a reduction in gas charge. The table can also be helpful with short pipe runs as the total charge can then be reduced to less than 3kg which can be useful for F gas regs.

[DEVIL]

the total charge can then be reduced to less than 3kg which can be useful for F gas regs.

i don't know about regulation because here in Romania we don't have regs that state something about small AC units.

And for the RXS, there is reason that they stated a minimum of 1,5 m for sound and vibrations reason or else they would just say a limit.
And it doesn't meater if it's a daikin or not , u cant have so much variations like piping from 2 to 10 m and for evaporation temperature from 0 , to -25-30 deg C, and the difference of the indoor and outdoor coil is and don't have something to coup with this variations in liquid quantities it's the physics of refrigeration and refrigerant, despite how ingenious or intelligent the engineers of a brand or another are u can't go around it.
And if it's called a muffler and not receiver/muffler it doesn't mean that it doesn't mean that the side effect it isn't beneficial for the system, it's a cavity and on the liquid side.

And finally i do agree we could go on for weeks but the idea is that others/and us, are learning from this (if someone else is still reading this thread), but as a final point of view i stick to my point and u to yours (in other words i agree to disagree) and the readers should do as they think its the write way.

[VRVIII]

i don't know about regulation because here in Romania we don't have regs that state something about small AC units.

And for the RXS, there is reason that they stated a minimum of 1,5 m for sound and vibrations reason or else they would just say a limit.
And it doesn't meater if it's a daikin or not , u cant have so much variations like piping from 2 to 10 m and for evaporation temperature from 0 , to -25-30 deg C, and the difference of the indoor and outdoor coil is and don't have something to coup with this variations in liquid quantities it's the physics of refrigeration and refrigerant, despite how ingenious or intelligent the engineers of a brand or another are u can't go around it.
And if it's called a muffler and not receiver/muffler it doesn't mean that it doesn't mean that the side effect it isn't beneficial for the system, it's a cavity and on the liquid side.

And finally i do agree we could go on for weeks but the idea is that others/and us, are learning from this (if someone else is still reading this thread), but as a final point of view i stick to my point and u to yours (in other words i agree to disagree) and the readers should do as they think its the write way.

Hi Devil,

In the UK systems with a total refrigerant charge of more than 3kg require to be leak checked at regular intervals to comply with F gas regs.

I respect your opinion and understand where you are coming from but the only place an RXS unit can store/back up refrigerant is within the condenser heat exchanger. This in my opinion is due to the following;
The units only have a discharge and suction muffler, the liquid line only runs from the heat exchanger into a small filter then enters the electronic expansion valve which is located in the outdoor unit (The actual length of the liquid line is about 200mm).
Approximatley 70% expansion takes place at the expansion valve and the final pressure drop takes place at the indoor heat exchanger header.

As you say we may have to agree to disagree but it has been interesting just the same. Hopefully we shall agree on future topic

[DEVIL]

Hi Devil,

In the UK systems with a total refrigerant charge of more than 3kg require to be leak checked at regular intervals to comply with F gas regs.

I respect your opinion and understand where you are coming from but the only place an RXS unit can store/back up refrigerant is within the condenser heat exchanger. This in my opinion is due to the following;
The units only have a discharge and suction muffler, the liquid line only runs from the heat exchanger into a small filter then enters the electronic expansion valve which is located in the outdoor unit (The actual length of the liquid line is about 200mm).
Approximatley 70% expansion takes place at the expansion valve and the final pressure drop takes place at the indoor heat exchanger header.

As you say we may have to agree to disagree but it has been interesting just the same. Hopefully we shall agree on future topic

RX.JPG

They don't have just one muffler on the liquid side, and if it would store extra refrigerant in the air heat exchanger it would be an inefficient procedure because the place were u store it, it doesn't add or remove heat.

With all respects u know a lot of useful stuff but if we would had agreed some time ago, we wouldn't had learned anything (pretending that we learned something ).

So let's end this as i stated before we have different opinions and the readers should do as they think is the best way

[VRVIII]

RX.JPG

They don't have just one muffler on the liquid side, and if it would store extra refrigerant in the air heat exchanger it would be an inefficient procedure because the place were u store it, it doesn't add or remove heat.

With all respects u know a lot of useful stuff but if we would had agreed some time ago, we wouldn't had learned anything (pretending that we learned something ).

So let's end this as i stated before we have different opinions and the readers should do as they think is the best way

Well Devil you don't give up easily and obviously enjoy the banter
The only thing I would like to say is that the liquid line filter mufflers you are referring to are basically a housing for a fine gauze filter to protect expansion valve. These are very small (about 16mm in diameter 60mm long) and could only hold a very very small amount of refrigerant.

How are things in Romania, what's the weather like over there this time of year?

[DEVIL]

The other way is inefficient and i stop

Well things are bad hard to find work, like in crises , i'm happy that it's not my case but it's pretty hard and as i understand harder then in other countries , and eave the weather is mushy like, yesterday it was 14.5 deg at 8 a clock in the morning, today is was 6 deg , one day is cloudy the next it's sunny and the next it rains ), but it's better then last year because it was colder then ever

[lomb]

Whats the minimum recommended pipe length for a MHI SRK hyperinverter?

[taz24]

Whats the minimum recommended pipe length for a MHI SRK hyperinverter?

Good grief Lomb, they have only just stopped argueing, don't start them off again

cheers taz

.

[VRVIII]

Good grief Lomb, they have only just stopped argueing, don't start them off again

cheers taz

.

Arguing no, just a bit of banter Devil's a quality bloke and I'm sure he would agree

Anyway the name "Taz" even sounds argumentative

As for the MHI min pipe run, I haven't got a clue

[taz24]

Arguing no, just a bit of banter Devil's a quality bloke and I'm sure he would agree

Ok I will reword what I said.

Good grief Lomb, they have only just stopped having a very indepth and heated discussion, don't start them off again .

Anyway the name "Taz" even sounds argumentative

Don't shoot the messenger

As for the MHI min pipe run, I haven't got a clue

Cheers taz

.

[DEVIL]

For shore it was a interesting discussion ).
In theory every day you learn something from everything that happens but what happens to the learning in reality is something else ).

and for MHI SRK hyperinverter
i have no clue, but you probably can find it in the manual
and i don't comment any more to don't get the ball rolling again

[exotiic]

With minimum pipe runs, do right angle bends allow any consideration? Id expect that since they add to the length in attaining maximum length then that would also be the case in minimum too?

Advice from our Panasonic distributor state that 90 degree bends are taken into consideration whilst MHI indicate a minimum of 3m for any of their units with or without bends.

[VRVIII]

With minimum pipe runs, do right angle bends allow any consideration? Id expect that since they add to the length in attaining maximum length then that would also be the case in minimum too?

Advice from our Panasonic distributor state that 90 degree bends are taken into consideration whilst MHI indicate a minimum of 3m for any of their units with or without bends.

Hi,

90 degree bends would not be taken into account for minimum pipe run lengths, this is based on volume.

Maximum pipe run lengths are based on maximum pressure drop, this is why bends are taken into account when calculate equivalent lengths.