Transmission wiring on Daikin VRV2

[Markie]

Hi fellers,
I have been installing a couple of floors of Daikin vrv and have a theoretical question for you.
The positions of the condensers compared to the indoors was more or less central and I rang daikin technical to see if it would be ok if i ran the 2 core transmission wiring (F1,F2) to the nearest unit in the centre then tee off one left and one right to the rest of the indoor units which would have drastically cut down the length of wiring compared to starting at one end then daisychaining all the way along to the last unit.
Needless to say they shot me down in flames saying I had to stick with the daisychain method.
They say that if you "star wire" any part of the system it will "confuse" it when it self addresses on initial start up.
I did as I was told and all is well but what I want to know is why?
Given that the wiring is just linked in then out off of the same terminals on each unit, i.e. wired in parallel like sockets on a ring main (without the return from the last unit to actually make a ring), surely the laws of electricity mean that all units receive voltage simultaneously on start up and not "jump from one unit to the next" as they address them selves.
The only thing I can come up with is that by daisychaining you are adding to the resistance of the wire after each unit and therfore guarentee there will be a different resistance to each unit. Whereas if you star-wire it willy nilly you may end up some units having very similar lengths of wire back to the condensing unit thus causing the "confusion" to the system.
This seems to indicate that the system is able to detect extremely slight changes in resistance in the wiring and uses this to systematically address the indoor units.
If this is the case then I could kind of understand it but if not then it seems to me that the daisychain idea is a complete crock and the condensing unit pc board uses some other way to randomly address the indoors and it should work even if you wire it however the hell you want.
I know its what they tell you to do and will do it as they say in case of problems as Im told if you mess up on initial start up the sytem saves a fault code and gives you even more grief.
Does anyone actually know or even actually wired it differently and what was the results.
I would love to know!!

[frank]

Consider on start up that the outdoor unit starts to communicate with the indoor units. It has to have some sort of logical method to do this.
So, based on the distance from the outdoor unit it can ping the indoor units and assign an address to the shortest ping response. Once done it can then move on to the second unit. Just as you would do if you were to ping from your computer. With the units in parallel this task is quite simple.

If you star connect you have multiple paths for the information to flow so the response from the indoor units can be mis-leading.

[Andy]

Hi Markie

Beter wire it the way they say or no warranty

Never do this but the way around this is to power up the outdoors in the sequence you want they to address in.

The problem with this is when you need to add to the system, especially if you are not the guy who set up the system originally.

Kind Regards Andy

[frank]

but the way around this is to power up the outdoors in the sequence you want they to address in.

This won't work. If you add additional indoor units or change a PCB you must reset the system to redefine the communication loop.
Once you have done the initial initialisation you can go in to the controllers and set up Groups or even force the fan coils on to "fan only" (command 45) so you can see which fan coil is which - address wise.

[Markie]

Consider on start up that the outdoor unit starts to communicate with the indoor units. It has to have some sort of logical method to do this.
So, based on the distance from the outdoor unit it can ping the indoor units and assign an address to the shortest ping response. Once done it can then move on to the second unit. Just as you would do if you were to ping from your computer. With the units in parallel this task is quite simple.

If you star connect you have multiple paths for the information to flow so the response from the indoor units can be mis-leading.

OK Frank, that makes sense so I guess I'll forget my "shortcut" ideas.
Thanks for reply.
Cheers,
Markie.

[Andy]

This won't work. If you add additional indoor units or change a PCB you must reset the system to redefine the communication loop.

We have found this out the hard way

you can initially set the system up by switching on in a sequence that you require. But as frank states the problem arises if you need to modify later.

Supermarket networks are the same, although some controller manufacturers allow radials on the network, I advise our guys to daisy chain, it's just easier in the long run

Kind Regards. Andy

[puddleboy3]

Can only say that i have seen systems that have been wired with star points all over the place, some times the system works other times it dont. So the lesson is dont star point. Oh and dont use screened cable its just going to lead to problems!

[steve bajada]

another thing

the indoor units i have are two pipes what does that mean ? are they cooling only ? where can you find it written? thanks for your time.

[nike123]

All indoor units have two pipes!

[frank]

another thing

the indoor units i have are two pipes what does that mean ? are they cooling only ? where can you find it written? thanks for your time.

If you have a 2pipe VRV then the easiest way to tell is to look at the model number of the outdoor unit.

You could of course try switching the indoor units into heating mode from the controllers (one will be set to Master on a 2 pipe heat pump)

[The Viking]

another thing

the indoor units i have are two pipes what does that mean ? are they cooling only ? where can you find it written? thanks for your time.

All VRV indoor units has 2 pipes. (as stated above)

If you got 2 pipes from the outdoor unit then the system is a heatpump. (all indoor units has to be in the same mode, heating OR cooling)

If you got 3 pipes from the outdoor unit then the system is a heat recovery system (the indoor units can be in different modes).
These 3 pipes would go to a BC box (actually, one per indoor unit), where the refrigerant flow control for the indoor unit is done, from there it would be 2 pipes to the indoor unit.

Regarding your other post:

There wouldn't be a problem replacing wall-mounts with cassettes, as long as you can get hold of VRV cassettes of the right series (look at the model number of the outdoor unit and give this to your Daikin supplier, they should be able to take it from there).
However, to do this and recommission the system afterwards you will need to have specialist knowledge about Daikin's VRV systems (like how to set them up and get them to communicate flawlessly with the rest of the system)

[sparrow]

Hi people, Just a quick question if I may I went out to a site yesterday for a friend whom was committed elsewhere. The System was an LG unit, number Auuh306c it was a R410A Charge anyway, the exterior coil had a quite substantial residue of oil on the suction line on the last flare before entering the service port.
The internal Cassettes had a fault code cho3 showing. I checked this with the internal wall mounted control panel and it stated Remote controller/main controller communication error. My question is this if a sufficient amount of refrigerant was lost and only one indoor unit was trying to come in would this then throw a communication problem to the second ceiling mounted slave unit.
I checked the free running of the internal fan on the second unit but it just refused to do anything other than move its louver vanes?

Sparrow

[The Viking]

Sorry Sparrow,
But I have very limited experience of LG.

However, I got a bit of experience of RE and I believe that you would get more answers if you start a new thread.....
(There are some good LG guys here, they would certainly click on all threads with LG in the header)

[nike123]

Hi people, Just a quick question if I may I went out to a site yesterday for a friend whom was committed elsewhere. The System was an LG unit, number Auuh306c it was a R410A Charge anyway, the exterior coil had a quite substantial residue of oil on the suction line on the last flare before entering the service port.
The internal Cassettes had a fault code cho3 showing. I checked this with the internal wall mounted control panel and it stated Remote controller/main controller communication error. My question is this if a sufficient amount of refrigerant was lost and only one indoor unit was trying to come in would this then throw a communication problem to the second ceiling mounted slave unit.
I checked the free running of the internal fan on the second unit but it just refused to do anything other than move its louver vanes?

Sparrow

Isn't that outdoor unit single split system? Then how it could 2 indoor units be connected to one outdoor if that is the case. If you have two indoor units connected to that outdoor unit it is suppose to have communication error.
Or maybe I am wrong and that unit could have multi indoor units, but that is not stated in literature for that outdoor unit no.

Auuh488c is first next (by capacity) unit from that series capable to serve more then one indoor unit. Again that is how it is described in literature and not my experience.

What is indoor unit model no.?
How are their pipes connected to outdoor unit? Does every indoor unit have their own set of valves at outdoor unit or pipes are welded in T-es.

[sparrow]

indoor unit model no.?
How are their pipes connected to outdoor unit? Does every indoor unit have their own set of valves at outdoor unit or pipes are welded in T-es.

Hello Nike123, Sorry for the lack of info but I was given very little myself and what I found on site made me curious, I have no knowledge of the indoor units numbers and sadly I shall not be returning as it was a warranty job only installed for a year and they asked that I visit to let site know they had things in hand as it were.

The young lad on site did however keep pointing to the outside coil along side the one I isolated, that also had its own isolation point. These units were twin piped heat pumps, When I turned off the unit I was concerned about the internal control panel was also blanked out. This lead me to believe both internal cassettes worked off of the one external coil.

Hi Viking I do visit your site regularly its very good I did have some difficulties when I tried to down load fault codes and as now still no codes on my lap top I was hoping to start with Dakin could you help?

Thanks lads

Sparrow

[zahra]

hi.can you give some information about vrv2 air conditioner plz?
thank you


I have been installing a couple of floors of Daikin vrv and have a theoretical question for you.
The positions of the condensers compared to the indoors was more or less central and I rang daikin technical to see if it would be ok if i ran the 2 core transmission wiring (F1,F2) to the nearest unit in the centre then tee off one left and one right to the rest of the indoor units which would have drastically cut down the length of wiring compared to starting at one end then daisychaining all the way along to the last unit.
Needless to say they shot me down in flames saying I had to stick with the daisychain method.
They say that if you "star wire" any part of the system it will "confuse" it when it self addresses on initial start up.
I did as I was told and all is well but what I want to know is why?
Given that the wiring is just linked in then out off of the same terminals on each unit, i.e. wired in parallel like sockets on a ring main (without the return from the last unit to actually make a ring), surely the laws of electricity mean that all units receive voltage simultaneously on start up and not "jump from one unit to the next" as they address them selves.
The only thing I can come up with is that by daisychaining you are adding to the resistance of the wire after each unit and therfore guarentee there will be a different resistance to each unit. Whereas if you star-wire it willy nilly you may end up some units having very similar lengths of wire back to the condensing unit thus causing the "confusion" to the system.
This seems to indicate that the system is able to detect extremely slight changes in resistance in the wiring and uses this to systematically address the indoor units.
If this is the case then I could kind of understand it but if not then it seems to me that the daisychain idea is a complete crock and the condensing unit pc board uses some other way to randomly address the indoors and it should work even if you wire it however the hell you want.
I know its what they tell you to do and will do it as they say in case of problems as Im told if you mess up on initial start up the sytem saves a fault code and gives you even more grief.
Does anyone actually know or even actually wired it differently and what was the results.
I would love to know!![/QUOTE]

[zahra]

some information abt vrv2 plz?

[nike123]

I don't know for Daikin but, MHI could make such wiring arrangement as you described without any problem.
I suppose that Daikin could do that too.
It is only forbiden to make loop, but branching (probably) should be possible.



And this is from Daikin manual.



So, you probably have misunderstanding/misleading from Daikin support.

Check here page 174!

[R1976]

Mitsubishi Electric also allow you to star wire in reality, the reason they may say not to is because they don't like three cables in a terminal.

[Coolie]

Mitsubishi Electric also allow you to star wire in reality, the reason they may say not to is because they don't like three cables in a terminal.

On a Mitsi vrf system you have to manually set the address of the indoor unit by setting the two pots on the indoor pcb.

So I'm guessing that star wiring is not necessary as important as it is with daikin. But it's good practice to stick to the daisy chain.

I have seen a star wired daikin vrv, but i was called in after modifications were made to the system by other contractors who added and removed units from the system.
They could not get it to run because they star wired it.
In fact they spliced the cable inbetween units and ran it off to another....

It can never work