Re: Re: Urgent help required: Star vs Daisy chain wiring for aircon con

["Frank Mc Alinden" <frankmc@xxxxxxxxxxxxxxxx>]

Hi Chris
It was getting late here in Oz  thats why i didnt get back to
you...
If you have confirmed that it uses rs485 comms then im sure the star wiring
system will work ,providing as Keith says its not a really high data
rate.....I have previously star wired alarm systems in large shops and it
worked fine..........

Frank


----- Original Message -----
From: "christopher purves" <CHRIS_PURVES@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Thursday, September 29, 2005 2:01 AM
Subject: RE: [ukha_d] Re: Urgent help required: Star vs Daisy chain wiring
for aircon con


> If I had done it, I would have used 8 runs of Cat5 (ukha TM!) but alas
it
> was an external contractor who used 0.5mm2 2-core.
>
> I am coming to the same conclusion you are I think. I am probably OK
as
> the
> runs are in cases as short as 2m and at most I think 8m. Over these
> distances I am probably ok.
>
> C
>
>
>>From: "Keith Doxey" <ukha@xxxxxxx>
>>Reply-To: ukha_d@xxxxxxx
>>To: ukha_d@xxxxxxx
>>Subject: [ukha_d] Re: Urgent help required: Star vs Daisy chain
wiring for
>>aircon control am I screwed
>>Date: Wed, 28 Sep 2005 15:11:48 -0000
>>
>>Hi Chris
>>
>>--- In ukha_d@xxxxxxx, "christopher purves"
>><CHRIS_PURVES@M...> wrote:
>>
>> > Each unit in the chain (including external units and the
>>touchscreen) has an
>> > f1 and f2 signal connection.
>> >
>> > Originally Daikin told our installer to wire as a 'star' back
to
>>the
>> > touchscreen location which required a single 2 core cable to
each
>>indoor and
>> > outdoor unit back to the touchscreen which of course they
did. In
>>effect
>> > join all f1's together and all f2's together and attach to f1
and
>>f2 on the
>> > trouchscreen.
>> >
>> > However when speaking to Daikin today, Daikin are claiming
the
>>internal
>> > units must be wired in a daisy chain (one to the next).
>>
>>The reason for specifying a Daisychain is that the cable run must
be
>>terminated at each end to avoid signal reflections which could
>>corrupt the data.
>>
>>With Starwired, you will have unterminated stubs of cable which the
>>signal will hit the end and bounce back possibly causing
corruption.
>>
>>
>> > Can we just ignore their comments and wire it a as a star ?
>> >
>>
>>There are two factors that affect how bad the reflections will
>>be.....
>>1. the length of the unterminated stub
>>2. the speed of data transmission.
>>
>>In a domestic environment the cable runs are probably quite short
>>and I would imagine that the data rate would be reasonably slow as
I
>>cant imagine there is that much information flying about
>>
>>Whether you "can get away with it" I wouldnt like to say
:-(
>>
>> > Certainly CBUS can be wired as either.
>> >
>>
>>Probably because they designed it with Star wiring in mind.
>>
>>Did you put in a single pair cable as specified, or have you used
>>CAT5 which has 4 pairs (or some other data cable with more than one
>>twisted pair)?
>>
>>If you have used a multi pair cable you can still fake a daisy
>>chain. Send the signal to the unit on the first pair and return on
>>the second, then join that to the first pair of the next unit etc.
>>
>>It doubles the length but RS485 is designed for long distancee
comms
>>anyway so shouldt be a problem.
>>
>>HTH
>>
>>Keith
>>
>>
>>
>>
>>
>>
>>
>>Yahoo! Groups Links
>>
>>
>>
>>
>>
>>
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