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

["christopher purves" <CHRIS_PURVES@xxxxxxx>]

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
>
>
>
>
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>
>
>Yahoo! Groups Links
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