Re: HA without fallback-CBUS

[Chris Hunter <cjhunter@xxxxxxxxxxxx>]

C-Bus, surely, must have good failure strategies built-in, to ensure
graceful degradation in case of failures ... I'm beginning to wonder !

EIB too ... ?

Chris



Neil Ball wrote:

> It is unusual to find electrical override switches on most modern
control
> systems - many for the overrides are done in software so if the
controller
> has failed these will not work anyway! It is relatively straight
> forward to
> add in switches or relays on the output side if the circuit if
> required as a
> manual override. It's just as easy to do what Nigel suggests and
> simply hard
> wire the lights in the event of a dimmer failure until a replacement
is
> sourced. If you use a system such as C-bus then it would also be worth
> installing MCB's on each output so that you have circuit isolation to
> control the lights when you've bypassed the dimmer electronics.
>
>
>
> Neil B.
>
>
>
>   _____
>
> From: ukha_d@xxxxxxx [mailto:ukha_d@xxxxxxx] On Behalf Of
> Nigel Giddings
> Sent: 14 January 2006 09:20
> To: ukha_d@xxxxxxx
> Subject: RE: [ukha_d] HA without fallback-CBUS
>
>
>
> Martin,
>
> It is my understanding that C-Bus is used in many commercial
> applications, including the new Wembley stadium...
>
> I don't know of any instructions supplied by C-Bus or any other BMS
> manufacturer which suggests that 'back-up' switches are required in
case
> of failure...
>
> I am also not aware of any safety regulations for commercial buildings
> which say that lighting must have mechanical switches, as opposed to
> electronic ones, for safety reasons. Of course emergency lighting will
> be part of the design but not linked into dimmer failure...
>
> The MTBF (Mean Time Before Failure) of a C-Bus dimmer, I hope,
probably
> exceeds a standard wall mounted dimmer. A total failure of C-Bus is
> unlikely to occur unless you rely on a single Bus power supply which I
> would suggest is bad design. C-Bus relies on a distributed design.
>
> I will have a number of self contained emergency lights (5) to cover
> mains failure or MCB trip but I don't intend to have over-ride
> mechanical switches. Worst case, your dimmer fails, you identify the
> problem you hard wire the light on till a replacement dimmer is
> installed...
>
> I am also using a Midon Temp05/Homeseer system to operate my central
> Heating in my existing house(the automation was retro-fitted) and I
did
> install changeover switches to enable the existing mechanical switches
> to act as a back up, in 3 years I've never used them. I will use a
> similar system in the new house, still being built, but will have a
much
> simpler override as the new house has 11 heating zones. I will
probably
> revert to a single centrally located mechanical thermostat in case of
> computer failure...
>
> HTH
>
> Nigel
>
>   _____
>
>
>
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