Re: RE: multi-zone central heating

[Kevin Hawkins <lists@xxxxxxxxxxxxxxxxx>]

christopher purves wrote:

>Hi All,
>
>I'm now getting a little confused by some of the replies on this topc.
As
>far as I am aware, SK use the HoneyWell Proportional Actuators with the
LON
>network (look very similar if they don't :))  room temp sensors and 
some
>smarts (along with an external sensor or two). I'm sure SK spent quite
some
>time developing algorithms and control interfaces and so on and ao
forth and
>thus I am happy they can justify their price (especially when when you
>include the design/installation consultancy part).
>
>Some people **seem** to be suggesting that this sort of system will not
>work.
>
>Do I understand correctly ?
>
>

Whooa...I am not in any way going to be draw into saying someones
product can't work - particularly as I am not in an informed position to
comment as I haven't tried them plus I made my comments on  input. from
others ie 'heresay'...

The comment was made in relation  to my idea of the remote room
thermostat being used in a feedback system to control the proportional
valve.  I have an (offlist) reply from an individual in the industry who
is suggesting this will not be workable. He says using proportional will
provide no benefit cf On/Off really. His reasons are that thermal
inertia and time lag would make the process parameters unsuitable for
implementing a suitable feedback/control system.My take on this is he
means that the time from applying heat to the radiator and the
thermostat registering the benefit and being able to modulate the flow
are just too long with too much inertia - and I can see that is likely
as it must have a reaction time of several minutes.  Now I have no
comment at all on how SK achieve this and how effective it is.  Their
modelling might be sufficiently sophisticated and they might base this
on different feedback mechanisms eg radiator temperature, outside temp,
flow temperature,  or room temp sensors actually in their actuators
which I guess would produce a tighter feedback system.  Plus they
obviously use knowledge of the particular room dynamics. So I am sure it
works  a lot better than my current system does.   Both Ake and myself
are I think saying that we are being 'told' that achieving stable room
temperatures, (ie not oscillating),  from these sort of systems in a
residential environmenmt is quite a difficult thing to do, particulalry
as flow temps vary with a modulating boiler. Neither of us quite want to
believe that but maybe it's true.

Kevin

>
>
>Chris
>
>
>