Re: Real HA - central heating control by the radiator

[Lehane Kellett <lehane@xxxxxxxxxxxxxxxxxxx>]

Kevin Hawkins wrote:
> Lehane Kellett wrote:
>=20=20=20
>> I have my doubts, for a domestic install anyway, whether full=20
>> proportional on a single rad is worth the
>> =A340-50 quid a go extra. For DHW mixing, definitely.
>>=20=20=20
>>=20=20=20=20=20
> For me - with very large cast iron radiators the hysteresis was too=20
> large without proportional control.   Some of my controlled valves=20
> control 3+ radiators as well which helps cost wise.   I was getting=20
> oscillations of nearly 3 degrees C in my room temperature using
ONOFF=20
> switching. this was quite noticeable. I tried three approaches to
fix=20
> this, I'm sure there are others,,
>
> 1) Getting the flow temperature reduced and hence more 'balanced',=20
> worked quite well but this had problems in satisfying any sudden
heat=20
> demand elsewhere.
>
> 2) Trying a calculated 'pulsed' on period that would estimate the
heat=20
> required and avoid overshoot. Never got far with this.
>
> 3) Using proportional (TRV's - with remote sensors as a lot of my
rads=20
> are encased) which I found achieves the best results as the system=20
> settles into a stable state with each rad staying fairly constant
in=20
> temp. I currently use Danfoss proportionals with a remote sensor
that=20
> has a small heater element underneath it. These were a commercial=20
> offering from Danfoss but are not manufactured anymore, You apply a=20
> small current to this element and it offsets the TRV's operation=20
> accordingly, at full voltage it turns off the radiator effectively. 
I'm=
=20
> hoping that those 0-10V proportionals might be able to replicate this.
>
> Having said that the 0-10V proportionals are proving very difficult
to=20
> source (seems not available in the UK) and I do suspect that with
fairly=
=20
> light modern radiators the proportional may not be needed.
>
> Kevin
>=20=20=20
At the risk of this thread boring to death everyone else...

If you are doing lots of rads with one valve then it is probably worth=20
spending
the money on something like the Siebe valve and a Belimo actuator.
Something like the R223/LR24-SR combo. About =A3100 (which
I think is actually pretty good when you see what you pay
for 'domestic' two port valves and on/off actuators).
See:

http://www.sontay.com/Downloads/SontayCatalogue2006.pdf

(I've never used them, except for price comparisons, but they say
they take cards)


Lehane


[Non-text portions of this message have been removed]