[OpenTRV-interest] Weather compensation

[John]

Hi Damon

On 22/12/16 12:57, Damon Hart-Davis wrote:

> I have always assumed that weather compensation is simply the part
> that adjusts settings (eg flow temperature) based on current external
> temperature, ie reactively.

Yes, that's what the boiler schemes I've fitted do. Worcester's Wave 
also senses internal temperature at the controller (as per regular 
programmable thermostats) which I think they describe as "influence" but 
I don't know exactly how they combine the factors.

> There are opportunities to do more than that with the forecast,
> getting heat into the house early/late/whatevs if the next little
> while is going to be especially hot/cold/windy depending on the
> thermal time constant of your house.  Potentially especially good for
> those with (say) UFH for example.

There's possibly some scope for some smart tweaking there, though I 
think the efficiency and therefore CO2-saving gains are mainly from 
reducing flow and return temperatures during milder weather.

> Note that the compulsory compensation suggestion is out for
> government consultation right now, and I voted against it given the
> long payback times and the other rather lower hanging fruit (ie
> better places to spend the money to save energy first), and even
> against compulsory timers since most people don’t use them:

Why do you think weather comp would have a long payback time? Even at 
the price manufacturers charge for their thermistor-in-a-box sensors and 
the labour required to fit them the total cost should be in the 
£100-£200 range which should give a payback well within the lifetime of 
the kit.

In my experience as a heating installer most people do use some form of 
time control on their systems, even if a significant minority don't. I 
think the Regs could do a service by assessing and mandating a usability 
factor for controls: there are some that even I struggle to set (looking 
at you Drayton!). But even if some people don't use their timers the 
building regs are there to mandate what installers provide: if time 
control isn't compulsory then cheapskate installers won't fit them and 
even householders who want and would use them won't have them. And given 
that a timer costs the square root of sfa there seems no justification 
for omitting them.

> https://beisgovuk.citizenspace.com/heat/heat-in-buildings-online-consultation/consultation/
>
>  Guess what I thought *would* be a good solution that policy should
> support?  B^>

Intelligent TRVs? That would mean mandating Honeywell and a few other 
mfr's currently very expensive (and in some cases rather flakey) kit, 
which would surely have an unviably long payback time?

-- 
John Stumbles                                    http://stumbles.org.uk
:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-: