[OpenTRV-dev] weather compasation

[Stuart]

My own project is a weather compensator (Wx) (plus quite some scope 
creep i.e. an ipad-based programmer on a web interface).

Even if you can't adjust the supply temp, you could blend incoming with 
the return water and use the cooler blended water in the circuit 
(assuming there is one incoming pipe and one outgoing). This is how 
water-based underfloor heating works. Assuming you are billed for the 
energy taken it would cut costs, possibly by 15% (according to claims).  
You need a blend valve, a pump and a thermostat.

My own Wx algorithm is this:

- when hot water priority is on (tank demand using a digital aquarium 
stat, not the rough and ready things sold to plumbers), the boiler is 
set to and runs at about 70C to heat the tank above 60C quickly.  It may 
not condense at this temperature if the return is above 55C, but that is 
a compromise with legionella prevention, and heating sessions are short.

- when HWP is off, the boiler is cut out (via the thermostat/programmer 
input) at a temperature according to the outside temp.  The flow temp 
currently (I'm experimenting) is 60C at 0C outside or less, reduced by 
2C for every degree outside above 0C, but cut off entirely when outside 
is above 15C.  So at 10C outside the circulating temp is 40C.  Rads are 
on longer but cooler. The return temp is also monitored but seems 
redundant at the moment.  It seems to work.

It runs on a picaxe.

It is particularly useful in a world of soft zones because it keeps the 
heat in the non-productive parts of the system (i.e. pipes and pumps 
etc. which in my case are well insulated but in the garage) to a minimum 
which matters when they represent an increasing proportion of the whole 
as zones turn themselves off.

Stuart

Stuart Gillies

On 15/12/13 21:31, Bo Herrmannsen wrote:
> np... i was just wondering why.... but guess in my own case it would not make sense since each rad is direct on district heating and i cant adjust ingoing temp.... only thing that matters for me is return temp :-D
>
>
>
> Den 15/12/2013 kl. 22.29 skrev Damon Hart-Davis:
>
>> Whoops!  Should have read your subject line!
>>
>> But anyhow, yes, slightly beyond this winter’s work.
>>
>> Rgds
>>
>> Damon
>>
>>
>> On 15 Dec 2013, at 21:23, Damon Hart-Davis <EMAIL ADDRESS HIDDEN> wrote:
>>
>>> Hi,
>>>
>>> It’s called “weather compensation” and is generally more relevant at/in the boiler to increase flow temperature to increase power output of each rad to compensate for increased power loss and thus help heat each room in a reasonable time.
>>>
>>> Slightly out of OpenTRV’s remit for now (since our control is currently binary), but nothing to stop boiler itself doing weather compensation: indeed I do it manually with ours.
>>>
>>> Rgds
>>>
>>> Damon
>>>
>>>
>>> On 15 Dec 2013, at 21:18, Bo Herrmannsen <EMAIL ADDRESS HIDDEN> wrote:
>>>
>>>> in the middle of the DOOM of TMP a thought hit me
>>>>
>>>>
>>>> whats the point/theoy behind messueing the outside tmp and use that to regulate indoor temp?
>>>>
>>>>
>>>> and could it be used to some degree also control indoor humidity? in winther it can get rather dry and it makes me itch like h****
>>>>
>>>>
>>>>
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