Alternative to TRVs?

[bengasman]

Ok so I'm after advice on the mother of all central heating systems.

Rather than fiddling with TRVs and adjusting them weekly (daily even) as ambient temps raise and fall, I want to automate the system as much as possible.

Why would ambient temperature changes cause a need to change trv settings?

 

[BigBurner]

Fit a Broag 39C combi and no TRVs
http://www.avantaplus.co.uk

Look at Combi option 16.
http://www.avantaplus.com/docs/Issue 5 -Avanta Schematics Booklet.pdf

 

[Hellcat]

Ok so I'm after advice on the mother of all central heating systems.

Rather than fiddling with TRVs and adjusting them weekly (daily even) as ambient temps raise and fall, I want to automate the system as much as possible.

Why would ambient temperature changes cause a need to change trv settings?

Depending on how hot/cold/windy/wet the wether is outside changes how fast different rooms cool down or heat up. It's an old house thing.

 

[D_Hailsham]

Why would ambient temperature changes cause a need to change trv settings?

Depending on how hot/cold/windy/wet the weather is outside changes how fast different rooms cool down or heat up.

Agreed.

You therefore need to individually size the radiator(s) in each room, taking into account all the relevant factors, i.e. rate of heat loss, internal/external temperature, orientation (N,S,E,W), number of air changes etc. If necessary use a worst-case scenario, e.g minimum outside temperature of -5°C. Then add 10-15% for heating up from cold. This will give you a radiator which is more than adequate for the room, which is essential because, if the radiator is undersized, it does not matter how sophisticated the control system, the room will either heat up very slowly or never reach the required temperature.

TRVs, in particular, need good Heat Authority, which is the ratio of Heat Available to Heat Required. This needs to be over 1 to ensure the TRV works properly with a small p-band (difference between TRV open and close temperature).

Installing a system with each room treated as a separate zone is no guarantee that you will solve the heating/cooling problem.