Combi boiler with 2port valve?

[sythai]

Evening Chaps...

(sorry I have a very basic knowledge of heating controls)

Part of a job I have coming up is re-siting all the boiler electrics up to the loft ( loft conversion)

Combi boiler, but also has a 2 port valve controlling heating via programmer? For some reason I always assumed a combi's heating was plumbed directly back to boiler?

Could someone help explain why it's done like this....

Many Thanks

Sy

 

[snowhead]

Zoned heating.

 

[sythai]

Just wondered what the benefit of this woud be.... Heating is all on just the one zone ?

 

[FrankUK]

Just wondered what the benefit of this would be.... Heating is all just one zone ?

Imagine if you had heating both upstairs (bedrooms) and downstairs.

Normally, you would heat the bedrooms to about 18C as you don't want to waste money during the day when they are un-occupied and we like a cool room to sleep in. But we like the living room downstairs and maybe the kitchen and dining room to be a bit warmer, say 22C.

This is how we 'zone' a space, be it an office building that faces North/South (sun comes up in the East and warms one side of the building while the other side is in shade) or a house with different levels.

How do you control the heating from one heat source/sink?

You use zone valves connected to a thermostat or other control method to shut off the heat (or cooling) when the space is at temperature.

 

[sythai]

Thanks Frank for trying to explain a bit better.....

Understand about different zones where required. Was just trying to work out why on this particular set up why a 2 port valve was actually required. At present all the heating is rads throughout the house controlled via 1 x room stat and 1 x single channel controller. What would happen if there was no 2 port valve, is it actually required in this case?

Please bear with me.....

Thanks again,

Sy