flow and return pipes

[dwalsh1]

Should the flow and return pipes on my radiators be of the same temperature when the boiler is fired up? The reason I ask is because one pipe on the rad is really hot and the other is warm and the same on another rad in the same room. is this normal? cheers

 

[villa_tom]

Ideally there will be 12 degrees difference in order for the boiler to condense properly.

 

[villa_tom]

Actually, what boiler is it first?

 

[kozak1968]

When the water flows into the radiator it looses its heat which is transfered from the rad surface into the room, by the time it reaches the return it is cooler.

 

[dwalsh1]

It's a Worcester Bosch 35CDi II. My hands can't distinguish between 12 degrees so I would presume my heating is working okay?

Actually, what boiler is it first?

 

[lame plumber]

ouch out and thats hot on the return

 

[doitmyself]

Ideally there will be 12 degrees difference in order for the boiler to condense properly.

Condensing is not connected to the temperature difference, but to the flue gas temperature, which depends on the return temperature. If the return is above approx 55C condensing will not occur. The lower the return temperature, below 55C, the more condensing will take place. If all the water vapour in the flue gasses is condensed the boiler output would be increased by a theoretical 11%. In most cases the output is only increased by 7-8%, when the return temperature is about 30C.

 

[Frelon]

As Lame Plumber says! Could not be more precise!