Radiator half hot half luke warm

[Ontario Plumber]

Hi All

I have nine radiators in my semi detach. eight work ok. One in the lounge top half gets hot bottom half only gets to luke warm. What is wrong. I am sure someone will know. Thanks in advance.

 

[chrishutt]

Probably not getting enough through flow (return connection cool). Balancing the system (restricting flow through other rads) should solve it. Other possibility is sludge blocking lower waterway, in which case return connection will be hot but middle section of bottom of rad cool.