Back boiler not heating downstairs

[knoxy777]

We have dual heating, back boiler and oil. The oil will heat the immersion tank and all radiators but the back boiler will only heat the upstairs radiators and immersion.

We only moved in a few years back with the system already installed and are not sure if it was designed to do this.

There is a separate pump for the back boiler which seems to be working. The upstairs rads are all piping hot but downstairs totally cold.

Would it be easy to change the system to heat all radiators?

 

[SimonG]

Sounds like a pump failure, gravity will heat upstairs but no force to heat downstairs.