Central heating flowing problem

[Monkeymick7]

Installed a ideal logic plus 35kw combi a few months ago in a house when we done the convention from the system to combi we left a central heating flow and return capped for the new loft extension.
The builder has not taken the two flow and return pipe work with was capped into the loft for the new feeds for one rad and towel rail.

The ground floor rads get hot
the loft rads get hot
but the 1st floor don't

so it seems like its taking the the shortest circuit

ive turn down the locksheilds up in the loft to quater turn
but still the 1st floor rads aren't getting hot at all

What's the best thing to do?

Thanks

 

[Howsie]

Sounds like the builder's messed it up. Time to rip up a few floor boards me thinks.