Acova radiators

[Robert Tyrrell]

I fitted a few of these about a fortnight ago for a customer of mine and although there's plenty of water (Bled the system a few times) two of them are getting warm, but not hot, and one remains cold.
[They] seem to think that the radiators might be installed the wrong way around. Is this possible, and if so what's inside them that makes it such a a problem?
I'm going back next Friday and I thought it might be good to ask on here first as I've fitted loads of these and never had a problem before

 

[Chalked]

It it a tubular rail one?
If so, some have a plastic dip tube that is inside the flow connection. I is about 2/3 of the height of the rad. And needs to be on the flow. It won't swap to the other side.
You might get away with turning the rad around ( back to front)