Plumber left me with luke warm radiator

[PhatEd]

Hi there.
I'm after some advice on some work that we have had done today in the house to replace a single panel radiator with a larger double panel one. The chap has been out, drained down the system, installed the new larger radiator and refilled the system. He then bled all the rads and left it for half an hour to get up to temp, but it wasn't really heating up. He said that there is probably air in the system and so closed all of the lock shield valves on the other rads in the house to force everything through this one new rad. He left it another 30 mins and this new radiator is only warm at the top and nearly cold at the bottom. He then said that it's not getting as hot as he would like but I need to leave it like that for a week to see if it improves and to call him back if it doesn't. He then tried telling me that the pump might need replacing as it might not be up to the job of the bigger radiator, but I really can't see that. It's only one radiator that has been replaced (single to double Type 21)...

Obviously I've done some investigation online since being told this and from what I am reading it doesn't seem right. It sounds like there is an airlock in the system that needs sorting out? I have since contacted him this evening to say I'm not happy and to ask him to advise / come back to sort it and he has told me that an airlock can take time to clear and to see how it goes over the next few days.

Does this sound right? Or am I being fobbed off here? As far as I was concerned, this new radiator should have been fitted and in a fully working state before he disappeared. If there is an airlock, it should have been sorted out as part of the job?

Any advice appreciated.
Thanks

 

[SJB060685]

I was just going by my college texts books. To be honest there is very little in it so I shouldn't worry.
[automerge]1579552595[/automerge]
My text book only allows for copper pipe though and not what you linked so I've saved that link anyway to calculate for plastic pipe etc.
We were only out by .7 of a litre a minute and pressure was minimal difference

 

[Best]

Think in basic terminology, the original radiator might have been small enough for the microbore pipe runs to cope with the heat loss of the rad.
Replacing with new rad has perhaps x3 or x4 the output and pipes not adequate.
But circulating pump could also be part of the problem.
Over to the installer to take on the problem now, whether he is at fault or not.