If I read your post correctly;
- you've recently had the boiler moved to another part of the house
- no powerflush or magnacleaning was carried out
- immediately since this work was carried out the rads have been warm at the top and cold at the bottom
- you have been since messing around with cleaning chemicals
- you used reputable tradesmen but haven't asked them why you only now have a problem after the work was completed
Rads cease to get hot all over due to poor water flow rate through them. Since the rads are the same ones you started out with, you must ask yourself what has changed. And the answer is, the pipework that linked them to the boiler.
Depending on how the boiler was reconnected into the existing heating system - there are two ways usually; the difficult way and the easy way - will affect how much pipe resistance has been introduced into the circuit. Too great a pipe resistance = lower flow. Lower flow rate means lukewarm rads not hot all over.
Finally, unlike some others here, I don't rate the chemical solution much. Chucking them into a system is like soaking your dirty kaks in a warm bowl of water overnight. No substitute for a washing machine.
In our industry we use Powerflush machines (akin to a washing machine and a similar size) and magnetic filters to do this work, and we run the substantial Powerflush unit's pump through just one rad (eg: shut all the others off) at a time, whilst we agitate that radiator with a vibro tool.
The magnets pick up the debris before it gets to the boiler, which considering it is haring along at 1.5metres per second, is not long. The worst thing you can do is stir up a load of debris, and then pass it through a combi, which is full of small apertures and plate heat exchangers with tiny gaps inside for stuff to get stuck and cause aggro for the rest of the boiler's lifespan.
Just as well you used reputable people, I'm sure they haven't done any of the above.
- you've recently had the boiler moved to another part of the house
- no powerflush or magnacleaning was carried out
- immediately since this work was carried out the rads have been warm at the top and cold at the bottom
- you have been since messing around with cleaning chemicals
- you used reputable tradesmen but haven't asked them why you only now have a problem after the work was completed
Rads cease to get hot all over due to poor water flow rate through them. Since the rads are the same ones you started out with, you must ask yourself what has changed. And the answer is, the pipework that linked them to the boiler.
Depending on how the boiler was reconnected into the existing heating system - there are two ways usually; the difficult way and the easy way - will affect how much pipe resistance has been introduced into the circuit. Too great a pipe resistance = lower flow. Lower flow rate means lukewarm rads not hot all over.
Finally, unlike some others here, I don't rate the chemical solution much. Chucking them into a system is like soaking your dirty kaks in a warm bowl of water overnight. No substitute for a washing machine.
In our industry we use Powerflush machines (akin to a washing machine and a similar size) and magnetic filters to do this work, and we run the substantial Powerflush unit's pump through just one rad (eg: shut all the others off) at a time, whilst we agitate that radiator with a vibro tool.
The magnets pick up the debris before it gets to the boiler, which considering it is haring along at 1.5metres per second, is not long. The worst thing you can do is stir up a load of debris, and then pass it through a combi, which is full of small apertures and plate heat exchangers with tiny gaps inside for stuff to get stuck and cause aggro for the rest of the boiler's lifespan.
Just as well you used reputable people, I'm sure they haven't done any of the above.