Radiator Flow Issue

[hashman007]

I have a 3 bed terraced house with ground floor fully concreted so all pipes feeding the ground floor radiators are dropped from the first floor.

I have a Combi Condensor Valliant 837 Boiler recently installed and rads on ground floor dont heat up uintil all rads on 1st floor have heatered and shut off via TRV.

The previous systems was a baxi back boiler running through the center of the house. New Valliant is fixed on the ground floor level feeds ground floor rads perfectly that branch from same level circuits however 2 radiators which are in the main house are dropped from the 1st floor dont get warmed up.

Any advice on how to overcome this problem without rerouting these 2 rads via a new pipe run avoding vertical drop.

I was thinking bout adding motorised valves but didnt see how this can work with Valliant Combi Condenser 837 Model Boiler.

 

[buryboy]

This looks like a balancing issue/problem.
From a cold start up, check and note which radiators get hot first.
The ones that gets hottest first, go to the lockshield valve and screw it shut, then do the same to the other radiators that heat up first.
Then go to the rads that are underperforming, make sure both lockshield and TRV valve fully open.
These rads should now get warm. Leave everything like that for around 15/30 mins, then shut down the boiler.
Just make sure no air in these rads with valves open, so bleed them.
Then turn boiler back on making sure roomstat is set at 30 degrees or more (so it doesn't turn boiler off.)
Once everything warmed up then (if possible this is better done by two people) very slowly open some lockshield valves with half turns so they start to heat up. At same time monitor the two underperforming rads that were not heating up. That's why its better if two people do this. One monitoring the rads while you open the lockshield valves.

At some point the downstairs rads that formerly didn't get hot will again start to go cold again.
You then need to screw back down some of the lockshield valves you where unscrewing on the ones that get hot easily.
So what your trying to achieve is a balance between the rads that easily get hot by closing down their lockshield valve, making it more "difficult" and increasing the resistance to the flow to these rads. Whilst at the same time endeavouring to make it easier for the system to flow to the rads you want to get warm.

Balancing large systems can be a long process of trial and error. It all depends on the initial piping runs and some times this piping needs to be changed if balancing the system as described above can't be achieved.