2 Tall radiators not getting hot only tepid

[Tally101]

Hi All
I have 2 tall rads in the kitchen thats only getting tepid, I have tried to balance the system and can get the 2 rads hot but when I open up the rest of the rads the 2 tall ones go tepid again, I have a Vailant Ecotec 615 plus with 13 rads. I had the pump in the boiler replaced about 2 years ago as it wouldn't heat upstairs.
Any ideas of how to solve this please.

 

[terryplumb]

Are they recently installed, or been in for some time working perfectly well ?

 

[Tally101]

Been in about 6 years they have all ways been a bit temperamental.

 

[terryplumb]

If you close every working radiator off by it's TRV ( or wheel head if no TRV),don't touch their lockshield valves ,do the two problem rads IMMEDIATELY heat fully ,or does it take quite some time before they do ?
If they do immediately heat fully the system isn't balanced. If it takes a long time there is an issue with the plumbing to those rads ,or the rads themselves.

 

[Tally101]

When I tried to balance them, they was the first I opened , 1st one heated up quick the other took a while , but the pipe coming into the rads get really hot so hot water is getting there

 

[terryplumb]

A lot of vertical rads must have the flow going into a specific side of the radiator,as they have a baffle inside to divert the incoming heated water upwards.
If yours are such ,and not correctly plumbed in they will never work well.
From a cold start the flow is the pipe that heats up first ,and quickly.
Are yours both the same radiators ,and is the flow going into the same side on both radiators ?
Microbore pipes and vertical rads are not ideal either ,what diameter pipes feed yours ?

 

[Tally101]

The flow into both are on the right hand side, yes they are the same rads , and both are fed by 10mm micropore. I will ring the rad company and ask if they have baffles in.
Thanks

 

[terryplumb]

Show us a picture of the rads

 

[Tally101]

just realised the rads have been in 6 years when fitted by the new kitchen people. I dont know what make they are. photo attached

 

[oilhead]

Are both rads off the same single 10mm feed? If so, you may be trying to get a quart out of a pint pot.

 

[Tally101]

No either side of the house

 

[dilalio]

It's down to hydronics.