Drained 2 rads for decorating. Now replaced but not heating

[ElCornDoggio]

Evenin'

I drained, removed and then replaced 2 large rads upstairs to decorate. And now they're only getting warm, and in patches, not evenly. The bottoms are almost cold, and some upper areas are actually quite hot.

It's a conventional boiler, gravity fed system.

I didn't touch anything in the loft, all valves are fully open on those two rads, and all other rads elsewhere are heating just fine.

Any clues to help get me warm please? I've a feeling that 'balancing' isn't the answer in this situation

 

[New Gas Engineer]

Sludge sat the bottom of the rad would cause something like this.

Although draining the rad should've eliminated that but I cant think of anything else. Sorry

 

[ElCornDoggio]

They're new rads, and I had a power flush last year, so sadly not that Cheers though.

These are bigger rads than the originals - could it be the boiler isn't able to produce enough heated water?

Or because I drained two rads, there's now not enough on the system? Guessing it can't be that as surely it would refill automatically from the loft..... But I'm an amateur, so who knows!

 

[New Gas Engineer]

They're new rads, and I had a power flush last year, so sadly not that Cheers though.

These are bigger rads than the originals - could it be the boiler isn't able to produce enough heated water?

Or because I drained two rads, there's now not enough on the system? Guessing it can't be that as surely it would refill automatically from the loft... But I'm an amateur, so who knows!

Possible air lock. Maybe

 

[ElCornDoggio]

Possible air lock. Maybe

Is there an easy way to check for that? Or cure it?

 

[dancinplumba]

Is there an easy way to check for that? Or cure it?

try turning off all other rads , flushing doesnt mean a great deal to be honest

 

[Best]

Unlikely to be an airlock if you haven’t drained the pipework and rest of system.
Slow flow through radiator, so might be air in radiator if it is a designer type. Or your radiator valves haven’t opened fully. A TRV can stick down

 

[ElCornDoggio]

I'll give the suggestions a go tomorrow.

Thanks. You're a helpful bunch

 

[Rob Foster]

I'll give the suggestions a go tomorrow.

Thanks. You're a helpful bunch

Shoot the system up with mains water , connect hose to outside tap, then on to drain off on heating system open drain off open outside tap slowly then bleed all rads lowest first. Watch out turn outside tap off cause you can overfil the little feeder tank in the roof, water comes out of over flow. A good blast like this cures most ills
Rob Foster aka centralheatking
Good luck and let us know how you get on