No heat to downstairs rads

[staithes14]

I have a fairly old vented system, hot water cylinder and a Glow-worm Fuelsaver30 boiler. The pump was renewed 2 years ago for a Gundfoss, which is running OK. I've just replaced the 3-way valve as previous advice on here indicated the head was shot. All seems ok; the electrics are working fine and there's no leaks.

Whilst fitting the valve I had the system completely drained down (incidentally the water was pretty clear). I turned the water back on and refilled it, then bled all the radiators, upstairs first, beginning with the one closest to the cylinder. All fine, but when I put the system on, only the two closest upstairs rads warmed up. The rest, mostly downstairs, stayed cold. Tried bleeding them again but no joy.

I balanced them all just last year. The new valve shouldn't require rebalancing the radiators should it?

Anyone any idea why this is? Is the order in which the rads are bled after refilling important? Could that have put an airlock in the system? Everything else seems fine, so I'm at a bit of a loss. Cheers.

 

[seco services]

sounds like an airlock in the pipework shut the hot rads and the flow should push the airlock out.
then reopen the other rads when the cold ones get hot.
if you have balanced the system count the turns on each rad so you can open then to the same position.

 

[staithes14]

OK cheers. Just closed down the hot ones and there's some heat coming through downstairs now. Not exactly toasty though. Just warm. I'll give it a while to see.