air lock after refill

[nomsmithy]

I have a gas Baxi boiler to radiators and a gravity-fed HW. The HW circuit to cylinder has a motorised valve controlled by a timer.

I have part-drained the system (using drain valve at bottom rad) to change a leaking TRV upstairs, tying-up the ball-valve in the header tank first. Then refilled. I drained the system into a large plastic water carrier and, when refilling, bled radiators in turn.

All is working well, except:

1 - I found that not all of the water will fit back into the header tank now. About 3 to 5 litres remains. There is no air in the radiators at all. I have just rechecked.

2 - the hot water (in the cylinder) is taking longer than usual to reach temperature.

The only thing i can think of is that there might be an air lock in the HW heating circuit. (I did, maybe, have the motorised valve closed when refilling. But wouldn't this just escape when the valve was open?

I could drain the HW heating circuit down by the boiler?

Any advice please, so i'm not on my own?

Thanks
nomsmithy

 

[Softus]

Clearly there's air in there somewhere.

Is your system fully pumped? If so, can you shut off the heating circuit to force flow through the cylinder coil?

I suspect that if you leave the system running for a few hours it will sort itself out, as long as the pump isn't airlocked.

 

[Bamber gaspipe]

Clearly there's air in there somewhere.

Is your system fully pumped?

Not with Gravity fed Hot water Circs.

Not wrong again are we?

 

[Softus]

Is your system fully pumped?

Not with Gravity fed Hot water Circs.

Some people say "gravity-fed" when they mean open-vented. I'm not making any assumption in either direction.

Do you have anything helpful to add to the topic?

 

[Bamber gaspipe]

Is your system fully pumped?

Not with Gravity fed Hot water Circs.

Some people say "gravity-fed" when they mean open-vented. I'm not making any assumption in either direction.

Do you have anything helpful to add to the topic?

Just a quick one, if he had gravity hot water circs would he have a motorised valve ? if so, why?

 

[Softus]

Just a quick one, if he had gravity hot water circs would he have a motorised valve ? if so, why?

Well spotted - whilst it isn't impossible that he has a MZV on a non-pumped circuit (after all, my own system is like that), it's unusual, which is precisely the reason I became suspicious and sought confirmation.

 

[Bamber gaspipe]

Just a quick one, if he had gravity hot water circs would he have a motorised valve ? if so, why?

Well spotted - whilst it isn't impossible that he has a MZV on a non-pumped circuit (after all, my own system is like that), it's unusual, which is precisely the reason I became suspicious and sought confirmation.

Why have you a motorised valve on a non pumped circuit? is it a three port?

 

[Softus]

Nope - it's a 28mm two-port.

I inherited a cr*p old system with no controls other than boiler stat, so I've added controls bit by bit, leaving the Concord WRS alone because remaking connections on the HEX tappings would be too much to ask of such an old unit.

Naturally I had to add a bypass to circulate water when both MZVs shut off with inertia in the water and heat still in the boiler.

It works. And one day the boiler will die, and then I can do it all properly.

 

[Slugbabydotcom]

Is there a manual air vent that you can open on the flow pipe to the cylinder?

 

[Bamber gaspipe]

Nope - it's a 28mm two-port.

I inherited a cr*p old system with no controls other than boiler stat, so I've added controls bit by bit, leaving the Concord WRS alone because remaking connections on the HEX tappings would be too much to ask of such an old unit.

Naturally I had to add a bypass to circulate water when both MZVs shut off with inertia in the water and heat still in the boiler.

It works. And one day the boiler will die, and then I can do it all properly.

You`re not a bad Heating installer for a plumber/computer geek.

(The three port was a red herring).