No hot water after drain down

[jamesab]

Hi folks, hoping for a bit of advice please!

I have an open vented system which I've recently drained down in order to adjust some pipe work for a new towel radiator in the bathroom (not yet fitted).

I've now refilled the system and bled all the radiators (with the exception of one which has a rounded bleed valve) and the radiators work as normal, but no hot water. The boiler kicks in for around 10 seconds, then cuts out and restarts. Now having to use the immersion heater as a backup.

Unfortunately I did not have the foresight to check the F&E tank before refilling, but I've since checked it and found that it is FULL of sediment, some of which will have made it into the tank.

I don't know whether the issue is an airlock or a blockage, so hoping someone can shed some light on possible causes and hopefully a solution.. I have attached pics of my setup.

Thanks in advance

 

[ianmcd]

on the pic of your HW cyl, turn everything off, then latch the motorised valve open, then open the bleed point at the top of that pipe till water comes out then close it and turn on the HW and see if it now heats the cylinder, for future referance when draining and filling a system you need to latch all motorised valves open while doing so , that is what the levers are for

 

[Madrab]

+1 coil's airlocked, needs bled.

 

[jamesab]

Thanks for your replies, will give this a go now and report back.

Regarding the F&E tank - is this amount of sediment normal or is it a good idea to remove and give it a good clean?

Cheers

 

[Madrab]

Seen a lot more filthy F&E cisterns than that. No reason not to clean it out though. Just bung up the feed before it gets stirred up to avoid any of it heading south.

(edit) Should really have a cover/lid to stop that happening.

 

[jamesab]

Ok thanks - will give it a good clean out.

Tried opening the valves with everything switched off and bleeding the cylinder as suggested - only a tiny bit of air came out then water, the boiler is still in a restart loop.

Both the flow and return pipes (above the boiler) are red hot. The pipes above the valves are also hot now and weren't before, but I'm not sure whether the immersion heater has something to do with that?

Any other suggestions?

Thanks again!

 

[Madrab]

Turn off the immersion.

Keep the manual lever open on the 2 port valve on the right hand pipe then run the boiler and then open that manual valve again and see if there is more air. Is the pipe with the valve on it hot and the one to it's left cooler but warm (would be hotter if the hot water is fully hot).

May need to crack the nut on the left hand pipe in case air has actually got into the coil. Gravity fed systems can be a pain to move airlocks like that.

 

[jamesab]

Thanks for trying to help me sort this!

Sadly still no joy with the bleed valve. The pipe below the valve is boiling hot, when the boiler is on and the pump is running, the pipe above it gets lukewarm, then freezing cold when the boiler switches off.

Strangely I've noticed since turning everything off that the boiler seems to be kicking in randomly, despite there being no demand. I'm not sure whether this happened before though.

I've loosened the nut on the return pipe, but the olive is tight in the fitting which I'm reluctant to pull on... unless you tell me otherwise!

Is there a possibility the feed pipe could be blocked from all the crud in the cistern?

Cheers

 

[Jajodu]

Possibly faulty valve?

 

[Madrab]

When you open the 2 port valve manual lever, can should feel resistance and hear the valve motor spin open?

As far as the olive is concerned, while pushing the pipe towards the cylinder, loosen the nut until it it's almost fully off, pushing the pipe in will stop the it from releasing, then tighten the nut back up about half way, with a towel below then tap on the pipe with the adjustables and wiggle it from side to side and the olive should crack free. Do this with the system off. Once the olive's free tighten back up and then fire the system back up and crack the nut again and pull the pipe a little (tub below the pipe) and there should now be flow through the valve, the coil and out of the loose pipe past the olive. Once it starts to warm up then tighten the nut back up and see if it all now flows happily.

 

[jamesab]

Yes the valve seems to be operating normally. The reason the boiler remained on was because I left the valve open (doh!).

I've just undone the nut on the return pipe and lo and behold, LOTS of air came rushing out! The pipe above the valve on the return valve is now hot too.

So I'm hoping that's solved the issue - the boiler certainly seems to be staying on for longer now. I won't know for sure until tomorrow as I've had the immersion on again today, but it's looking positive.

Can't thank you enough for your help, you've saved me potentially hundreds in engineer costs!

 

[Madrab]

Glad to be of help, one of the reasons we help on this site

Basically air had had gotten into the coil during the drain down and due to it's design it had ended up trapping it when the system was filled back up.

As long as the return pipe start to warm up now as the water in the cylinder heats up and it should just keep getting warmer as the cylinder reaches set temp.