Air Trapped in sealed Boiler system

[SproutsDad]

I have a sealed heating system with Vaillant Thermocompact boiler. It was working fine then yesterday I drained it to fit new radiator and revised pipework in hallway with new drain off valve.

Before refilling the system I noticed the filler loop check valve screw was weeping water and was stuck, so I fitted a new similar one R24 from Screwfix, also with non return valve but now two black valve knobs, no fiddly screws.

I refilled the system and bled radiators bottom to top of house. All air appeared to be removed and pressure was up at 1.5 bar, as heating engineer had earlier advised and written on the boiler. That was last night, no apparent problem so far, very small amount of air in system but that could be bled out over the coming days.

This morning I noticed the pressure was at 2.2 bar, too high? So to reduce it I tried what I have read, to uncouple the filling loop 'in' end and opened the service valve to let some water out into a bucket and pressure on boiler would drop. Nothing, no water, that must be the non-return valve stopping water coming back. So I opened the new drain valve in hallway and let water out via hosepipe, approx 6 litres I would think, to reduce the pressure - was that wrong?

I then put boiler heating on, turned it off after a few minutes, let it settle and bled the radiators again, lots of air came out but the pressure has only reduced slightly to 1.9 bar. Turned boiler on again and there is clearly air in it. When it fires up the temp rises then races up to approx 90 deg C then cuts out. I can hear air or lack of pressure in the boiler and have turned it off. Tried again but it won't clear the air or fire up for long. There is a small separate expansion vessel but can't see the schreider valve normally on them, it's also pretty inaccessible, hope I don't need to go near that!?

What have I done and how can I put right what had until then been quite a successful job? Seems like I have screwed up the last stage, or worse?

Your help would be much appreciated.

 

[Dan Robinson]

You put the filling loop on the wrong way. Otherwise just let the system settle down.

 

[SproutsDad]

Dan, thanks for the reply.
Appreciate your help but if the direction of the new filler loop is wrong, then it was always wrong? Please see photo below and confirm if you still think is the wrong way round.
I replaced like for like and the non-return valve is in the same position and the flow direction arrow is in the same points the same way as the original one.

I'm letting the system settle but for how long? A few hours have passed and the boiler won't even fire up now. Pressure shows 1.8 bar.
Many thanks

 

[SproutsDad]

Any other views on this please?
I am stuck with a system that won't fire up, the pressure has come down to 1.8 bar and the radiators seem to be bled out and free of air. I think that draining from the hallway drain valve may have made the air lock situation bad. It should have been done from the filler loop, but it wouldn't drain that way, see first post on this thread.
From the pics, is my filler loop the right way round?

Any help to get this fired up and air free would be much appreciated.

Many thanks

 

[mcmoby69]

sounds like air has collected in the pipe work above the boiler, if you dont have any way to get rid of the air (automatic air vents) you are going to have to get rid of it manually.

you will need to run off more than 6 litres. set the boiler stat to very low, put your hose pipe back on in the hallway and drain again, keep topping up as necessary. you will hear lots of noise as it starts to clear, rads will need bleeding as the water circulates.
whole procedure might take a while.

 

[SproutsDad]

Thanks for the response.
I understood that this Vaillant Thermocompact boiler was auto-venting.
Somebody suggested bleeding/ venting the pump, but it is inside the boiler.
If I have to bleed it manually, should the the boiler be turned off during the bleeding?
With the stat turned down (Danfoss TP5 programmer stat) the boiler shouldn't fire up anyway I thought?
I normally bleed starting downstairs and working upstairs -then reach the boiler. 16 radiators in all.

>>I'm not sure if it is relevant or not, but this boiler is upstairs in a large airing cupboard, so all pipework goes downwards from it, nothing above it.
The only thing higher than the boiler is a 6ft high column radiator in the bedroom next to it.

Somebody suggested bleeding/ venting the pump, but it is inside the boiler and isn't the whole unit supposed to be self/ auto venting?
Youir advice is much appreciated.
Many thanks

 

[Dan Robinson]

You put the non return valve on the heating side instead of the main. That was what I meant.

 

[SproutsDad]

Thanks Dan.

Filler Loop - this loop was really an aside I think, it was the method I had read of for draining off some of the water to reduce the 2+ bar pressure. If you really think it and therefore the non-return valve is on the wrong way round, then so was the old one installed on the system when new 12 years ago by what I understood to be a reputable CORGI installer, local medium sized company who have done good work for the family in the past? But it could be wrong?
>> See my picture of both old and new ones.

But when it's turned off on both service valves it surely shouldn't affect the system with regard to the air in the system? It's just when as I did, tried to drain out some water and it wouldn't flow back because of the non-return valve. So I drained via the radiator drain valve, then I got the current problem with all this air in the system.

This is what I really need the help with >>>>
Current status on air in system:- This morning the pressure is down to 1.5 bar. When the room stat was turned up to 22 deg it fired up, orange light came on, but only for 10 secs then temp raced to 102 deg and it cut out.
Wish I had left it at 2.2 bar yesterday and not drained any water off, it might have dropped and settled anyway??
Do I do as has been suggested and carry on draining and bleeding?
Please note the boiler is upstairs and the highest part of the system, so no pipework above it, the highest thing is a 6ft column rad, on same height as boiler.

>> Help please anyone with how I get from where I am?
Currently using immersion heater for hot water but with this 'summer' will need heating soon.

Many thanks

 

[gigz]

Is there not a drain off on the boiler pipework ? If not, turn the gas off at the meter and run the boiler. You will have to keep resetting it but this will stop it overheating.

 

[simond]

There's an automatic air vent inside the boiler above the pump.

If the cap has been closed you will never get the air out.

On the thermoCOMPACT you can remove the white casing without touching the combustion seals, so will not affect the safety of the thing as long as you don't fiddle.

Simply undo the two screws on the plastic fascia by 90 degs, hinge it down. Then lever the white painted metal case away from the wall at the bottom (there are two spring clips that will let it go), and lift off the upper rear hooks.

You will see the pump at the lower right, with the air vent.

Don't open the metal square combustion box above, you will need an RGI if you touch this (there is no point in opening it anyway).

Refit in reverse.

 

[SproutsDad]

Thanks very much, I assumed the pump might be running dry by the sound of it.
I have the front panel down and case off, where to now?

See my picture, the pump has a switch/speed selector on top and this cylinder with a black cap on behind it, is it that?
What am I looking for and how do I bleed/release the air?
And is this all with the boiler on or off and room stat triggering the heating or what? Sorry, don't want to make further wrong moves.

I haven't touched anything yet.
Awaiting your instruction.
Many thanks

 

[nortonj]

Thanks very much, I assumed the pump might be running dry by the sound of it.
I have the front panel down and case off, where to now?

See my picture, the pump has a switch/speed selector on top and this cylinder with a black cap on behind it, is it that?
What am I looking for and how do I bleed/release the air?
And is this all with the boiler on or off and room stat triggering the heating or what? Sorry, don't want to make further wrong moves.

I haven't touched anything yet.
Awaiting your instruction.
Many thanks

View attachment 84369

Make sure the cap circled isnt screwed down tight, they sometimes leak so people screw them down when all the air is released.
Unscrew (not all the way) and you should hear air hissing out

 

[simond]

Good luck

 

[SproutsDad]

Thanks again everyone.
Nortonj - I opened the (shut) black cap and air rushed out then stopped with a gurgle, but no leaking water. I suppose if it is a one way auto vent (?) it should just let the air out and stop at that?
Do I now leave it slightly open? Half a turn?
The boiler pressure now shows 1.3 bar.
Can I put the case back now and re close the front - I could probably have accessed that cap without removing the case, but no problem.
>> Where from here now?
> Should I close up and run the boiler with heating on?
> Or bleed anything out in the rads first while still cold?
> And what about this filling loop? Is it / has it always been the wrong way round? See picture. << someone please confirm, I am confused by this? Doesn't the arrow on these valves indicate the normal low of water?
If the non-return valve is working the wrong way then it will need swapping around. Otherwise it won't protect the clean water supply. And I might need to release more water/pressure in the future and then it won't drain off.

All help very much appreciated.
Thanks

 

[gigz]

Would'nt worry about the filling loop, just disconnect hose and cap ends when not using it. Does your boiler not have the purge program (p0)? See M.I.'s on how to do this.