Do I bled rads before -repressuring boiler?

[t45]

Hello,
Was wondering if anyone could give me a step by step guide on how to re-pressurise my boiler and also bleed radiators?
Have detached a rad and reattached it.
Have not at this stage opened the lockshield valve nor bled the rads.

Do I:

1. Check all nuts are tight so no leaks
   
   
2. Open lock shield valve (5 turns for me) - should i hear water filling the rad?)
   
   
3. Open bleed valve using key? (turning anti-clockwise)?
   
   
4. Run to the boiler and start to fill it with pressure using the filling key – aiming to reach 1.5 pressure reading?
   
   
5. Then run back to radiator and close the bleed valve (clockwise)?
   
   
6. Run heating then switch off
   
   
7. Re-check boiler pressure to see if pressure stayed 1.5
   

OR DO I:

1. Check all nuts to check tight for no leaks.
   
   
2. Open lockshield valve (5 turns)? Should I hear water filling the rad?
   
   
3. Walk to boiler and repressurise using filling key until reached 1.5?
   
   
4. Return to rad and open the bleed valve (anti-clockwise)? Listen for air coming out and look for water squirting out?
   
   
5. Lock the bleed valve once water started to squirt out?
   
   
6. Run heating then switch off
   
   
7. Re-check boiler pressurise stayed at 1.5
   

Have the gist of it but a little confused over the order for bleeding rad and topping up boiler pressure.
Any help would be gratefully received.
Also once pressure topped up are there any things that i should be looking out for just to know that I’ve done it right. Of course will look for leaks on valves as I may not have tightened then enough.

 

[Stadan20]

Make sure all bleed valves are closed first , then fill system and bleed one rad at a time

 

[t45]

That’s really helpful Stadan – thank you so much – so i shall fill re-pressurise to 1.5 the run to rads and then bleed each rad one at a time using my bleed key and turning a/c - -i expect to hear air and see water squirting out, yes? So maybe a cop or bowl would be useful.

Could I just check that after I bleed each rad do i then check to see if the pressure drops
OR
Is it best to bleed all rads then go back to boiler and check pressure?

 

[t45]

silly question but how do I know if the bleed valves are closed - I assume they are currently closed

 

[terryplumb]

bleed valves are closed by turning clockwise. leave boiler off and raise pressure to 1.5 bar using filling loop.close filling loop valves when 1.5 bar reached. go to rad that you have worked on and open lockshield and the other valve ( wheel head or trv). check for leaks on the joints. open bleed valve ,only half a turn or so ,having a towel ready . air comes out first then a constant stream of water ,at which point you close the bleed valve.re check joints for leaks.go back to boiler and check pressure ,if less than 1.5 bar top up. check other rads ,and bleed air / top up boiler as needed. be aware with bleed valves if you open them too many turns they fly out !! And so will water ! half a turn is usually enough to open ,maybe a bit more if no air comes out. when all rads have been bled and boiler pressure is 1.5 bar ,turn on boiler and run central heating ,pressure may drop a bit so top up if it does. go back and check radiator for leaks ,which may develop when heated up due to expansion. hope this helps .

 

[t45]

Many thanks Terry - this is really helpful and very much appreciated.
My entire boiler/CH system has been switched off for a while whilst worked on rad so i assume I should switch it on (and perhaps reset it) and then follow the procedure of repressuring and bleeding rad until correct pressure is met. I have a WB combi Greenstar compact.
Could I ask one more question please relating to the LOCKSHIEDS ON EACH RAD – should these be opened fully – I am led to believe that these valves should remain fully open once system is up and running.....
I shall set up TVrs too to about 3/4
Very much appreciated

 

[D_Hailsham]

Could I ask one more question please relating to the LOCKSHIEDS ON EACH RAD – should these be opened fully – I am led to believe that these valves should remain fully open once system is up and running

Quick answer: Do NOT touch the lockshield valves; they should have been set by the system installer.

Explanation: The lockshield valve is used to adjust the flow through the radiator so the correct temperature drop is achieved across the radiator. This ensures that the correct heat output is produced. This is called "balancing". I said "should" as some installers mistakenly believe that it is not necessary to adjust the LS valve if there is a TRV fitted to the rads as the system will be self-balancing. This is not true!

I shall set up TVrs too to about 3/4

It's a TRV; TVR is a car!

You set a TRV so the room temperature is what you want it to be. It may be 3 in one room and 4 in another, for the same room temperature.

 

[t45]

Thanks Hailsham

Im afraid i closed the Lockshield valves when I isolated the rad in order to take it off. I was advised to do this.

I have now put the rad bac on its brackets but i am unsure about the LS valve – i believe i turned it 5 times so I assume if i turn it in the opposite direction 5 times it will open the valve.

I understand about the manula control vales

And yes you’re correct TVR is a car!! Fast one too!

PLEASE COULD SOMEONE CLARIFY FOR ME WHAT I SHOULD DO WITH LS VALVE. I ASUME THAT THEY NOW NEED TO BE OPEN and RADS BLED.

I am not skilled enough to 'balance' the whole system

 

[terryplumb]

have you closed lockshield on All your rads ,or just one you worked on ? if just the one open it up fully and see how it performs. if you have closed all other rads ,without noting how many turns ,ON EACH one , it took to close ,then you have a bit of work to do to balance the system , as DH posted above. you could open all lockshields fully ,and see what the results are . if all else fails you may need to get someone in to do it for you.

 

[t45]

many and much thanks terry
I have closed all bleed valves on all rads (clockwise turn)
On the rad I have just worked on I have opened the LS valve (5 turns and TRV (set to 3)
However, there is one radiator which is baffling me as I cant remember if the LS has been opened or closed and what its current position is with the LS valve. I assumed that the LS valve was closed and so tried to turn the spindle (turning anti clockwise) but it wouldn't budge so would this suggest that it is indeed already OPEN???
What made me scratch my head though was when I went to turn the TRV (It was fully closed) there was sound of water coming through pipes and perhaps into rad...in your opinion what would this suggest?
I am ready to repressurise boiler but now that I have hit this hurdle I have to try to work out this radiator and what to do...
Any thoughts on this? Just to clarify it's when I turn/open TRV from being fully closed that the water sound occurs???could this be linked to LS valve?

 

[terryplumb]

water goes into a radiator thru both pipes when filling the system with water. so have the trv 's open fully when you are bleeding air out.when you opened the trv you just allowed water / air into the rad. no problem .crack on.

 

[t45]

Hi Terry,

Much thanks – I did crack on and i bled the rads and repressurised system with success.... so thanks very much for your guidance and ideas.

When I bled the rads I only had trv’s open at 3 and 4 - i now see that i should have opened them fully at 5 when bled.

There is one rad that is a bit cold along the top so would you just bleed it again and open the trv to 5 and then repressurise again?

The pressure seems to be fine staying at 1.5 but i would like to deal with this cold spot rad now before winter is upon us.

Do you think it’s good idea to just bleed it once more with trv open fully?

Much thanks!

 

[terryplumb]

if it's cold at the top ,and hot lower down , it's got air in the rad .so bleed it and top up pressure if need be.