Filling the system

S

surfrider

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Is there a procedure for filling a central heating system ? I drained the system down to replace two radiators and I'm now having problems getting some of the radiators to heat up.

I have done the usual things like bleeding & shutting down certain rads to try and force the air round.

I understand that there is a valve that has to be opened to manual before filling the system.

I would be grateful for any advice
 
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I think your talking about the three way valve . If the rest of the system is full its not that. Turn off all the radiators that are getting warm this can push airlocks through. Some systems can be a bit picky when refilled and usually settle eventually. Unless during drain down a glob of sludge has blocked pipework but this is very rare. Have you made alterations to the system?
 
Yes - fitted two new rads. I have tried to closing down radiators to move the air lock but still can't get some of the rads to heat up. Normally this method works fine but on this occasion it's not.

The 3 way valve was set to auto when filling.
 
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No. The new rads are they an extension to the system or just replacements?
 
Leave valve on auto for now. Turn h/w off, turn pump up to full speed, close by-pass valve if you have one, then close all other rads as you did before and try it. Don't forget to bleed the heating circuit next to the h/w cyl at some point.

Where are the rads? if they are on drops in a bungalow for example you may need to cut in 2 auto air bleeds on pipe work, or perhaps you have these already but you didn't bleed these if they are manual versions.

If they are ground floor in a house then ignore this!
 
Please could you explain more about the by-pass valve. What actually happens when it is closed.

In another post it was said that the boiler might start to bang !

Is it safe to close it down ?
 
I only mean close it whilst the pump is on full and you are trying to push air out, not to leave it closed forever :rolleyes:
 
As I only have a gate valve and not an automatic bypass valve could this be a reason why my boiler seems to dip in heat output when both water & heating are required.

The boiler never seems to operate at it's full capacity. It has an indicator which indicates between 1 and 4 which may relate to the number of burner that are in use. But when ever it goes to 4, it quickly drops back to only 1.

Obviously when I need hot water & heating I would expect the boiler to run at full capacity but this does not happen.

Would the fitting of auto bypass help or do I have some other problem
 
No that sounds like another problem, maybe pipe sizing or even boiler not powerful enough.

gate valve by-pass should only be open at minimum usually about 1/4 to 1/2 turn.

Auto by-pass is better option but I don't think this will cure your problem.
 
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