Here's the story.
Completely redecorated the top floor of the house (new floor / window blocked off & covered / twin velux windows installed etc. / replastered / new skirts & archtitraves etc.)

As part of the process all walls / ceiling & floor have been really well insulted with rockwool - (i'm a sound engineer - the top floor is my studio)

The result so far is staggering - I'm over the moon with it, but........

1. I have removed the two radiators that were there & connected the pipes together under the floor - I have access panels to all four pipe stems. My idea is to have a very basic underfloor heating system from the way that the pipes run around the room.

2. I have fitted 2 bleed valves (1 for where each raditiator was).

3. Repressurised the system - no leaks.

4. Bled the valves / removed what air was there - but the pipes do not get hot, but the rest of the house is roasting!

5. I then carried on bleeding the valves & simultaeniously repressurising until the water ran hot, but as soon as I shut of the valves the pipes go cool again! It's almost as though the water is stagnant.

I'm stumped!
Could there still be an air block in the system (between 2nd & 3rd floor) even if water is coming out of the valves?
Do i need to fit another 2 bleed valves at the other corners
Is it because there is no vertical force from a radiator to keep the water moving in a circuit?
Do some of the pipe need to be terminated rather than looped.

Hope one of you geniusses can help.
Tim.

Other info:
The house is 100 years old but alot of the central heating system has been replaced over the years including a new codensing boiler 5 years ago (Saunier Duval F30 e).

When both radiators were there - I kept having to bleed them cause they kept going cold at the top.

Thanks in advance.

Going to need an as fitted drawing.

Clearly there was already a design/system fault and you have made it worse.

How have you connected the pipes and what order.

What type of system is it, open vented or sealed.

Some system information may help later.

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Hi the scruff.
Photos attached - hopefully this explains / shows the idea. The right hand pipe (where the bleed valves are) is where thermostatic valves were - so I assume the water feeds in from that side.

The system is sealed, pressurised to 1.5 bar. I've often thought is there a leak? But in 10 years & some hardcore decorating I have seen no sign of water marks / leaks at all!

I've now accepted that the whole underfloor heating will probably not work & I've just ordered a 600x900 rad to go where radiator 2 was & I am therefore thinking of just capping off where rad 1 was.

What do you think?

Tim

You'll never get enough heat from the pipes, but there's no reason from the pics why they shouldn't get hot.

Have you tried turning most of the working rads off for a while

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Wow - turned off all the other rads & instantly hot pipes!!

The boiler also making alot of water noise - almost like it is filling or emptying itself

Pressure on boiler is dropping - gone down from 1.5 bar > 1.0 at the moment.

Does this tell us anything.

Cheers
Tim

Yes, you have air in the system.

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Looks like I'm in business.

All I've got to do next weekend is drain the system again to fit the radiator.

Thanks to thescruff.