Radiators not refilling


Postby legspinner » Tue Oct 23, 2007 5:14 pm

We live in a terraced house with a loft extension that has an extra bedroom and ensuite bathroom. We had a couple of rooms on the middle floor redecorated over the summer and they removed two of the radiators. Now we have turned the heating back on again. I cannot get any heat into the 2 rads in the loft extension. Bleeding the rads has no real effect.

Is it likely that we have a sealed system that needs refilling? Or is the fact that the water tank is now at the same level as the 2 top floor radiators mean that they are impossible to fill, due to gravity?

The ground floor rads and 3 on the middle floor are OK, it is just the top floor ones that are cold.

Any help greatly appreciated.
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Postby htg engineer » Tue Oct 23, 2007 8:13 pm

You have bled all radiators, are the top two radiators full ?

The tank has to be higher than the radiators, also what type/make/model is the boiler that's in ? is the pump capable of heating the radiators in the loft or has a second pump been added ?
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Postby legspinner » Tue Oct 23, 2007 9:21 pm

I do not think the top 2 rads are full. When I bleed them there is an initial small escape of air, but this gradually stops and no water comes out.

Boiler is a Valiant turboMAX plus 837/2. No second pump has been added.

Thanks for replying
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Postby The Heating Doctor » Wed Oct 24, 2007 4:52 pm

The Turbomax is a sealed system boiler, so the system requires filling through the filling loop and a air vent should be fitted to the highest point. Now you have the third floor the heating engineer should have fitted an additional expansion vessel. 18litre should suffice but have it checked out by Vaillant tech services as you have now increased the static head of the system beyond the capability of the boilers internal expansion vessel.
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Postby htg engineer » Wed Oct 24, 2007 8:13 pm

Heating doctor - I have a Vaillant Turbomax and mine is tank fed too - not a pressurised system.
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Postby htg engineer » Wed Oct 24, 2007 8:26 pm

Changing the boiler to a pressurised system is an option.

When combi's are installed that are tank fed - the pressure relief valve is normally removed and replaced with a feed from the tank. So changing to a pressurised system you would need to fit a pressure relief valve and a filling loop. The tank and pipework would now be redundant.

But the pump still may not be able to get heat the top two radiators, especially if the boiler is on the ground floor. Normally pumps fitted to combi boiler are a 6 metre head.
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Postby elscripto » Fri Oct 26, 2007 8:47 am

What has changed here? As I read it, the loft extension is not new. What is new is the redecoration on the middle floor. When the radiators were put back after redecoration, were they properly balanced or were the valves just opened up fully? Could it be that the radiators on the middle floor are getting all the heat?
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Postby The Heating Doctor » Fri Oct 26, 2007 4:53 pm

I think it was this phrase that had us thinking the top floor had alterd.

Is it likely that we have a sealed system that needs refilling? Or is the fact that the water tank is now at the same level as the 2 top floor radiators mean that they are impossible to fill, due to gravity?
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Postby htg engineer » Fri Oct 26, 2007 10:56 pm

I was under the impression that radiators had just been added to the top floor - and that's why you were asking about the tank being at the same level as the radiators.

If it has worked in the past - then the tank being at this level was a pretty pointless bit of information. That's where it sent us off in the wrong direction.

As all posts in here - the clear the question / query the easier and quicker it is for us to offer advice.
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Postby coaster » Sat Oct 27, 2007 10:11 pm

just back fill the system using mains pressure balance up and hey presto all will work
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