Gravity fed CH issue

hicky

Old-Salt
Ok, I've had a loft conversion and the header tank has been moved into a storage cupboard in the loft eves raised on a platform roughly 10 inch from the flooring level.
We've had two rads fitted to the rooms created in the loft, the plumber has said these won't work properly due to it not having enough pressure(I presume gravity).
He said he's filled them the best he can and they're only warm half way up as if they're ha;f filled. This was last Friday and I've since bled everywhere and they're the same.
There's a pump under the floorboards in the first floor.....am I expecting too much from the system or is he being a mong?
I've only had experience with pressurised CH before so this older system is "new" to me.
Ta
 

DAS

Old-Salt
It's easy enough to convert an open system to a closed (pressurised) system. Would have thought the plumber would have mentioned it.
 

Mrsheeny

Old-Salt
The clue is in the title - it’s a header tank and needs to be at the highest point in the system e.g. the head.

If the header tank is on a level with the radiator the radiator won’t fill up past it’s equal height in the header tank, just like a U gauge (google it).

What you’re thinking is to try and bleed the rad when the pump is running thinking there’s pressure in the system but you’re wrong, if this was the case you’d have water piss out everywhere from your header tank when you turned your heating on, I understand why you think that but it won’t happen.

Can you not raise the F & E (feed and expansion) or header tank above the rads? That’s the only way or its Hobson’s choice.
 
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hicky

Old-Salt
I wasn't there when the plumber was....the builder done most of the remedial and the plumber to finish off as the whole conversion isn't done yet.
I understand the principle of it but wondered if there was a workaround.
 

Mrsheeny

Old-Salt
I wasn't there when the plumber was....the builder done most of the remedial and the plumber to finish off as the whole conversion isn't done yet.
I understand the principle of it but wondered if there was a workaround.
You might have gotten away with underfloor heating.
 

DAS

Old-Salt
As Mrsheeny says or convert. Those are the options.

Edit: Also what Maximus says. Any which way money leaving your wallet is involved.
 

hicky

Old-Salt
Ah bugger. The rads were an afterthought as the loft has more insulation than screwfix stock but living on the edge of the moors I wanted something to take the edge off the room. I suppose half full will have to do unless I can source shorter rads cheap.
Thanks all.
 

DAS

Old-Salt
I have a cunning plan................


Cut a hole into room below and lower rads to below header tank height. Hey presto - fully working rads
 
You might have gotten away with underfloor heating.
He'd have gotten away with it if it hadn't been for that pesky plumber...
 

hicky

Old-Salt
Is that as high as the header tank can be raised ?

A rad half full of air will be prone to corrosion.
I'll be looking at the 300mm rad solution when I get home to try to avoid this, I think that and additive will be the only solution.
 

giatttt

Swinger
Is it a closed (pressurised) system? If so the pressure would normally come from the mains side of things and the hot circuit pressurised from that at setup.

Otherwise it is down to the circulation pump to be able to provide enough head to get the hot water to your upstairs radiators. Try closing all the downstairs radiators and if it improves upstairs then get a bigger pump.
 
Loosen the joints on the rads and turn them to 20 degrees off the horizontal. Tighten joints, bleed rads and job jobbed.
Beat me to it, I did that in my loft conversion and it worked a treat, in saying that there was loads of room and it wasn't being used as a living/sleeping space.
 

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