Cold radiators in loft

[loftissue]

If your radiators are getting warm at the top , but cold from the middle downwards, that suggests to me they are full of sludge. Have you tried removing them and flushing them through outside? Having said that, it's hard to imagine they have sludged up so much in only 1 year, so maybe flow may be the issue.

I did successfully remove the sludge from all the pipes in the loft, but it took a long time and required me to take up floorboards under the radiators so I could remove T joints/elbows to push in long pieces of wire to dislodge the incredibly hard sludge that had built up at various places within the pipe (connections) and which couldn't be removed by chemicals.

Last year I refurbished the house bathroom and installed wet underfloor heating. I needed to run a brand new flow and return to the bathroom, which is at the other end of the house to the boiler, so designed this to also provide a new flow and return for the loft. I ended up installing two new runs of 22mm pipe which provided the loop (supply and return) for the new bathroom underfloor heating manifold, but also for the loft radiators, by fitting a Honeywell 2 port valve, just after the UFH manifold supply. I also took the opportunity to modify the routing of the pipes in the loft so that it was no longer a "star", and they are now connected up in parallel i.e. one after the other. In addition to this, and at the advice of a heating engineer I use, I also had a Low Loss Header installed and an additional pump, both of which I'm sure would help with flow rates in my system.

So far, I haven't had any further issues with the loft radiators, but I also ensure their valves are always fully opened to keep water moving through them. In the Summer, when the CH isn't really being used, I tried to remember to turn it on every week or so. When I say turn it on, I mean increase the temperature of the thermostat so that there's a demand for heat and leave it like that for an hour.

My system is getting quite complicated and now looks like this:

View attachment 80253

Hi there, thanks for your comprehensive reply. We've removed the loft radiators this morning and flushed them. Not much sludge in them so back to trying other things you've mentioned. Our loft rads are added on to current heating system and someone did mention we need a 22mm pipe from boiler upto loft rads for flow and return...which we think is what you suggest? Hubby now looking at a pump. Our loft pipework is along skirting boards thankfully so no taking up floor boards but we're unsure if there could be a dent in the plastic pipework going from loft bathroom to bedrooms one and two. It's driving us mad, especially paying out soooooo much money for extra bedrooms!