messed up my central heating system

[little_poppet]

hey guys, so i'm having issue with my central heating.
it's kind of a long story but here's the gist of it.



(a note on the diagram, the radiators in red have issues, i am not sure of the pipework from the top floor to bottom so i've labelled them as ?)
hallway radiator stopped working, had plumber come and have a look, he bled it and said if it still doesn't work, it needs replacing.
after a while, room 2 started becoming lukewarm, and then stopped working.
room 1 was starting to get a lukewarm at best instead of hot.
it'd been 10 years since the central heating and rads were installed, so i replaced all except bathroom and bedroom 1.
in all of them, i replaced singles with doubles (i was getting rid of 2 gas fires and this would be only source of heating).
at this point, top floor worked fine, of the bottom floor, room1 was lukewarm, room 2 and hallway remain cold.
i had a feel of the pipes on each of the downstair rads and got the following:
room1: 1 pipe hot, 1 pipe lukewarm
room2: 1 pipe hot, 1 pipe cold
hallway: 1 pipe lukewarm, 1 pipe cold.
i tried turning varying the flow from the upstairs rad only by turning the flow completely off was i able to get the hallway and room2 rads to heat up, although they were barely lukewarm.
i've tried adjusting water pressure in the boiler from 1 to 1.5,2,2.5 but no luck.
i've bled all the rads, and as soon as i open them, water comes out which indicated theres no air?
after a while, the bathroom rad stopped heating up, i'm having the bathroom redone and will be looking to get it replaced by a towel rad.
i appreciate it is impossible to diagnose these things online, but would appreciate advice on the possible issues and how i can go about investigating/eliminating possible issues.

thanks

 

[ChrisR]

Balance it. Shut the upstairs 3 rads at the lockshield end. If downstairs don't get hot, turn down the ones which do. If it's not happening, the downstairs rads may be sludged up, or your pump could be stuffed.
If they DO get hot, open the upstairs rads a tiny bit. "A tiny bit" is something like 1/16th of a turn. Full open would be about one turn.

A wide open bathroom towel rail would stop the heating working, completely.
Hot water would go straight back to the boiler and it would turn itself off.

 

[little_poppet]

i don't think it's sludged, they're brand new rads and on the occasions i've drained the system, emptied the rads, the water has been completely clean.
on the issue of the towel rail, when my central heating was installed, the bathroom rad was installed without a trv, i think installer said first rad on the system needs to be left fully open
in any case, my towel rail is going to be quite small and it is serviced by 10mm pipes if that makes a difference....

 

[Swwils]

You need a more accurate diagram of that is going on, including the boiler spec, pump spec, pipe sizes, lengths and rad specs.

Once you have this, you can check if the design as it stands would actually work properly.

Otherwise you could be endlessly "troubleshooting" something that is a fundamental error rather than something that is physically broken.

 

[Hugh Jaleak]

i don't think it's sludged, they're brand new rads and on the occasions i've drained the system, emptied the rads, the water has been completely clean.

Did you replenish the Inhibitor after refilling the system?

 

[little_poppet]

You need a more accurate diagram of that is going on, including the boiler spec, pump spec, pipe sizes, lengths and rad specs.

Once you have this, you can check if the design as it stands would actually work properly.

Otherwise you could be endlessly "troubleshooting" something that is a fundamental error rather than something that is physically broken.

ok, i'll try to get that info, but just to note, the system was working fine for many years, and the only things i've changed are the rads from single to doubles....

Did you replenish the Inhibitor after refilling the system?

i did indeed

 

[Hugh Jaleak]

Given your explanation so far, I'd go with Chris's thoughts above, and suggest you try balancing it first. (See FAQ's for how to do it.)

Don't worry about specs, most systems run perfectly well with a standard pump, and the fact is, it worked previously. My guess would be you've upset the balance when you changed the rads.

 

[little_poppet]

ok great, will give a a go in the next few days and see what turns up!