Advice with balancing radiators (Worcester Combi)

[warehouseman]

Worcester Combi 24 cdi . 7 Radiators. No TRV's. Testing system prior to winter. Radiators 1-3 upstairs get very hot in a few minutes. Radiator 4 downstairs in lounge hots up a few mins later. Radiator 5 on other side of lounge gets just about OK, Radiators 6 (in extension) added a few years later gets luke warm, radiator 7 furthest away in extension 'cold'. That's the order of heating up. They were working earlier in the year albeit not too hot. The pump in the Combi is new. Brit Gas engineer said system this size didn't need balancing ( he didn't even try) but left me in the lurch unable to get radiator 7 working at all. Have tried a bit of re-balancing myself but not sure of a couple of things. I completely turned off both ends of radiator 6 in utility room (as not really needed) and radiator 7 started to get warm! Upstairs I've turned down the lockshield valves so there's probably less than a quarter turn up on each one. Done the same on radiator 4 downstairs. Of course this makes those radiators slightly noisy by the reduced stream but they still get hot albeit more slowly. It's made radiator 7 warmer but not nearly hot and it takes about an hour to get it to that 'warm' state
Firstly, is it normal and ok to turn the lockshield valves even further down to almost closing point? Secondly, I've noticed that Radiators 1 and 2 have the 'flow' at the opposite end of the lockshield valve which I understand is normal, whereas 3 - 5 has the flow at the lockshield end, radiator 6 is like 1 and 2 and unsure of radiator 7 as caps are missing. If I open up lockshield valve 5 downstairs (even though the flow comes through it), it gets hotter to the detriment of 6 and 7 but I don't want to turn it down as itself will then go to 'warm'. Throughout all this I've completely opened up the 'heat control' valves at the opposite end to the lockshields. Is this correct? My main aim is to get final radiator 7 hotter but am presently failing.

 

[ShaunCorbs]

Croppie's Balancing Thread.

this should help

 

[warehouseman]

Croppie's Balancing Thread.

this should help

Yes I did read all that while searching for help but I haven't got the appropriate thermostat and, in any case, the temperature of the 'flow' pipe constantly changes, depending if the combi is pumping or not.

 

[ShaunCorbs]

appropriate thermostat ??

You mean trvs ?

 

[warehouseman]

appropriate thermostat ??

You mean trvs ?

No, 'croppies balancing thread' says special thermometer to measure the pipes to a differential of 12c should be used Firstly most plumbers say this is unecessary and can be assessed by hand and secondly no one round here seems to have one. Also, I do not have trvs .

 

[ShaunCorbs]

Just an infrared thermometer

And it can't

Bet they don't balance the system

 

[Old Account]

If you have got lockshield valves I'd turn them down ... furthest away full open and closest one just cracked open. But as shaun mentioned croppie way is ideal

 

[JusKel]

Sounds like your system is under-sized. It's most likely the especially the extension has been piped in 15mm pipe tee'd from 15mm pipe.
Alternatively, if the boiler has a modulating pump then it could be modulating too low to get heat to the downstairs radiators. Some pumps modulate down to 30% while others only go as low as 70% ( 70% is usually enough)