we have just had a radiator removed upstairs and a new towel rail fitted about a meter away since then 2 of the radiators downstairs won't work. If we turn all the other radiators to off and leave these 2 on full then they work. We have bled all the radiators and there is no air that we can get out. We were told they fitted the towel rail using an airlock rather than draining the system.
I am having exactly the same problem but the plumber drained the system down and did not use an airlock method. I have a microbore system and was told that this could cause airlocks due to the hanging down of the pipework between the joists - seems reasonable. I also tried running individual rads bleeding out air and building up to the full system and everything worked. BUT when the system ran up in the morning I found the problem was back with me. I thought that maybe the pump was not getting enough water around the system to feed all 16 rads or the Mid Pos Valve was stuck. I used the locking lever to place the valve in the mid position. to ensure that both CH and HW systems were being fed equally and I found that all my rads warmed up. It may be that I had a problem for some time but it was only when I came to closely examine the system operation that I found an existing problem. You may have a similar situation, especially if you have a number of addons due to extensions.
Since then I have replaced the valve actuator but while the rads and water heat up OK, the boiler does not shut down even with the programmer and stats not calling for heat or hot water. If I drop the power off at the fuse and then reset all is fine until the calls cease and the boiler still takes no notice! I am now studying the electrics carefully as, frankly, given the obvious state of the wiring at the central JB anything could have been fudged when the system was installed in 1985 and mapping new colour codings onto the original is not easy and may not be logical either.
I'm not quite sure what balancing your plumber will do for a whole day unless you live in a 10 bed mansion!
You are in a difficult position: clearly they are looking for excuses for the failure of their installation work and I suspect will suggest power flushing the system, this may or may not work and further work will then be recommended.
You could try some basic balancing of your system by restricting those radiators which are hottest - use the valves you can adjust by hand initially and see if this improves things.
If valves were fitted on the new towel rail try restricting these as well.
If this is unsuccessful I can only suggest you get in a different plumber.
AdAstra sounds like similar problems we have a drop radiator plan so not an upstairs ring and downstairs but the pipes go up and down and so have lots of elbow joints which can get clogged easily. The pump is slightly undersize too so I think we will be saving up and getting a new pump, the system powerflushed and some new radiators, the wiring looked at and eventually a new boiler.
Can't think it is going to get fixed quickly or cheaply. The problem with old homes and bad diyers!
Just to show you what I mean, since my post to you, I have found the gremlin in the wiring. I had a condensing boiler installed about 3 years ago and from investigation of the actual wiring it would now appear that my plumber ran out of cores and used the boiler to pump cable to carry two live feeds - one for the pump and one for the switched control feed which needs to be dropped before the boiler will switch off. It would seem that the system did work before so I am now trying to find out what has changed since he fudged it.
Incidentally, anyone out there know if picking up the neutral for my pump at the terminal block, instead of taking the Live and neutral feed from the supply fuse on the one cable, is OK. I think it should be OK as the neutral connection will still be back to the mains supply but by a different path but there may be problems with residual voltages that effect the control signals.
The tank and room stats seem to operate correctly with the boiler switched off. Any advice appreciated.