Bypass valve heating rads

Finally got round to pulling up the floors and tracing enough of the pipes to make some sense of what's there (there's a substantial piece of pipework in a fully enclosed void, with no access hatch, above the boiler that I can't get to without wrecking her - decorated - kitchen).

The system has a common return with the heating in multiple loops coming off a 22mm feed with 15mm returns. The general layout is the same as that shown in the idealboilers pdf in the first post of this thread, section 12, open vent with the twin motor valves instead of the 3 way valve, with the exception of the bypass valve location, which is installed just after the pump, and before the two valves. I think I read somewhere the bypass valve should be as far from the boiler as possible, or did I imagine that? If so why would the schematic it show it closest?

All the CH returns are closer to the boiler than the cylinder return, and the bypass valve (both of which can be seen in the photo above) which seems at odds to the 3Ts rule I read about. Does that mean it's inevitable that there will be some degree of reverse circulation when the HW only is on? If so, then the reverse circulation is not the end of the world, what's a genuine PITA is the extent to which air gets in the system. There's substantial air within days of bleeding all the rads and venting the cylinder I thought this might due to some issue with the vent and cold feed, however they are close coupled just before the pump, which seems to be allowed in section 10 of the boiler manual, and they have plenty of head.

If the boiler is switched from 'low' to 'high' on it's front panel it's very noisy, loads of air/creaks and bangs from the system - makes me wonder if the bypass valve was set with it on 'low'.

Does anyone have any final words of wisdom before we try and find a professional to look at it?

 

Powerflushed the system with a DIY rig and got quite a bit of sludge/limescale out, enough to let the boiler run normally for the first time in the last couple of years, even on high output.

Final dilemma is whether to put up with the reverse circulation - these guys clearly never heard of the 3Ts rule - or install one way valves in several branches. I expect they'd have a reasonable service life, and if fitted as close as possible to the main feed pipes the likelihood of silt in the pipe should be minimised (impossible to flush in both directions in future).

 

Southend/Westcliff

 

No, Westcliff-on-Sea, on the mouth of the Thames: http://www.google.com/maps/place/Westcliff-on-Sea

 

Thanks for the offer, but I can see what the issue is, it's not worth the money to have it fixed "properly". It's either a case of putting up with warm rads on summer mornings or fitting some one way valves.

 

Thanks, I appreciate everyone's input and help.