I have only ever had vented systems, where the occasional bleeding of a radiator or two is automatically followed by the system recharging itself with water from the header tank. And with a natural convection feed to the hot water cylinder (controlled by motorised valve) but a pumped feed to the radiators, everything just sorts itself out. However, my daughter’s unvented system gets me – and she got no advise on how to manage it when she moved in, not even told of the incoming mains cock or the cylinder isolating cock!
I have now found the cocks, the (oil) boiler has been serviced, and I have investigated the system layout. From the boiler there is one common feed pipe (28mm - pumped) that soon splits into a 22mm pipe feeding the hot water cylinder (but also a few radiators and a heated towel rail on one side of the house), and another 22mm pipe feeding the rest of the radiators. However, the hot water cylinder and the towel rail return back to the boiler via one motorised valve (at the boiler), while seemingly ALL the radiators return via a second motorised valve (both valves being thermostatically and programmer controlled). Is it normal to have these valves at the end of the circuits?
However, it does seem to work OK – until you need to bleed something, or replace a radiator or a leaking valve. I have hunted for and found a fill loop (located behind a cupboard), so I can top up the indirect water – with both the motorised valves manually set to open. I have read that I need to recharge the boiler expansion tank (pancake) using a car foot pump – OK, I see why it needs compressible air space, and that’s probably why the boiler started cutting out despite the cylinder water not being up to temperature (but works OK with the immersion heater). The hot water cylinder is a Megaflo (CL210 Mk5), so has internal expansion volume above the water takeoff – but I probably need to regenerate the volume - by draining the cylinder and venting it via the temperature/pressure valve.
Hopefully, I can now get it all working properly again – and get the cylinder serviced (there is no record of previous servicing). However, I would like to know about what could be air venting facilities on the Primary Heating circuit. The Boiler and the Megaflo are on the ground floor, and the 22mm primary flow and return pipes come down from the ceiling. The pipes basically bend to follow the joists, but each include a short (approx 300mm) vertical spur ending in knurled knob (same diameter as the pipe). It looks as if the knob might unscrew, but why? To insert a pressure gauge or to access a bleed point? Are they required? They do rather impinge on the use of the loft space.
I would be grateful for any helpful comments on the various features of the heating system I have described.
I have now found the cocks, the (oil) boiler has been serviced, and I have investigated the system layout. From the boiler there is one common feed pipe (28mm - pumped) that soon splits into a 22mm pipe feeding the hot water cylinder (but also a few radiators and a heated towel rail on one side of the house), and another 22mm pipe feeding the rest of the radiators. However, the hot water cylinder and the towel rail return back to the boiler via one motorised valve (at the boiler), while seemingly ALL the radiators return via a second motorised valve (both valves being thermostatically and programmer controlled). Is it normal to have these valves at the end of the circuits?
However, it does seem to work OK – until you need to bleed something, or replace a radiator or a leaking valve. I have hunted for and found a fill loop (located behind a cupboard), so I can top up the indirect water – with both the motorised valves manually set to open. I have read that I need to recharge the boiler expansion tank (pancake) using a car foot pump – OK, I see why it needs compressible air space, and that’s probably why the boiler started cutting out despite the cylinder water not being up to temperature (but works OK with the immersion heater). The hot water cylinder is a Megaflo (CL210 Mk5), so has internal expansion volume above the water takeoff – but I probably need to regenerate the volume - by draining the cylinder and venting it via the temperature/pressure valve.
Hopefully, I can now get it all working properly again – and get the cylinder serviced (there is no record of previous servicing). However, I would like to know about what could be air venting facilities on the Primary Heating circuit. The Boiler and the Megaflo are on the ground floor, and the 22mm primary flow and return pipes come down from the ceiling. The pipes basically bend to follow the joists, but each include a short (approx 300mm) vertical spur ending in knurled knob (same diameter as the pipe). It looks as if the knob might unscrew, but why? To insert a pressure gauge or to access a bleed point? Are they required? They do rather impinge on the use of the loft space.
I would be grateful for any helpful comments on the various features of the heating system I have described.
