Bit of a long story this and I am still learning my way around heating systems, so my apologies if I don't specify enough info or get my details slightly muddled.
System details: Open vented, with a Potterton Prima 60F in the kitchen, F&E tank in the loft, a recently-installed Grundfos 15/50 pump, Sunvic 2-port valves on each circuit, and a Danfoss FP715 controlling everything. All 10 radiators except the highest-placed (in the upstairs bathroom) have TRVs. Hot water is heated via a cylinder in the airing cupboard. Auto air-bleeders are placed just after the pump and on the return side of the water cylinder. With the exception of the new pump, the system is as we found it when we bought the house four years ago.
For years air has been finding its way into the highest-placed radiator whenever the CH is on, and though we've dutifully bled this radiator periodically, we've never found the time or inclination to get it looked at.
In late December the old pump (a BG Multihead III) started making noises akin to a hammer drill hitting brick, and clearly was on its last legs - though to be fair, it had always been noisy. Following a lot of research on this forum I took the initiative and ran some Fernox F3 through the system for a week, then flushed it out. Whilst the system was drained I fitted a new Grundfos 15/50 pump and replaced the ball valves that were either side of it, then added a dose of F1 inhibitor when refilling the system.
A fortnight has passed and the Fernox treatment + new pump has clearly made a difference. Radiators heat-up quicker than ever before (even on the lowest pump speed) and the house seems warmer overall. I've noted no problems with the hot water either.
Unfortunately the change of pump hasn't solved the air getting into the system, and now we are hearing brief hissing sound emanating from the new Grundfos pump after the boiler has finished its cycle. The noise lasts about 10-15 seconds, and is sometimes preceeded by what sounds like sloshing water - I assume these noises are air passing through the pump itself? I wonder if these sounds have been happening all along, but were previously masked by the old pump's significantly louder operating noise.
Gathering a variety of ideas from this very useful forum, I have now done the following to no avail:-
- Checked (and have had someone stronger double-check!) that the pump nuts and gates were on right; they are.
- Verified the pump is definitely on the right way round!
- Bled the new pump various times; water immediately trickles out upon releasing the screw.
- Bled all the radiators multiple times.
- Tried different boiler thermostat settings.
- Experimented with all three pump speeds.
- Ran the system with only the top radiator on for a day.
- Re-balanced the radiators.
- Replaced one of the air bleeders.
- Tried holding a jar of water under the expansion pipe; it didn't get sucked into the system.
I had considered X200 to descale the boiler as we definitely live in a hardwater area, but is a scaled boiler likely to be creating that much air in the system? Surely the F3 would have cleaned it anyway?
So... after all that: does anyone have ideas of what I should investigate/try next?
Failing things that I can check or try myself, could anyone recommend a reliable heating engineer in the Portsmouth area?
System details: Open vented, with a Potterton Prima 60F in the kitchen, F&E tank in the loft, a recently-installed Grundfos 15/50 pump, Sunvic 2-port valves on each circuit, and a Danfoss FP715 controlling everything. All 10 radiators except the highest-placed (in the upstairs bathroom) have TRVs. Hot water is heated via a cylinder in the airing cupboard. Auto air-bleeders are placed just after the pump and on the return side of the water cylinder. With the exception of the new pump, the system is as we found it when we bought the house four years ago.
For years air has been finding its way into the highest-placed radiator whenever the CH is on, and though we've dutifully bled this radiator periodically, we've never found the time or inclination to get it looked at.
In late December the old pump (a BG Multihead III) started making noises akin to a hammer drill hitting brick, and clearly was on its last legs - though to be fair, it had always been noisy. Following a lot of research on this forum I took the initiative and ran some Fernox F3 through the system for a week, then flushed it out. Whilst the system was drained I fitted a new Grundfos 15/50 pump and replaced the ball valves that were either side of it, then added a dose of F1 inhibitor when refilling the system.
A fortnight has passed and the Fernox treatment + new pump has clearly made a difference. Radiators heat-up quicker than ever before (even on the lowest pump speed) and the house seems warmer overall. I've noted no problems with the hot water either.
Unfortunately the change of pump hasn't solved the air getting into the system, and now we are hearing brief hissing sound emanating from the new Grundfos pump after the boiler has finished its cycle. The noise lasts about 10-15 seconds, and is sometimes preceeded by what sounds like sloshing water - I assume these noises are air passing through the pump itself? I wonder if these sounds have been happening all along, but were previously masked by the old pump's significantly louder operating noise.
Gathering a variety of ideas from this very useful forum, I have now done the following to no avail:-
- Checked (and have had someone stronger double-check!) that the pump nuts and gates were on right; they are.
- Verified the pump is definitely on the right way round!
- Bled the new pump various times; water immediately trickles out upon releasing the screw.
- Bled all the radiators multiple times.
- Tried different boiler thermostat settings.
- Experimented with all three pump speeds.
- Ran the system with only the top radiator on for a day.
- Re-balanced the radiators.
- Replaced one of the air bleeders.
- Tried holding a jar of water under the expansion pipe; it didn't get sucked into the system.
I had considered X200 to descale the boiler as we definitely live in a hardwater area, but is a scaled boiler likely to be creating that much air in the system? Surely the F3 would have cleaned it anyway?
So... after all that: does anyone have ideas of what I should investigate/try next?
Failing things that I can check or try myself, could anyone recommend a reliable heating engineer in the Portsmouth area?
