Central heating weirdness

[Rob Morley]

Vented system - there's some sort of debris in the circuit[1]; it periodically (every half hour or so) rattles and causes pumping over as it goes through the pump and into the water cylinder heating loop (only with the radiators switched off). I stuck a MagnaClean in the HW circuit[2] but it's not catching anything apart from magnetite. I thought these were supposed to trap non-magnetic crap too. I'm wondering if I should stick something like wire mesh in the MagnaClean to help it along, or is there a better way? I could probably jury rig a power flush but that seems like a load of wet messy hassle compared to my (failed) solution.

[1] No idea where it came from - the header tank is covered so it's unlikely anything got in there. [2] There's no easy access to fit a trap in the return line without ripping out bits of floor and/or ceiling, and possibly not even then.

[alan_m]

I once had a jelly like growth in a CH heating header tank.

[John Rumm]

Are you sure it is actually doing a full circuit of the heating system? I have had cases where something rattles in a pipe, but gets trapped by a rad valve or similar. So it never gets flushed through.

[Brian]

Sounds like air. If you’ve vented the rads to eliminate that, or it won’t vent.

Check the header tank isn’t furred up. Sometimes you get brown stuff collecting.

If it is. Drain the system, clean the tank, refill will system cleaner and run for a week- including the radiators.

Them drain, fill with fresh water. Plus inhibitor.

Don’t forget to vent radiators when filling.

Ideally, after the cleaner has done its job and you’ve drained down, remove each rad, take outside, and rise through with a hose.

If the system is slow to refill, check the pipe from the header tank isn’t blocked.

[Rob Morley]

Nothing but a sprinkling of rust in mine.

[Rob Morley]

Fairly sure - if it was going through the bypass valve I think it would be circulating a lot faster. I don't want to touch that if I can help it as the valves are heavily corroded and the joints not much better.

So far this seems to be stuck in the HWC circuit - pressure drops when the MPV opens the heating circuit and the weirdness pauses.

[Rob Morley]

Rads didn't need venting, I've opened the manual vent valve by the pump and not much air there either. It definitely sounds like something fairly solid, I don't think an air lock would have it pumping over every time it went past the pump. I'm wondering why the pump hasn't broken it up by now, as it's clearly passing through it.

Not a significant amount here.

First thing I did was drain the header tank and stick cleaner in it. Didn't wait a week but three or four days. I partially drained the system (not the radiators, so most of the cleaner should still be in there) to fit the Magnaclean.

I did that a while ago on a couple of radiators that showed signs of sludge, and I've been adding inhibitor fairly regularly since.

It drained just fine.