Cannot shift CH airlock

45yearsagasman said:
MikeAustin said:
I have tried magnets around the F&E pipework and have not noticed any attraction. I did not expect to because I used the fill to refill the system and, when hot water was going up the feed, I temporarily closed it to prove it was free to go up the expansion.
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That's not a test that proves anything, other than the feed and expansion pipes are clear. I still think your problem is around your pipework upstream of the pump, and yes, this can be non magnetic. Are your motorised valves operating correctly?
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This is my system (although pump has been replaced):
[GALLERY=media, 11028]Untitled by MikeAustin posted 29 Apr 2009 at 11:18 PM[/GALLERY]
The motorised valve works fine - hot in either/or HW and CH pipes as selected. HW is no problem at all. There is a 15mm return from the HW tank tee'd downstream into the 22mm radiator return. Hence my assumption that it is the return (up to this tee) and not the flow that is the problem. As you can see from the picture, there is not much room for a blockage to occur. Am I making any sense?
 
Can't make out what those gate valves are doing, especially the one on the CH flow. Why is it there, and is it fully open? What's the one above the pump? Not enough of the pipework is visible from your pic.
 
45yearsagasman said:
Can't make out what those gate valves are doing, especially the one on the CH flow. Why is it there, and is it fully open? What's the one above the pump? Not enough of the pipework is visible from your pic.
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One above pump will be for balancing hw

One on ch flow will probably be so you can completely isolate the 3 port valve for maintenance without draining (presuming the tee on the hot water flow pipe on the top left goes to an air vent?)
 
45yearsagasman said:
Can't make out what those gate valves are doing, especially the one on the CH flow. Why is it there, and is it fully open? What's the one above the pump? Not enough of the pipework is visible from your pic.
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Gate valve above pump goes to HW cylinder. Return from cylinder on right of picture with drain plug. Pipe above 3 port valve has a bleed screw. All valves fully open.
 
For the sake of @£20, dose it with x800 and leave heating on constant for the day and see if it makes any difference! Then you can start wrangling with pipework if there's no change at all!

Try isolating each of the drops so that are open to flow with all other rads closed.
 
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dilalio said:
For the sake of @£20, dose it with x800 and leave heating on constant for the day and see if it makes any difference! Then you can start wrangling with pipework if there's no change at all!

Try isolating each of the drops so that are open to flow with all other rads closed.
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Yes, thanks. Your advice suits me the most. I bought the X800 yesterday and I am in the middle of emptying the F&E tank to add it to the system. I intend to leave it for a couple of days.
 
I suppose you've done it by now, as I was going to advise you to drain the system and try and put it into one of the lowest rads so that it gets right to the spot(s).

Not a big issue... If you get some results with it and you think it's doing "some" good, you can always get some more and give it another dose!

Let us know how you get on.
 
dilalio said:
I suppose you've done it by now, as I was going to advise you to drain the system and try and put it into one of the lowest rads so that it gets right to the spot(s).

Not a big issue... If you get some results with it and you think it's doing "some" good, you can always get some more and give it another dose!

Let us know how you get on.
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Thanks dilalio. Yes, that would have been a good idea - removing the bleed valve inserts and putting it in there - but I wanted to speed things up. (On second thoughts, I could have easily siphoned out some of the radiator contents - the X800 is heavier than water.)
I emptied, cleaned and refilled the F&E tank (lot of non-magnetic sludge). I opened the return drain near the boiler and carefully poured the X800 into the F&E tank as close as possible to the F&E pipe as it refilled so as not to dilute it too much.
Running for 5 hours, there is negligible muck in the Magnaclean - just a thin film on the plastic sleeve. One of the most difficult rads seems to have loosened up a bit, judged by its return being a bit warmer than it was. The other group of three rads, while eventually getting hot on the feed side and most of their depth, still have cool returns.
I hope I will get the system to limp through the winter. Next year, I will replace rads and pipe runs. Some of the pipework is between 30 and 50 years old and behind plasterboard dry-lined walls - and in Imperial dimensions (as I found when I fitted a new bath)!
 
The fun of plumbing eho_O

If you're gonna replace rads & pipework next year, you should consider sealing the heating up and pressurising it, that way you won't get the air intake problems associated with a vented system.
 
My CH has only slightly improved since a 24 hour flush with X800. It still takes ages to heat up. Eventually, it reaches temperature with the ground floor rads hot all over, except near the lock shields. It is not operating properly but I can live with it for the moment. I note that, immediately aftet starting up from cold, the level in the F&E tank drops about 10mm. When shutting down and the pump stops, there is a gurgling sound and a surge back into the F&E tank. Is this normal?

This is what I did in the last two days. I drained the system and cleaned out the F&E tank. The water was brownish, but no sludge. There was a lot of brown, non-magnetic sludge in the F&E tank.

I filled and ran for 24 hours with X800. I removed the Magnaclean and there was just a thin brown film on the plastic sheath. I took the opportunity to use the strong magnet to check the pipes and joints for magnetic debris.

I drained completely and mains flushed all ground floor rads (bleeds open so the water sloshed along the bottom) for about 30 minutes total until the water coming out was clear.

I completely opened a drain cock at the lowest part of the system where there was old pipework and the possibility of hardened sludge. I used a bit of drain unblocking wire - the thin flat spring-like stuff - to poke along the return pipe to some pipe bends. No obstructions. I removed the lockshield from the most critical rad (rad too large and heavy to remove myself) and was able to poke the wire all along the bottom of the rad without obstacles.

I refilled the system and ran for about 12 hours, bleeding the vents. Then I added Fernox FB1 to the F&E tank. That is all for the moment. I may have a major overhaul of the system next year.
 
Close all the rad valves apart from the radiator furthest from the pump, turn the pump to full speed and then turn on the heating. Do that sequentially for all radiators. The turn the pump back to normal, rebalance and see what you get.

I've had a similar issue with an airlock after a mains flush. I could not get rid of the airlock until i did the above.
 
Sorry to harp on about my CH problems again.
My boiler (Viessmann Vitodens 100C) is only firing occasionally, and never reaches full temperature of 80C on the maximum setting (it has, in the past, reached 75C). Even using just the nearest rad (upstairs), the boiler heats up from 41C to 64C in about a minute using 2 bars of a possible 5. It then drops back to 41C in about 4 minutes before firing again. I think this is due to airlocks in my system.
When I start up, there is a lot of whooshing and gurgling and water is taken from the feed. Some of the radiators gurgle. It sounds as if there is air in them even though I have bled them many times. One rad managed to hiss a bit of air from the vent after I banged it all over with with a rubber mallet, suggesting it had several locked pockets of air.
When I switch off the system and the pump stops, there is again a lot of gurgling in the pipes - particularly round the pump, mid-position valve and HW cylinder. I have bled the vent near the pump (a self-venting Wilo Yonos Pico) and the Magnaclean near the boiler. I don't know how to get at the air remaining in the system.
I think that there are pockets of air in the system that compress when the pump starts and water is drawn in from the F&E pipe. When the pump stops after switching off, the air pockets expand again pushing water up the F&E pipe. Both events are noisy.
Any suggestions? The current temperature that the radiators reach (after a long time) will not be adequate in freezing weather, so my plan to limp through until next summer may not be practical.

The following boiler temperature plots show what is happening.
The first is with only the two nearest rads upstairs, so no effects from ground floor drops. I have only recorded the boiler on/off temperatures and joined them with straight lines:
[GALLERY=media, 96709]BoilerTemps_20151214 by MikeAustin posted 16 Dec 2015 at 3:32 PM[/GALLERY]
The second is with all rads on. I have added the boiler on/off periods (on for only 25% of the time). After 5 minutes, I also recorded the lowest temperature reached a few seconds after the boiler fired up:
[GALLERY=media, 96708]BoilerTemps_20151216 by MikeAustin posted 16 Dec 2015 at 3:32 PM[/GALLERY]
 
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