Air and pumping over

[teejay246]

Hi
I am a newbie here so here goes:
I have an open vented system 30 years old. Old house mix of old cast iron rads and newer ones- 18 in all. The system is divided by two zone valves into 1. Downstairs Bathroom, office, living room and hall 2. 2 bedrooms plus 3 public rooms downstairs and 2 upstairs plus upstairs bathroom. With circuit 1 ON and 2 OFF, system was sucking air from somewhere.
Pump ( new Grundfos 15/60 ) noisy with air. I bleed the air manually from the pipe at the top of the system - all goes quiet for a couple of hours. I put on both circuits 1 & 2 and all is quiet for hours but eventually the noise at the pump. Also from time to time I get overflow from balance tank in loft.

( Its a bungalow so loft is on same level as the bedrooms upstairs thus very little "head". Big old hot water storage tank, secondary hot tank with immersion heater, cold water storage to feed hot tank and CH balance tank mounted high as poss under rafters. All worked fine for 29years after piping down to 8mm from 2" and new boiler 1983
Boiler is an ideal Mex 26kw located in a downstairs utility / shower room. Top Flue through roof 4mtrs.

I know that the sytem has a fair amount of sludge and also black deposits ( seen on valves and pipe ends ) so last weekend I decided to put 2ltrs X800 in the system and run the system for 4 hours ( this after taking advice from Sentinel to run for 1 hour or up to a few days...and also reading many posts in favour of X800 left in for a few hours even without the power flush bit.)
Well after four hours - whole system running at normal temp. during which system is quiet as a mouse and running beautifully - no over pumping no pump noise....I drained down the system as per normal procedures etc. Disappointed that the outflow wasn't a really dirty sludgy colour....looked pretty clean- just a beige soapy stream and no sedimentary deposit left by the grid/drain either. So, fitted a brand new auto trickle air vent at top of system ( Italian float type - nice looking piece of kit )- the old bleed valve was clearly sludged up and quite rotten.... re-filled the system, added inhibitor, bled all the rads lowest first etc.and off we went.

With circuit 1 ON and 2 OFF, pump started to get noisy again, clicking in one of the rads ( air ) so sucking air from somewhere such that the trickle vent does not cope. Pump ( new Grundfos 15/60 last year ) noisy with air. I bleed the air manually from the pipe at the top of the system - all goes quiet for a couple of hours. I put on both circuits 1 & 2 and all is quiet for hours but eventually the noise at the pump ( which was installed on the RETURN all those years ago ) starts up again requiring me to manually vent again. ALSO for a long time been getting overflow from the balance tank in the loft. No contamination at all in the hot water, no discolouration, no taste, smell etc.( separate system but thinking of a coil issue if it has a coil - suspect its direct though - unless the small immerser tank DOES have a coil).
Is it the amount of sludge/crud in the system?? I have now bought 3 ltrs of X400 with the intention of starting again - leaving the X400 in the system for about 3-4 weeks??
Ideas/ suggestions please.
Many thanks

 

[Nostrum]

Your 'Rad feed' pipe looks like 28mm in the loft, but both the connections in behind the pump (one on top of the tee, one which runs parallel under the pump then tee's in) are both in 15mm?

Does this 'rad feed' pipe reduce down, or does it connect in somewhere else?

Pic's would help (maybe a bit bigger than the last ones!)

 

[teejay246]

Reply to "dontknowitall" who said: "To give some examples, I bled the air from a heating system a couple of days ago. The bleed valve was about 10 feet up in the airing cupboard, hidden in the corner. Another house I've been to has two bleed valves in the loft as well as another on the first floor. Other houses don't have a bleed valve and rely on the heated towel rail to collect the air in the system."
I have the towel rail arrangement. On rare occasions it goes stone cold with air. There is no vent on it but the rail is connected to the pipe with the auto vent on it in the loft. When that was gunged up I had probs with towel rail as well. With the new float type vent working, towel rail works great.
Sambotc: The rad feed is actually 15mm connected to one of the CH pipes from the "boiler room". The fresh water feed above it is also 15mm.
Talking about the F+E and following a comment made earlier stating that there could get into the system only through the "open the event" -- believing, obviously wrongly, thanks Bren, that the open vent meant the feed entry, I decided to check the level of the water above this and found that it barely covered the aperture, at cold. So I adjusted this giving 25 mm approx, having thoroughly cleaned the inside of the tank and removed the small amount of sludge. Put a new washer on the ballcock valve, then with the M.valves locked open I checked all the radiators for air. That done I switched on the system and it has been running silently ever since -- but that is only a few hours so I will need to wait and see how long this silence lasts. BUT, first thing this morning when the system fired up after being off all night, I got about a litre out of the overflow into the drive as the water heated. Apart from that all the rads are nice and hot except for one -- it is one nearer to the boiler and it's normally one of the first radiators to heat up. It is warm but not as hot as the others -- even the ones furthest away. I tried bleeding it but there is no air in it. On past performance, I don't expect the system to pump over ( overflow) again unless I turn on the bigger zone. That said, when I restarted the system last evening and ran it for the last 4 hours or so before bed, there was no "overflow". With this system running, I note that the water level in the F+E is only about 5mm from the overflow pipe. So very little tolerance here ( the F+E is as high as it will go against the rafters too ) and maybe having raised the cold water level so that it is 25 mm above the rad feed, that has also affected overflow? But so far, nice and quiet and no air apparent. Later today I will try to draw a schematic of some kind of how the system is laid out. Not easy because it's all covered in insulation and there are two or three pipe chases -- two pipes deep in places.
I am only too aware that I really need someone who understands old systems and who can be trusted to take the time to cast his experienced eye over the whole thing. I am making enquiries. I have some experience of friends who have had new systems installed locally and up in Glasgow. All of them have had and continue to have problems and all were combi systems. Mine is a big ole house with two bathrooms and a shower room. At present, apart from the lack of a trustworthy, proven pro, we also have a lack of funds. One can imagine our reluctance to use our savings on an "upgrade" when we may never be done with probs from it. Thanks for all the help so far guys. Its appreciated and I am learning. By the way I am in Prestwick, Scotland.

 

[Brendan Rodgers]

Wow...

 

[Nostrum]

....except for one.....

 

[dancinplumba]

eh ??

 

[teejay246]

teejay246

sounds like you've done yourself some research or know a bit or too?

You mention 2 zones. How is your hot water heated?

After checking the level in the F+E cold and adjusing it. It's sounded less "airy" BUT still getting some air being dealt with constantly by the float chamber. Still pumping over at start up though.
Put in X400 and am letting that do its job for a week or two. Rads are hotter and more surface on the old ones heats up.
Decided to take time to map this old system. Took some time and here is the pic. Surpised to find the cold feed tees into the hot water for starters.
I suspect a faulty zone valve too. When off, the pipe below is warm and there is warmth in one of the rads at the top of the circuit. Not a lot but should it be??
Also my Grundfos pump ( 1yr old ) needs the bleed screw tightening a heck of a lot to stop weep from bottom of the black name plate. Grundfos say the casting may have a hairline crack in it. It's not leaking at present - what do you think?
From the diagram would you conclude that the HW tank has a coil in it? Could that be the issue even without any apparent colouring of the hot water?
Getting a pro in now I have a diagram ( hope I tracked everything major properly ) Also discovered the open vent out on the roof ( plenty of height ther I think. Well its all worked well for many years.
Hope you can see this picture OK will it be far too small? It was an A4 doc?

 

[teejay246]

Hi guys
Been monitoring the whole thing for a few months. Seem to have isolated the "air problem" to the HW circuit. On it's own the HW circuit is not heating the water as it should. No more than tepid unless I run one zone of the CH. Noticed that the pipes below the zone valves are warm/hot even when HW is on alone. CH system runs perfectly, rads hot etc. and little if any air. Only get noisy at the pump when running HW only??
BTW: Bought new zone valves- after 30 yrs the old ones don't owe me anything but will need the pro to install them. Controller is sending the message to the ZVs. Pro reckons the old copper tank was so heavily built it will outlast my house, coil in it - same and scrap- it's worth a small fortune.