Air in all radiators every morning, HELP!

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Hi
Last two days have woken up to cold radiators because of air in the system. When I bleed a rad, they all heat up again.
Bit of background:
System is Baxi Bermuda back boiler. Two rather small cold water tanks in cupboards about 6ft above hot water tank.
Had a new shower pump and auto air vent fitted in July by reputable company (thought charge was excessive at 787).Afterwards, shower worked fine but radiators not very hot.
BGas serviced boiler two weeks ago. Engineer turned up water temperature (to 75 deg). Rads now very hot, shower now too hot, difficult to adjust. Turned water down to 70 deg. This was the last service before I cancelled agreement (because too expensive and each year covers less and less).
Three days ago found bit of air in shower room rad. Bled it. Next day, air in all rads, all cold. Same today. Auto air vent has been throwing out a bit of water by the look of it.
Am a complete novice with plumbing, but have been badly ripped off a few times and want to try to avoid it again.
Before I call a plumber, just wondered if anyone can help suggest a reason and remedy?
Is the problem likely to be related to any of the recent work carried out?
Anyone know a good plumber in central London? :-)
Sincere thanks for any help/advice.
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snipped-for-privacy@virgin.net (jeanne) wrote:
Hello jeanne

I suspect overpumping, and as it's easy to test for worth checking first.
CH pump - turn speed selector down. As well as messing with the thermostat, your BG Guy may have twiddled the speed also. Most houses don't need more than "I" - but in all cases, the pump should be set to the lowest speed THAT STILL HEATS ALL RADIATORS.
If I'm right, would explain water being pushed out the air valve - which if I'm not, would be the next suspect.

Why do you think so many of us in here prefer to struggle and learn this particular skill?
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On Wed, 03 Dec 2003 15:24:23 GMT, snipped-for-privacy@digdilem.org (Simon Avery) wrote:

I rebalanced all 12 radiators in my house recently. It had obviously never been done properly as I ended with many valves screwed down to about 1/2 open (at most) and some left fully open. They all have TRVs fitted.
However, when I experimented with nudging the pump down from 3 to 2 (one or two radiators are a bit whooshy noisy as a result) this could set up some amazing banging and clanging noises. I think the pump was struggling against some of the TRVs. It sounded like one rad trying to shake itself loose of its fittings. The pump is back at 3.
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snipped-for-privacy@digdilem.org (Simon Avery) wrote in message

Hi Simon
Thank you for your suggestions. Forgive my ignorance, but how do I turn the speed down? The pump is GRUNDFOS UPS 15-50x18 with a large "screw-head" at the front with an up arrow on the right and a down arrow on the left. Is this the speed selector? It doesn't have any settings on it, but is currently "aligned" at "twenty to two" :-) or it would be if it was a clock!

OK, point taken :-)
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On 4 Dec 2003 08:57:05 -0800, snipped-for-privacy@virgin.net (jeanne) wrote:

That's a cover for the motor spindle I think (which you can turn by hand/screwdriver if it's stuck). The speed adjustment is a plastic rotary dial on the side of the pump. It will show 1, 2 or 3 in a window to the front. (Well, it does on mine, which is a slightly different model. But the 15-50 designation means adjustable from 15 to 50 somethings. On the front, is there a sticker showing wattage or flow rate at the 3 settings ?)
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(jeanne) wrote:

Thanks John. Your description helped me find it! Have turned it down.
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snipped-for-privacy@virgin.net (jeanne) wrote:
Hello jeanne

Nono - that's the bleed screw (undo it slightly only if you've got air stuck in the pump, ie, it's making a hell of a noise).
No, the speed selector is usually (at least on my grundfos, and the one before it) on the side cover where the wire enters. (On mine, to the left of that shiny screw)
It could be yours doesn't have one of course, in which case my suggestion is completely wrong. :)
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snipped-for-privacy@digdilem.org (Simon Avery) wrote in message (jeanne) wrote:

Many thanks, I found it and have turned it down. There is a "whooshing" noise coming from the system, so - as we already know - there is a lot of air in it. Guess I'll end up calling in a plumber :-(
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snipped-for-privacy@virgin.net (jeanne) wrote:
Hello jeanne

Give it a day or two. I drained my system yesterday with the result that it got full of air and I had the whooshy syndrome also.
However, I don't now.
I have an automated air bleed valve (two actually, but one's so badly sited it doesn't actually do anything). This doesn't expel any air whilst the pump is running since it's before the pump so is subject to some suction pressure.
But, if I turn off the pump as soon as I hear its sound change (whooshing) then that pressure is released and I can hear air escaping through the valve.
So here's what you might like to try now you've turned down your pump:
Turn off hot water (shorter loop so doesn't tend to collect as much air), either at the controller or by turning the tank stat right down.
Turn ON boiler, but not the room thermostat.
Turn ON the thermostat. Pump will start. Boiler /may/ fire. Wait until pump starts whooshing (usually within 10-30 seconds) then turn OFF the thermostat. Wait 2-3 mins (if you can easily access the air bleed vent, check it - maybe loosen the red plastic top if it has one - to see whether it's venting. Faint hissing noising)
Repeat until whooshing stops. Can take a few dozen goes if there's a lot of air there.
If done, go round and bleed all your rads.
Note this is only for purging a system of air. Once purged, it shouldn't need doing again unless you've worked on it and drained water for something. If this works, but you get the same symptoms again - then you probably have a leak in your pipework. Air can get sucked into a leak, but also if it's losing water then fresh is introduced which carries air with it which is then chucked out along the route. (And adds to corrosion - stagnant water is what you want for CH systems, preferably with an anti-corrosion additive like Fernox)
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snipped-for-privacy@digdilem.org (Simon Avery) wrote in message (jeanne) wrote:

This is exactly the same here. The auto air bleed valve hisses if I turn off the pump.There is a lot of noise in the header tank too (bubbles).

Very kind of you to spend your time on this, thank you so much for explaining it so well for me.I'm away this weekend, but will give it a try as soon as I get back on Sunday.

I have checked it isn't hydrogen and the system hasn't been drained just before it happened (it was drained in July; boiler serviced a few weeks ago), so I guess it will end up being a leak somewhere. That will be fun :-(
Thanks again,
Jeanne
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Difficult to comment without a few more details. Where exactly is this auto air vent - is it in the primary circuit - which includes the boiler, radiators and indirect coil in the hot water cylinder - or is it in the feed to the shower?
How is the domestic hot water temperature - as opposed to the boiler flow temperature going to the radiators - controlled? Is there a thermostat fixed to the hot water cylinder? (not one incorporated into an immersion heater, if any)
Roger
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Hi Roger
Auto air vent is situated between the hot water cylinder and the "mid position valve" (above the central heating pump).
The temperature controller ("Drayton") is on the hot water cylinder and adjusted with a screwdriver. This is the only hot water storage.
Thanks,
Jeanne
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jeanne wrote:

Ok - that's useful - the air vent is clearly in the primary circuit. I can think of 3 possible reasons for your problem - in no particular order of likeliness:
* The air vent could be faulty - and could be drawing air IN [Is it possible to disable it, and see whether that makes any difference?]
* Your system could be "pumping over" - and drawing air in through the header tank [Is there a constant flow of water through the vent pipe into the primary header tank when the system is running?]
* It may not be air at all - it may be hydrogen, caused by corrosion in the radiators if the system doesn't have inhibitor in it [When you bleed a radiator, try sticking a match to the "air" which comes out. Does it burn?]
You mentioned earlier that when the boiler temperature was turned up, the shower became too hot. But, the shower is presumably fed from your stored hot water tank? From what you say, you have a cylinder stat and a mid-position valve. If so, it is possible to control the temperature of the stored hot water so that it is cooler than the water going to the radiators. [The boiler flow temperature should be about 80 degC, but the domestic hot water only 55-60 degC]. This should enable you to have hot radiators without the shower being excessively hot - but you *must* sort the air problem first.
Roger
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Many thanks for your helpful suggestions, Roger. I'll check these out. I suspect it is air rather than hydrogen because it is affecting the whole system and happened so suddenly, but what do I know about central heating systems? :-).
There is a "whoosing" noise coming from the cupboard where it's located. I know it is important to sort it out, so no doubt will have to call a plumber :-(. At least I'll have some idea of what they should be looking at after I try your suggestions.
Thank you also for the information about sorting out the temperatures. I wish the BG engineer had as much knowledge about the system as you! :-)
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snipped-for-privacy@virgin.net (jeanne) wrote in message

I'm not sure how to do this, it is throwing out air and water when the pump is off.

Yes and bubble noises in the header tank.

No it doesn't burn, so is air.
Will try the steps Simon lists below next.
Thanks again for your help.
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did u get an answer
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jeanne wrote:

Good grief!

Good move.

Its rumoured that plumbers there can make >100k /year now ...

First of all, never use a real email address on Usenet because it will get intolerable amounts of spam thereafter.. A Baxi Bermuda back boiler must be getting quite long in the tooth now. I wonder if the increase in the temp by B Gas has found a weakness somewhere that is now leaking.
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BillR wrote:

Nonsense! I use my real email address with pride. Not doing so is giving into spammers.
Even then, only a small percentage of my spam is Usenet derived (<5%).
--
Grunff


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Grunff wrote:

How can NOT using your email address be giving it to spammers?
Another reason not to use your real address: I only know 2 people who were emailed the swen virus: my spam account, and a guy at work. Both addresses were used in newsgroups. The swen virus looks in different types of files to find email addresses, and will post fake messages to newsgroups. As far as I can see, there is nothing to stop it reading newsgroups to trawl for email addresses.
Bob
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Bob Smith wrote:

Because if spammers didn't spam, you *would* use your real email address. By *not* using it, you are allowing spammers to influence your behaviour, ergo you are giving in to them.
It's like allowing burglars to influence your behaviour by fitting locks to your doors.

First time I've heard of swen (or any other virus) trawling Usenet for addresses.
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Grunff
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