Air in the CH/HW pipesystem?

[TonyK81]

Hi,

We have a weird situation with our HW/CH system. When there's a demand for either of them, the boiler tries to switch on, I see the green light (firing the gas) switching on for approx 10 sec, then switches off. At the moment, we have the controller in the following position:
- HW always on
- CH off (controlled by wireless room thermostat)

Compartments:
- Honeywell ST400C main controller
- Digistat SCR + RF3 wireless thermostat controller
- Honeywell V4073 3-way valve
- L641A Cylinder Stat
- Worcester Greenstar 12Ri boiler
- Grundfos pump

The pump makes a continuous sound as if it's working, but not the usual sound it used to make. I have a feeling that there's air in the system. Why? A couple of days ago I realized that one of the radiators was pretty cold, so I used the key and emptied the air from it. I had done that again just 1.5 month ago.
Furthermore, there is a small "overflow" pipe right next to the tank (right after the B-position of the valve). Whenever I unscrew that (there's a tiny hole there), there's no water coming out of it. It's completely dry. Also, the last couple of days we would hear weird noises from the pipesystem. As if water is dripping inside of them, though there is no leakage. So I believe it's some air in the system, and the dripping sound is from the water moving around inbetween air masses.

My guess is this: The pipe leading to the boiler has air, so the boiler kinda realizes that and switches off. I also guess that the pipe coming back from the boiler to the pump has air (it's completely cold at the moment), and the pump just runs without pumping water really, but it's just air inside it. That's why it makes a different kind of noise. This is the input pipe AB. Then output pipe B which leads to the tank, probably only has air now, that's why the overflow pipe is so dry.

Question is, what do we do if there is air indeed? Do we have to call a plumber for this issue? Or is it a boiler problem, and we have to call a gas engineer instead?
More importantly, how would air come into the system? What malfunction would that indicate?

As a note, we keep switching on and off the boiler regularly, since we generally had some issues with the CH/HW system, which we haven't completely solved yet
(that's a link to the previous issue we had:
http://www.ukplumbersforums.co.uk/c...-stopping-honeywell-v4073-greenstar-12ri.html )

Any help is very much appreciated, since I'm afraid we're gonna run out of hot water very soon, as soon as the tank empties!

Thanks

 

[chrispow01]

Your nearly there tony, the flow from the boiler comes directly to the red pump in your cupboard, from there it goes to the silver mid position valve, pipe AB, pipe A goes off to the Central heating where it circulates round and returns back to the boiler to be reheated as u guessed, pipe B goes into the cylinder, through a coil to indirectly heat the cylinder water, this then comes out the bottom of the cylinder and also returns to the boiler. There is normally a Tee on this return pipework going up to the Feed and Expansion tank (this is about 18" x 12" x 12" black plastic tank with a ball valve in) this replenishes the system with water. The system could well be airlocked as you guessed but the cause of this would also have to be remedied. As gray said, u may have to get a plumber in to sort it....

 

[chrispow01]

Sorry, the pump on the floor is for the shower, hot and cold in, hot and cold out, operates only when you operate shower!

 

[TonyK81]

OK!.. Interesting update!

I climbed up on a wall, where I figured there may be some cavity there, and behind a fake wooden board I discovered a whole tank!! So it seems you guys were right, there IS an f&e tank (or something else, I'm not sure how to categorize it). There is a black big tank, which is covered with a lot of plastic bags wrapped up in duckt tape. Next to it is a smaller red spherical looking tank, with a gauge below it. That's the one in the photo below.



(What does that make my heating system? Is it a Open Vented / Conventional System? Or an Open Vented / Sealed System? I checked these terms from here:
Glow Installations - CORGI heating and plumbing installations; our engineers fit boilers, combination boilers, central heating systems, megaflos (unvented hot water cylinders), underfloor heating and secondary hot water circuits. )

Now... I had everything switched off, and the gauge read 0 (out of max 4). When we switched everything on (meaning, switch on the power), I think it raised to 0.2. I think the meter reading is in bar.
Next to it, there was a switch, which from what I understood by reading diagrams and other stuff online, is the WRAS filling switch. I switched that on, and I heard a lot of water going through the pipes. Bubbling noises as well, and I got a feeling that some tanks started filling up.

We switched the CH and HW on, in order to have the most circulation possible. We did have CH and HW at the same time. The pressure meater reading started rising, pretty slowly, but steadily. After about 45 min, the reading was to 1.1. We tried switching the CH off, and after a while it dropped to 0.9. We switched it back on again, and reached 1.1 again. At that point (and since I was almost hanging there for an hour!), I decided it was OK to switch the WRAS off.

So, it's been 1.5 hours now. 10 minutes ago we started hearing that bubbly noise again. But now, I can confirm it was coming from the big black tank. There's a couple of pipes that go inside it (can't tell for sure since all the pipes go that way, I guess most of them pass below it and into a cavity wall). The bubly noise I heard sounded like water dropping from a tap in a pond of water. So I kinda guess that the black tank is not completely full, and one of those pipes drips water in it. That's the kind of noise it made. I checked the gauge and it read 0.6 bar now.

So what does all this mean? Towards the end, I checked the boiler and it was on, and since no CH was on, I guess it was demand for HW?... Does all this makes sense? I checked for a leak, but I couldn't find anything. And I assume that if it was a leak in a hidden place that we couldn't see, it must have come out in the flat below us, but the neighbours didn't say anything...

Any idea what may be the problem?

Many thanks again,
Tony

 

[TonyK81]

actually, to correct myself. Once the bubbly noise started, and I started checking the system status again, I think that at some point the bubbly noise stopped, and that's when the boiler fired up. At the moment I have shut everything down, cause I didn't want the pumps etc to keep going over the whole night, and having air come into the system again.

 

[chrispow01]

Right tony, you may have solved this problem. Weirdly you have a sealed CH system, with that Y plan arrangement you have in your cupboard you nearly always have open vented which is where u expect to see the black tank. In place of that you have the red expansion vessel, which takes up water expansion when the system gets hot.
Them gurgling noises are just the air and water sloshing round the system.
What u need to do is get rid of the air. VENT EVERYTHING, top up pressure again to 1 - 1.5 bar, vent again. Fire boiler, and u should be ok.
Big black tank is your Cold water storage tank, which supplies your hot water cylinder below and possibly your bathroom with Cold water. Ball valve inside, which is where u can hear the dripping from (they often drip)

 

[TonyK81]

OK, makes sense... So I guess the reason why the pressure dropped from 1.1 to 0.6 yesterday is because we switched the boiler off, so the expansion vessel did not not have hot water inside it anymore, therefore the pressure dropped. So we should switch the WRAS on without having the boiler on, I guess, until it reaches 1.5 bar? Is that right? Will the WRAS feed manage to insert water inside the vessel if there's no circulation in the radiators?

When we tried to ventilate the radiators yesterday, they all came up with water, no air (except for one, I think, which had a bit of air inside it, but that can be normal). I guess we may have to repeat that whole process a few times, cause air may be stuck in various places.

I'm a bit surprised about the ball valve inside the tank making that "filling up" noise. I don't believe I had heard that water-running noise before, or at least I never noticed it before since that whole pipesystem is in my flatmate's room 🙂. Just to confirm, there's (at least) two pipes I can see that go into the tank. The one is the same that provides the red vessel with the WRAS feed (so I guess that's the main water supply that fills up the tank with the ball valve), and there's also another pipe which seems to be one of the others, and comes into the tank from the top. From the various diagrams it seems it comes from the hot cylinder, maybe as an overflow pipe to put water back in the tank for safety.

I will deal with all this in the evening again. Many thanks for all the help! I would hate it if I had to call in a plumber, and all he did was just turn a switch on!
Also, pretty useful to finally figure out what the heck is going on with all those pipes 😀
I will update again in the evening.

Thanks again,
Tony