Central Heatin Noises & Air

[Minty_Cymru]

I hope you guys can help me?

Our central heating system was proabably installed in the 80s. about 8 years ago the pump failed (went really noisy). I don't know what make/model or rating is but I remember it being a red/purple colour. This was changed and the new one fitted (by a an 'odd job' guy) was blue, and physically smaller than the one that came out.

The system is over a two story house, cold water storage in the attic, hot water storage tank and central heating pump on ground level of first floor, heated by a back boiler on ground floor. Running 6 rads.

We had a rad replaced last year (about June) and another rad revalved (all existing rads have the dreaded twin bore, new rad and revalved rad have traditional 'one either side').

One night over christmas the central heating system started making bad noises. A combination of vibration wobble (from the pump?) and wooshing sounds. I assumed it might be air in the system so I bled all rads. The rad closest to the pump let out about 30 seconds of air, the rest were fine. This made no difference to the noises. I checked the pump setting, it was on maximum flow, I turned it down to medium, then minimum, both times the noises decreased, although they are still there and gradually getting worse.

I bled the pump, a little spatter of air but nothing impressive.

I bled the rad closest to the pump again a week later, and got a further 15 seconds air, and again last night I got another 15 seconds. It seems there's air 'getting in' to the system somehow. I'm tempted to blame the pump (maybe the bearing is collapsing - causing the vibration wobble - and throwing the spindle off centre and thus compromising the seal, sucking air in as it pumps????).

Any advice you can offer would be great.

Thanks.

 

[diamondgas]

You checked the little header tank in the loft has water in it? Could be as simple as that. However it may be something more serious... Could really do with a visit from an expert IMHO

 

[Minty_Cymru]

As far as I can tell, there is only one tank in the loft, the cold water storage tank. I recently fitted a new valve to the feed on that. (Thread about it HERE)

Is it fed from there. or should there be another just for the heating system?

I had a friend pop round yesterday, not sure if you could call him an expert but he has been fitting kitchens and systems for many years - but not troubleshooting. He said there is definately air still in the system but he can't think of any way in which 'more' air would get in without any water leaking out (and there isn't), he thought it could be that air was still trapped in the system from when the new rad was fitted in June and it's recently been 'released'. We did a little more bleeding yesterday and the noises went away temporarily, but we could hear air pass through the pump later on, then into the rad (that's when the noise reappeared).

Back to the cold water tank (and if that is feeding the central heating), the valve I fitted was a Fluidmaster, and it had a section in the instructions which explained how to remove a flow baffle within the valve if the tank was filling too slowly - could it be this?

Thanks for your attention by the way, it is appreciated.

 

[Minty_Cymru]

Thanks for tkaing the time, it is very much appreciated.

Strange, I've replied to this twice but none has appeared, I hope this works (it's probably because I included links to webpages).

Header Tank - I dont' think I have one, I believe I have a vented system working out of the cold water storage tank. Which I (curiously enough) changed the float valve in about three weeks ago. The valve that came out was a run of the mill ball valve, the one I fitted is a Fuildmaster - I think the model is: Float Valve 747UK074 (got that off the B&Q site), and I seem to remember the instructions stating that if the tank is taking too long to fill then I should remove the flow reducer inside the valve. It seemed ok at the time, but maybe with the heating on, and someone filling the bath it could run the cold water tank dry?

Sound possible? Perhaps I should get up the attic and remove the flow reducer from the valve to see if it makes a difference.

Also, on another note, I noticed last year that the nearest rad to the hot water tank was getting warm when only the hot water was on - I've read that this is probably a faulty check valve. What would one of these look like?

 

[jtsplumbing]

Am i understanding you right ! you say you have a vented system working off your main storage tank ?? can you check and see if you have a small tank in loft that should be connected to heating system ! if not you may have one of the combined type tanks but this is usely a squaire tank, please check, if you only have a standerd tank doing both then you have a big problem .
:ack2:

 

[diamondgas]

Minty, do you have your appliance maintained? If so I'd assume you trust this person? Why not pay them for their advice?

Air in a system rapidly increases corosion and sludge build up. My advice to you is get it looked at sooner rather than later! As mentioned, you should have 2 tanks if your system is an open system unless its an old stile Primatic cylinder gravity hot water.

 

[Minty_Cymru]

I think it's a 'vented' system, it has a pipe going from the top of the hot water tank and feeding back to the cold water tank (open ended above the tank.

When I was in the loft changing the float valve in the cold water tank, I didn't see another tank - to be honest, if there is another one up there it would probably be above the hot water tank and the loft is so small I wouldn't be able to get to it.

The system (what ever it's design) has worked well since I've been there, around 15 years, so maybe I'm wrong. I guess I'm going to have to call a plumber?

 

[fuzzy]

try to see if you have a second smaller F&E cistern (tank) then let us know

 

[JohnRMoore]

This happened to our system that we inherited when we moved house. I suspected the boiler thermostat, but it turned out that the flow pipe was being used as the return pipe. As a result, the thermostat was measuring the temperature of the return, and so not kicking in early enough to prevent an overheat (whooshing and banging). Got a new bolier now, but fixed that temporarily by turning the thermostat down.

 

[Minty_Cymru]

Well, I've not had the chance to get up there toay (and won't tomorrow either, going away) but the since we've bled it well it's not made any noises.

So either:

- it was air that got trapped when the rad was changed
- or air got in to the system somehow when I changed the float valve in the cold water tank
- or the new float valve is too restrictive and on teh odd occasion we run fill the bath, run the heating, flush the toilet AND run the water elsewhere, the storage tank runs dry.

I am still curious about the header tank though, and I won't be forgetting about this too soon so if anything happens I'll be back with more info.