Loud rumbling, steam and hot water coming out of vent pipe into expansion tank

[alastairpearce]

Hello,

Relatively new to this forum - did post on here a couple of months ago when I had a faulty thermostatic valve on my hot water cylinder.

Except for the aforementioned thermostatic valve, the system has been running fine for over a year (since I moved in) and has been reliable for what can only be described as an old system.

Anyway, I have an Ideal Classic boiler, Grundofs Selectric Pump, Myson Aerjec (all shown in the attached picture).

Like I say up until a day ago the system has been running smoothly. Then all of a sudden last night I heard a deep rumbling sound, gradually increasing in volume and then some serious rumbling in the pipes in the cupboard containing the cylinder, which ceased when the boiler shut down.

Upon further investigation this afternoon, this rumbling/rattling culminated in an ejection of dirty brown water and a gush of steam out of the vent pipe into the f/e tank.

The pump seams to be working fine and continues to work after the boiler cuts out, so I don't think this is a faulty pump issue.

I've seen 'Kettling' mentioned on other threads but don't really know what 'kettling' means.

Could this steam be caused by limescale buildup? Or a buildup of sediment in the boiler? I'm in London, so i'm gessing limescale could cause a problem.

Can anyone give any helpful suggestions?

Much appreciated.

 

[alastairpearce]

One more thing - the heating coil in the cylinder has a drain valve, but I can't find a drain valve of the Ideal Classic boiler.

The boiler is downstairs and the cylinder is upstairs in the bathroom.

Presumably, if I drain from the cylinder in the bathroom this will not remove any sludge below in the kitchen?

 

[tamz]

It is either
a) the pump (because it is turning don't mean it is pumping).
Is the water circulating through the pump and back to the boiler (feel the pipes)
b) boiler stat
turn it down and check it turns off
c) system blockage
feel the pipes
d) lack of water
choked feed , stuck ballvalve, stopcock off

 

[alastairpearce]

Thanks for the reply.

I think the pump is pumping - how can I determine if it is not pumping?

The boiler stat seems to be working - when I turn it down, the boiler turns off. When I turn it up again, the boiler turns back on.

There is plenty of water in the system, i have checked the water level in the feeder tank, and ensured that the feeder refills when the ballcock drops.

Other than the pump, it would seem system blockage is the only other issue.

 

[alastairpearce]

Just an update - when the really loud rumbling occurs (it has just happened again) there is a sound like a crunching of machinery coming from either the pump or the Myson Aerjec.

Could it be a blockage in the Aerjec causing the pump to come to a grinding halt?

I don't know how to get into the Grundfos pump to check it's intact.

Can you advise?

 

[tamz]

Thanks for the reply.

I think the pump is pumping - how can I determine if it is not pumping?

Is the water circulating through the pump and back to the boiler (feel the pipes)

There is plenty of water in the system, i have checked the water level in the feeder tank, and ensured that the feeder refills when the ballcock drops.

Because the tank if full doesn't mean the system is. The feed pipe may be chocked.
Because of the way it has been piped the aerject is the highest part of the system. If the water level drops below that your pump cannot pump anything.
Try sticking a magnet to the feed into the aerject (the pipe to the left). If it stick it is full of sludge, maybe to the extent of blocking it.
Wrap a towel around the pump and slacken the nut on the top of the pump valve and see how much water comes out.

 

[tamz]

Just an update - when the really loud rumbling occurs (it has just happened again) there is a sound like a crunching of machinery coming from either the pump or the Myson Aerjec. It is coming from the pipes. That will be the steam.

Could it be a blockage in the Aerjec causing the pump to pump nothing

You can get a good tune out of it if you practice

 

[stevetheplumber]

could just be the boiler stat

 

[alastairpearce]

Could it be a blockage in the Aerjec causing the pump to pump nothing

If the pump pumping nothing sounds like grinding machinery, then yes it seems likely that this is the cause.

You can get a good tune out of it if you practice

Doesn't sound like any tune I'd like to listen to - sounds more like some sort of industrial techno.

 

[alastairpearce]

could just be the boiler stat

I think the boiler stat is functioning fine - it turns the boiler off when the stat is turned down, so would suggest it is working?

 

[alastairpearce]

Further to my previous posts - can anyone please explain to me how my heating system works. I have tried to figure out how the circuit works, but can't fathom all the pipes.

The flow outlet from the Aerjec goes to the pump, and from there into the heating coil in the cylinder, or into the radiator circuit via the motorised valve? Am I correct so far?

I've checked all pipes coming into and out of the Aerjec, and all pipes are hot after the boiler has been running for a few mintues and the banging/grinding noises have commenced. Any ideas what this signifies?

I'm sorry for the bombardment of info/questions; but I'm a heating novice and I'm struggling to get to grips with how my heating system functions.

 

[tamz]

Which pipes get hot when it starts banging. It will be the flow from the boiler and the vent with maybe a bit heat on the feed and down towards the pump.

If the pump is working and it is full of water the flow from the boiler through to the system flow should slowly rise in temperature.

Take the big silver screw out of the pump ( a bit water might come out but not much) then get a small flat screwdriver and put it in through the hole. It should rattle against the shaft of the pump if it is turning. If it is turning slowly try spinning it with the screwdriver. some muck will be trapped. If not turning the pump is knackered. If it is turning quickly the impellor may have broken off.
If you are not confident to do this you will need to get someone in.

 

[alastairpearce]

Hello,

An update to this post I left thee weeks ago.

I have since removed the pump, and it was full of black metallic deposits. So I cleaned the pump out.

Then I have had someone undertake a power flush of my system, to remove any sludge. Following the power flush, the problem persisted, so I had a new pump installed.

Therefore, I think I have ruled out blockages in the system and a faulty pump as the cause of this problem.

The problems only seem to occur when I want hot water only, which narrows the problem down to the hot water circuit. With the pump speed turned down to 1, and the boiler thermostat set to 2, the problem doesn't seem to occur. It is only when the boiler thermostat and the pump speed are turned up that the banging occurs and steam comes out of the vent pipe.

The pipework forming the hot water circuit is smaller in diameter, which could in effect cause a bottleneck on the flow when the hot water circuit only is selected.

Which leads me to conclude that if the pump speed/boiler thermostat is turned up too high, the thermostatic cylinder valve (smaller diameter pipework) acts to restrict the flow in the hot water circuit and hence the boiler is overheating the water causing a jet to rise up the vent pipe.

Would anyone concur with this diagnosis?

I guess the answer to the problem is to have a little more discipline in turning the thermostat down in summer when heating is no longer required, and also keeping the correct pump speed so the pump is not restricted?

 

[Nas]

sounds like airlock to me