Boiler kettling - now I'm confused ?

[andyaveyard]

History.

The boiler is about 20 years old and was fitted new when we bought the house, I believe it's an Ideal Elan II.

A couple of years ago I was advised to use some descaler to clean the system as we had bad boiler kettling, prior to this I had renewed the pump after being told that that could have caused the problem, unfortunately it wasn't that. The descaler seemed to do the trick until just recently when the kettling/banging started again. Although the pump did appear to be stuck at one point, I freed it and it ran ok afterwards (it still seems ok).

In the last couple of days I have used Sentinel x400 de-sludger then flushed with clean water, that didn't seem to help although lots of brown water drained out. Yesterday I drained the system again and now have Sentinel x200 de-scaler in the system, I've bled the radiators again and balanced them.

Last night after doing the above, the boiler once again started kettling/banging but when I manually turned down the stat (to 50c) on the hot water cylinder it seemed to run ok for the rest of the evening .

This morning my wife turned the heating off until I returned from work, as the boiler was kettling and banging again. I got home and turned the heating on, it ran fine for 10 - 15 mins before playing up again, I fitted a new cylinder stat as I thought that could just be the cure, it wasn't.

The system has a 3 port motorised valve, the clock/control has 2 heating options, HW or HW/CH.

I'm wondering if the 3 port valve could be at fault but I don't know how to check this, can anyone help me with some advice ?

Sorry if it's a bit long winded but I'm trying to give as much info as possible.

 

[andyaveyard]

Any ideas folks ?

 

[ollski]

You could get someone in to make sure the gas pressure is set as low as it can be on that boiler, but you won't get a quiet 20 year old ideal elan!. I found salamander boiler silencer can make a difference.
If it is a sudden onset though I would be looking at the pump first ie slow / sticking.

 

[Agile]

In the last couple of days I have used Sentinel x400 de-sludger then flushed with clean water, that didn't seem to help although lots of brown water drained out. Yesterday I drained the system again and now have Sentinel x200 de-scaler in the system, I've bled the radiators again and balanced them.

You must learn to read the instructions! In any case regardless of what the instructions say you must leave X400 in the system for 3-4 WEEKS and not 2 days !

You need to treat your boiler with a dose of sulphamic acid !

Tony

 

[andyaveyard]

Many thanks for the replies, I ditched the X400 and used the X200 de-scaler thinking that scale build up was more likely to be the cause of the kettling as the radiators heat up fine.

One point I should have mentioned is that when the pump runs it does seem to vibrate more than it used to do, there's also more of a water movement sound (does that make any sense?), sometimes it sounds like particles may be moving through the pump too. I'll leave the descaler in and perhaps with time that might help. The pump works on all 3 settings, it's currently set on the highest. I have bled the pump several times via the large screw on the side.

Last night the boiler kettled again, when I manually turned the cylinder stat down to 50c the 3 port valve moved over to H only and the kettling stopped. I can turn it back up and it'll run ok for a while. It seems to kettle more when the cylinder requires the water to be heated (i.e if someone runs the bath / shower).

 

[Bahco]

You could try opening the bypass (if fitted ) a little and see if that helps.

Do you have one rad without a TRV

 

[andyaveyard]

A TRV ?

 

[wanleg]

Look here for definition

//www.diynot.com/forums/viewtopic.php?t=37582

 

[andyaveyard]

Thanks Wanleg, in that case I don't have any TRV's at all.

 

[lxbn]

I have a similar problem as andyaveyard, albeit with a newer Bosch boiler (2 years) installed, as I too have a 3-way motorised valve.

I mention the valve because the kettling sound seems to occur when the HW heating starts up. Today I turned on the Heating (before the HW came on at the programmed time) and all seemed quiet until the HW came on. Also when I turned off the HW the kettling stopped. Could the valve itself be the problem? It's just an un-informed observation - to-morrow it may do something else and prove me wrong.

I haven't tried anything in the way of treatments etc. - when the boiler was installed the system wasn't powerflushed because the engineer checked the system and didn't think it necessary.

 

[Agile]

I haven't tried anything in the way of treatments etc. - when the boiler was installed the system wasn't powerflushed because the engineer checked the system and didn't think it necessary.

Presumably the engineer did not think that it needed inhibitor either!

Tony

 

[gas4you]

In reply to op you may have a blockage in the cold fill pipe, so system has not filled up completely. X400 is very good but it will only clean system within 1/2 hours if used with a powerflush machine.

I agree with other replies, check pump first. Banging is usually due to lack of flow through boiler and as this is a low water content boiler will be more susceptible to this problem

 

[lxbn]

Presumably the engineer did not think that it needed inhibitor either!

Yes he did put in the inhibitor - does it lose potency over time and needs replenishing? If so, what do I use and do I simply put it into the expansion tank - will this help with the kettling?

 

[Bamber gaspipe]

Presumably the engineer did not think that it needed inhibitor either!

Yes he did put in the inhibitor - does it lose potency over time and needs replenishing? If so, what do I use and do I simply put it into the expansion tank - will this help with the kettling?

It could be that your three port valve is sticking between H/W & C/H. Inhibitor is used to stop corrosion in your system.

 

[lxbn]

I think I'll have the 3-way valve checked. Sometimes it clicks rapidly about 3 or 4 times, so it seems a good place to start. Thanks.