Very noisy boiler after new pump fitted

[MJ]

Hello,

I hope someone might be able to assist me with this problem.

I have an old central heating system, a Servowarm Elite 30 which has served me very well until this summer, when the boiler stopped working and the problem was diagnosed as a failed pump. After having been told by the company that I needed a specific pump which was not available and the only recourse was to replace the boiler, I had a plumber look at it who said a standard pump would work just as well, although it would not fit inside the boiler as it also necessitated replacing the valves either side. This was subsequently fitted about a month later.
Since then, the water has been nice and hot, the radiators almost too hot to touch and some of the radiators and pipes 'tick' while the system is working. I don’t know how long the pump had been working at a reduced rate but the system is certainly much better now.

However, the boiler now makes a terrible racket when it is running (both water and heating), groaning and moaning with all sorts of howls and knocks and vibration. It keeps us awake at night if it starts up, so I have had to reduce the [programmable] thermostat overnight with the overall temperature lower than ideal. I think that if this carries on, something is going to break and be very messy and expensive, so cannot be allowed to continue. It stops making a noise when the flames go out. I have the pump on the lowest setting.

I know that replacement parts are not available so I have done some research to try and find out what is wrong, with limited success. I can’t see anything this specific on your site.

I thought that it might be due to dirt and scale etc in the system - specifically the heat exchange as this is where I believe the noise to be coming from - and thought that the Fernox products introduced into the system would hopefully cure this. As the system would need a power flush before a replacement boiler is fitted anyway, this would not be a waste of money.
I am worried though that it may cause leaks in the system.

A neighbour has suggested that it could be air in the system, and I can get air out of the vent in the airing cupboard by the water tank almost on a daily basis although I don’t think that there is air in the radiators.

But it has occurred to me that it might simply be that the system is running far too hot now.

Is it possible to open the compartment where the flames are (boiler off of course) to have a look and see what is in there with the idea of maybe taking the exchange out and cleaning it? Could it be the thermocouple, which I know has been replaced in the past and which I think is a standard replacement? How do I tell it is in the correct position? How do I tell it is working?

Could it be due to the new pipework joining the in and out pipes where the pump used to be, in which case I will have to get the plumber to come back and have a look at his work?

Thank you in advance.

 

[zimmers]

Why not,get a auto air vent fitted,on the circs and also drain down add a light cleanser,leave for 2 weeks,drain down and add inhibator.and see it helps,didnt servowarm used to leave there header tanks without mains to fill up,surely it fills properly now?

 

[zimmers]

THE O/HEAT STAT ?

 

[MJ]

Zimmers,

Thank you very much for your reply. There is actually an AAV at the very top of the system in the loft, and yes, the expansion tank has no mains feed. As far as I can tell, the system fills up ok, with no loss of water from the expansion tank being noticed.

I noticed this morning something that may help.

I had run out of hot water, due to the fact that I had turned it off a couple days ago and forgot to turn it back on. As the boiler is water priority based, it shut down the heating and for the next 45 minutes the boiler was absolutely silent while it did its business, with the flames on as well. It was wonderful! When it reverted to heating mode the boiler immediately started its din again.

I’m beginning to think that the problem has somehow been caused by the installation of the pump, especially as the noise was not there prior to the pump failure. Is there any way of confirming this? Is the pump pushing the water through too fast (I’ve got it on the lowest setting at the moment)?

I have a feeling that the plumber said something about the water circuit between the boiler and the water tank is much smaller than that of the heating circuit. Does it actually use the pump in hot water mode?

I’ll do some more experimenting over the next few days and report back with my findings.

What is the o/heat stat, please?

Thank you again.

 

[Nige F]

,didnt servowarm used to leave there header tanks without mains to fill up,

have you ever seen the "flower vase on the wall" "Header Tank"......... from way back when the boiler had a hinged radiator on the front Still, they made a fortune ££££ Allegedly

 

[bengasman]

sludge in system, always the same with open vent

 

[MJ]

Bengasman,

Thank you for your advice. How likely is it that leaks will appear if I use something like Fernox to clean the system? And if they do, is there anywhere they mostly occur? Will they be easy to fix?


An update:

On at least two occasions now the boiler has been absolutely silent, so much so that I had to keep checking that it was working!!!

However, for the majority of the time it is a nightmare, and I have now had a complaint from a neighbour to get it sorted.

As far as I can tell, the noise is inside the boiler. It is nowhere else in the system. Some of the time, it sounds as if the boiler is filling up with water. I know that the radiators have no air in them. I regularly get air out of the vent in the airing cupboard though – where is that coming from then?

This has only started since the pump failed. It would have made itself evident earlier if it was due to muck in the exchange, surely?

Is it possible to remove the exchange myself and have a look at it?

Thank you.

 

[bengasman]

Leaks are not caused by cleaning, they might show up though if they are there. Not likely to happen with fernox as it will only get half out.
You can not clean the heat exchanger yourself, but it is unlikely it has major problem anyway.

 

[JohnD]

give it a simple chemical clean for a start. It is an easy DIY job.

Corrosion generates gas in the system and black sediment.

Sentinel X400 is a mild and non-aggressive cleaner. it is not acidic but it loosens black sediment so you can drain it out. You can leave it in for four weeks or more. You will probably find the water goes very black as it washes out the sediment. this is good.

The chemical will cost you about £15 for a litre bottle.

Sludge deposits are a very common source of problems in old systems. If you still have problems after cleaning out the sludge you can work on them afterwards.

If you want to occupy yourself with some basic plumbing, add a mains feed with ball-cock to your F&E tank (fit a new F&E if the old one is not suitable) and make sure you have a good drain cock at the low point of the system - you will be needing them when you flush and refill. If you enjoy plumbing splash out £100 or so on a Magnacean as well and fit it on a vertical 22mm return pipe. It will trap circulating black sediment and prevent it forming new blockages. You still have to drain and flush after the clean though to remove the detritus which is not black iron corrosion.

When you have got the system resaonably clean you will have to add a corrosion inhibitor chemical such as Sentinel X100 which prevents future corrosion. it will cost you another £15

 

[tryitandsee]

When the plumber replaced the pump outside the boiler, did he put it on the flow pipework or into the return side into the boiler. Also was the speed setting simular to the old one. I don't know if this would make any difference, but seeing as it has only started since the change of pump, it may be the problem.

Can the pump cavitate if fitted near the vent pipe

 

[MJ]

Thank you Bengasman, JohnD and Tryitandsee for your assistance.

I'm not sure which pipe he has fitted it in, but as you'll see below it appears to be irrelevant.

As the noise was coming from the boiler and nowhere else, we decided to try the X200 noise reducer first, with the option to do the X400 full cleanse if it did not work and next year in any case when we have more time and can deal with any problems if they arise, followed by some X100 inhibitor.

I drained some water from the system to start with and added the solution to the F&E tank. Once refilled, it took a while to get the air out of the radiators but after that we started the boiler and immediately no noise whatsoever! I left it running for over two hours and it was bliss.

After a night with no noise, what we have concluded is that there was absolutely nothing wrong except for an air pocket in the boiler, that did not go away by bleeding the radiators but cleared itself when the system was drained.

Something to remember for the future, I think.

Thank you again for all your help.

Merry Christmas and a Happy New Year to all.