Another noisy central heating problem...driving me nuts

Hi all.

My first post but hopefuilly someone can help

As the post might suggest I've got a very noisy central heating system..and its definately the pump. Essentially it sounds like the bearings of the pump have had it ..but ..can only be so if I have had 3 duff pumps in a row. It does sound very similar to a system I had before (in a different house) when it was full of air..but I am fairly convinced this isn't yhe problem..see later.

System is mostly new (boiler, H/W tank, pumps controls etc all new with only a few old pipes remaining). Boiler is a Worcester Greenstar 29 HE installed 3 years ago in the porch down stairs miles away from the pumps which are located in the airing cupboard upstairs. The pumps are a 'Grunsfoss pump plan' with a 15/50 to the hot water cylinder and a 15/60 to the heating system. 'It' is mounted vertically with the H/W pump on the top and C/H on the bottom. Pipework is 28mm from the boiler up through the loft and down into airing cupboard with separate 22 MM to H/W and C/H.

It is a sealed system (around 1.5 bar cold and 2 bar hot) with automatic air traps on the 28mm flow & return in the loft and one above the pumps.

Most of the rad's have TRV's apart from the bathroom (to ensure there is a bypass)

Tried so far:

1) Bleeding everything 1001 times > no evidence of air in the system + noting coming out of the automatic vents

2) Emptying system and refilling (only additive is fernox inhibitor)
3) Replacing pump (twice .. so 3 in total)
4) Replacing pump plan housing
5) Increasing system pressure
6) Turning pump down...still noisy..not as much but really need to run it on '3' to get the heat around..its a fairly big old house.

Professional plumber installed the system and he hasnt' been able to resolve (he changed pump housing and pump once).

OH, one last thing, its been noisy since day 1 but its now driving me nuts...

Anyone?
Cheers
Jon

was there any debris in the other pumps.

I am left wondering from everything you have said if the problem is just that you expect it to be totally silent? I assume you know the pumps should be on setting "2"and not on max.

The facts are that you have changed so many pumps and your "professional plumber" is unable to resolve it.

It also worries me that you seem to be paranoid about bleeding it so often. That often causes more problems than it solves.

I would ask the plumber what he thinks the problem is if any. Please could you email me his name and number so that I can ask him. My email is in my profile.

Tony

Fitz.
There wa no obvious debris in the pumps, whats your thoughts...?

Agile,

I'm not expecting it top be totally silent but this is something else!!

The bleeding the system bit I was probably overstating somewhat, I was more trying to make thw point that I was convinced that there was no air in the system..havn't actually touched it in months. To be honest I wasn't aware that pumps should be on '2' rather than max, rather begs the questions as to why there is a '3' ? In any case, it still very noisy in '2'.

The plumber that installed the system thought it was the pump housing ...if thats what you call it..when that was changed the first new pump was installed. The second was because I always like to have a spare hanging around for that inconvenient time when one does pack up (yep happened to me once with a pump in a new build that was less that one year old). Last Christmas the noise was bugging me so much that I chucked the spare on anyway...no difference.

Cheers
Jon

Only know about the two pump "plan" in theory ...not fitted any .......but may be something to do with cavitation in a pump....there is a thread on this ........and a wild guess is that it could be occuring because of incorrect pipe work .........so manufacturers website/helpline may be useful