Boiler - Surging And Kettling

[Vern1961]

About a week ago we had our heating engineer to change out the pump as it was grinding and squealing on start-up and sometimes when running. While changing it, we discovered the cold feed pipe from the header tank (it's an open system) was blocked by sludge so he had to cut in a bypass to refill the system. System filled alright and new pump working, but when it's running you can hear the boiler banging and occasionally kettling, accompanied by surging and gurgling from the pump and three way valve. I've tried bleeding the pump, the rads and the air valve on top of the pipework to no avail.

We have used this engineer for some years but I'm beginning to doubt whether he can fully sort out the problems. I'm also beginning to wonder whether the system itself is just basically shot. I could try getting a power flush done but we had one just over five years ago and if the whole thing is so badly sludged is it really worth spending the £250 - £300 which could go towards getting it all replaced?

 

[Nightglow]

How old is the boiler, number of possible causes, scaled up system, pump speed to high, sludge build up, pointlessly throwing good money away, keep repairing existing boiler.

Better in my opinion, is to get a closed system, get rid of the header tank in loft, etc, & install a more efficient combi boiler,Valiant ecoTEC plus 824, is a particularly good boiler
Valiant gives up to a 5 year warranty, if installed by approved fitter.

 

[Vern1961]

It's a British Gas RD1, not sure of the vintage though it was already installed when we moved in just over seven years ago.

 

[Nightglow]

I seriously consider a new boiler, as your present boiler, basically a Ideal Classic boiler, tarted up, it is in Band D, about 78% efficient whereas a new one is Band A, which means it's 90%+ efficient, saving you gas, plus you have anything up to 5 years warranty.

 

[Maccapacca]

Sling some fernox f1 and f2 in it that'll quieten it down

They have changed the brand it used to be 100 and 300? I managed to get another 5 yrs from a kettling boiler that way now it's our rental so who cares about the bills

 

[Vern1961]

Still trying to bottom this out, no end of bleeding both the pump and the air valve seems to be clearing the problem - which seems to be when the hot water is running rather than the radiators.

One thing I have wondered, is when the engineer recut the feed pipe, he may have joined it into the vent pipe - could this be responsible for throwing the system off balance? I've also noticed in the pipework above the boiler in the kitchen is a draincock, might opening this release some of the trapped air?

I may have a go at draining the system down fully myself and refilling, though not really the time of year as ideally I want to run some cleaner round the circuit for three to four weeks before draining down again and refilling with fresh inhibitor. However not much point if it's only going to scrub the HW circuit and not the rads.

Really I should call the engineer back to sort out his mess but missus insists we never let him set foot in the house. May have to resort to getting British Gas in if the above steps don't help but I can already hear the screams of protest from my current account...

 

[peterwalkley]

Is your 3-way valve working correctly. I had something similar a few years ago that we didn't get to the bottom of, but it stopped after the 3-way was replaced after it had died completely.

 

[the_dead_parrot]

It sounds like either the system is air locked or there are further restrictions causing poor circulation and overheating/noise. If it is an air lock it can be removed but it can take time. Usually having the heating and hot water on then turning the system on/off or using the pumps speed switch can shift the air. Though it has been weeks since the work was done so the air should have moved on its own accord by now.

It is fairly common to combine the feed pipe into the open vent. Its done because it is usually easier than repiping back where the pipe originally went. Though it is not a perfect solution, it should get water back in the system and get it working again.

There is still the high likelihood that if the feed pipe was blocked the surrounding pipework is in the same or close to the same condition. Usually where the cold feed would have originally tee'd into the system (or in the air separator if system design included one.) Try a magnet on the pipework around where the open vent and cold feed originally went. Due to the age of the system you will get a slight magnetic pull on some pipe but if there is anywhere with a strong pull this maybe the location of a partial or full blockage.

Hope any of that helps.

 

[darren73]

Sling some fernox f1 and f2 in it that'll quieten it down

They have changed the brand it used to be 100 and 300? I managed to get another 5 yrs from a kettling boiler that way now it's our rental so who cares about the bills

Fernox havent changed the names they are still called f1,f2,f3
sentinel are x100 x200

i would suggest putting some cleaner in the system and running it for a few days either sentinel x800 or fernox f5 after a few days drain down flush with fresh water and refill the system then dose it with inhibitor sentinel x100 or fernox f1 one bottle does upto a 100ltr system so dose it to your system size,
it may help if the system is that sludged but if its kettling that normaly points to a scaled up heat exchanger and you would have to use a different product hope thats helps.

 

[Vern1961]

Quick update... Gave in and got British Gas out last week (signed up to a 12 month contract). Engineer changed the 3 way valve then when he came to refill the system discovered the feed still blocked via the vent pipe.

Appears all that happened when the previous engineer ran the cold feed bypass was to fill up the vent pipe. Upshot is we have been running a half filled system for the last two months - no wonder it was noisy and a miracle it didn't break down altogether.

British Gas guy had to cut the pipe at the T junction and clean it enough to get the water flowing. System now filling okay and running quietly apart from the odd bump from the boiler, probably limescale from running half full.

British Gas coming back at the end of the month to do a power flush and fit a magna-filter which will hopefully improve things. One question, is it worth adding some cleaner to the system now before the power flush or is that not going to achieve much, bearing in mind the rads won't be on?