Gas central heating boiler kettling, testing weak circulation pump?

[tigdlo]

My Mum has had a plumber recommend a new circulation pump due to it being weak and a probable cause of the kettling. He said the pump is too easy to stop manually meaning it has gone weak. I wouldn't have thought it would have a great deal of torque anyway, anyone tested a pump by removing the screwcap and stopping the pump with a screwdriver?

Would a weak circulation pump cause kettling?

Just don't want my Mum to spend £250 on a new pump if she doesn't need it. I had to turn the boiler temp down to 48°C from 60°C to stop the kettling, after 2 weeks like that it is now running at 55°C without issue, but can't go higher.

Thanks in advance for any advice.

 

[OJCar]

He said the pump is too easy to stop manually meaning it has gone weak. I wouldn't have thought it would have a great deal of torque anyway, anyone tested a pump by removing the screwcap and stopping the pump with a screwdriver?

I have only see it done by a plumber who turned out to be an utter cowboy.

 

[brightspark]

is it a 3 speed pump.if it is turn it up and down . if its 2 fast and running properly it will spin the water on full speed and you will hear it

 

[Bornfree]

The last time I bought a grunfoss 15 50 it was about £50 I had to Google the price now. Unbelievable increase.

 

[Tim.S]

You shouldn't be able to stop pump by sticking screwdriver in the end, if you can then either the pump has had it or more rarely the impeller is jammed up with rust, but either way if the boiler kettling it normally means it's full of crud and changing the pump won't make a blind bit of difference.

 

[DanZac]

either way if the boiler kettling it normally means it's full of crud and changing the pump won't make a blind bit of difference.

Not saying its not the pump but with my limited experience I'd agree with this.

The boiler here kettled like a good un the first winter we moved in. A couple of good flushes, some descaling treatment (really hard water here) and a refill with inhibiter and touch wood it's been fine ever since (10 years).

Now I've tempted fate, watch this space for my next post saying the boilers packed in after ten years on Christmas day.

 

[Ross365]

When was the inhibitor last replaced (they don't last for ever) and did you use a quality one (i.e. Fernox)?

As well as being an inhibitor, I think that Fernox has anti-kettling additives. With Xmas so soon, I wonder if the lesser of many evils would be to go get some Fernox inhibitor in one of the cartridge packs which allow it to be added via a radiator bleed valve and see if the kettling goes away?

 

[DanZac]

When was the inhibitor last replaced (they don't last for ever) and did you use a quality one (i.e. Fernox)?

Mine? Drain and replace the inhibiter every couple of years, and I refill the Magnetic cleaner bowl with inhibiter when I clean that out every year too as a top up, which takes pretty much a full bottle.

You've got to look after these things haven't you, you wouldn't run your car on the same oil for ten years, so likewise you can't expect your heating to keep going without a bit of love now and again.

 

[Morrisman]

Many years ago we had very noisy central heating. The Homecare guy came out twice and replaced the pump, over a two year span. Third call out he refused, saying the system was full of rust and needed a power flush and lots of copper pipe replacing. He stuck a magnet to the copper, to demonstrate how it was lined with rust. £750++ he reckoned.
I went to the local plumbers to ask them how much they would charge... and the guy just handed me a bottle of Fernox and said "Don't bother". It worked, 24 hours later no noise from the heating.

 

[Tim.S]

When we say the system is scaled up we mean with rust flakes not limescale and the kettling is when those flake get heated up individualy and starting to boil the water in the boiler, the boiler silencer treatments glue those flakes together at the bottom of the boiler, the problem with it is you have now increased how much metal that now has to be heated before it hits the water and you are reducing the surface area of the heat exchanger so the boiler is now very inefficiant and you are burning lots of gas also if you want to powerflush the system later on, you are never going to shift that big lump of rust sitting right at the bottom of the boiler.

 

[Wozzaaah]

Some time back our boiler was overheating badly, to the point it would overpressure and dump water via the PRV.
I did the usual and swapped the old DHW heat exchanger for the clean one I always have to hand and it didn't cure it.
It turned out that the pump wasn't spinning so I span it up with a cordless drill both ways several times and a fair bit of black silt came out of it. It worked fine afterwards.

 

[Morrisman]

... and a fair bit of black silt came out of it. It worked fine afterwards.

That stuff is the strongest black dye known to man. I got some on a light coloured carpet once, and could never get the stuff out no matter what I used.

 

[brightspark]

That stuff is the strongest black dye known to man. I got some on a light coloured carpet once, and could never get the stuff out no matter what I used.

i managed it once spilt some on a punters new white carpet from a bit of plumbers pipe took half an hour using neat undiluted carpet cleaner solution and a load of scrubbing and wetting was verry lucky as u say its virtual;y impossible to remove

 

[Ross365]

Yes, the black stuff (magnetite ?) is pretty clingy. Citric acid might be worth a try, but suspect it would be slow.

 

[tigdlo]

Thank for all the replies.

2 years ago the heating was drained, refilled with a cleaner and flushed with fresh water before finally draining and refilling with an inhibitor, both cleaner and inhibitor were branded Corgi from Toolstation.

A few months ago I did the same, with the same products but fitted a Magnaclean before the final fill with inhibitor. Also replaced a stuck drain valve, a couple of TRV's, cleaned the growth out of the header tank. Had it serviced, the overflowing condensate fixed and a seal replaced by a plumber. There was a plastic tray catching the condensate which had quite a bit of flakey black rust in it once the plumber had finished so I guess he got into the heat exchanger, i guess that shows it had some rust build up. The magnaclean still picks up some rust so there is definitely some floating around the system.

I did get some kettling while I was refilling but put it down to air as it went away once it was fully bled and run for a bit.

The pump replacement has been cancelled. The Magnaclean came with a cleaner and inhibitor so I will give it clean and flush, then some fernox before throwing parts at it.

 

[gaz1]

magnaclean will not clean this type of heat exchanger within a boiler



not even reverse flow will clean them as it takes some doing and theres no guarantee it will work

the best way is to flush your system seperate with a pump or high pressure water through the system and flush the whole system out so its purly clean with each rad and the copper pipe

then flush your boiler out

pump is pump try stopping it yourself it takes some doing if it is stalling then its on its way out or has failed if it does stop

you can swap to a cheaper pump if you want to do just direct connect both fittings as a straight through or find fittings that will drop down to the new fitting sizes

with a straigh through connection fit the pump elsewhere close to the boiler

 

[Wozzaaah]

A magnaclean is not designed to clean a boiler, it’s purpose is to prevent the magnetite particles from entering the boiler.

 

[brightspark]

A magnaclean is not designed to clean a boiler, it’s purpose is to prevent the magnetite particles from entering the boiler.

and stop them settling in the bottom of radiators .sludge

 

[OJCar]

Here is a UTube about them ...

 

[gaz1]

A magnaclean is not designed to clean a boiler, it’s purpose is to prevent the magnetite particles from entering the boiler.

yes it does but it hasnt stoped enough particles from already entering your boiler from the bad services and poor maintenance that your boiler has already suffered

you still have particles within your heat exchanger and pump as well as within the pipes of your boiler

if anything the main parts that possibly would need replacing are the heat exchanger or flushing it well out and your pump

oj im a plumber so i tend to know more than you may think

i also know the old systems that many dont know some that you should still come across in scotland whilst theres many that still exist in my own area of the old designs