Help Please - Noisy Central heating

craiginuk · 26 Mar 2010

Please can someone help me. We have a Potterton Suprima 100L Boiler mounted in our kitchen downstairs. I know these boilers have problems with locking out due to pcb but but I think my problem is slightly different.

Approx 1-2 times a week the boiler starts making a scary pressurising rumbling sound. The tank upstairs (in my 3 year old son's bedroom!) makes the same sound. A few seconds later the boiler locks out (flashing red light) If I reset, it will run for another week or so and do the same thing again.

I have had a plumber round who said it may be air in the system. He's bled all the radiators and the circulating pump upstairs in the water tank cupboard. Still doing the same thing. To me it seems like the boiler is overheating in some way. Could there be a faulty temp sensor somewhere that is letting it run too hot?

Any suggestions appreciated as I am at my wits end. Just had to comfort my little boy again after waking up to this noise.

Thanks

Craig

Gasman28 · 26 Mar 2010

When you say the 'tank' in your sons bedroom is making noises, do you mean the hot water cylinder or small expansion tank?
It could be that your system is partially blocked ( normally where the cold water feed to the system joins from the expansion tank )
Try a magnet on the pipework where this joins. If it sticks to the Copper pipe, then the system has Manganite in it and requires cleaning.
This partial blockage could cause the boiler to go to overheat, requiring re-setting.

darren17 · 26 Mar 2010

how old is the system
when was it last serviced
does the boiler make a noise like a kettle boiling
when does the noise happen is it on start up
what is the pressure reading on the system

craiginuk · 27 Mar 2010

Thanks for the quick replies!

Hi Gasman,

It is the hot water cylinder in my son's bedroom. I will try a magnet on the cold water feed into the hot water tank.

Craig

Hi Darren,

The boiler was installed around 2003. The hot water tank has a dual coil (gas + solar panel)
The system is gravity fed from header tank so I don't think there is a "system pressure" - or if there is, where would I read that from - don't seem to be any gauges anywhere - except the one that is for the solar panel system

Boiler was serviced about 10 months ago. Boiler doesn't make a noise like a kettle boiling. It is more like the sound of water being forced through a small opening if that makes sense.

Sorry - central heating all very new to me - where I'm from (South Africa) you just put a jumper on if you're cold

craiginuk · 27 Mar 2010

Oh - and I don't think it's on startup. Boiler is normally running and then changes tone/makes the noise.

darren17 · 27 Mar 2010

it sounds as the flow is restricted by sludge
get your system chemically cleaned
no there is no pressure guage as it is an open vented system
are the rads cold in spots
fernox do a cleaner called heavy duty restorer
drain down the system and add to f&e tank
refill system and vent rads
if the magnet does'nt stick to the copper then use the fernox and leave it in your system at normal operation temp for approx 4 weeks
if there is a blockage in the feed pipe simply cut it out and refit new pipe
then you can go ahead and put the fernox in

craiginuk · 27 Mar 2010

Thanks Darren,

Magnet doesn't stick to the cold feed. Boiler is being moved on Monday(just into a new cupboard about a metre to the left) I will get the guy to add a cleaner to the system when he does it. Will I see if it is sludge causing it when he drains the system?

There don't seem to be any cold spots on rads. If I bleed the highest radiator upstairs (a towel rail) after the boiler has done its noisy lock out, I alway get a bit of air.

darren17 · 27 Mar 2010

what speed is your pump set at 1/3
get your installer to check the the location of the feed and expansion pipes
pump could be pulling in air
yes you will the water will be black dirty
get your installer to do a test on the water from the rads with a tds meter this checks the ratio of solids to water

craiginuk · 27 Mar 2010

pump is set at 3 - Is that about right? (highest setting)

Will get installer to check the water and look at the expansion and feed pipes.

I know it is hard to say but is this installation dangerous as it is now?Really don't like the sound it makes.

Alangas · 27 Mar 2010

As with the other people check for sludge etc. Also these boilers need to have 28mm flow and return. Has the plumber checked the pump impellor is working, I had one the other day where the spindle was going around but the impellor wasn't.

darren17 · 27 Mar 2010

pump only needs to be set to 2
no it's not dangerous the noise is only an irritant
if you take center screw out of the pump when the pump is running and put a screwdriver in the impellor should hit of it

craiginuk · 27 Mar 2010

Thanks Darren, Can pump being set at 3 be causing this?

darren17 · 27 Mar 2010

yes it could be drawing in air to the system
depending on the position of your feed and ex pipe
the air being drawn into your system is what causes the magnite as it attacks the inside especially if you have not got enough inhibitor in the system
you can always try no 1 setting on the pump

craiginuk · 28 Mar 2010

Thanks aLl and especially Darren. I am hoping I may have found the cause

We had a TRV fitted in the bathroom when they fitted a heated towel rail few years back. Has always been cranked up to max but I noticed today it was set on 3. Also, the only other radiator without a TRV fitted upstairs was closed. Could this cause a problem with no means of circulating heat when the HW and CH are no longer calling for heat?

darren17 · 28 Mar 2010

how many rads have you got and how many have trv's
do you have an abv or were they using the rad upstairs as the bypass

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Help Please - Noisy Central heating

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