Forever bleeding upstairs rads - cold, hot, cold, hot.......

[thomo2710]

Hi all,

Brought my house in the summer - 9 rad, 5 down 4 up.
Vaillant Turbomax Pro 24e Combi boiler

All radiators downstairs brand new (double panel) with brand new pipe work (15mm copper) All rads downstairs have new TRV's.

They all work fine - get nice and warm and never have any air in them.#

Upstairs is a different story.

4 single panel old radiators not replaced.
3 bedroom rads were taken off wall and flushed out of all black gunk and sludge.
Dont ask me why for some reason we never took the bathroom rad off to clean up!

Upstairs rads are fed by microbore (correct?) copper with 15mm tails from the rads.

Im constantly having to bleed the rads upstairs. Once bled they get warm and appear to work ok for 2 weeks or so then just stay cold or luke warm at best until bled again.

Bathroom rad always has masses of air out of her.
Small bedroom doesnt appear to have much pressure to force the air it does have out and when it gets to water it drips out rather than being pressured out.
Other 2 bedroom have a little air but not much.

All rads upstairs also have TRV on - new in 2 bedrooms and old existing in small bedroom and bathroom.

System has been drained down umpteen times throughout the summer as we were putting the new system in downstairs.

Boiler pressurises correctly (1.5bar when idle, just over 2 bar when running CH)

Also recently there is a loud bang that comes from a pipe somewhere when the cold water from the kitchen tap is turned off and also when the downstairs toilet is flushed.

Can anybody please help me get to the bottom of this - i am quite confident with most DIY so will try virtually anything you guys throw at me.

many thanks for your time in advance.

 

[JohnD]

Did you use a cleaning chemical? Did you add a corrosion inhibitor?

Does the system often need to be topped up with fresh water?

 

[Nige F]

Re pipe the upstairs

 

[thomo2710]

Did you use a cleaning chemical? Did you add a corrosion inhibitor?

Does the system often need to be topped up with fresh water?

no chemical - just hose pipe and washed through
No inhibitor

System has only been topped up after alot of air has been let out of the rads, otherwise it not needed doing

 

[thomo2710]

Re pipe the upstairs

not possilbe - the goverment would kill me, we have only just finished the house as it had a renovation from top to bottom, wall to wall.

Carpets newly laid etc!

 

[JohnD]

no chemical - just hose pipe and washed through
No inhibitor

That explains it then

Give it a clean with Sentinel X400, run it for 4 weeks as usual then drain and rinse. You will be surpised how much extra sludge comes out. When the circulating water goes black you will know is is starting to work, the black is dislodged sediment. On final refill, add Sentinel X100. If you are in a hard water area and your boiler sometimes sings like a kettle, or bubbles and knocks, add X200 Noise Reducer and leave it in - it softens limescale deposits.

Find the Pressure Relief Valve which probably goes through an external wall close to the boiler, and look for any sign that it has been venting or dripping. Every time you top up the pressure, you are adding fresh oxygenated water which encourages more corrosion and gas.

 

[thomo2710]

no chemical - just hose pipe and washed through
No inhibitor

That explains it then

Give it a clean with Sentinel X400, run it for 4 weeks as usual then drain and rinse. You will be surpised how much extra sludge comes out. When the circulating water goes black you will know is is starting to work, the black is dislodged sediment. On final refill, add Sentinel X100. If you are in a hard water area and your boiler sometimes sings like a kettle, or bubbles and knocks, add X200 Noise Reducer and leave it in - it softens limescale deposits.

Find the Pressure Relief Valve which probably goes through an external wall close to the boiler, and look for any sign that it has been venting or dripping. Every time you top up the pressure, you are adding fresh oxygenated water which encourages more corrosion and gas.

excuse my ignorance but this sentinel x400 - where do i put it? Into the radiators? ALl of them or just 1 of them?

4 weeks then a total drain down and refill of whole system?

The bathroom rad splurges out black stuff after its left all its air out but we never took that 1 off (dont ask why, i dont have the answer!)
Could that be circulating black cak around the rest of the upstairs rads and blocking them up?

Thanks

 

[JohnD]

the sediment can cause partial or complete blockages. otherwise it just makes the heating system less efficient, and can cause radiators to be cold in the middle.

you only need one litre of each chemical for a typical house. It will circulate round. If the system is partially drained, you can pour it down an open pipe or through a vent plug hole in a radiator. If not, and yours is a sealed and pressurised system, you need to get it in a cartidge and force it in using a gun (I have never had to do that as I have always had open-vented systems, where you can pour it into the loft tank)

more info on http://www.sentinel-solutions.net/product/category/central-heating/

Sentinel and Fernox are the two leading manufacturers, avoid cheaper or own-brand substitutes which may not be as good. Some Cleaning chemicals are aggressive and acidic.

P.S. It is possible, though not likely, that you have a leak on the suction side of your pump, pulling air in. Inspect for any signs of leakage - especially limescale or green deposits at or under a joint. The gas that comes out of radiators is usually Hydrogen, released when the steel radiators corrode. You can test this, if it burns with a blue flame when you open a rad vent, that's it. Clear the area of curtains or other flammable objects first.