Odd throbbing noise from radiator after repairs

[icundell]

Hello there,

I had a blocked cold feed which took some time to get sorted courtesy of the first BG engineer being a numpty (he backfilled the system to get it working again). The second one cut out the relevant bit of pipe and cleared the blockage, the system refilled and all seemed good.

One result of this was a dose of Sentinel x400 entering the system (I had tried this not realising there was a blockage, so it just sat in the F+E tank for a couple of weeks while BG got its whotnot in gear). I do not know if it is a full dose, but the water in the tanks is an interesting shade of ditchwater at the moment. (I am guessing there is/ was a fair bit of crud in the system, despite the rads heating up properly and any 'bleed' water being nice and clear until the x400 arrived).

I was happy to let the x400 do it stuff for a bit and then drain/ refill.

However, I am now getting an odd throbbing noise (a bit like a badly tuned engine idling - thrum-thrum-thrum) in my bedroom radiator and to a lesser extent a nearby one. It starts around 30-45 mins after system start. It lasts anything from ten minutes to an hour, rising in intensity and then easing off, finally stopping - but comes back every now and then.

Both boiler and pump sound normal (silent in the pump's case) while this is happening.

I thought it might be the pump grinding, but the BG man (the same guy who fixed the original problem) reckons it is scale (and therefore not covered by Homecare). Does this sound right?

I was thinking of leaving the x400 to do its stuff until after xmas (time!) and then having a crack with Fernox Heavy Duty Restorer or similar.

Anything else (or better) I should do/ expect?

(It is an old system with an old Apollo Fanfare boiler - late 80s council installation)

Thanks for any advice,

Ian.

 

[ChrisR]

TRy the boiler on Low
TRV's? If so adjust lockshield.
LEave the X400 for several weeks for full effect.
If 2 people, remove rad and flush with hose in the garden.

 

[JohnD]

it is possible that by X400 breaking up sediment the flow has improved. see what speed your pump is set to. If the heating still works on a lower speed, turn it down. It might have been turned up to overcome the clogged parts.

if you have a full dose of X400 in it (and it was not lost by cutting pipes) then the water should go deep black.

 

[icundell]

Many thanks. Interesting.

Looking at the TRV on my bedroom rad, it is the original and was a tad "crunchy" when turned. Also, it does not seem to shut off the rad, so I guess that will need replacing whatever else happens.

The bleed water is almost clear, with just a hint of a rust colour (while that in the tank resembles rather muddy water). Is there any harm in over-dosing with x400 (on the in-for-a-penny principle)?

I have just turned the pump down (to 1 from 2) and the system still seems quite happy. Will monitor.

 

[JohnD]

I don't think another bottle will do any harm. It is not aggressive or acidic.

http://www.sentinel-solutions.net/en/heating/X400/application

you have to drain a bucket of water out of the drain cock downstairs to draw the chemical down from the F&E.

 

[icundell]

Oh, cool. I'll do that then. I suspect quite a bit of the original dose may have disappeared out of the overflow while it was blocked anyway.

Sadly, turning the pump down did eventually lead to a downstairs rad going cold. Pity - the system was noticeably quieter.

edit: oops. forgot the basic courtesies - many thanks!

 

[JohnD]

do some balancing - turn down the hotties and the chilly one will warm up

 

[icundell]

Yeah, I did give that a go, no real joy. Even with the pump on 2 the return pipe from that rad is pretty slow to warm up.

 

[JohnD]

might be a partial sediment blockage

if it is, and water can circulate through, the X400 will help soften it.

you will know it is starting to work when the water goes black (unless you have a very unusual system with no sediment in it)

 

[bengasman]

If the water coming out of the rads is clear and in the tank is mud, it is unlikely that the tank is filling the system.
Tie up the float valve, drain a bucket of water from the system, and look in the tank, it should be empty. Remember to release the float afterwards

 

[icundell]

It would be very tiresome if it had got blocked again already (there was a cold feed blockage - the muddy/ rusty colouration of the water only arrived after that was cleared - and a day or two later at that). The bleed water isn't 100% clear - there is a definite rusty tinge to it that might, in large quantities, look like what is in the F+E .

Investigation will have to wait now - someone wandered off with my tools.

I think I have traced the throbbing vibration to the boiler - although not for certain. If it is then the system as a whole is one spectacular amplifying echo chamber.

 

[patagonia]

I came to the same conclusion about our system - i.e. that noises starting from the boiler and pipes in the cellar were echoing round the system. This was proved by the fact that when one of the motorised zone valves in the cellar got stuck and sounded like a machine gun going off, the sound was repeated in the upstairs rads even though that circuit was off at the time. Unfortunately, nobody has come up with a solution. Let us know if you solve the problem.

 

[icundell]

Update: Draining a bucketful had the expected effect on the F+E tank (phew). Now a new dose of x400 in doing its stuff. Everything disconcertingly quiet.

Once flushed I have in mind an x200/x100 combi.

The drained water was similar to that in the tank - a decidedly brown cast to it, so I am guessing that points to rust and that I should start thinking of a programme to replace the rads.

Thanks for the tips - will report back.

 

[gas4you]

X800 is a stronger cleanser.