Water rushing sound in a couple of rads even after bleeding system

[swebb99]

Hi I've recently had a new extension built and some changes to my kitchen. As part of the work a new Worcester Bosch CDI combi boiler was fitted to replace the old one and a three new vertical rads were fitted.

I've been trying to get to the bottom of why two rads in particular make a lot of water rushing noises. I've bleed the system twice, got rid of all the air, balanced the system ..... but still two rads in particular make a fairly loud water rushing sounds as though there is a lot of pressure going through them. These rads are in the hallway (very loud) and in the lounge next to the TV. They are a couple of the older rads. Being a combi I have noticed that the sound goes up and down depending on the stage the boiler is at in the heating cycle (! not sure what its called). It almost sounds like the water is running at too much pressure if you know what I mean.

If I turn the lock stops off the sounds goes away, well I say away you can still hear fairly quietly the water running through the pipes but that's not too bad. If I open the locks then the noise increases the more they are opened. The problem is if I open them so I just get an acceptable amount of sound there rads don't warm enough.

Friends have also commented that they seem loud so I know it's just not me an OCD.

Any idea's at all ? Maybe bad lockstops, thermostats on the rads, air still in there that bleeding the rads isn't releasing. I'm basically out of ideas.

Thanks

Steve

 

[oldbutnotdead]

You are bleeding from cold with the pump off aren't you?

Are the TRVs fitted the right way round (should be an arrow on the valve body indicating direction of flow, some are fine either way but not all)

Pump speed- can't remember whether Worcester pumps have an auto setting or whether pump is a user adjustable item- if it is then try auto (your noise is caused by water speed not water pressure, pressurised systems can run at much higher velocity than vented (no vent for it all to fire out of)

'Balanced'- as in proper job, 20 degree drop? If not then open the lockshields on the rads furthest from the boiler & work backwards towards the boiler.

 

[swebb99]

Hi thanks for the quick response

I must admit me and my father bleed the system while it was on a warming but not up to temp. He went round each rad and as he said he was about to open the bleed screw on each rad I opened the fill lever slightly on the bottom of the boiler.

I didn't realise the TRVs could be directional, I'll check them out. These would be the old ones (not sure how long they have been there). I assume if I need to replace I would need to totally drain the system.

You can hear the pump adjust as it warms/cools. Yes you are correct about the speed now I come to think about it as the pressure on the boiler sits a 1.5bar

I balanced the system by figuring out the order of the rads getting warm water, opening up all locks a couple of turns and then locking the first few down a quarter/half turn based on other rads being a little cooler. I must admit I don't have the kit to tell the temp diff. Maybe I need to get a heating engineer in to do the job properly.

Thanks

Steve

 

[oldbutnotdead]

All you need is one of those IR non-contact thermometers and a bit of time- there's a sticky on here tells you how to do it & what order to do it in. Usually the lockshields on the rads nearest the boiler will be closed down a bit (flow rate will be higher cos losses due to pipe friction increase the further away from the pump you are)

 

[swebb99]

Great thanks for the info I will dig out the article and get hold of a thermometer

Found the balancing page : https://www.diynot.com/wiki/Plumbing:faq2

 

[oldbutnotdead]

Also worth checking what temperature the heating side of the boiler is set to- if it is too high then air dissolved in the water will be being released, causing most of the noise (if there's no air in the system even water moving faster than the usual 1 m/s is quite quiet). Do check the boiler manual for 'recommended' settings- modern boilers will only get near their rated efficiency on a narrow range of parameters (so I am told)

 

[snb]

Just shut all rads apart from 1 rad and open up both lockshield and trv on full. Run on heating mode for 2 or 3 mins. Do this on every rad individually. You will hear the air get pushed in the offending rads. Then shut all lock shields to 1.5 turns open. This should have the balancing pretty close

 

[swebb99]

I've bought a temp sensor to check the heat in and out of the rads and I plan to attempt to balance however I have also noticed something that causes the noise to die down a fair bit, probably by half.

The house has a small bedroom that has two small rads in it. I don't usually have them on as it is a room i have been working on and it has a sloping roof above it and I've yet to insulate it. Anyway I have noticed that if I turn them both on then for some reason the noise in the offending rads downstairs instantantly reduced, as I say about half as noisy. So I am now puzzled why turning on two small rads upstairs causes less noise downstairs. When I close them the noise goes up again. I've also noticed that with both the small rads on I hardly hear the water going through them but if I turn off the smallest rad then the noise of water flowing through the other rad goes up a fair bit.

Idea's ?