High pitched whine that rises and falls for hours after central heating has been on

[morty1]

Hi All,
Recently had a loft conversion done. 2 bedrooms and a bathroom. One large radiator in one room, bathroom has a towel radiator & the other room has one large radiator & a small one on the opposite wall. I obviously expected it would take a bit of time to get rid of the air after a bleeding the radiators over a couple of weeks & a few glugs and rattles from the radiators when in use is to be expected. There's also an auto air vent fitted at the end of the pipework after the last radiator.
The problem is that an hour or so after the heating goes off i get a high pitched whine that rises and falls and seems to resonate to the small radiator. I've adjusted the lockshields a little bit not that the radiators need balancing they are all so hot you could cook steak on them within minutes & I mean ferociously hot above setting number 2.
The whine goes on all night hour after hour its that bad you cant sleep in the room. The sound rises and falls about 6-8 times a minute so at night you can imagine 8 hours of it. jeez
I think its trapped air but i thought I'd ask around to see if there's any way of resolving it as the plumber seems to not have a clue.
I've left the heating on for 3-4 hrs to see if that purges it. ( the rooms are desert hot in 20 mins)
Your help is appreciated.
Oil fired central heating system. heating system is vented. standard s plan down stairs and added an extra 2 port valve to operate heating upstairs.

 

[cross thread]

I would be looking to see if your pump is switching off after the heating has switched off or your system needs a by pass fitting.

 

[morty1]

pumps runs on for about 5-10mins after shutdown. I'm pretty sure there's a bypass fitted on the circuit at the boiler. I'll post a pic

 

[Daveydub]

heating system is vented

How high above your highest radiator is the header tank?

 

[cross thread]

Try turning cold water off to the property ,when its doing the noise

 

[morty1]

Hi Davy,
The tank is still about approx 1m above the radiator as its now in the garage as we moved from he loft. i did expect the rads to fill a little slower due to this but i checked the tank today and its full so its not drawing air in from there & we've set the fill level to max in the tank.

 

[morty1]

cross thread I'll give that go.

 

[Stuart981]

Maybe the ball valve in the header tank not shutting off completely. Any sign of water dripping out of an overflow anywhere?

 

[dilalio]

If you think this is a CH issue then you should be able to repeat it during normal hours.

Or the noise may be there all the time and you're just not noticing it during the day as it's not as quiet and maybe you're not in the bedroom!

Note that water supply pressures tend to rise during the off peak hours so the comment about the ball valve is a valid one.

 

[morty1]

Maybe the ball valve in the header tank not shutting off completely. Any sign of water dripping out of an overflow anywhere?

Hi Stuart, ball valve definitely closing off as it should.

 

[morty1]

If you think this is a CH issue then you should be able to repeat it during normal hours.

Or the noise may be there all the time and you're just not noticing it during the day as it's not as quiet and maybe you're not in the bedroom!

Note that water supply pressures tend to rise during the off peak hours so the comment about the ball valve is a valid one.

yeah, yesterday I've started putting the heating on in the morning & the afternoon to see if it happens. got up this morning and it started for an hour again. Plumber vacuum tested the new pipework before it went live to check his joints cos i did say "could it be a joint pulling air???" (press fittings)

 

[Daveydub]

we've set the fill level to max in the tank.

You need the level low enough to allow for expansion when heating gets up to temperature.
Turn off the cold main supply to the tank for a day and see if the problem goes away.

The tank is still about approx 1m above the radiator as its now in the garage as we moved from he loft.

Your garage is taller than your house?

 

[dilalio]

Your garage is taller than your house?

Same thought

 

[dilalio]

Your garage is taller than your house?

Same thought :

yeah, yesterday I've started putting the heating on in the morning & the afternoon to see if it happens. got up this morning and it started for an hour again. Plumber vacuum tested the new pipework before it went live to check his joints cos i did say "could it be a joint pulling air???" (press fittings)

Tried turning one rad off at a time, overnight, in case it's one of the rads?

 

[morty1]

You need the level low enough to allow for expansion when heating gets up to temperature.
Turn off the cold main supply to the tank for a day and see if the problem goes away.

Your garage is taller than your house?

no garage is lower but the expansion tank is still a few feet higher than the radiators upstairs in the house. Tank was put right up in the apex of the garage roof. you still need a 4 step ladder on the garage roof beams to reach the expansion tank. House was a bungalow built with attic trusses to save ripping the roof apart when we planned for the extension years ago.