Pipes/Pump - Quiet with CH, Noisy with HW

steve99

Hi,

I have a vented fully pumped hot water/ heating system in a four bedroom two storey house. The header tank is in the loft, a potterton netaheat boiler is fitted downstairs. A grundfos selectric pump, three way valve, hot water storage cylinder all stored in the airing cupboard upstairs. All works well and even though the boiler is old it is regularly serviced and works very well.
A month ago I changed some lock shield valves on a number of radiators as they were leaking. I refilled the system and added Corgi System Inhibitor and Corgi Boiler Noise Silencer. I did have problems with airlocks and had to turn off all the rads and open 1 at a time to get rid of the air. That all worked fine and I also balanced the rads and they now all come on and get very hot.
The problem I have is with the water cylinder coil circuit. The CH comes on and makes very little noise. When the hot water switches on I get all sorts of rushing/gurgling noises by the pump. When it first happened I turned the gate valve that is connected to the water heating system near the bottom of the cyclinder to almost shut in the hope that any air would go through the CH circuit. It did send some air to a radiator and I bled that. However I just can't get rid of the noise. It doesn't matter if the CH and HW and on together or just the HW I get the loud whoshing/gurgling noise. If only the CH is on it's pretty quiet. I have tried turning the cylinder stat to max for a few hours and fully opening the gate valve. The cylinder stat in normally set to 65c and the gate valve is about 2 turns open. If I do almost shut the gate valve then the noise is much less but the cylinder does not heat up. I normally leave the pump set to speed 2 or 3.
There is an automatic air vent that is newly fitted and I have also taken the centre screw from the pump temporarily to remove any air I could.

Can anyone help as it's waking me up every morning !!

TIA

Steve

karl-123

it will go eventually,

i allways fit a 15mm lever valve with a manual air vent above so i can service/unblock it,

i hate automatic airvents they get blocked all the time on combis,
and when air gets trapped in the heat exchanger it turns to steam,
and trips the overheat stat,

keep your old heating system they are the best.
as a last resort,
provided the overflow works on your feed and expansion tank in the loft, if it does not shift you could blast it out using mains cold,attatched to a drain off or radvalve,but dont flood your house out,
bye karl :xmassign:

karl-123

on second thoughts you could remove the autoairvent and replace it with a,
15mm lever ballvave and a manual bleed vent,same as i do,
then the airlock will clear,

steve99

karl-123 wrote: »

on second thoughts you could remove the autoairvent and replace it with a,
15mm lever ballvave and a manual bleed vent,same as i do,
then the airlock will clear,

Thanks for the advice - do you really think that the automatic valves are so poor that it won't allow air to escape? Could it be 'sludge' that is causing this ?

Steve

steve99

I can find a 15mm lever valve but not sure about the manual bleed vent. Can you point me in the direction of what I specifically need and how it would connect to the lever valve.

Thanks

Steve

karl-123

automatic air vents are basically a brass bottle with a plastic float and needle, that seals a hole above, when the chamber fills with water,
the holes in them are small so are the holes in 15mm manual vents,

1. turn off the power !
2. turn off mains, or tie up ballvalve.
3. close all radiator valves flow and return to save the (fernox f1)
inhibitor,why throw it down the drain it costs money,
3. drain the pipework ,push the three port valve to manual if its a honeywell one it will have a lever,
fill and vent the system after you have done the work,
reinstate the system........ fully...and check for leaks on radvalves :mad:
get the right fittings/adaptors, and yes sludge has caused it, it also nackers pumps,
leave fernox f3 in for a few days flush out , then use, f1, £15 for the two e-bay, if you want to clean it,
have fun karl :santa2:

steve99

Thanks for the process I need to go through. Are you still recommending that I replace the auto air vent with a manual one ?

karl-123

can you solder fittings ??? do you have a blowlamp ???

if not there is a male version of this fitting, this one is female,
the male type might go in a compression fitting ?
which will save you any soldering,
just use a half inch male, to 15mm compression fitting......

http://www.screwfix.com/p/end-feed-air-vent-cap-15mm-pack-of-10/49839

if i was there i would switch off the pump and release the air,
from the cylinder nut,without spilling hardly any water !
how confident are you ?

steve99

I have a blow lamp that I used years ago when I fitted some radiators. Perhaps it will still fire up. I will give that a go before I do the complete flush through.

Thanks again for your advice.

ormus

i just make me own with a 15mm compression fitting and a rad bleed valve.

simple and cheap.
BES want 9 quid for one!

karl-123

radiator bleed valves, are half inch male iron,
they will not fit in a compression fitting,

the picture is wrong, but the idea is great,

a female half inch iron, to compression,fitting,

http://www.pegler.co.uk/en/ProductDetails/Main?Id=4ec23a44-30af-4529-8f29-15c6961a3098&Rid=6f9d57f2-0c2a-4e23-8edb-0fc7666b10da

with a half inch radiator bleed vent screwed in,
loose the auto airvent on the system,
loose the backnut and olive from the new fitting,
p.t.f.e. on the "right way" screw it in,