whooshing around watter cilinder

Hi, whenever I turn the central heating on there is this whoosh and whoosh again and again then stopes then starts again. At the same time hammering noise that appears to be coming from the 3 way mid-positioning valve. when the valve is switched to opposite position (water boiler only) everything is fine and no noise can be heard. The pump and 3way valve are close to each other and are on 1st floor.

Have also let the air out through the manual vent many times. This looks like every time i unscrew the tap there is always some air (very small amount) until water comes out. Have also let the air out of radiators but again this looks like a never ending process as air seams to always accumulate for some reason.
Any help would be appreciated.

There is gas (which may not be air) in the heating system. I suspect the pump is pumping downwards, which is always a nusiance. You probably need a bleed point adding to the system to allow this gas to be removed, either a manual or automatic vent.

In reality, most systems end up with the pump pumping down! Otherwise you end up with more difficult plumbing around the HW cylinder / zone valves / open vent / cold feed area. Installers try to minimise install time!

Anyway, why should it matter? If the pipework is 'conventional' and properly laid out, any air between the boiler and the pump inlet SHOULD find its own way to the open vent by itself. Air that collects beyond the pump (assuming 'pumped flow' rather than 'pumped return', which is also a perfectly good way of plumbing a system) should be driven out into the rads, where it can easily be bled out. To make bleeding even easier, there may be a 'finger vent' for bleeding air out of the pipework near the top of the cylinder coil connections.

If the gas collecting in the system is NOT air, you should find out what it is and where it's coming from. If it's hydrogen (gas coming out of a radiator bleed valve LIGHTS with a match - DON'T set fire to the curtains!!!) then you have electrolysis going on somewhere in the system. This needs to be located and fixed. Otherwise you'll soon have rads with holes in.

Alternatively, irrespective of whether you have pumped flow or pumped return, there will be parts of the pipework under partial vacuum. This means any small leak (eg. through the gland seal on a pump isolator) may be letting air INTO the system. Check for this too.

oilman said:

There is gas (which may not be air) in the heating system. I suspect the pump is pumping downwards, which is always a nusiance. You probably need a bleed point adding to the system to allow this gas to be removed, either a manual or automatic vent.

Click to expand...

Thanks for the reply. Unfortunately Have also let the air out through the manual vent many times. This looks like every time i unscrew the tap there is always some air (very small amount) until water comes out. Have also let the air out of radiators but again this looks like a never ending process as air seams to always accumulate for some reason.
Any further help would be appreciated.

might be worth checking in the loft that the system isnt pumping over
back into the header tank(small tank)!!

I too am suffering from the same problem and have reduced the speed of the pump to help. But this is OK if you are not wanting to switch the heating on.

As the weather has become a bit chiller now, I occusionally use the heating but have found that the radiators furthest from the boiler do not heat up to well.

I have tried draining the system and refilling, but no change. I too am stuck.

Have you had any joy since posting your message.

Rakster

parmarr2 said:

I too am suffering from the same problem and have reduced the speed of the pump to help. But this is OK if you are not wanting to switch the heating on.

As the weather has become a bit chiller now, I occusionally use the heating but have found that the radiators furthest from the boiler do not heat up to well.

I have tried draining the system and refilling, but no change. I too am stuck.

Have you had any joy since posting your message.

Rakster

Click to expand...

if the flow of water through the boiler is insufficient, the the boiler can be noisy. Its very important to have the correct water flow rate, especially in wall hung boilers. try fitting anti-vibration brackets to help reduce the noise. If this doesn't help, check that the speed of the pump hasn't been set too high.