Help! - Noisy central heating system – not heating water well ……

[Garzie]

As suggested above make sure the system is properly dosed with inhibitor or you might be getting a hydrogen build up because of corrosion. Other than that the best way to prevent air ingress is to seal the system.

thanks

will add some inhibitor -

ref sealing the system -

do you mean - ensure the existing system has no tiny leaks anywhere?

or

do you mean - change the system design to one with some form of closed expansion tank ?

if the former - how do you go about tracking down any tiny leaks - there is certainly nothing obvious visible - so is there a recognised method for doing this ?

 

[gmartine]

The later...removing small feed and expansion tank in loft and replacing with an expansion vessel and a filling loop.

You can't really trace a leak without visually locating it unless you put some cheap strong cologne in the system and have a sniff around (never done this yet btw) or have the system pressure tested. If you suspect a slow leaking pipe or valve it's common to wrap a bit of tissue paper around the area to see if it becomes damp over time.

One advantage of sealing the system is you can tell straight away if there is a drop or change.

 

[Garzie]

OK thanks for the input

latest

bled the system yesterday - lots of air in the upstairs radiators - all of them - not just a bit - my guess is several litres in each

central heating ran fine - and all radiators got nice and hot all over ( after bleeding) - no gurgling noise after it started up /first 30 seconds

started the HW today and again loads of air in the system and boiler is now throwing an error code - FD - which according to Ideal Logic is _ no water detected in the boiler - which makes sense given the huge amount of air in the system.

so - narrowing it down
- it cannot be hydrogen build up producing this much volume of gas overnight - so it has to be from another source

- there are no places in the house where even 1-2 litres of water could leak out of a pipe and not be visible - most pipes are exposed and visible and show no leaks - there are just a few short runs under the floorboards upstairs - and none under the ground floor floor and i think if a few litres of water were leaking into the space under the floorboards it would start to be visible through the ceiling - i am assuming for many litres of air to get in, the same approx. amount of water has to come out / go somewhere

so does this mean the air is for some reason being drawn in through the expansion pipe / overflow

if so what would cause that ?

 

[gmartine]

Yes, sounds like air is being drawn in by the vent pipe, do the suction test as mentioned earlier by our friend Tamz.

Could be poor positioning of the F/E pipes in relation to each other the pump, or if pump has been changed neutral point has changed. Turning down pump speed may help.

 

[Garzie]

Yes, sounds like air is being drawn in by the vent pipe, do the suction test as mentioned earlier by our friend Tamz.

Could be poor positioning of the F/E pipes in relation to each other the pump, or if pump has been changed neutral point has changed. Turning down pump speed may help.

cheers - i will take a look

interesting that it doesn't do it when n Central heating - only on HW

will take a photo of the pump/pipe layout and post it in case it sheds any light

 

[Garzie]

here is the pipework around the pump and the motorised valve.
its hard to get in there to get a decent photo that captures everything clearly without one pipe obscuring another - but i have


labelled

where they go in the hope that it helps

 

[Garzie]

is the fact that the expansion tank pipes are both connected so close together an issue?

 

[gmartine]

No, if I understand it correctly the F/E pipes are positioned as such that it can't but help suck air into the system, usually they're positioned differently and behind the circulator (pump) . There should be a pipe feeding the pump from beneath, where's that coming from because that should be coming from the boiler and the pipe you've labelled "To boiler " going to radiators.

 

[Garzie]

hey, thanks for your input !

i have just checked the pump direction and i do believe its direction of flow is in the direction you indicate. i couldn't find any arrows on it - and there is nothing in the user manual - but the shape of the casting shows the fitting at the bottom goes to the centre of the impeller scroll - so its sucking from the bottom and pumping upwards

in terms of air getting "sucked in" through the expansion pipe - what i don't get is that the water feed and expansion take off both appear to be on the "high pressure side" of the system.
by high pressure i just mean that the coil in the hot water tank are downstream of the expansion pipe - so to my novice brain - i would have expected the circuit to be boiler - pump - expansion pipe take off point - coil in hot water tank - back to boiler

so assuming there is some restriction due to friction in the coil in the hot water tank - on starting the pump i would have expected positive pressure at the point where the expansion pipe is taken off - so i would have expected it to try to push some water up - at least a little against gravity - rather than draw air in -

what am i missing / do i have it wrong ?

will add a couple more photos in case it helps

 

[gmartine]

Have a google of any open vented diagram, the F/E pipes are always behind the circulator on the circuit and never in front, that is the cause of your air ingress issues.