Help! - Noisy central heating system – not heating water well …… | Central Heating Forum | Plumbers Forums

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Hello !

I have recently moved into a new house – or rather a 1960s built house.

The central heating system looks to be around 10-12 years old

Its conventional mains gas boiler central heating system (not a combi)
the boiler is an “Ideal logic 18” –
with hot water tank in an upstairs airing cupboard - and header tanks in the loft above.

There is a single 3 way valve to direct the boiler circulation to the tank or the rads

Everything has been working fine - but I noticed when I teste it in the summer that the system was rather noisy when running either the rads or hot water – lots of whooshing water and gurgling noises. I bleed all the rad several times - and loads of air came out - but it didn’t seem to help much with the noises. The rads got hot and it heated water fine - so I thought maybe that just how it is.

However, the last few times I have used it to heat hot water - its not heating the water well - after 2 hrs the tank is still not fully hot - ie not hot enough for a full hot bath – when it defo was before.

So, things I have checked so far

  • Boiler is firing – and displays no errors
  • 3-way valve is changing position fine from all the way left when HW system is off - and all the way right when its on.
  • CH pump is coming on and running -
  • Pipes from boiler to HW tank are getting warm / hot
What’s not quite right / maybe

  • The boiler comes on and fires – but the actual burner seems to shut down soon after – maybe after 30 seconds to 60 second – then sits that way for a few minutes - then cycles the same
  • CH pump is also going off when this happens
  • All the whooshing noises
Any ideas what could be up with it / what to check next

Where could all the air in the system be coming from and how come its not finding its way out when bled?
 
Does sound like an airlock. Check the smaller of the 2 tanks in the loft for water?
thanks for your reply -

yeah - i wondered that - went up in the loft an checked last night - in case the expansion tank had run dry - but it had 3 to 4 inches of water in it and the ball cock was working fine

i bled the system only a few months ago - where could so much air be getting in ????
 
Air can get in via a number of ways unfortunately, this might be why sealed systems are preferable, although can still get air in.

Examples of air getting in: undetected leak, micro air leaks, the vent pipe, hydrogen buildup in a sludged up system.
 
Air can get in via a number of ways unfortunately, this might be why sealed systems are preferable, although can still get air in.

Examples of air getting in: undetected leak, micro air leaks, the vent pipe, hydrogen buildup in a sludged up system.

ok - understood - but how do i go about tracking down where its coming from ?
 
Here is something for you to try since you are too miserable to pay a pro.
Take a glass of water up into the loft (well you can always scoop the water up there) and hold it with the expansion pipe dipped in and see what happens when you get the wife to turn the heating on.
Unfortunately i won't revisit here for ages but i'm sure someone else will provide an answer to you. Its not rocket science.
Btw i know exactly your problem but as i am persona non grata on here after years of educating people (i wish i had deleted the lot before they banned me) i'll let the smart asses who are left figure it out.
 
Here is something for you to try since you are too miserable to pay a pro.

Wow! - Nice.
Actually the reason i am investigating this in the first instance is that i cannot afford to pay a "pro" at this point in my life.
Around 8 years ago i developed a chronic illness, lost my job,, spent 5 years almost house bound and am only now able to function at around 30% of my previous level, i am in considerable pain and unable to work.

Before this i was very fit and well, did lots of sports, had a good job, ate well, looked after myself - but these things can happen to anyone.
it could happen to you tomorrow....
 
OK - so back on topic - i bled the rads again today and there was indeed a lot of air in most of the upstairs ones - no so much the downstairs ones.

the heating seems to be working fine. no loss of output as far as i can tell - is quiet apart from a bit of gurgling when it first starts - an doesn't seem to cycle on off like the HW was doing.

how can i track down why / how the air is getting in ?
 
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.
 
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 ?
 
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.
 
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 ?
 
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.
 
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
 
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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
boiler pipework.JPG
where they go in the hope that it helps
 
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.

boiler pipework.JPG
 
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

mot valv and bypass.JPG
pump lower.JPG
 
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.
 
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.
Thanks again

this is rather frustrating - seems like i have inherited someone's shoddy work ....

i have had a quick google and found there are examples of both ways though

the system does not do it if on central heating central setting - only on hot water - why is that ?

and does this suggest it might be possible to run this configuration and tune the problem out somehow - maybe by fitting a restrictor or something ...?

or is the only solution re-plumbing the F/E to alternate locations ?

thanks again for your help!

open vented 1.JPG
open vented 2.JPG
 
Actually the later example shows the feed pipe is nearer the rear of the circulator than the front on the circuit. Still I don't think it's a reliable example (DIY website) , needs replumbing.
 
Actually the later example shows the feed pipe is nearer the rear of the circulator than the front on the circuit. Still I don't think it's a reliable example (DIY website) , needs replumbing.
OK - i am following you - thanks for the explanation - will have to have a think about how i could replumb the pipes in practice

or - if going that far anyway -

it may make more sense to redesign the system to be a closed boiler circuit system - and also create a mains pressurised hot water circuit - as hot water flow / pressure is currently too low for an effective shower upstairs - and i was going to install an additional pump for that purpose -

but installing the appropriate expansion vessels and regulators would achieve both .....

its a big job for me in my current state of health thou - and don't want to be without heating all together for long in the middle of winter - so will need to give it some thought....
 
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Sealing the central heating circuit should alleviate all your current problems. Cap the F/E feeds, add an expansion vessel and filling loop shouldn't cost too much or take too long to have done.

You can't pressurise an open vented HW cylinder but adding a single or twin shower pump should be straight forward enough.

Good Luck.
 
You can't pressurise an open vented HW cylinder but adding a single or twin shower pump should be straight forward enough.

thanks

i had wondered about that - my guess is the system was installed around 12 years ago - probably just before pressurised systems became the norm - there are no pressure rating markings on the HW tank - so i guess it is the non-pressurised type
shame

will go with the pumped shower solution - think i just about have room to install this and a pressure vessel in the airing cupboard

ref the expansion vessel for the boiler circuit - is there a rule of thumb i should follow for the size i should use

i guess its based on volume - the system is smallish - 5 radiators and the HW tank coil - smallish 3 bed house
2x 6ft double layer radiators
1x 3ft double layer radiators
1x 6ft single layer radiator
1x 3ft single layer radiator

any other gotcha's i should look out for

thanks again !
 

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