Pumping over query

[diamondgas]

Hi Rautospoon,

As asked by fuzzy, where do the header tank feed and vent pipe connect to the system? A photo of those would help... It is there relative position in conjunction with the pump that determines pumping over issues!

Regards the pump pointing down over ... Just bad practise IMO.... Any large amounts of air tend to stop circulation as the impeller spins freely moving nothing!

Regards the radiator ... It will work but is piped wrong and will reduce circulation through your boiler!

Regards your boiler .... it cannot be fitted to a sealed system or combined feed and vent system. However in the instructions you can fit a 'surge arrestor'. Seen it done a few times Hopefully this image will help you understand what I'm talking about if it uploads okay

 

[Rautospoon]

Hi Rautospoon,

As asked by fuzzy, where do the header tank feed and vent pipe connect to the system? A photo of those would help... It is there relative position in conjunction with the pump that determines pumping over issues!

Regards the pump pointing down over ... Just bad practise IMO.... Any large amounts of air tend to stop circulation as the impeller spins freely moving nothing!

Regards the radiator ... It will work but is piped wrong and will reduce circulation through your boiler!

Regards your boiler .... it cannot be fitted to a sealed system or combined feed and vent system. However in the instructions you can fit a 'surge arrestor'. Seen it done a few times Hopefully this image will help you understand what I'm talking about if it uploads okay View attachment 4203
View attachment 4202

Can't find where the header tank feed and vent pipe connect to the system, but I'm not really sure what I am looking for !
Few more pics attached but not sure they will help ?
View attachment 4209View attachment 4210View attachment 4211View attachment 4212


Regarding the "surge arrestor", is this a "bought" or a "made" item ? Can you confirm that this will remedy the "pumping over" problem despite the "root cause"(whatever that might be) not being identified and remedied ?

 

[diamondgas]

I can't access your pics ... however without knowing where the two main pipes in question are connected the surge arestor will not fix pumping over, especialy if it's a constant flow of water! The pump is raising the 'head' of water to a level above the height of your vent pipe if the flow is constant. A surge arestor isn't there to prohibit that.

 

[Rautospoon]

I can't access your pics ... however without knowing where the two main pipes in question are connected the surge arestor will not fix pumping over, especialy if it's a constant flow of water! The pump is raising the 'head' of water to a level above the height of your vent pipe if the flow is constant. A surge arestor isn't there to prohibit that.

No idea why you can't access the pictures - I can, with no problem.

The flow is in no way constant. There is only ever a max of about 3 inches of warm water in the F&E tank which has never risen to the level of the overflow pipe of the F&E tank. The slight drip outside seems to be being caused by condensate forming in the overflow pipe from the warm vapour in the F&E tank.
Just out of interest I have now located the Installers Instructions for the boiler on the internet.
My "gut instinct" is that it is a small problem (if anything serious I reckon it would have escalated itself before now, in the 17 years since the system was installed) that is causing this - the difficulty being in precisely identifying what - will see what the latest visit of BG on Monday brings. As previousl stated the whole system works perfectly (all radiators get hot quickly from top to bottom, loads of hot water that quickly heats up, pump and pipewok not noisy etc.) with never a problem, other than this "pumping over".
Would turning the pump (BG Multihead III) down to 1 of 4 (it is presently set at 2 of 4) be "worth a go" ?
Thank s again.

 

[diamondgas]

Rautospoon .... Just re-rad the posts to see where "pumping over" was mentioned ... 1st post, your friend of a friend mentioned that it was happening and duly noted no longer happens with the pump on a lower speed. Your theory of condensation in the overflow pipe has some credence 🙂 The fact that the water gets warm is an issue however as it shouldn't in theory. Most likely cause, if not pumping over, is surging up the vent when the pump switches off or a very short cold feed pipe allowing expansion water to enter the header! To over come these two you increase volume. The volume of the 'air' gap if surging and the volume of water in the cold feed pipe if it's expansion...

 

[Rautospoon]

Rautospoon .... Just re-rad the posts to see where "pumping over" was mentioned ... 1st post, your friend of a friend mentioned that it was happening and duly noted no longer happens with the pump on a lower speed. Your theory of condensation in the overflow pipe has some credence 🙂 The fact that the water gets warm is an issue however as it shouldn't in theory. Most likely cause, if not pumping over, is surging up the vent when the pump switches off or a very short cold feed pipe allowing expansion water to enter the header! To over come these two you increase volume. The volume of the 'air' gap if surging and the volume of water in the cold feed pipe if it's expansion...

Hi, Reckon it is pumping over, please see the final sentence of this paragraph from my OP:

"A "friend of a friend" is a (private) CH engineer and he had a look and confirmed the system was "pumping over" but when he turned the pump speed setting down from 3 (of 4) to 2 (of 4), it appeared to stop and he also suggested fitting a relacement sealed vessel which would be a reasonably priced solution to solve the problem if it continued. He thought the pump was in the correct position and no problem with the HW cylinder and no obvious incorrect piping (although he did say that the precise cause of "pumping over" can sometimes be hard to establish). He said I would be mad to replace the whole system ! However the next day (and continuing) there was/is still the drip and warm water in the F&E tank".
Would turning the pump (BG Multihead III) down to 1 of 4 (it is presently set at 2 of 4) be "worth a go" ?

Regarding the vent pipe see my post 3.

Fancy a trip over to the Wirral to "sort the problem" - cash waiting !!

Cheers !

 

[diamondgas]

Now I show my geographical ignorance as i haven't got a clue where you're talking about ... lol

Here's my advice though taking all into consideration ....Try your pump on minimum and see if all is still heating as before, if not then raise the open vent to its max and see if the water in the header is still getting warm. If it is still getting warm then bung a bit extra inhibitor in and live with it, or increase the volume of water in the cold feed pipe! 17yrs old, your boiler is past it's sell by date and owes you nothing. When you renew it your system will most likely then be sealed... 🙂

I'm now gonna Google the Wirral 🙂

 

[doitmyself]

However the next day (and continuing) there was/is still the drip and warm water in the F&E tank.

The water will get warm when the boiler is running. but it should go cold when the system is off.

You say that the level is only a few inches when the boiler is running. Does the level go down when the boiler is off and the water has cooled down? It should do. If it doesn't, there is a blockage in the feed pipe from tank to the heating system.

Have you actually seen water coming out of the vent pipe when the boiler is running?

 

[Rautospoon]

Thanks for the informative replies.


Just turned the pump down to 1 and turned the CH on - no noticeable difference in the time taken to heat up all radiators. Is it ok to run my system all the time with the pump on 1, it won't strain the pump at all ? There was 5" of lukewarm water in the F&E tank prior to me turning the CH on. The CH last "went off" at 7.00am this morning having "been on" for an hour Will check the level when next the system is turned off and cold.

No, I have never actually seen water coming out of the vent pipe when the boiler is running!

Cheers.

 

[diamondgas]

The water will get warm when the boiler is running.

Hi doitmyself ... I don't think that is strictly true! The only place it could get its warmth would be from the heating system. If system water was entering the header tank then likewise oxygenated water would be entering the heating system. From my old school head I kind of remember that you're suppose to calculate the system expansion and make sure that the feed & expansion pipe volume can accommodate system expansion otherwise every time the heating heated up and cooled down fresh oxygenated water would be introduced into the system which in turn would increase system corrosion etc. Does that make sense? I may well be totally wrong! It's how I remember it though!

 

[diamondgas]

Is it ok to run my system all the time with the pump on 1, it won't strain the pump at all ? Cheers.

If all is okay then it'll do the oposite I'd say ... Running at less speed means less power used IMO

 

[doitmyself]

Hi doitmyself ... I don't think that is strictly true! The only place it could get its warmth would be from the heating system.

That's correct.

Heat rises up the feed and expansion pipes by convection (like gravity HW systems) so the water in the F/E tank will warm up, but not to the same temperature as at the bottom of the pipes (flow temp).

Yes, you have to allow for the expansion of the system water.

 

[diamondgas]

I see where you're comming from doitmyself I'm not sure if convection is that easily achieved in a single 15mm pipe but hey! It is possible i guess 🙂

 

[Rautospoon]

Now confused !!

Is the fact that I get warm or hot (never very hot or boiling) water in my F&E tank, that may not be due to "puming over" and with no other problems other than the slight drip from the overflow pipe I mentioned previously, a problem or not ??

Cheers.

 

[doitmyself]

The only way you will know if you have pumping over is to watch the vent pipe when the system is running.

Let the system cool right down and then check the level in the F/E tank it shouldn't be more than a third full.

Now turn the system on and bring the water up to temperature. The level in the F/E tank should rise due to the water expanding. If it doesn't the feed pipe is blocked. In this case you may get the water spilling out of the vent pipe as the level rises in that pipe.

You can also get pumping over if the pressure at the bottom of the vent pipe is too high.

Try running CH and HW separately and together to see if it causes any water to come out of the vent pipe.

 

[BLOD]

If lowering the pump speed has stopped it pumping over I'd suggest adding some system cleaner, and running it round for a couple of weeks.
Then flush it out and refill adding inhibitor.

 

[Rautospoon]

EUREKA - SORTED !! BG engineer (top man - old school - 34 years experience) turned up and diagnosed the problem within 5 minutes. He confirmed the system was indeed "pumping over, due (as stated by a number of helpful previous posters) to restrictions in the cold feed and open vent section which he quickly identified using a long thin magnet.
He suggested that the offending sections be cut out and replaced, the system be power flushed, a Spirotech fitted (he said BG no longer fit Magnaclean, due to problems with leaks) and inhibitor put in. He "left me" an "all in" price (with lifetime guarantee) - what do members reckon would be a fair price for all this ?
Cheers and thanks again for all the help.

 

[Gray0689]

£700 to £900 without seeing work

 

[Toned.f]

£700 to £900 without seeing work

They charge £600 for a powerflush alone!!.

 

[Phil Stenning]

I used to work for BG, shop around using the BG quote, although i would say if BG bugger it up they do come back, but their prices are way to high!