CH venting into header

[marshian]

1 minute ago, Peaklander said:

I still don't understand what's supposed to happen.

The pump sucks and creates pressure downstream, pushing hot water around the circuit.

This returns to the boiler and is reheated (and expands?) and comes back to the H pipework where it tries to go up to the vent but is sucked away by the pump.

 

Why does do you think it tries to go up the vent

 

The level of water in the vent is the same as the level in the tank - it has to be

 

The only reason the vent pipe (and the cold feed) get warm is convection

1 minute ago, Peaklander said:

Does the pump pull cold water from the cold feed?

If no, why doesn't it?

 

It will pull water from the cold feed under certain circumstances - when you have a leak in the system or bleed a radiator that has a lot of air in it.

 

Rest of the time it's a static head above the pump

 

1 minute ago, Peaklander said:

If yes, is that to make-up for expansion? What happens when it cools back down?

 

Water expands when heated - the tank provides a safety element allowing water volume changes due to temp to be accepted without causing system pressure changes

 

When the system cools the volume increase in the tank is given back to the circuit

[Mattg4321]

Am I correct in thinking that pump over isn’t the only problem (symptom) here?

 

The original (and also current) problem is lack of circulation and radiators not getting hot enough. Is that still the case?

[marshian]

34 minutes ago, Mattg4321 said:

Am I correct in thinking that pump over isn’t the only problem (symptom) here?

 

The original (and also current) problem is lack of circulation and radiators not getting hot enough. Is that still the case?

 

I was under the impression that once air had been removed from the system the heating was working again but I could be wrong?

[John Carroll]

Its a pity that the UPS3 doesn't at least display the pump power in watts, W, from which the flowrate that then easily be read off from the pump cuves, most A rated pumps now not only display this but display the flowrate as well in m3/hr, very useful for trouble shooting, however, a plug in energy monitor which are very accurate can be bought for £15/£20, the pump cable is removed from its JB after noting the ter. numbers/locations, a short length of cable with a socket is then connected to these ter. points, the energy monitor is plugged into the socket, a 3 pin plug is attached to the pump cable and plugged into the energy monitor, I installed one of these a long time ago for someone and its still permanently monitoring the pump power.

[Peaklander]

Hi, thanks for the ongoing advice and comments.

After plumber #1 had visited and then couldn’t return for a week, I managed to get the radiators hot by a combination of new pump, some bleeding and a little bit of lock shield adjustment at one radiator.

Later, plumber #2 advised a flush and fitting of a mag filter. When we refilled it was very hard to get the air out and good circulation but eventually we did.

That was done on 21/12 and the heating has worked since then but with venting.

The boiler temp has been decreased and it modulates nicely although the temperature is still quite hot at the radiators, which is a little surprising.
 

Today I managed a quick visit and tests that have been suggested.

 

With HW only, there was little change. I didn’t leave it long but nothing obvious happened and venting continued.

 

Switching the pump to ‘constant pressure #1’ caused immediate increase in the water over the vent. This was inspite of the pump sounding slower. So I reverted to ‘constant curve 1’.

 

That’s how I have left it. I’m now wondering if that 150mm pipe between the vent and feed Ts is the culprit. Hopefully plumber #3 will listen before giving advice.

 

Edit. I will reiterate that I don’t know when the venting began but it may well have been since the new pump. The header didn’t have a lid, just a loose fitting bag of insulation and the condensation in the loft was excessive. 

Edited January 2 by Peaklander

[John Carroll]

 

The plot thickens but first this pump over conundrum.

Expansion effect first, a system with 100L of water and a average flow/return temp of 60C will expand by 1.62%, so 1.62L, this will increase the level in the F&E cistern and in the vent by equal amounts (since its a U tube) so ~ 10 to 15mm as 99% of the expanded volume is taken up by the F&E cistern (well named) but the U tube effect means the level in the vent pipe will rise by the same amount even though the vol of water is tiny.

With a perfectly clean system there will still be a very very slight pressure loss in that short piece of pipe in the H as the full circulating flow passes through it, if, for any reason a restriction start building up in that pipe then the U tube starts to become unlalanced with the level  in the vent rising and the level in the cold feed falling, eventually, if the restriction becomes very bad, the water will reach the top of the vent and start "filling" the F&E cistern, and water will start flowing down the cold feed.

 

Re UPS pump settings, this is very strange, on CC1 the pump head (4.2M) will be greater than 3.0M (CP1 constant setting) until the flow rate reaches 1.3m3/hr, 21.7LPM, and will not fall below 3.0M until the flowrate is 1.4m3/hr, 23.3LPM so there is no logical reason for this behaviour IMO.

 

However, that as it may, one could fill a small book with pump over problems just because the circ pump was changed, As I said previously a few have changed to my 52 year old system exactly as it is, see below, problems disappeared even though there were no blockages apparent in the H.

 

 

[Peaklander]

Totally distracted atm because we are babysitting three grandsons who are not yet in bed.

One thing that is now clear is that  water in the ‘cold feed’ moves up as well as down. 

[marshian]

5 hours ago, John Carroll said:

Its a pity that the UPS3 doesn't at least display the pump power in watts, W, from which the flowrate that then easily be read off from the pump cuves, most A rated pumps now not only display this but display the flowrate as well in m3/hr, very useful for trouble shooting, however, a plug in energy monitor which are very accurate can be bought for £15/£20, the pump cable is removed from its JB after noting the ter. numbers/locations, a short length of cable with a socket is then connected to these ter. points, the energy monitor is plugged into the socket, a 3 pin plug is attached to the pump cable and plugged into the energy monitor, I installed one of these a long time ago for someone and its still permanently monitoring the pump power.

 

Bloody ingenious - I wish I'd have thought of that before I fitted a replacement pump - still got the info anyway now but it would have been nice to compare the old grundfos 3 speed pump - pretty sure the new one uses less electrickery but pumps harder.

 

Actually I still have the old pump but the speed control is broken - if I can get a second hand pump with a working speed controller I could swap it over and refit it - perhaps I should sling a wanted post up.

[marshian]

1 hour ago, Peaklander said:

Totally distracted atm because we are babysitting three grandsons who are not yet in bed.

One thing that is now clear is that  water in the ‘cold feed’ moves up as well as down. 

 

Because the level doesn't change in the F&E tank?

[Peaklander]

39 minutes ago, marshian said:

 

Because the level doesn't change in the F&E tank?

 

No just from the description given:

 

4 hours ago, John Carroll said:

system with 100L of water and a average flow/return temp of 60C will expand by 1.62%, so 1.62L, this will increase the level in the F&E cistern and in the vent by equal amounts

 

Edited January 2 by Peaklander

[John Carroll]

5 hours ago, Peaklander said:

Hi, thanks for the ongoing advice and comments.

After plumber #1 had visited and then couldn’t return for a week, I managed to get the radiators hot by a combination of new pump, some bleeding and a little bit of lock shield adjustment at one radiator.

Later, plumber #2 advised a flush and fitting of a mag filter. When we refilled it was very hard to get the air out and good circulation but eventually we did.

That was done on 21/12 and the heating has worked since then but with venting.

The boiler temp has been decreased and it modulates nicely although the temperature is still quite hot at the radiators, which is a little surprising.
 

Today I managed a quick visit and tests that have been suggested.

 

With HW only, there was little change. I didn’t leave it long but nothing obvious happened and venting continued.

 

Switching the pump to ‘constant pressure #1’ caused immediate increase in the water over the vent. This was inspite of the pump sounding slower. So I reverted to ‘constant curve 1’.

 

That’s how I have left it. I’m now wondering if that 150mm pipe between the vent and feed Ts is the culprit. Hopefully plumber #3 will listen before giving advice.

 

Edit. I will reiterate that I don’t know when the venting began but it may well have been since the new pump. The header didn’t have a lid, just a loose fitting bag of insulation and the condensation in the loft was excessive. 

Right, if possible, before your plumber arrives tomorrow??.

Just to be sure to be sure, check that the pump is on CC1 as shown by the one green LED.

Then change to PP2, as shown by the combination of flashing LEDs on the right, see if you've still got pump over.

 

 

 

 

 

[marshian]

15 minutes ago, Peaklander said:

 

No just from the description given:

 

 

 

Ahhh OK but it's not a flow it's just a rise and fall of the level - water level increased due to expansion and drops due to cooling

 

However if the system is pumping over constantly into the F&E tank then potentially it could be creating a circuit where the F&E tank is acting like a very poor radiator...........

[Peaklander]

4 minutes ago, marshian said:

then potentially it could be creating a circuit where the F&E tank is acting like a very poor radiator

 

Yes that’s exactly what’s happening with the pump-over. Hot going up the vent and down the cold feed. Everything is hot up there.

 

 

16 minutes ago, John Carroll said:

change to PP2

Ok I can do this. I can see that the PP2 curve should give a lower pressure at reduced demand.

[Peaklander]

On 02/01/2025 at 10:08, marshian said:

The level of water in the vent is the same as the level in the tank - it has to be

Of course - I should and do know better.

 

OK, well now I have seen Plumber #3 and we had a good chat which started with me explaining the timeline and steps taken. Then he had a look around and finally gave his verdict.

 

He thinks that looking for a restriction is not going to be fruitful and instead wants to change to a combi system. So new boiler, remove HW tank and the airing cupboard pipework and the pipes to the DHW and CH headers.

 

The HW tank comes out "because that might be restricted". (It can't be IMHO as the problem is there when the DHW is off and the zone valve is closed).

 

The common flow pipe into and the CH flow out of the airing cupboard will be cross-connected and a small towel rail rad will go in there, T-eed from the flow and using the existing bypass return pipe.

 

The combi can pick-up on the existing boiler position but the DHW feed-out needs to connect into an existing DHW pipe 2-3m away, running through an understairs cupboard to T into a cloakroom sink supply and the rest of the house. That's not too difficult.

 

A new 22mm gas supply pipe from the meter will be run (about 15m, some outside) as the existing is 15mm.

 

It just seems to be an overkill but I would be able to step away. Cost is £5k.

 

I think the alternative is to partially drain, remove pump and the isolating valve above it, cut the lower right leg of the H, release the header (and take away to clean it) and then be able to examine the H for any restriction.

 

Plumber #3 solution just does away with the H pipework, doesn't sort any CH circuit restrictions that there might be, unnecessarily removes the DHW tank - but does provide a Building Control certificate which would possibly be useful when the house is sold (parents 89 & 97).

Edited January 3 by Peaklander

[marshian]

1 minute ago, Peaklander said:

Of course - I should and do know better.

 

OK, well now I have seen Plumber #3 and we had a good chat which started with me explaining the timeline and steps taken. Then he had a look around and finally gave his verdict.

 

He thinks that looking for a restriction is not going to be fruitful and instead wants to change to a combi system. So new boiler, remove HW tank and the airing cupboard pipework and the pipes to the DHW and CH headers.

 

The HW tank comes out "because that might be restricted". (It can't be as the problem is there when the DHW is off and the zone valve is closed.

 

The common flow pipe into and the CH flow out of the airing cupboard will be cross-connected and a small towel rail rad will go in there, T-eed from the flow and using the existing bypass return pipe.

 

The combi can pick-up on the existing boiler position but the DHW feed-out needs to connect into an existing DHW pipe 2/3m away, running through an understairs cupboard to T into a cloakroom sink supply and the rest of the house. That's not too difficult.

 

A new 22mm gas supply pipe from the meter will be run (about 15m, some outside) as the existing is 15mm.

 

It just seems to be an overkill but I would be able to step away. Cost is £5k.

 

I think the alternative is to partially drain, remove pump and the isolating valve above it, cut the lower right leg of the H, release the header (and take away to clean it) and then be able to examine the H for any restriction.

 

Plumber #3 solution just does away with the H pipework, doesn't sort any CH circuit restrictions that there might be, unnecessarily removes the DHW tank - but does provide a Building Control certificate which would possibly be useful when the house is sold (parents 89 & 97).

 

Oh lovely - replacing it all is pain free process apart from the financial impact and he's on the receiving end of that 5K and some uplift in the process due to a stupidly large combi being a big draw gas wise.

 

On top of that you are going to end up with a presurised system - weren't you worried about pipes buried in the concrete floor?

 

My advice find a better gas enginer/plumber or go with your plan B

 

Maybe consider @John Carroll suggestion to combine Feed and Vent

[John Carroll]

48 minutes ago, Peaklander said:

Of course - I should and do know better.

 

OK, well now I have seen Plumber #3 and we had a good chat which started with me explaining the timeline and steps taken. Then he had a look around and finally gave his verdict.

 

He thinks that looking for a restriction is not going to be fruitful and instead wants to change to a combi system. So new boiler, remove HW tank and the airing cupboard pipework and the pipes to the DHW and CH headers.

 

The HW tank comes out "because that might be restricted". (It can't be IMHO as the problem is there when the DHW is off and the zone valve is closed).

 

The common flow pipe into and the CH flow out of the airing cupboard will be cross-connected and a small towel rail rad will go in there, T-eed from the flow and using the existing bypass return pipe.

 

The combi can pick-up on the existing boiler position but the DHW feed-out needs to connect into an existing DHW pipe 2-3m away, running through an understairs cupboard to T into a cloakroom sink supply and the rest of the house. That's not too difficult.

 

A new 22mm gas supply pipe from the meter will be run (about 15m, some outside) as the existing is 15mm.

 

It just seems to be an overkill but I would be able to step away. Cost is £5k.

 

I think the alternative is to partially drain, remove pump and the isolating valve above it, cut the lower right leg of the H, release the header (and take away to clean it) and then be able to examine the H for any restriction.

 

Plumber #3 solution just does away with the H pipework, doesn't sort any CH circuit restrictions that there might be, unnecessarily removes the DHW tank - but does provide a Building Control certificate which would possibly be useful when the house is sold (parents 89 & 97).

I would advise to get a plumber (not a salesman) to cut out that H and inspect/clean it out/renew it., If the original pump was a Selectric (a pretty low head pump) then the clean out of the system + the installation of the UPS3 might have started that pump over, you can try and establish the blockage by trying that PP2 setting or, if still pump over, try PP1 even though that will almost definitely not satisfy your circulation requirements but will give some idea of the state of affairs.

Edited January 3 by John Carroll

[Peaklander]

Thanks for the feedback; I'm not surprised by it and it seems to be sensible.

I did try the PP2 setting this morning but again only for a short time. The noise from the vent water sounded louder from the bottom of the loft ladder, so I changed back to the (slow) CC1.

 

This is the pump that was replaced.

 

 

 

 

And the new one

 

Edited January 3 by Peaklander

[Peaklander]

1 hour ago, John Carroll said:

you can try and establish the blockage

What do you mean John?

[John Carroll]

27 minutes ago, Peaklander said:

What do you mean John?

By running the UPS3 at its lowest setting PP1 then if you are stlll getting pump over, you have a serious blockage problem, a few other thoughts, those UPS3s  have a very poor reputation around here, I know several people who will not install them but I would be a bit surprised if it wasn't  running properly in its requested mode. That 50W model of 5M Selectric is one of the lowest head pumps so wouldl expect little or no pump over with it.

Are you absolutely sure that there isn't a circ pump in the boiler and that is being boosted by the UPS3 .

Anyhow try PP1, if still pumping  over then problems. Can you post a photo of the pump LEDs when running in CC1 just now and also when/if running in PP1.

 

Also check both isolating vaves on pump fully open.

 

Edited January 3 by John Carroll

[Peaklander]

I'm not there now but there's no internal pump. The best I can do is a screenshot of the page in the manual.

 

 

Also I appreciate that I might be incorrectly setting the pump mode and so I will go in the morning and try again and gather evidence!

 

I could put the old pump back...

 

Also, I have just spoken to the plumbing company rep. who visited this morning (I'm sure he's a plumber too BTW) and asked why the HW tank has to come out and why we can't "replace all the H pipework".

 

His answer is that with the full job, the problem would be solved and without it, in his experience, "it's never satisfactory".

 

He said that they wouldn't be interested in the pipework alone.

 

I would like to rid myself of the problem (and so would my wife), as I have been trying to keep things going since a couple of weeks before Christmas and then this week into the New Year is a nightmare for getting anyone interested. I can go to one more company on Monday (who access to several plumbers) and perhaps get a final assessment.

 

I don't want to redo the H pipework myself but I could. The only things I need are a 28mm cutter and the pipe & fittings. My parents would also pay the money for the 'full solution' but something says that's just wrong.

 

I guess it's down to confidence that it's the H pipework only. After all, the radiators all get hot so why not?

[John Carroll]

If you can do the H yourself then, as you say,  why not, at least you will get great satisfaction once you prove it one way or the other.

[marshian]

Where is your parents place - rough location?

 

It's really not a massive job to replace that H section - I don't like compression fittings but it could be done with those - I much prefer solder fittings but if you can find a plumber that has press fit in 15mm and 22mm that section would be easy to replace with minimal drain down and I'd very much suggest that you do the combination vent and fill that @John Carroll recommends

 

I going to do that on my system fairly soon to solve a different pump issue I have with the new pump being a bit too meaty for the application compared to the old selectric I had.

[marshian]

1 hour ago, John Carroll said:

Also check both isolating vaves on pump fully open.

 

 

Oh that's a good call - I guess they did isolate when the pump was changed or maybe a partial draindown was carried out so no need to close the isolation valves??

[Peaklander]

 

Location is middle Peak District.

I did the pump change myself. I usually do things correctly but I will check tomorrow and I will also test the other pump modes too.

 

I have just got Plumber #2  lined-up for Tuesday and we will investigate the H together / clean out the header / check the pump valves are clear.

 

Also he told me at the pre-Christmas visit that he would like to remove the header and replace with an expansion / pressure vessel, PRV and a cold fill pipe. I might well get those items 'in stock' so that if we go that route I have it covered.

 

However the @John Carroll mod to tee the cold feed to the vent is an easy option that I will suggest.

[John Carroll]

You could check the H (but requires a bit of care) by installing a isolating valve (if not allready) on the F&E cistern mains supply to the ballcock, make up a few fittings and attach a hose or whatever to the vent pipe end, shut the pump inlet valve and carefully crack open the mains to see what kind of flow you are getting through the H and back into the F&E cistern.