Has our plumber put us in danger?

[Agile]

If you have air being sucked in then you could usually identify where by covering each joint with shaving cream and looking for a disturbance when the pump is activated.

I am still concerned by such an apparent big difference between the pressures at the feed and the vent. As they are less than 150 mm apart they should be at virtually the same prressure!

They dont appear to be at the same pressure!

Tony

 

[vexation]

If you have air being sucked in then you could usually identify where by covering each joint with shaving cream and looking for a disturbance when the pump is activated.

I am still concerned by such an apparent big difference between the pressures at the feed and the vent. As they are less than 150 mm apart they should be at virtually the same prressure!

They dont appear to be at the same pressure!

Tony

Good tip with the foam. The thing is now Tony, they've cut the cold feed out and linked the feed into the vent just below the F+E tank. Now the suction pulls on just the one 22mm pipe. The vent is still open, looping over the top of the F+E so it's exposed to air - and it's still gulping it in.

 

[Agile]

Good tip with the foam. The thing is now Tony, they've cut the cold feed out and linked the feed into the vent just below the F+E tank. Now the suction pulls on just the one 22mm pipe. The vent is still open, looping over the top of the F+E so it's exposed to air - and it's still gulping it in.

Thats good!

Its now a combined feed and vent which is what I recommended at the beginning.

Whilst it has not cleared the fault it has eliminated any aspect related to the relative spacing of the feed and vent pipes!

Now you should be concentrating on anywhere it may be sucking in air!

Resist the temptation to spray the shaving cream over the wife however much she may be gulping!

Tony

 

[vexation]

Been running the system for a couple of weeks now and it's no better for having the combined feed and vent. Its hard to describe just how much air can be heard in the rads and pipework.

Putting it as simply as possible, air has been getting sucked in whenever the pump starts, and it all comes in down the vent pipe. Despite being T'd into the outlet of the F+E tank, the suck would still empty a jam jar of water held under the open end of the vent pipe. And despite having a path (via a short run of 15mm) into the F+E tank, in addition to the swell that you can see in there, water would still make it up and out of the vent when the pump started up as well.

I speak in the past tense as on my suggestion the plumber and I raised the tank by 1.6m (as high as we could get it) and reinstated the separate 15mm feed and 22mm vent. Clearly this has had a significant effect although it has stopped just short of curing it completely.

As of now, it doesn't appear to suck in air when the pump starts but a little bit (about an inch in the bottom of a jam jar) gets thrown out when the pump stops. This is very different to how it was when it was 1.6m lower.

Now, here's my theory for shooting down: The main lines between pump and boiler are in 28mm pipework. The vent is in 22mm. When water flows in dissimilar diameters of pipework it undergoes a change in velocity. So the surge at switch-off sees water accelerate up the vent as it goes from 28mm into 22mm pipework. Similarly, when the pump starts, rather than pull the water around the 28mm pipework it's easier to pull down on the 22m - emptying it briefly - or to be more realistic, pulling down bubbles of air for a second or two.

I wanted him to redo the vent in 28mm but he didn't carry any. I personally think that's what's needed to solve the problem completely. It seems like a basic hydraulic principle to me and I'm surprised I'm not finding recommendations to match bores of vent pipes with the main system pipework elsewhere.

 

[vexation]

Now, here's my theory for shooting down: The main lines between pump and boiler are in 28mm pipework. The vent is in 22mm. When water flows in dissimilar diameters of pipework it undergoes a change in velocity. So the surge at switch-off sees water accelerate up the vent as it goes from 28mm into 22mm pipework. Similarly, when the pump starts, rather than pull the water around the 28mm pipework it's easier to pull down on the 22m - emptying it briefly - or to be more realistic, pulling down bubbles of air for a second or two.

I wanted him to redo the vent in 28mm but he didn't carry any. I personally think that's what's needed to solve the problem completely. It seems like a basic hydraulic principle to me and I'm surprised I'm not finding recommendations to match bores of vent pipes with the main system pipework elsewhere.

Update (seeing as I've been posting again about yet another problem with this installation). As per "theory" above - re-doing vent pipe all in 28mm totally eliminated the problem last year. Maybe this might help solve some of the many pumping over mysteries I keep reading about

 

[DP]

When water flows in dissimilar diameters of pipework it undergoes a change in velocity. So the surge at switch-off sees water accelerate up the vent as it goes from 28mm into 22mm pipework

The pipe between boiler and pump will be at negative pressure. The vent on this pipe will also be at the same pressure. The feed and expansion pipe (fitted no more than 150mm past the vent pipe) will be at this negative pressure too. When the pump switches on, be it at atomic speed or soft start, pressure on vent and feed/ expansion pipes remains the same. You will however, get pump over if the 150mm space between vent and feed/ expansion pipe is bunged up.What happens here is the feed/expansion pipe is at negative pressure because the pump is 'pulling' on this section. In effect the level in the header tank is 'pulled' down to push water up the vent pipe.


There is no surge in the pipes going to the header tank. Pumped surge is confined to flow in flow and return legs. In the setup described, the pump does not pull water down the feed/ expansion or vent pipe as both these are at same pressure.


Me thinks you have chopped the plumbing and redone in 28mm has little to do with original fault. If the plumbing was done in like for like pipe size, that too would have worked.

I would loose the bypass. There is no need for it.

 

[Nige F]

7 pages and counting was the plumber Gas Safe registered - If he was that`s all that matters nowadays

 

[Nige F]

It's not just four engineers Tony. Once they'd started to scratch their heads (about the time I started this thread) each visitor spent as much time discussing the problem on the phone to HQ as they did indoors. This is a big firm that cover a wide area and I find it hard to believe that nobody on their books has the transferable knowledge to resolve it. It does now appear, however, that my faith may have been misplaced.

As I sit here typing this, I can hear the crackle of air bubbles squeezing past a TRV.

Big Firm - ROK ? they hit the rocks . Then try a 1 man band aid - If you`re in travelling distance of Eastbourne I know someone ONE THING I would do to that system - irrespective of all that`s gone before - IS get that pipework re configured so that the Vent and cold feed are on a horizontal run of pipe @ certain distances . blah de blah . THAT is textbook Next best would be the `orrible H layout - at least the vent is then in a position to , er vent

 

[londonboy]

I havent read all the pages ( ) but can you not have the f and e removed and have it converted to a sealed system?

 

[Andygasman2010]

I've not read all of this so sorry i'm repeating anything.

Tee the feed into the vent pipe near the pump.

A pump pointing upwards into the mid-pos valve I always find noisy anyway. It's probably not practical here but if it was to be ripped out i'd be pointing the pump downwards into the plan with a combined feed/vent above it. No need for an AAV (which I really don't like on open systems)or manual AV for that matter.

Feel free to strike me down!

 

[PEDANTICVINDICTIVEMAN]

I do sympathize, I lost about 12 hours sorting out a bloody air problem on a boiler swop, took out a Netaheat, put in a Solo, new pump, new 2 port valves, connected vent and feed together above large existing air seperater, I did that because I could see someone had had problems with a blocked cold feed before, everything else all as original, air problems from the off, Solo kept locking out, put in a bigger pump and it shifted it, obviously cant see under floors but lady adamant all was ok with old boiler, still it took some time to settle, no pumping over or sucking down the vent, but air going round and round circuit, just one of those jobs which take the ****, not heard from her for a few weeks so keeping fingers crossed, I am a bit suspicious about the heat xchangers in Solos, they seem very easy to air lock.

 

[silverback18]

Sorry if I am missing something, but from your picture it appears the installer has put the spirovent filter on the flow to the radiators, it should be on the return to the boiler to protect the boiler and pump, are you sure its not pumping the wrong way

 

[D_Hailsham]

DP, Nige F, londonboy, Andygasman2010, PEDANTICVINDICTIVEMAN and silverback18

You are wasting your time. This topic is two years old.

 

[PEDANTICVINDICTIVEMAN]

Yea but regardless, it's still a problem on some boiler swop jobs, so still relevant, wonder if the OP got it sorted and what it was ?

 

[Agile]

DP, Nige F, londonboy, Andygasman2010, PEDANTICVINDICTIVEMAN and silverback18

You are wasting your time. This topic is two years old.

Er................

D Hailsham, its the Original Poster who added an update today to his two year old thread.

So its quite appropriate that DP & Co should reply!