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Who's right ? (Read 655 times)
londonman
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Re: Who's right ?
Reply #40 - Yesterday at 1:53pm
 
It's an Akvaterm...2500 litre.  But all that is connected is a coil inside it that comes out to the flow and return pipes for the HW cylinder an CH.   You are correct in that the Akvaterm and boiler are on a separate circuit with their own open vented system.  

We tried feeding the flow into the other CH pipe - just in case the original pipe tapped into wasn't the flow.  If anything it made things worse.

He's talking about a more powerful pump to push out any airlock as we are in Catch-22.  If we beed the radiator to remove the airlock then that introduces fresh water into the system which will release any dissolved air which will form another airlock which will .....

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thescruff
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Re: Who's right ?
Reply #39 - Yesterday at 11:01am
 
The longer this goes on the more I think he messed up somewhere.

What is the make, model and size of the store please.
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Re: Who's right ?
Reply #38 - Yesterday at 10:55am
 
Valves on the magnaclean are fine.

To be perfectly honest I don't know why you have a vent or neutral zone. The store heating circuit doesn't need it, and I can't see any connection for the boiler to store, which must have a vent or other safety devices elsewhere.

Can you tell me is it a two or one pipe system. You would need to check one of the old rads to tell whether it has 2 pipes serving it or if both tails are connected to the same pipe.
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londonman
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Re: Who's right ?
Reply #37 - Yesterday at 9:22am
 
thescruff wrote on Yesterday at 12:39am:
Unfortunately, I don't have enough information to answer your question, you could feel the radiator tails to see which end gets hot first.  Tricky as I did not take any notes as to flow/return on the rads when the original system was running and no guarantee that the original installer got it right in the first place.  So I ensured that all the new rads and TRVs were bi-directional.  It was your comment re backflow or short circuit that made me wonder about possible mixing up between Flow and Return

What size pipe is the flow from the store and can I assume there are no valves of any description on it.  22mm . Yes, on the Magnaclean

The first problem is to get the plumber to sort the sucking air in. For what it's worth it should be labour free.  I agree.  For what it is worth, I temporarily capped the end of the vent pipe (to eliminate air being sucked in from there at pump switch on but no cigar



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Re: Who's right ?
Reply #36 - Yesterday at 12:39am
 
Unfortunately, I don't have enough information to answer your question, you could feel the radiator tails to see which end gets hot first.

What size pipe is the flow from the store and can I assume there are no valves of any description on it.

The first problem is to get the plumber to sort the sucking air in. For what it's worth it should be labour free.


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londonman
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Re: Who's right ?
Reply #35 - Jan 21st, 2018, 9:59pm
 
The blue pipe is marked Heat store return.  It is the combined return of the CH and cylinder.  The HW cylinder return is shown in blue ..it's the pipe that ends below the D in Downstairs.  

When I bleed the 'bleed rad' I will turn off the TRV and the lockshield.  

1) Then just open the lockshield.  See if I can get that flowing again (usually needs suction).  

2) Then turn of the lockshield.  Turn the TRV on and try to get some flow out of that.  

3) Repeat 1 until it all starts working again.

The backflow is VERY interesting.  The modification to the CH flow now introduces it halfway down ...see this and earlier diagrams.  Now what if he cocked up and that it isn't the original flow that he has tapped into but, in fact, the return ?
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Re: Who's right ?
Reply #34 - Jan 21st, 2018, 6:31pm
 
I'll try and get my head around the drawing.

A, it all looks wrong, so I'll do some imaginary connecting.

What is the blue pipe from the store running alongside the flow, and where how does it connect.

Where does the HW return connect, I assume by HW you mean the cylinder.

The pump should always be off when bleeding.

If there's an airlock say in the flow or return pipe leading to the bleed rad then water will still come out the other pipe so you need to shut one valve to draw the air out. so, if the return is airlocked you need to turn the flow valve off, or vice versa.

Your plumber needs to sort why it's pulling air into the system.

Guessing at this time but it looks like you may have cross connections that are causing a backflow or short circuit
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londonman
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Re: Who's right ?
Reply #33 - Jan 21st, 2018, 12:04pm
 
Just thought I'd give an update and a drawing of the system.

...House ch layout

Where it says 'other rads' these are upstairs ones.  Flow from heatstore is hidden by the heatstore return pipe.

The radiator marked 'bleed' rad is approximately in the right position and is the one (a) highest in the circuit and (b) furthest rad upstairs from the pump.  My plumber called me up yesterday to see how things were going as he has a free day tomorrow. We agreed that I'd try switching off the pump to see what happened.  Answer....an airlock when I started it up again.

I have a permanently connected drain cock in place of the bleed valve on the 'bleed' rad.  So connect up a hose and open the lockshield.  Some air bubbles and then nothing.  No more air.  No water.  Remember the system has been working fine and that radiator was hot and so has water in it.  So there's not enough head to push out any water/air in the pipes..  Unless ....unless  :idea:   you switch the pump off when you bleed, yes ?  In that case doesn't the pump act as a block to the flow...which explains why nothing comes out ?  But then surely the head in the tank is still acting to push the water out as it's acting back through the flow from the heat store, through the heat store and back up the return to that bleed rad...so it should vent.  You have to stick suction on the end of the hose to get it flowing again,whereupon air and water comes out of the hose/lockshield route.

This time was also different in that when I closed the lockshield and opened the flow on the rad, I got a lot of air out.  Very confusing
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Re: Who's right ?
Reply #32 - Jan 14th, 2018, 8:57am
 
No that is the normal combination, bigger systems could be 22/28.
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londonman
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Re: Who's right ?
Reply #31 - Jan 14th, 2018, 2:32am
 
Does it make any difference if the cold feed is 15mm and the vent 22mm ?
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Re: Who's right ?
Reply #30 - Jan 13th, 2018, 11:09pm
 
Image 5   

Assuming the flow/pump is the direction marked, then the problem as said is likely in the circle, eg blocked/restricted cold feed.
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Re: Who's right ?
Reply #29 - Jan 13th, 2018, 10:58pm
 
Image 4   

A little fag package sketch I knocked out for you.

Cold feed and vent should be as close as possible. When the pump starts and shortfall should take water from the cold feed and NOT the vent, doing the later highlights a problem, normally a blocked or semi-blocked cold feed.
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Re: Who's right ?
Reply #28 - Jan 13th, 2018, 10:30pm
 
Sort of, you have a problem with air in the system, now you know where it's coming from.

Maybe the pump is at the wrong speed, the connections are wrong, the tank and or vent is too low, but that should make any difference if the neutral point is correct.

To comment further one needs information, and preferably a good as fitted drawing, or seeing the job which is unlikely.

If it wasn't new one would say the cold feed is blocked.
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Re: Who's right ?
Reply #27 - Jan 13th, 2018, 10:22pm
 
thescruff wrote on Jan 13th, 2018, 10:16pm:
Separate post to avoid confusion.

......
The bubbles when the pump stops is because the pump is sucking air in when it's running


Can you please clarify this one for me as I'm struggling to understand this.  Are you saying that there is constant air being drawn into the system and escaping via the vent pipe while the pump is running ?
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Re: Who's right ?
Reply #26 - Jan 13th, 2018, 10:16pm
 
Separate post to avoid confusion.

A heating pump doesn't pump, it circulates at a high velocity, You would find near as a 1bar pressure differential across the inlet and outlet of the pump.

The bubbles when the pump stops is because the pump is sucking air in when it's running
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Re: Who's right ?
Reply #25 - Jan 13th, 2018, 10:06pm
 
No gold star only for effort and finding a problem.

The neutral point isn't neutral as nothing should happen.

The Plumber needs to come back and sort it.

If the engineer wants help get him to improve on the sketch.
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londonman
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Re: Who's right ?
Reply #24 - Jan 13th, 2018, 11:46am
 
thescruff wrote on Jan 9th, 2018, 1:24am:
Back too one of my earlier post.

You have a header tank for the heating, hold a jar of water under the vent, turn the pump on and off a few times, does it drink the water or blow bubbles.

Can you post a pic of the neutral point.



OK.

Switch the pump off and air bubbles come out.

Pump back on and the water gets sucked into the vent pipe.

I'm not sure what I was expecting....part of me was thinking nothing hence the 'neutral point'.

EDIT:  OK, think I understand what's happening and it is as expected.  We've got a body of water circulating by virtue of the pump running. When the pump stops, the momentum of that water pushed up the vent pipe a bit ...pushing out air in the downspout of the vent pipe (the bit hanging over the header tank).

When the pump starts up again there is a momentary low pressure at the neutral point as the pump starts sucking and the inertia of the water in the CH circuit takes a tad to get moving again.  So that sucks water into the vent pipe.

Ergo the pump is running the right way round.

Do I get a gold star ? Grin
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