vent pipe run
- Thread starter Tinkler
- Start date
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I did, but I don't follow your logic. The vent is on the flow just before the feed connection. The pump is either before the vent (as shown by Viessmann), in which case vent is obviously under positive pressure, or it is after the vent/feed (as is conventional), in which case the positive pressure of the pump will extend all around the circuit, through rads, boiler and vent until the feed connection, which is the neutral point. The only negative pressure zone is from the feed connection to the pump inlet.
Perhaps you don't appreciate that the feed tank connection must be the neutral point in an open circuit simply because the water level in the feed tank is the reference point against which all positive and negative pressures in the circuit are compared.
Perhaps you don't appreciate that the feed tank connection must be the neutral point in an open circuit simply because the water level in the feed tank is the reference point against which all positive and negative pressures in the circuit are compared.
to create a positive or negative pressure on any point you must have a circuit,
therefore if you have the feed on the positive side of the pump and the expansion on the negative the expansion will be under negative pressure, and vice versa
but if you have the feed and expansion on the same side, lets say positive, then they are both under positive pressure but with no corresponding negative pressure then they under neutral pressure as they are under equal pressure
so if you follow best practice and install the feed and expansion within 150mm of each other on the same pipe you create a negative point.
as for the pump being front of the expansion, I really dont know what the best practice on this would be, would the pump really represent a significant restriction??? I would not have thought so. but that would be a judgement call.
as check me GSIU regs again and found no reference to open vented expansion pipes at all
Sorry i edited this a bit to add stuff
therefore if you have the feed on the positive side of the pump and the expansion on the negative the expansion will be under negative pressure, and vice versa
but if you have the feed and expansion on the same side, lets say positive, then they are both under positive pressure but with no corresponding negative pressure then they under neutral pressure as they are under equal pressure
so if you follow best practice and install the feed and expansion within 150mm of each other on the same pipe you create a negative point.
as for the pump being front of the expansion, I really dont know what the best practice on this would be, would the pump really represent a significant restriction??? I would not have thought so. but that would be a judgement call.
as check me GSIU regs again and found no reference to open vented expansion pipes at all
Sorry i edited this a bit to add stuff
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The neutral point is where the feed pipe connects. If the feed connection is on the flow pipe and the vent is immediately (e.g. 150mm) upstream of this (as it should be) it will be under positive pressure from the pump, irrespective of where the pump is in the system.
Hmmm...so basically, I......................? 
1, Tell 'M' it's possibly as incompetent as I may be and needs to seek advice from a body that it supersedes on such matters - courtesy of Doitall.
2, Try and locate a potential Installers (CORGI of course) and find one that has no qualms about M's instrucions - although had trouble getting a quote off them for original plan to change to a combi as they had differing views on original loft siting plans.
3, Abandon nightmare boiler change project - incidentally done for reasons of efficiency/economy/safety (some found present flue and air-vent situation as "not right") - shut down boiler and stock up on thermal-wear.
By-the-way, regarding venting, where and how do I "vent" my frustration?... does it have to be orally or physically?...any regs or BSs... to follow?...does a CORGI type person have to be involved?...and will he inevitably be wearing a white coat?!
1, Tell 'M' it's possibly as incompetent as I may be and needs to seek advice from a body that it supersedes on such matters - courtesy of Doitall.
2, Try and locate a potential Installers (CORGI of course) and find one that has no qualms about M's instrucions - although had trouble getting a quote off them for original plan to change to a combi as they had differing views on original loft siting plans.
3, Abandon nightmare boiler change project - incidentally done for reasons of efficiency/economy/safety (some found present flue and air-vent situation as "not right") - shut down boiler and stock up on thermal-wear.
By-the-way, regarding venting, where and how do I "vent" my frustration?... does it have to be orally or physically?...any regs or BSs... to follow?...does a CORGI type person have to be involved?...and will he inevitably be wearing a white coat?!
Called Viessmann. They admit that this is a "typo" in their installation instructions and the vent and feed should go before the pump. Gordon Bennet what happened to kraut quality and efficiency?
I think we all know what we mean re pressures in the circuit. "A" will be slightly higher pressure than "B" HERE but if they're connected close, so little it makes no difference.
I think we all know what we mean re pressures in the circuit. "A" will be slightly higher pressure than "B" HERE but if they're connected close, so little it makes no difference.
Tinkler said:Hmmm...so basically, I......................?
1, Tell 'M' it's possibly as incompetent as I may be and needs to seek advice from a body that it supersedes on such matters - courtesy of Doitall.
2, Try and locate a potential Installers (CORGI of course) and find one that has no qualms about M's instrucions - although had trouble getting a quote off them for original plan to change to a combi as they had differing views on original loft siting plans.
3, Abandon nightmare boiler change project - incidentally done for reasons of efficiency/economy/safety (some found present flue and air-vent situation as "not right") - shut down boiler and stock up on thermal-wear.
By-the-way, regarding venting, where and how do I "vent" my frustration?... does it have to be orally or physically?...any regs or BSs... to follow?...does a CORGI type person have to be involved?...and will he inevitably be wearing a white coat?!
Tinkler,
If you send me an email (in my profile) i will send you a drawing of how it should be.
MIs override building regs.
both, i think.
Your diagrams are not quite right, Chris.ChrisR said:
A 5 metre nominal head would only actually occur if the pump were pumping without water movement, e.g. supporting a 5 metre column of water. When water flows at a reasonable rate the actual head is much lower.
You show the pump end nearest the feed connection at static head. That would only be the case if there was no resistance at all between feed connection and pump. Resistance on that leg may be negligible, but it's important to show it to demonstrate the right principles.
You show the red line (pressure = atmospheric) passing through the radiators. Assuming equal resistances on flow and return pipes, and no resistance between pump and cold feed, the head at the rads would be -0.5 and the red line would come upstream of the rads.
Finally you haven't offered any justification for your jibe (Harry Enfield) against my earlier explanation. Am I right in assuming that's because you can't justify it?
Mmmm
but dont the diagram on the viesman have the f and e under positive pressure????? like everyone is going on about
or has chinese whisper taken over and you all mean negative pressure
also Chrisr thanks for the diagram but the chances of air ingress (which its my undersatnding the whole reason for this old chin wag) on it are miniscule
Seeing as I am out numbered I must accept that i am wrong (ish)
but, humour me, why does it have to be where you all say it should be
GAWD I love a arguement
but dont the diagram on the viesman have the f and e under positive pressure????? like everyone is going on about
or has chinese whisper taken over and you all mean negative pressure
also Chrisr thanks for the diagram but the chances of air ingress (which its my undersatnding the whole reason for this old chin wag) on it are miniscule
Seeing as I am out numbered I must accept that i am wrong (ish)
but, humour me, why does it have to be where you all say it should be
GAWD I love a arguement
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