Bypass when using Grundfos Alpha2 pump

[mysteryman]

Do the job properly, simply and effectively with the best equipment, and you will not need 2 port valves. The best boilers have a built-in diverter valve. Why make the job more complicated than it needs to be?

 

[Dan Robinson]

We've been saying that for 6 pages now

I need a drink.

 

[Agile]

But do the "best" boilers have the three valves which would be needed for the OP's installation?

 

[gaswizzard]

Turning now to your temperature settings for Radiator flows I need a bit of reassurance. My understanding of radiator output power is based on fairly standard figures of 75C flow and 65C return thus giving a notional mean of 60C.

I think you mean 50c?

 

[Agile]

I would expect the mean of 75 C and 65 C might rather be 70 C ?

But I like to have a differential of closer to 20 C with a condensing boiler rather than the 10 C suggested above.

 

[gaswizzard]

Your forgetting room temperature , is this not what mean temperature is based on?

 

[gaswizzard]

I would expect the mean of 75 C and 65 C might rather be 70 C ?

But I like to have a differential of closer to 20 C with a condensing boiler rather than the 10 C suggested above.

This has nothing to do with Smokeboxes quote.

 

[smokebox]

For your information, though you know a great deal more than I about heating installations, the Alpha2 pump works perfectly on overrun. What are you talking about?

They have not given me a warranty - you are right, but he did not think it had to be condemned thank goodness. The Plumber will be placing a new HE in front of me with all relevant parts before I pay his bill!! I decided not to accept his offer of a twelve year free guarantee in lieu as I doubt his firm will exist that long!

smokebox

I realise the smart pump runs on the over run. But it is not providing an over run flow as required by the boiler because it does not increase the pressure in order to open the auto by pass.

Unfortunately I did not explain that in a simple form.

Smart pumps are fine for the application they are designed for. I fit them when appropriate.

Recent permanent magnet pump motors however are much more efficient and are easily modulated.

You have now brought in a new revelation of not paying your nupty installer until he brings you a new ( expensive ) spare HE. As the problem seems from the evidence to have been as a result of your insistance on having an incompatible smart pump then I dont see that your installer is to blame.

Based on just what you have told us he does not seem to be terribly clever at system design. But that should not make him to blame for system failures as a result of following your specific requirements.

But I could criticise him for not refusing to fit unsuitable components. I always take the view that no installer should fit anything that he does not fully understand. But if everyone did that then very little would ever get installed.

The customer always thinks that he is right !

Tony

Step away from that autobypass! Actually you have to put one in, but you could add my solenoid or fixed 5% flow bypass. in parallel. You'd have to logically set the opening pressure for the auto bypass above the top pressure of the smart pumps range. So long as the solenoid opens quickly, the smart pump will run OK in overrun unless there is something simple you'd like to add. There you go again implying Iam a simpleton - remember you have no idea about my education background, studies experience and work! You earlier suggested I may not even know what parameters the Alpha2 measures and uses to reach its conclusions - I do, and how quickly it does so. There are quite a number. I have spoken to the most senior UK designer who also writes much of the UK technical advice sheets. Do you as a matter of interest know of the parameters considered by the Alpha"?

If the installer designed the system poorly, who should I blame, assuming I want to blame someone. I can't expect him to solve a problem that a very senior Vaillant man admits is difficult! He has perhaps undersized the smart pump, but when fully and accurately balanced maybe not. I will admit design is not his strongest suit and so does he! He agreed that a smart pump would be no problem [I agree] and so does the Grundfos literature. Part of the damage was also probably due to his miswiring the pump so that there was no overrun for the first week until I drew it to his attention. But that has only been an irrelevant part of the bypassing issue. He was willing to do it, and did it poorly. His electrician first time rudely told me he didn't want to look at the installation manual. He is not blameless and I reckon in law I could enforce a new warranted boiler but I am not that mean and he's a nice guy.

Here the customer does think, but a bit late!

smokebox

 

[Dan Robinson]

Why do you insist on fitting an auto by-pass? It is not mandatory.

The fact that this has killed a Vaillant HX is even more reason for me never to fit another one.

 

[gaswizzard]

Smokebox , if you insist on using the alpha then maybe you could install a 15/60 in place of the 'solinoid' , gotta be a winner all round.

 

[Dan Robinson]

 

[smokebox]

Why do you insist on fitting an auto by-pass? It is not mandatory.

The fact that this has killed a Vaillant HX is even more reason for me never to fit another one.

I think that is debateable, but you could be right. Part L regs strongly suggests it at the very least I gather, though I ain't actually read them.

The death was complex. electrics and the plumber put the bypass way above the top of the auto top pressure. I adjusted down because of explosions - its not quite dead but I fear it will die young hence my wish to be ready with a spare heat exchanger right at hand. The Plumber clearly has a bit of a conscience, and is n't objecting. In the context of the whole quite big contract both he and I are being very reasonable I reckon.

 

[Dan Robinson]

You have a strange viewpoint of the industry, but not totally uninformed (often more dangerous than no knowledge at all).

Your plumber is probably under-qualified, under-experienced and worried about not being paid. He has possibly bought an entire boiler to hold as spares in order to supply your new HX.

Even so, if such a minor error of installation could actually cause this type of damage to a HX then I sure as hell wouldn't want one in my house.

Think about it. This is a pretty minor error on the part of the installer and should in no way have caused HX failure after a few months (I am assuming) or operation.

Shoddy manufacturer IMO.

But again. Why do yo insist on overcomplicating the installation for such a minimal gain in efficiency? The cost of the computer and internet time sp far will probably out weigh any benefits you will gain.

 

[smokebox]

You have a strange viewpoint of the industry, but not totally uninformed (often more dangerous than no knowledge at all).

Your plumber is probably under-qualified, under-experienced and worried about not being paid. He has possibly bought an entire boiler to hold as spares in order to supply your new HX.

Even so, if such a minor error of installation could actually cause this type of damage to a HX then I sure as hell wouldn't want one in my house.

Think about it. This is a pretty minor error on the part of the installer and should in no way have caused HX failure after a few months (I am assuming) or operation.

Shoddy manufacturer IMO.

But again. Why do yo insist on overcomplicating the installation for such a minimal gain in efficiency? The cost of the computer and internet time sp far will probably out weigh any benefits you will gain.

I enjoy this chat - I am retired and don't charge myself! I did not buy my computers o broadband for this purpose!

Do you really understand that a bypass set within the auto range of pressure is going to obviate the whole point of a condensing boiler to a greater or lesser degree this is daft - the whole point of the idea is to maximise efficiency - electrically and gas wise, but the regulations are now getting ahead of the execution of the technology. It is a soluble issue and will have to be solved by Jan 2013 when grade A efficiency pumps will be enforced! They are already looking at A* grading I hear. Permanent magnet DC motors mayl help, but I doubt if they will manage without some sort of intelligent sensing and reaction in the pump along these lines as well.

I will have to calculate the range of potential loss of efficiency to clarify, but across potentially 25 million houses even 2% counts.

 

[matt1e]

Hi all
Forgive me if I have missed anything or repeated anything as i'm not too well at the mo but just read most of the thread with interest and have to say most of you have raised some valid points
I work in the commercial sector and bar destrat pumps,UFH pumps and secondary return pumps all the others modulate, including shunt pumps but most of the systems I work with are BMS/PLC controlled and as agile pointed out earlier, low loss headers are always involved mind you IIRC some viessman boilers modulate their pumps as standard
smokebox there are many solutions to your problems it depends how sofhisticated you want them to be, because as agile has pointed out in a domestic situation it might just not be worth it

you could use a plc/bms to operate the system
you could use pressure transducers to operate a proportional valve
you could use temp sensors to do the same
you could, as you say use a relay to operate a valve
you could use a relay solution to keep one of your existing valves open while the system is in overrun
etc
I will draw you a circuit if req

ps dan do you mean a momo valve or mimo ?

Matt