M
mysteryman
Yes, I mean a Vitodens 200-W with weather compensation, plus a Sub Mounting Kit with Mixer if a second heating zone is required. This boiler has everything on board and will do everything you could want.
Bypass when using Grundfos Alpha2 pump
- Thread starter smokebox
- Start date
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Don't see why not.
The flow sensor within the pump will realize there is no flow when the zone valves are closed and immediately increase speed, giving a higher head, until the ABV opens.
The installation instructions for the Alpha pump tell you how to set it up for an ABV.
RTFM!
Thought as much, one of the building plants we look after has three of these on a cascade
I had bother with viessmann tech getting a part no for the viessmann badged grudfoss pump though. it was the modulating one we wanted, they sent the standard one........ twice!
Good boiler though
Matt
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Agile Haisham and mysteryman etc,!
You will all be horrified to find I live on, AND on line with shaky on line connection from hospital.
Agile
The HE was partially blown by the crafty wiring from the 'expert' professional electrician because he knew better than me, and wired the pump to boiler, not to the pump connection. Hired by the plumber. The Vaillant senior guy said there was evidence of damage. THAT is why I wish to have a new HE at hand for when the damaged one blows, of which he has stated there IS increased risk Do you really think I should pay!!! They have not absolutely refused warranty, but the vaillant guy said it was unlikely, and I can't blame Vaillant.
The wish to have an autopump is not evil! It is Not incompatible with the boiler according to vaillant and grundfos.
A professional heating engineer is attracted to a "package" 'cos it is quicker and easier, But that is not my concern. I wanted a vaillant open vent, and the plumber specified this one (ecoTEC plus 428), not me. He agreed to the Autopump, which I wanted for long term economy of electricity, and grundfos claim that is fine for this boiler.
Please all stop trying to blame me! I may be an awkward efficiency stickler, but I am not the dolt Agile sometimes implies!
A bit of thinking is needed to make this pump run in this house with correct bypassing, and for me that is enjoyable though the heating engineer simply want's the 'job done'. Different approach!
Although Haisham suggests an auotadapt can be set up with auto bypass, doing so will inevitaby push the boiler needlessly out of condensinng state more than neccessary, assuming the auto bypass pressure is so set that it will actually bypass. I don't want to buy an expensive condensing boiler and then throw out its whole point and potentially 12% on gas!
Haisham, where does grundfos have instructions on how to set the bypass press on an auto bypass with an Alpha autopump? . Of course you CAN put one in, set somewhere in the pumps operating region, but at a loss of efficiency, and since that is the purpose of the pump, this seems foolish to me! One might save a little on electricity and loose far more on gas.
Grundfos may have told you it is possible to use an auto bypass. They also have a pdf correctly stating this is illogical , AND SHOULD NOT BE DONE. Their solution is small preset standing bypass but even this is slightly wasteful! This is presently installed and wasting condensing potential. The solenoid solution wastes nothing in fuel though has a cost. Unloading into a zone is the perfect solution.
When the circuit resistance rises with eg TRV closure, the pump progessively reduces its output speed (and Pressure), down to 1 metre where output is virtually zero, if the pump's internal electronics have taken it there. Does Grndfos want the auto pressuree below 1Metre!!!!. If the autopressure is set at less than max head (for my present Pump 5 M) it will not bypass. If it is set within the "auto pressure operatingzone" it will needlessly bypass at some point. On my pump (15-50 Alpha2) this zone extends up to 3.8 M.
Where does grundfos say Hailsham?!
Smokebox
My Lord
Where do you find information that the pump will increase speed again if it has shut down to 1 Metre and then meets total closure of zones?
I thought it would just churn away fruitlessly!
smokebox
My Lord
Where do you find information that the pump will increase speed again if it has shut down to 1 Metre and then meets total closure of zones?
I thought it would just churn away fruitlessly!
smokebox
I just had a look at the instructions for the alpha pump and see that the ABV is thermostatically controlled not pressure controlled, can you explain how it would work ? not sure what grundfos mean by manually operated bypass valve anyone know ?
Hi Picasso
A previous poster noted this 'thermostatic,' and it was thought to be a typo for the usual pressure ABV.
Interestingly enough on talking to a high level UK Grundfos technician, he did mention thermstatic valve as bypass, thogh for this specific purpose an almost instant response at zone shut off is required and they were all too slow.
With regard to instructuions, there either were none with the pump in the box, or, and the case of my plumber more likely, they were quickly disposed of before anyone awkward could read them!
smokebox
That includes himself!
As mentioned above I got an email direct from grundfos with very sepcific and helpful discussion of bypassing Alpha pumps. In this it specifically said a pressure controled auto bypass should not be use, and was wasteful and illogical. They are right.
I wish I could find some way of uploading that pdf onto this thread from the email where it came as an attachment
Not nly insists on keeping, but may need to get a larger one that should have been specified first off!
smokebox
I can see I am driving you all crazy!
I had thought of that earlier, but as Tony pointed out - something like that might not open/close quickly enough.
If I remember correctly ?? they or it is supplied with certain Dunsley Baker neutraliser applications/ installs ? as a safety control / device ? how quick it opens ????
It's not inevitable. If the bypass is correctly set up, it will only open when conditions demand it. I have demonstrated, in an earlier post, that your system can be run at low temperatures, even in the coldest weather.
http://net.grundfos.com/Appl/WebCAP...FAM&appcode=HEATING&pdfid=776425&language=ENU
The problem is that that you need to know the minimum flow rate through the boiler and many manufacturers do not supply that info or, if they do, the info is inaccurate (e.g Vaillant).
Grundfos say that ABVs are not compatible with Autoadapt and recommend using PP2, the highest proportional pressure setting instead.
Have you considered that your pump may not be large enough for your installation?
At max output of 30kW with a 20°C differential the flow rate is 1220 litre/hr and the pressure loss through the boiler is 2.4m (see installation manual). At that flow rate the pump can deliver a maximum head of approx 3.4m so the head available for the loss round the system is approx 1m. You said earlier that you have 24kW of rads but not how many; I would guess at between 15 and 20. In that case the system loss is likely to be more than 1m.
You can work it out using the info given in Small Bore heating Systems and Copper Tubes in Domestic Heating Systems
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