Bypass when using Grundfos Alpha2 pump

[smokebox]

Matt and MM have both given hints on how you could ( at first sight ) deduce a logical output when the pump is in over run.

External assistance was not intended or hoped for but will certainly be of very great help to you.

The objective is to derive a signal to be used to open a solenoid valve to produce the required pump over run.

There is no reason why that should not totally protect the boiler by providing the required bypass flow.

But this would be a non standard method and probably hardly understood by anyone connected with Vaillant. It might not be sufficient to convince them the boiler is correctly installed and thus entitled to a warrantee.

Tony

Agile
Hi
Yes i have been cheating!. Actually too exhausted to swing brain into gear yet - bad night cardiac failure (a sort of pump).

My own idea so far is simpler and more elegant. Further news later!!

I appreciate Vaillant's position on the matter, but because of the installation story, no warranty anyway! Installed finally end of May 2011 as I recall.
smokebox

 

[Agile]

I can see what you are trying to do, but can't work out how it would be connected. The solenoid valve only needs to open if all zone valves are closed. A relay could do this, but you need to make sure that there is no back-feed between the zone valves.

All he wants to do is have a solenoid valve which immediately opens when the boiler goes into pump over run to provide the bypass to protect the boiler.

Its totally feasible, needs a solenoid valve which are not standard heating components and so would be more expensive perhaps about £100.

Its probably best to just connect it as a plain bypass although strictly even that should involve several metres of tube to dissipate heat.

It would be more efficient to connect it across the hot water zone valve so the heat is dissipated usefully in the cylinder heating coil.

The actual amount of heat is very small but does have to be removed quickly to prevent damage to the boiler heat exchanger which is thin metal and low volume.

He needs to solve the challenge I have posted above in dark red to solve how to power the solenoid valve.

It would be so unusual for a domestic system that Vaillant may well not accept it as satisfying correct installation for warrantee purposes.

Tony Glazier

 

[smokebox]

Agile
Exactly!
Mattle raised possibility of bypassing back into system - eg a cylinder which I like.
I think this can be done. Certainly with a wee bit of plumbing, maybe even electrically.

smokebox

 

[smokebox]

Surely a simple 2 port solenoid operated 15mm valve can't be £100!
I'll look at prices

smokebox

 

[Agile]

You cannot use motorised valve for this purpose because they dont open quickly enough.

You need a proper solenoid valve which opens within 100 mS !

They are not cheap!

Many years ago there were shops selling surplus electrical equipment where those kind of things could often be bought however they have all disappeared as hobyists have died and been replaced by computer and facebook nurds! ( Sorry I should have said geeks )

Equally years ago men met girls in coffee bars and dances at the Hammersmith Palais, the local Locarno or the Winter Gardens. Now they do that online and risk encountering a fraudster.

Tony

 

[D_Hailsham]

All he wants to do is have a solenoid valve which immediately opens when the boiler goes into pump over run to provide the bypass to protect the boiler.

But it's only when the pump goes into over run and all three zone valves are closed that you need the bypass opened. In all other cases - one or two zone valves closed - there will still be a path for the water and the auto pump will be able to cope with the changes.

The pump over run is timer controlled on Vaillant OV boilers. The pump starts as soon as the boiler ignites but does not stop immediately when the boiler goes off. So just connecting a solenoid valve across the boiler switched live or pump connections is no good.

 

[Agile]

Quite so, hence my challenge in dark red!

Unfortunately, Matt and MM both gave serious hints!

Must go now, have boiler to install ( properly ).

Tony



PS

The auto bypass is 22 mm. With a high boiler coil resistance like this model I would recommend a 22 mm solenoid valve.

Its common for the actual valve orifice to be less than 40% of the nominal pipe size.

 

[smokebox]

All he wants to do is have a solenoid valve which immediately opens when the boiler goes into pump over run to provide the bypass to protect the boiler.

But it's only when the pump goes into over run and all three zone valves are closed that you need the bypass opened. In all other cases - one or two zone valves closed - there will still be a path for the water and the auto pump will be able to cope with the changes.

The pump over run is timer controlled on Vaillant OV boilers. The pump starts as soon as the boiler ignites but does not stop immediately when the boiler goes off. So just connecting a solenoid valve across the boiler switched live or pump connections is no good.

my Lord I believe I am on top of all this, believe it or not........now where is my pencil? i am envisaging two or three steps of smple Boolean binary logic may need 3 relays. I had better put my money etc!!
smokebox
ps there are actually 4 zone valves, but at the moment I am simply planning to yoke the 2 DHW valves electrically in parallel for want of another control channel from the VR61

 

[smokebox]

Quite so, hence my challenge in dark red!

Unfortunately, Matt and MM both gave serious hints!

Must go now, have boiler to install ( properly ).

Tony



PS

The auto bypass is 22 mm. With a high boiler coil resistance like this model I would recommend a 22 mm solenoid valve.

Its common for the actual valve orifice to be less than 40% of the nominal pipe size.

Agile Thanks for this advice - I take your point - we want immediate good flow, and 22mm valve sounds wiser. I had forgotten orifices are usually smaller than the pipe diam by quite a margin sometimes.
Ilike the glowering , threatening dark red !

Smokebox

 

[D_Hailsham]

i am envisaging two or three steps of smple Boolean binary logic may need 3 relays. I had better put my money etc!!

One relay will do the job!

 

[smokebox]

i am envisaging two or three steps of smple Boolean binary logic may need 3 relays. I had better put my money etc!!

One relay will do the job!

Damn you! my lord
smokebox

 

[matt1e]

i am envisaging two or three steps of smple Boolean binary logic may need 3 relays. I had better put my money etc!!

One relay will do the job!

yup agreed, one if you want to take the extra valve route
or two if you are just going to hold one of the valves open whilst on overrun

Have you sussed it yet smokebox?

Matt

 

[smokebox]

i am envisaging two or three steps of smple Boolean binary logic may need 3 relays. I had better put my money etc!!

One relay will do the job!

yup agreed, one if you want to take the extra valve route
or two if you are just going to hold one of the valves open whilst on overrun

Have you sussed it yet smokebox?

Matt

matt I had to see Doc this afternoon about own pump failure, but am preparing a drawing on a cheap CAD programme as we speak.
I shall be intersted in other solutions when I have submitted!

smokebox

 

[Agile]

My initial expectation was that three relays might be needed but that was without considering how it might be done.

Later I decided two would be enough.

I have not yet thought of a way of using just one if one used "proper" connections as might be used in commercial applications.

But then I also look at what if any other features might be compromised and even my two relay solution risked lesser frost protection.

Tony

 

[smokebox]

My initial expectation was that three relays might be needed but that was without considering how it might be done.

Later I decided two would be enough.

I have not yet thought of a way of using just one if one used "proper" connections as might be used in commercial applications.

But then I also look at what if any other features might be compromised and even my two relay solution risked lesser frost protection.

Tony

Agile, you guys are terrifying me.I hadn't even thought about Frost!
Truth is I am a bit ill today and full of funny drugs etc Should be improved tomorrow I hope.
Smokebox
Brain on Bypass !