Bypass when using Grundfos Alpha2 pump

[Agile]

I expect that the boiler has built in frost protection which runs the pump if the temperature goes below 5 C and fires the burner if it goes below 2 C.

My system would allow the boiler to circulate water through the bypass only.

If it was my house then I would prefer that it circulates water through all the heating zones if there is a freezing threat.

You have to understand that the standard boiler installation tries to do the best with the least!

Start adding multiple zones and basic features may no longer still work.

Tony

 

[matt1e]

I expect that the boiler has built in frost protection which runs the pump if the temperature goes below 5 C and fires the burner if it goes below 2 C.

My system would allow the boiler to circulate water through the bypass only.

If it was my house then I would prefer that it circulates water through all the heating zones if there is a freezing threat.

Hi Tony
Mine would only circulate through the bypass too but that is no different to any other house in the country on standard s-plan but at least it would be a bypass zone rather than just a bypass valve
you could of course do it if need be but that involves more relays

 

[matt1e]

Hi smokebox
I suspect you may be struggling so there you go but take note of the writing in red
View media item 38617I didn't have time to add a discription of the circuit (or check it really ) as going out out the pop but if you have any questions, ask
some points to note:
This will do the job while the boiler is in pump overrun/pump protect mode and frost mode but it will offer no protection against a situation where you have all trvs shut down, you will have to have some sort of bypass on each zone anyway
and you will have to maintain the boilers req minimum flow rate anyway

Remember Tony's (agile) post concerning over complicating things?

Matt

 

[smokebox]

Hi smokebox
I suspect you may be struggling so there you go but take note of the writing in red
View media item 38617I didn't have time to add a discription of the circuit (or check it really ) as going out out the pop but if you have any questions, ask
some points to note:
This will do the job while the boiler is in pump overrun/pump protect mode and frost mode but it will offer no protection against a situation where you have all trvs shut down, you will have to have some sort of bypass on each zone anyway
and you will have to maintain the boilers req minimum flow rate anyway

Remember Tony's (agile) post concerning over complicating things?

Matt

Matt
I have a circuit very similar - I was a bit stuck with what exactly to do in your Relay 2, But am undergoing personal cardiac disaster right now and have to go into hospital tomorrow.
Been rather difficult to focus.

Hopefully will be in touch again

Incidentally there are differences, but largely related to the absence of a mains voltage signal wire from the stats/timers etc to instruct the Vaillant. It is instructed through an "eBUS" serial digital low speed 24volt system! I am rather pleased mine is so similar in principle to the real men! The Zone valve micro switches are not actually used to switch the Vaillant and are free to all comers.

Thanks indeed for a very neat diagram and presentation. I do note your caveats and cautions, but I regard this as an overall correct and logical and elegant triumph. I will obviously join you in marketing it to the boiler makers.


smokebox

 

[Agile]

I have not followed that circuit in much detail but its not exactly what I was anticipating and its stated application is not for what the OP was apparently thinking of doing.

What I had in mind was two relays which produced an output when there is a pump output from the boiler but no call for heat. That would drive a 3/4" solenoid valve from BES part number 9698 costing about £63. That could be connected across the HW motor valve so the bypass would in theory dump the latent heat into the cylinder.

All looks good in theory at first sight. The reality is that it would probably end up taking more heat OUT of the cylinder than it adds!

However, as the OP is now controling the boiler from the Ebus I suspect that will scupper my intended logic input to represent no demand for heat.

The OP should be concentrating on relaxing/managing his own circulation rather then thinking about his boiler.

I hope that works out OK.

Tony Glazier

 

[D_Hailsham]

I was thinking of something on this lines.

Untitled

• D_Hailsham
• 14 Oct 2011
• 1

The end switches on the zone valves are not used at present so they are free to activate the relay. The relay is wired "normal closed"; i.e. there is a circuit through the relay when there is no power to the relay coil. If a zone valve is open the relay switch will be open, so no voltage can get onto the solenoid valve from the pump live. If all zone valves are closed there is no voltage on the relay coil, so the relay will be closed, but voltage will only get onto the solenoid if the pump is running.

The solenoid will only open if all zone valves are closed and the pump is running.

 

[matt1e]

I was thinking of something on this lines.

Untitled

• D_Hailsham
• 14 Oct 2011
• 1

The end switches on the zone valves are not used at present so they are free to activate the relay. The relay is wired "normal closed"; i.e. there is a circuit through the relay when there is no power to the relay coil. If a zone valve is open the relay switch will be open, so no voltage can get onto the solenoid valve from the pump live. If all zone valves are closed there is no voltage on the relay coil, so the relay will be closed, but voltage will only get onto the solenoid if the pump is running.

The solenoid will only open if all zone valves are closed and the pump is running.

yes, correct you could do it that way way to open a valve even if the end switches were getting used (you just need to use the "boiler on" s/live to hold the relay contacts open)

I have not followed that circuit in much detail but its not exactly what I was anticipating and its stated application is not for what the OP was apparently thinking of doing.

what the op was thinking of is easy to do, (see D_Hailshams post) The Op expressed an interest in keeping an existing valve open too

Actually your idea of holding an existing zone open for pump overun duration has just sunk in and appeals to me - it may be cheapest as well!
smokebox

Though I wish I'd took more notice of the thread and knew that the boiler was controlled via EBUS and the end switches weren't being used........ it would have been a lot simpler!
so there you go Smokie

View media item 38655
Finally don't take the following the wrong way Tony its not a dig at you as I'm sure I could learn a lot from you too

the bypass would in theory dump the latent heat into the cylinder.

All looks good in theory at first sight. The reality is that it would probably end up taking more heat OUT of the cylinder than it adds!

If that was a concern then use a heating circuit to dump to

However, as the OP is now controling the boiler from the Ebus I suspect that will scupper my intended logic input to represent no demand for heat.

no not necessarily as the motorised valves are 230v and each have a separate on and off state that can be used

The OP should be concentrating on relaxing/managing his own circulation rather then thinking about his boiler.

I hope that works out OK.

Tony Glazier

Agreed and I hope so too

Matt

 

[mysteryman]

Just buy an off-the-shelf boiler with all this on board - frost protection, weather comp, timing for up to four channels [dhw plus 3 heating], holiday mode, the lot. The manufacturers have thought it all out and done it all for you. There is no need to beat yourself up about designing your own controls!

 

[Agile]

I think that even THAT boiler still needs an external bypass!

And the heat only version would still suffer the same problem if the owner chose a smart pump which maintains the same pump pressure when all TRVs are closed and thus will not open an auto bypass.

Tony




PS Do you have design information on the ZIG 2/12 ?

 

[mysteryman]

No it doesn't, as long as there is one rad on lockshields - and there is no heat only version of the domestic model I have in mind. The pump is built in, a variable speed pump is currently an optional extra.

 

[Agile]

The solenoid will only open if all zone valves are closed and the pump is running.

That was the obvious simple approach.

However, I wanted to keep the boiler protection circuit associated with just the boiler so that if anyone later decides to reconfigure anything then the protection will still operate.

I also wanted to ensure it was not going to fail if a motor valve failed.

One of the unfortunate aspects of heating systems is that people panic if there is no hot water and call any passing plumber who is then faced with a system they dont understand. ( KISS )

Tony

 

[Agile]

a variable speed pump is currently an optional extra.

I had not been told about that by my local rep. ( or about anything else for that matter! )

Will have to remember to ask that German fellow about it next week.

Tony




PS ZIG 2/12 ???

 

[Dan Robinson]

KISS is not something that can be applied to anything in this thread.

I can think of a few other adjectives, but the KISS principle? Most certainly not.

 

[Agile]

These ten pages all result because the OP insists on keeping a smart pump which does not operate the auto bypass.

The standard pump would have been cheaper and would have saved damaging the boiler HE ! And the poor installer having to pay for a spare HE !

KISS




PS Dan if you are bored and want to drive to N London tomorrow evening then text me.

 

[matt1e]

No it doesn't, as long as there is one rad on lockshields - and there is no heat only version of the domestic model I have in mind. The pump is built in, a variable speed pump is currently an optional extra.

out of interest are we talking Veissmann here? as I know they do one

Matt