Vaillant ecotec plus cycling on HW only demand

[scoobydo123]

Sorry pictures seemed to be firing blanks uploading more

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• scoobydo123
• 3 Apr 2012
• 1

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• scoobydo123
• 3 Apr 2012
• 2

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• scoobydo123
• 3 Apr 2012
• 1

Pipework picture HW valve on the left CH on the right, pump just above HW valve, gate valve just below gas meter you can just about see it

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• scoobydo123
• 3 Apr 2012
• 1

 

[Agile]

You have still not said what temp you think the cylinder stat is set to.

I would also love to know what the actual cylinder temp is when the stat turns off.

Tony

 

[scoobydo123]

Cylinder stat set to 60, didn't have my temp gauge but it doesn't seem to be scalding hot.

 

[Agile]

Try turning it to 55 C.

That is still adequate and gives more headway for the boiler flow temp.

Why did you drain from the drain cock instead of turning taps on?

Tony

 

[scoobydo123]

Tony drain cock as the cylinder is on the gnd floor it is a bungalow. Did try to turn down to 50 on my last visit just as a temporary measure but got a call from tenant following day saying that she was in the shower and hw ran out. As my previous tests have shown if I have a partial drain recovery rate is very slow due to 4 second burns after initial burn so guess someone else had showered and used more hw due to less mixing of cold and it had not recovered due to short firing. Don't forget it also appears to be happening on CH as well.

Thanks

 

[Agile]

The recommended temps for HW are 55-60 C.

The scale on those stats is not accurate! Thats why an accurate measurement would be a good thing.

It is fairly critical to have the correct relationship between the boiler flow and the cylinder temperature!

Tony

 

[UpgradeME]

D40 down to 39 and D41 was down to 32. Other timings all elapsed

Was the boiler firing at this point?

2min D40=45 D41=40
5min D40=52 D41=43
15min D40 =59 D41=50

Do you have the d.0/d.41 figures for the first minute? (did you check d.33?)

27min D40=67 D41=58
34min D40=71 D41=63
39min D40=75 D41=67

These figures show you have a flow rate of 17.54 litres per minute. The "Minimum flow rate" as per the ecoTEC 428's instructions is 20 litres per minute. They also show that your delta T is approx 8-9°C, however your 428 is designed for a delta T of 20°C!

On my system (418), it works okay with 0.72 * output kW i.e. for you that would be 0.72*11=7.92 l/m HOWEVER, as mentioned in a earlier post, even though you have down rated your output, the 418 has a different HEX/burner so this may not be the case with your boiler! The fitting of the 15/60 circulator you have ordered should rule this out if it's an issue and you may need to adjust the balancing valve (if fitted).

Do you know what kW your megaflo coil is rated at? If I have done my calcs correctly, it seems to be absorbing only around 7kW!? (my assumptions being to heat 145l by 45°C and taking just over 1hr... (145*4.18 * 45) / (7*60) = 64.9minutes -- Can anyone confirm if that's the correct calc??)

Boiler then went into micro fire mode with D40 dropping to 69 D41 67 and then 4 second burns with D40 shooting up very quickly and overshooting target flow rate.

Did you check what s.xx code was being displayed as requested? Were you getting the 3.x minute wait times between the "4 second burns" as per your previous measures? Did you check what d.33 was displaying during the burn?

This gave me a burn of over 40 minutes didn't time it properly but on restart after the boiler shut down with call for heat not satisfied I was then presented with micro firing on the CH circuit as well.

What was the s.code? during micro firing? - You have given us lots of detail about when the system is working properly (i.e. during the long burn times), however at the two points that make a difference (the initial 1 minute and when micro firing) there is a distinct lack of information as to what the boiler is doing!?

Did you take any other photo's of the pipework? The zoomed in one is okay if accompanied by some zoomed out photo's (of the valve area and megaflo). What pipe is the "gate valve" (under meter) on and is it open/closed? What were your conclusions of looking inside the tank? (it's difficult to see anything on the photo's your've posted.)

 

[scoobydo123]

Was the boiler firing at this point?

Yes drop was caused by gas rate dropping to D0 value after stupid timer


Do you have the d.0/d.41 figures for the first minute? (did you check d.33?)

Will have to check audio file that I recorded to see if I was checking at this point, no I did not check d.33


These figures show you have a flow rate of 17.54 litres per minute. The "Minimum flow rate" as per the ecoTEC 428's instructions is 20 litres per minute.

On my system (418), it works okay with 0.72 * output kW i.e. for you that would be 0.72*11=7.92 l/m HOWEVER, as mentioned in a earlier post, even though you have down rated your output, the 418 has a different HEX/burner so this may not be the case with your boiler! The fitting of the 15/60 circulator you have ordered should rule this out if it's an issue.

Hopefully it should be with me soon the new pump, however I am not sure it is going to stretch out a 4 second burn to around 40 second burn.


Did you check what s.xx code was being displayed as requested? Were you getting the 3.x minute wait times between the "4 second burns" as per your previous measures? Did you check what d.33 was displaying during the burn?

Will need to check again for this sorry (S code was 7 during one shutdown). Yes 3 minutes inbetween no d.33 info.


What was the s.code? during micro firing? - You have given us lots of detail about when the system is working properly (i.e. during the long burn times), however at the two points that make a difference (the initial 1 minute and when micro firing) there is a distinct lack of information as to what the boiler is doing!?

S7 was displayed for this microfiring. Will get the additional info

Did you take any other photo's of the pipework? The zoomed in one is okay if accompanied by some zoomed out photo's (of the valve area and megaflow). What pipe is the "gate valve" (under meter) on and is it open/closed? What were your conclusions of looking inside the tank? (it's difficult to see anything on the photo's your've posted.)[/quote]

Megaflo only got the flow and returns and obviously inlet and saftey valves. Gate valve is on the return from the HW and is open by around 10 turns. No serious scale on the coil (although not totally bright steel anymore) within the megaflo attached is a sketch of the layout of the pipework.

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• scoobydo123
• 3 Apr 2012
• 1

Tried Vailliant tech support again to try and establish if there is a PCB revision that does not ignore d0. for the first 35 seconds approx and he wasn't aware of this feature on first burn from cold let alone all the time on my PCB.

Sorry quotes got messed up also the coil on the megflo is rated at 18.7kw

Thanks again

 

[scoobydo123]

The other thing I am failing to understand, is if there is a problem with flow why and how could it modify the start up sequence (or at least give the impression that it is modified) ignoring D0 during the start up sequence.

To see the issue I would imagine a lot of service engineers or CP12 issuers would not be onsite long enough to see the issue and would think everything is ok.

Or do I have a PCB issue as well as perhaps a flow issue , I have a variant on the issue as reported with the advanced controls on the cycling blog.

Pump hasn't come unfortunately. But with how the start up logic is behaving on mine I am going to have to find a lot of additional flow and circulation/heat transfer on both HW and CH from somewhere to be able to shift 22kw after the boiler has shut down with call for heat not satisfied. With a refire after 3minute circulation not sure if that is possible?

Got some more photos off the camera of the pipework

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• scoobydo123
• 3 Apr 2012
• 1

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• scoobydo123
• 3 Apr 2012
• 1

 

[UpgradeME]

Tried Vailliant tech support again to try and establish if there is a PCB revision that does not ignore d0. for the first 35 seconds approx and he wasn't aware of this feature on first burn from cold let alone all the time on my PCB.

Where did 35 seconds come into the equation??? (also re-read my previous posts as d.0 has little influence on the initial burn kW on my system!)

also the coil on the megflo is rated at 18.7kw

Can I ask where that figure has come from as it's vastly different to my calculation above of 7kW. (i'm not 100% confident on my calc but also very much doubt it's delivering 18.7kW due to the reheat times!)

The other thing I am failing to understand, is if there is a problem with flow why and how could it modify the start up sequence (or at least give the impression that it is modified) ignoring D0 during the start up sequence.

Your boiler is currently running at 2.5 litres per minute (flow rate) below the minumum specified and has a 11°C delta T below what the manufacturer has designed. Due to these differences, I would imagine the system PCB logic is struggling to cope with the vast differences from specification.

i.e. if your system had a flow rate or 20 litres per minute with a delta T of 20°C (as per the manufacturers design / instructions) I doubt you would have a problem! (<- how you achieve this is a totally different question! )

 

[scoobydo123]

Where did 35 seconds come into the equation??? (also re-read my previous posts as d.0 has little influence on the initial burn kW on my system!)

Time the gas symbol is on the display ie 15 seconds after pump has started fan rpm checked etc. Perhaps with your advanced controls or behaviour is different when PCB is set to 418 mode?

Can I ask where that figure has come from as it's vastly different to my calculation above of 7kW. (i'm not 100% confident on my calc but also very much doubt it's delivering 18.7kW due to the reheat times!)

From the MI, remember boiler is only currently rated at d.0 11kw and it took an age for flow to come up to 75 (45 minutes)

Your boiler is currently running at 2.5 litres per minute (flow rate) below the minumum specified and has a 11°C delta T below what the manufacturer has designed. Due to these differences, I would imagine the system PCB logic is struggling to cope with the vast differences from specification.

Understood hopefully the pump is my magic cure, although it seems there is a reverse logic on initial fire where if flow and return are bad stick even more KW at it. Does you boiler always maintain a delta of 20°C right up to when it does eventually cycle perhaps I have an NTC issue as well as wrong pump

Thanks for sticking with it

 

[UpgradeME]

Can I ask where that figure has come from as it's vastly different to my calculation above of 7kW. (i'm not 100% confident on my calc but also very much doubt it's delivering 18.7kW due to the reheat times!)

From the MI, remember boiler is only currently rated at d.0 11kw and it took an age for flow to come up to 75 (45 minutes)

If your cylinder was absorbing all 11kW (which should be possible with a 18.7kW coil), it would take approx 40-43 minutes to heat all 145 litres to 60°C (assuming incomming mains water was 15°C). Your earlier tests showed the cyclinder not satisfied after 1hr. If you have a thermometer capable of measuring it, next time you perform any tests, can you also measure the incomming cold mains and the tank/hot water temperature? (when it's cycling)

Does you boiler always maintain a delta of 20°C right up to when it does eventually cycle perhaps I have an NTC issue as well as wrong pump

I have a 16yr old open vent cyclinder (approx 2-3kW coil) and get around 8-10°C deltaT. The cyclinder is heated twice per day for a maximum of 30 mins (the VR65 will not allow over 45mins).

 

[scoobydo123]

Current water. temp is 12 obviously to get anything meaningful I need to get what the dhw got up to. I have found info from mickyg on here that some had ntc's fitted incorrectly I will check this out perhaps this is giving perceived Delta issues and messing up the logic? Has anyone got resistance values for ntcs at various temps? Still no pump yet

 

[gaswizzard]

You can get a 15/60 over the counter at any parts supplier.

 

[Agile]

But no body would want to pay their prices!