Vaillant ecotec plus cycling on HW only demand

[UpgradeME]

Will also see if it will let me set D77 without having the VR controls.

It will make zero difference even if you can! Without the Vaillant controls, your boiler is just heating water, it has no idea if that water is for CH or DHW so d.77 is meaningless. When using the Vaillant controls, your boiler knows when it's heating DHW (and CH) so can use the d.77 value.

When re-visiting it would be handy to know the S.code when the boiler is cycling (i.e. after it's initial long burn) as well as the d.40/d41 values.

Whilst visiting, it might be a good idea to take some photo's of the pipework between boiler around the megaflow, showing any valves etc and post on here.

 

[Agile]

OP, your previous data showed the initial burn was for about 6-7 min.

This tells me the 50 sec initial higher level is not causing any problem.

Yet you still seem to think its a problem! Why?

Unless the cylinder is cold, you are creating a situation which is confusing you.

Tony

 

[scoobydo123]

Yes I appreciate without the ebus controls it is just a call for heat and the boiler does not know if demand is for either CH or DHW but as we all seem to be aware that the firmware on these valliant boilers seems to be a bit screwy and just perhaps with these two parameters set it may stop the boiler being ignorant of the setting of D0, long shot I know but your boiler seems to behave very differently to mine during the initial firing sequence obviously this could be due to you having advanced controls (maybe mrV could confirm if the connection of Ebus controls has an impact on this). Or if it is purely down to the revision of firmware on the boiler. Out of interest is the control software stored on an EPROM that is of the removable type?

Tony after the initial burn the boiler will no longer fire for any length of time always less than 10 seconds I would say this is not normal and not good for both gas usage and longevity of the boiler. I will try to get round there and empty the cylinder and see if we can get two consecutive fires but even if we get 2 or 3 which I think is doubtful given the poor software on the boiler it will then go into short cycle mode. Hopefully this explains why I think the 50 seconds is an issue. But as you say I am not quite running it in a real world situation but I would say 30L of draw off is not too far from a real world quick shower and this only created one good burn and the cylinder took an age to replenish due to the short firing.

Really appreciate all your help.

 

[MrV]

I'm not aware of any logical changes to the software however, the ramp up sequence is both dynamic and dynamically different between modes when ebus controls are used. The ignition sequence is standard and set. As the book says, it requires a minimum flow related to each model. This doesn't mean that if you down rate it to 11kw, it becomes a 411. It's still a 428 and still requires the same minimum flow. That said, if the cylinder is requiring multiple fires to heat the cylinder, it is most likely to be lacking heat transfer. As a guide, a 200ltr cylinder should fully recover in less than 20 mins. I would invest your money in upgrading your cylinder rather than a buffer, which wouldn't solve your problem.
UpgradeME rightly said that your 11kw capacity should have proved adequate performance and it didn't. This backs up the lack of heat transfer if the delta T is ok.
On the ebus subject. The only difference and improvement you will see as well as a new cylinder is that currently your cylinder stat will reactivate demand with a ca2 degree loss and ebus controls wait for 8 degrees so there is more energy to replace.

 

[scoobydo123]

The multiple refires I believe is due to the lack of ramp up due to the 50 seconds bug/emission control. Do I really need a new cylinder it is a 145L megaflo running 2 showers with flow restrictors. If someone could tell me 100% that the upgraded controls would stop the boiler ignoring D0 / D77 then that is what I would go for. Or if there were markings present on the PCB then I do not mind getting a new PCB that does not exhibit the bug/feature.

 

[UpgradeME]

Out of interest is the control software stored on an EPROM that is of the removable type?

Its not and TBH, I wouldn't recommend even attempting to modify the code! I've just looked at my system PCB to identify the revision, on a sticker it says:

0020028402
0494 0340 B

Then screen printed onto the PCB is:

TM-AC1 V132_C1 0020028453 TL-AC PM-03

However, a quick google reveals the manufacturers part number is 0020036861 (not printed on my PCB) and I find a photo of another PCB which has different components on it yet has almost identical markings (The spark generator and another component on my PCB are white but black on that photo) The only difference in markings is one code which doesn't look like a part number more like a date or manufacturer code ("0494 0340 B" on mine, "1043 0066 G" on the photo does anyone know what it represents?)

After doing some more tests using d.33 as a reference, I was wrong, d.0 does not have any effect on my system (other than its use of limiting max kW). However, I can confirm it doesn't have the initial xx seconds at a higher kW either! - In summary, my 418/VRT392/VR65/VR10 will operate WITHOUT the initial high burn kW and will modulate as necessary upto the d.0 / d.77 setting.

I believe on my previous tests, the difference I heard was due to the boiler instantly modulating to the kW it needed. When d.0 was set to 18, it could modulate higher so was therefore louder and then modulated down after 20 seconds as it needed. When I set d.0 lower, obviously it could only go up to what I set it at so was quieter giving the impression that d.0 made a difference to the xx seconds kW.

 

[Agile]

You seem to be missing the point.

The d77 setting is only used by the boiler when it has been told by the ebus signal that it is being used to heat DHW.

The 50 secs only applies to the first fire of a sequence when the makers think its seeing a cold system. Subsequent fires are at the required power according to the d41 and d42 readings.

Currently you seem to be telling us that the cylinder stat is not satisfied but the boiler has turned off because it has achieved the set flow temperature.

If the cyl is set to a max of 60 c and the flow to 72 C then as the cyl is not satisfied either the coil is scaled or its simply that the cyl absorbtion is less than the minimum power output of the boiler because its over specced.

Since its heating the water, I am not sure why you are so concerned!

Whilst I have not heard of anyone doing it, I expect it would be possible to change the burner and gas valve parts to make it operate at the power levels of a 418.

 

[The831Bunny]

Its not often I get annoyed, but it does seem to me us experts are telling you OP, and you're not listening or doing anything creative about it.

(Mr.V/UpgrageME please advise if you think I'm wrong.)

There is no software revision.
There is no other legal/approved PCB change.
No tweaking of the boiler parameters will cure your perceived problem.
The burner can't be legally changed for a 418.
Any modulating boiler on on/off controls will cycle 2/3 times as the set point of the cylinder is approached and heat transfer narrows.
Addition of a VR65 and controls will help heat the cylinder more efficiently, but will not help if the pump is blocked/poor rpm/15-50/scaled coil etc etc.
Heat transfer/flowrate is possibly down but we are all guessing. NO FACTS!

Get an engineer in to diagnose correctly.

Sorry but my free advice has just expired...

 

[MrV]

I am not changing settings willy nilly and wouldn't without first understanding how it interacts.

Fan speeds, ignition sequences, timeouts, shut down sequences etc. Are all there to ensure SAFETY! And then you think you can go replace the processor without knowing the consequences.

I back up 831's comments as he is correct in what he says and most of the advice that you have been given and chosen to ignore is sound advice that is worth considerably more than the time they spent to write it for you.

I'm afraid a "scoobydo" is what you haven't got, and as 831 said, you need a competent heating engineer to correctly diagnose your fault, as on here, advice can only be based on your feedback and that can be very subjective.

 

[scoobydo123]

I will of course take all your advice for when I can get round there again. Inbetween I am only just trying to gather as much information as possible so I can run as many tests as possible during my next visit. Sorry if you feel I am ignoring your valuable advice I can assure you that I am not.

The reason I ask about the PCB is only simply if there is a PCB revision that does not exhibit the same behaviour, yet is one that is supplied for my boiler then I would try to source one. This is assuming that I am correct in what I have heard and I believe witnessed by the speed of ramp up.

Next visit I will drain the cylinder of all water and inspect the coil with an endoscope to see if it is scaled, also then I will have a cold cylinder to reheat and get some more d40 d41 readings.

Thanks

 

[kevindgas]

li'm following this and other threads on the issues experienced with 400 series boilers and have come to the conclusion that vaillant need to get these issues sorted! surely they can rewrite the software to include a slower burner ramp, a system of control like D.0 and D.77 that can control the boilers output according to load demand
I:E

say a 28 kw boiler

heat demand 15kw via VR61 or 65
hot water demand 6kw via VR61 or 65
UFH demand 10kw via VR61

then simply
D.0 = 15
D.77 = 6
D.? = 10

so a load demand for hot water and heat would produce a boiler fire for 15kw at 15/28ths of maximum, but a hot water /under floor would produce 10kw but at 10/28th of max power and hot water only at a reduced like it already acheives via D.77
obvoiusly it would need to flow share the higher output in each case but again by use of Vr10's it could then modulate and/or control zone valves to each circuit?
surely there is someone at vaillant that could sort this out, as it appears to let otherwise excellent boilers down badly.

 

[kevindgas]

This doesn't mean that if you down rate it to 11kw, it becomes a 411. It's still a 428 and still requires the same minimum flow.

but as they all share a common PCB then surely its not beyond vaillant to add additional parameters to allow the boilers to operate as i suggested in the post previously?
also are the small boilers not the same boiler but with different software settings on the pcb? or are they in fact structurally different?

like a potterton suprima the 30,40 & 50 and the 60 & 80 are actually identical except for the injector size and gas rate setting!

 

[scoobydo123]

Still not got 100% confirmation that without the advanced controls whether D0 is ignored for the first 50 seconds and subsequent burns. I am sure that I have read somewhere that the behavior is designed to reduce NOx within the CC during the first burn. Obviously if there is some sort of software glitch or oversight where this behavior does not get switched off when CC is still relatively hot then this could be where my problem lies. Those with 415 and 418 series may not get the problem as there heating coils may be able to dissipate the output of the boiler whilst it behaves like this assuming this is normal/expected but those who have 428 or 438 on hot water only mode will suffer.

I must set aside sometime when convenient with the tenants to check for scale in the base of the megaflo, set the boiler to 6Kw as suggested to see if it fires at 6kw (which I believe it doesn't) and also get the required D40 & D41 settings.

 

[UpgradeME]

also are the small boilers not the same boiler but with different software settings on the pcb? or are they in fact structurally different?

HEX & Burner: 415/418 use same part, 428/438 use same part
Gas valve: 415/418/428 use the same part
PCB: 415/418/428/438 use the same part number

 

[scoobydo123]

Good info there UpgradeME perhaps due to the HEX & Burner differences between our boilers that is why they behave differently BUT if the PCB are the same then perhaps not. Next "but" is that if I remember correctly you do set the PCB to the model that you are installing it in so perhaps the software is set differently just by this software switch so everything does work out in the end.