Vaillant EcoTech Boiler Heating Partial Load auto feature

[TaberL]

It appears that the auto feature (D0) is no longer working on my boiler. My rads are taking 45 mins to get warm and the flame is now a lot lower than it used to be. I have tried gradually increasing the kw on partial load. I started using 14kw (have 9 rads) no change, and it only kicked in when I used max 18kw. It's working fine now at that level, but is it OK to leave it at there?

If Vaillant have an auto feature, then it should be working and the boiler should not change how it operates over night I would have thought.

any info and advice gratefully received.

 

[John.g]

What Auto should mean in effect is that the boiler will fire at its maximum rated output and then modulate down once the target flow temperature is reached. With range rating then it should limit the max firing to whatever rating you have allowed and then modulate.
Clearly not doing this, there was a post on here with a problem like that (with a combi boiler) and even on HW would take ages to ramp up, the problem just disappeared after switching a few times from range rated to Auto.

 

[TaberL]

Cheers John, I'll give that a go.

 

[TaberL]

Cheers John, I'll give that a go.

John, meant to say, when I change setting boiler works OK for around 7 days before returning to 'sluggish mode'. Should I wait until then, or should I just change a few times when working OK? Cheers.

 

[John.g]

Can you post on the boiler model and can have a look.

 

[TaberL]

Can you post on the boiler model and can have a look.

It's a Vaillant ecoTEC Plus 418. Thanks.

 

[John.g]

In states below, partial load only, full load only and Auto. Does this mean that there is only 2 range rated settings or else put it to Auto?
Don't know if auto looks at the boiler flow& return temps or whatever and controls the firing based on this.
The next time its on Auto and acting up see if the target flow temperature is showingless than your normal target flow temperature and compare the actual flow temperature with it. So look at d.71 (target flow temp) and d.40&d.41, (flow&return temps)
Vaillant my be able to throw some light on this?.

Also have a read through this.

Vaillant ecoTec 418+ Taking Longer to Reach Desired Temp

Have noticed over the last view days the process has slowed considerably. Normally, the boiler fires up soon after the room stat clicks in and it gets up to desired temp within a few minutes. Have noticed the boiler is much quieter when it does ignite (approx 10 mins after being switched on) and...

www.plumbersforums.net

 

[TaberL]

Thanks for the further info. The range of settings I have are D0 and then incrementals by kw up to 18 max. For 1-17 the boiler operates the same as when auto is set, in other words I have to change it to 18kw before there is a decent flame. It usually operates OK for around 7 days then slips back even on 18kw. Then, if I change to auto it's fine again for a while. So, bearing in mind what you said previously, I'm going to change it every time it slips back for a period of time and monitor, and hopefully it will be OK in D0.

This has been going on for some time, but in the Summer when the rads were off I didn't pursue as it was just the water I needed heating and over a period of 30 mins it heated up to temp required, although on a lower flame.

Target flow temp is 75 degs and it gets there on low flame, but would like it working properly before my warranty runs out. What I can't understand is it worked fine for 4 years and then overnight operation suddenly changed. This seemed to happen around the time of a boiler service, but maybe just a coincidence. Incidentally, not sure how I access d.71

 

[John.g]

That's extraordinary as "Dunbar" said in the last post (attached) above that his only started acting up after 4 years as well and a new PCB cured it. I would be inclined to put a bit of pressure on Vaillant as its clearly not normal operation.
D.71 is shown below but as you can set the target flow temp to 75c on the screen presume this is also set to 75C.

 

[TaberL]

Hey John, not so extraordinary, Brad Dunbar was my partner. He is no longer around. I thank him for leaving me the house but not the frigging boiler.

Had two separate visits from so called Vaillant expert engineers. The first said seems to be OK, but I'll fit a new pcb. It worked for a bit then went back. Second one said the same and fitted an new sensor, same outcome. I'm nearly 5 years in on my 7 year warranty, so they won't get away with it. I just wanted to try and get some advice from people who seem to know more about the boiler than the people who built it.

I new Dunbar had gone on-line to get advice, but wasn't sure which site.

Thanks again for the info, it will help a lot when I contact Vaillant, and it will make me look like I know more than diddly squat about boilers.

 

[Timmy D]

I can’t quite remember fully so feel free to correct me but I’m sure if Vaillants detect too quick of a temp rise on start up, they restrict heat output.

This would fit with what I’ve skim read of your problem.

Cleaned the filter recently?

 

[John.g]

That's correct, that's why I suggest checking flow/return temps and also check status codes S.53 & S.54 next time although strange why the problem disappears when switched from Auto to rated and visa versa. Would like to know what exactly Auto means, it says somewhere that it matches the boiler output to the system demand which may just mean that it allows the boiler to fire at 100% output until Flow target temperature achieved.
This boiler can also be run on return temperature control which would also be interesting as it should give condensing benefits but havn't seen any reports of anyone running in this mode.

 

[TaberL]

Filter gets cleaned when serviced annually. This also could be relevant. Sometimes when boiler is called, the flame goes right to the top of the display, but only for a few seconds then drops back to the bottom before it fires again about 30 secs later. I have contacted Vaillant, and explained the symptoms again. I said that I was changing between D0 and 18kw, and I will stop doing that the next time the boiler isn't working properly and they said they would send someone out then.

 

[John.g]

Next time the boiler if firing hard note the flow/return temps, d.40&d.41. and also just note them when the boiler is modulating normally.

 

[TaberL]

OK, here are some numbers. Boiler is still operating normally with d0 set at 18kw (max).

Water only - D40 = 72, D41=56 (after around five minutes of good flame). D40 =75, D41=61 (when modulating. Diagnostics taken at 5 mins intervals after that D40 remained static and D41 = 61, 63, 64 and 66,

Heating - D40 = 56, D41 =32 (after around 5 mins of good flame), then D40 = 67, then 73 and finally 75. Boiler took 15 mins to reach flow target and D41 = 43, 49, 53 and finally 63.

It will be interesting to see what these numbers are when the boiler goes back to low flame operation.

 

[John.g]

You would expect and are getting low deltaTs on HW as the incoming mains water is very cold.
On CH, after 15 minutes, first deltaT, 75-43, 32C, might have flagged a S.53 or S.54 but others at 26C,22C&12C probably means that the boiler has now modulated down once the target flow temp of 75C has been reached.

32C deltaT will definitely cause some pause or low flame for some period, don't know if it actually causes the boiler to cycle or not.

If the boiler was firing at 18kw with a deltaT of 32C then that means the circulation rate is only 8 LPM but there could be many reasons for this.

 

[TaberL]

Kept D000 at 18kw for one week. During that period boiler worked well. Changed to D0 and carried on working OK for 10 days, but the went back to taking a long time to get going and then at a lower flame. Back now to 18kw. I'm going to leave it at that as Vaillant have been out twice and didn't have a clue. Installed a new pcb and new sensor which I didn't need. Question I have is, will running at 18kw cost me more than at D0. It seems to modulate OK whatever setting I have it on. Thanks.

 

[TaberL]

Clearly not doing this, there was a post on here with a problem like that (with a combi boiler) and even on HW would take ages to ramp up, the problem just disappeared after switching a few times from range rated to Auto.

Yep has worked for me too. Switched a couple of times and now has been working on Auto for around three weeks.

 

[Ciaran (vaillant)]

If its a 418 its only 18kw, make sure your not having the dhw on at the same time as the ch, as this takes heat away from the rads. Time the dhw to come on seperately during the night.

 

[John.g]

Hi Ciaran, see your "vaillant" associated, if so, can you say or find out if these boilers still maintain their ignition settings for up to 60 secs after fire up at ~ 65% of rated output?, all gas boilers fire up at ~ 60% to 70% of rated output but generally allow modulation almost as soon as they fire up. The 60 sec delay causes a lot of problems as the flow temperature can exceed the target temp (by +5C) and cause burner trip and rapid cycling.
I see the Vaillant "new" range of EcoTec Plus boilers now have optional dT control of the flow/return temperatures by using the circ pump variable speed control, this defaults to 20C but is settable, a very nice feature.