Weather compensated Vaillant spends a lot of time in anti cycling mode

[Deleted member 281264]

Does anyone know why this may be? have range rated the boiler down to 12kw. What is a normal amount of time the boiler should spend in anticycling mode?

 

[old duffer]

my system works with return temp and incoming air temp so its way more advanced than something you have to tell what to do rather than it react to environmental changes.
Setting the "keep the pump running but don't switch the burner on even if it really could do with some heat input" is going to be difficult as sudden temp drops or indeed rises (at this time of year) are going to alter the efficiency. This is then impacted by heat cycle settings (on-off) so they would need synced as well.
Seems like a lot of effort and guess work.
ps my equivalent of the anti-cycling can last a few hours at a time especially when the outside air is warming

 

[old duffer]

forgot to add, this anti-cycling thing requires a balanced system and one that eliminates the possibility of short circuit local loops. This is where system design is important as it will have been added to and modified over the years probably. I took the brave decision to re-pipe the entire property when I upgraded to super efficient...so glad I bothered now with the "new high energy prices that won't come down to anywhere near where they were just 12 months ago"

 

[Johntheo5]

Does anyone know why this may be? have range rated the boiler down to 12kw. What is a normal amount of time the boiler should spend in anticycling mode?

Probably1, because its minimum output is higher than the heat demand and2, it might be taking a number of cycles to get away if it's weather compensated SP is too low to avoid reaching SP+5C and burner trip before it can modulate down, vaillants are notorious for maintaining their ignition settings of up to 65% for 1 minute before modulation. Can you post the curve also boiler max output.

 

[Deleted member 281264]

Probably1, because its minimum output is higher than the heat demand and2, it might be taking a number of cycles to get away if it's weather compensated SP is too low to avoid reaching SP+5C and burner trip before it can modulate down, vaillants are notorious for maintaining their ignition settings of up to 65% for 1 minute before modulation. Can you post the curve also boiler max output.

it is a 30kw ecotec running two different heating curves and then hot water priority

one is for UFH which is controlled by a pumping station and esbe mixing valve - weather curve is 0.8

other is radiator circuit set at 0.95

I am experimenting with range rating it down and changing pump settings of the UFH and radiator pump to faster speeds, let me know if there's anything else I can change to try and stop the anti-cycling

the boiler is definitely oversized for the house, could of done with 15-18kw

 

[Deleted member 281264]

my system works with return temp and incoming air temp so its way more advanced than something you have to tell what to do rather than it react to environmental changes.
Setting the "keep the pump running but don't switch the burner on even if it really could do with some heat input" is going to be difficult as sudden temp drops or indeed rises (at this time of year) are going to alter the efficiency. This is then impacted by heat cycle settings (on-off) so they would need synced as well.
Seems like a lot of effort and guess work.
ps my equivalent of the anti-cycling can last a few hours at a time especially when the outside air is warming

mine works from the outdoor weather sensor and then sensors on the flow pipes for each zone. that's good to know your anticycle does the same thing, it could be normal behaviour on my boiler but a couple times an hour seems a bit too much.

 

[Johntheo5]

Don't know what particular set of curves its working off but taking the one below as a example then curve 0.8 asks for a flowtemp of 42C at 0C and 38C at 5C, assuming the boiler fires at 60% output or 18kw and assuming a system temp of 28C after anticycle then a flowrate of 1.11m3/hr is required to prevent the flowtemp exceeding 42C and 1.55m3/hr to prevent it exceeding 38C, if the burner is staying on for > say 2 minutes then I would think that the boiler is getting away OK and it will then keep firing until the flowtemp reaches 47C at 0C and 43C at 5C.
I think these boilers have a adjustable internal bypass so ideally it should be closed ot throttled down if a external ABV is fitted.
At the end of the day the burner run time is determined by the heat demand and the minimum output of the boiler.

 

[Deleted member 281264]

statistics greek symbols

This is the heat curve it is working off set on the controller, can set two differet curves on my setup


Thanks for the info, so hopefully the anticycling isn't too abnormal. The anticycle time on the boiler has been set to 11 minutes do you think this ideal or should I change it?

 

[Johntheo5]

I don't think that 11 minutes anticycle time is allways set in stone, a lot of the vaillants use a lookup table where the actual anticycle time depends on the set anticycle time and the flowtemp, the lower the flowtemp the longer the anticycle time, you may find one for your boiler in the manual but if the boiler is performing OK then maybe leave well enough alone.

 

[Deleted member 281264]

I don't think that 11 minutes anticycle time is allways set in stone, a lot of the vaillants use a lookup table where the actual anticycle time depends on the set anticycle time and the flowtemp, the lower the flowtemp the longer the anticycle time, you may find one for your boiler in the manual but if the boiler is performing OK then maybe leave well enough alone.

Yes you are right about that, I only was able to see it was 11 minutes because I went into the D settings while it was in anticycle mode but when in normal heating mode you are unable to change the settings. Thanks for the replies, I will leave it alone probably best not to fiddle too much

 

[ScottishGasMan]

Was 11 minutes the remaining anti cycle time in the menu or was that the setting for the maximum anticycle "D.2"?

Essentially as has been said, the actual time spent in anti cycle is dependant on the flow temperature, lower flow temp = longer it can stay off for. Since your using weather compensation with reasonably low curves then the flow temperature will be fairly low thus the anticycling time will activate for longer.

Not necessarily an issue, its meant to do that, so long as the house is getting warm and its not cycling off so much that you struggle to maintain the correct temperature in the house.

As you've alluded to, if the boiler is over sized, cycling will happen more, theres not a lot you can do about that.

aillants are notorious for maintaining their ignition settings of up to 65% for 1 minute before modulation

Actually thats just one older model that does this, not "Vaillants" in general.

 

[Deleted member 281264]

Was 11 minutes the remaining anti cycle time in the menu or was that the setting for the maximum anticycle "D.2"?

Essentially as has been said, the actual time spent in anti cycle is dependant on the flow temperature, lower flow temp = longer it can stay off for. Since your using weather compensation with reasonably low curves then the flow temperature will be fairly low thus the anticycling time will activate for longer.

Not necessarily an issue, its meant to do that, so long as the house is getting warm and its not cycling off so much that you struggle to maintain the correct temperature in the house.

As you've alluded to, if the boiler is over sized, cycling will happen more, theres not a lot you can do about that.

Actually thats just one older model that does this, not "Vaillants" in general.

11mins was the remaining anticycling time, I've been monitoring what the boiler does and as you say the anticycle varies. The last one I saw was 14mins from the beginning of the cycle

I've been unable to find the D.2 setting you mention on the boiler installer settings but I probably won't fiddle with it anyway

Good to know it's not abnormal. The boiler is functioning fine I just wasn't sure if it should anticycle so much

The controllers are quite complex but I'm getting a grip of it, my aim is to try and run the boiler fully weather compensated with no room influence. It has worked well so far, but the only issue I'm having is I set a night time setback temperature and expected the boiler to shut down but the pumps and zones seem to stay on all the time, I've heard this is normal with weather comp though and everything is on and open all of the time. I'm now testing it on the Active setting as you suggested and will see how this functions in comparison to full WC.

It's an amazing bit of kit and I'm looking forward to getting it dialed in, only regret was finding out about WC after I bought the boiler, I would of either got the green IQ 27kw Vaillant ecotec or a Viesmann 200W. I think my 30kw is quite a bit oversized.

 

[Johntheo5]

Here's a example of a Ecofit Pure 830 anticycle times.

On this model a target temp of 35C + 11min set anticycle time = actual anticycle time of 8.2 mins
and 45C + 11min = actual anticycle time of 6.5mins

 

[Deleted member 281264]

Thanks, I'm mainly running my system boiler at 35-40c. But when the cylinder needs a recharge it will shut off power to other zones and shoot to 45-50 until it's charged and then the boiler rests for a while after.

 

[old duffer]

OR....use a combi that does all of this for you....for less than £1000....