Vaillant TurboMax Plus 828E - CH always cycling

[dinzi91]

Hello,

I have a Vaillant TurboMax Plus 828E which I’m experiencing an issue with persistent cycling using the central heating.

For years I’ve thought this was normal and that’s just how it operates, but maybe we’re just feeling the cold more because it’s becoming uncomfortable.

I’ve got the central heating dial set to 55C, it reaches this temp, ignition goes off, and quiet for 6 minutes then cycles again.

This constant cycle means the boiler has to fire up several times within an hour, the radiators go from hot to luke warm frequently and subsequently the rooms lose heat.

It’s a 3 bedroom house, double glazed, 10 radiators and all Honeywell Valencia TRVs are set to 5 on their dial. Grundfos pump set to 3 but according to the front label it’s only got 1 mode?

After some reading through the forum, I’ve taken note of all the d.* values from my boiler, please see below, right column for values set (mostly default).

Display	Indication	Displayed values/adjustment values	Set values (mine)
d.00	Part load setting	0, 1, 2 …15 (factory-adjusted to 15 = max. rating)	15​
d.01	Water pump over run	1, 2, 3, …60 min (factory adjusted setting: 5 min)	5​
d.02	Maximum burner anti cycling period at 20 °C flow temperature	8 - 60 min (predelivery setting: 15 min)	15​
d.05	Flow temperature setting	°C	55​
d.07*	1. Vantage hot water temperature (not applicable) 2. Warmstart temperature setting (applies to TURBOmax Plus only)	1. 15 - 75 °C 2. 40 - 65 °C	15​
d.08	External controls heat demand	0 = open, no demand 1 = closed, demand	0​
d.10	Pump status	1 = ON 0 = OFF	0​
d.11	External pump status	1 = ON 0 = OFF	0​
d.22*	Domestic hot water demand	1 = ON 0 = OFF	0​
d.23	Summer/winter function (control knob)	1 = winter 0 = summer	1​
d.24	Air pressure switch	1 = Closed 0 = Open	0​
d.25*	Warmstart status (TURBOmax Plus)	1 = ON 0 = OFF	1​
d.30	Gas valve status	1 = ON 0 = OFF	0​
d.35*	Diverter valve position (THERMOcompact)	1 = hot water 0 = heating system	1​
d.37	Modulator current	mA	0​
d.40	Actual flow temperature	°C	38​
d.50	Maximum flow temperature	°C	114​
d.60	Number over heat cut off operations		0​
d.61	Number of lock outs		24​
d.64	Average ignition time	s	1.4​
d.65	Maximum ignition time	s	7.9​
d.67	Remaining anti cycling period	min	0​
d.68	Number of unsuccessful attempted 1st ignitions		43​
d.69	Number of unsuccessful attempted 2nd ignitions		16​
d.71	Maximum target value for heating system flow temperature	0 = 82 ° C 1 = 87 °C (factory setting: 82 °C)	0​
d.72*	Pump over run (for loading warmstart or Vantage cylinders)	0, 1, 2, … 250 s (factory-adjusted to: 80 s)	80​
d.73*	Offset warmstart temperature value	-15, -14. +5 K (factory-adjusted -15 K)	-15​
d.75	Maximum hot water priority operation time (Vantage only)	20, 21, 22 … 90 min (factory-adjusted to: 30 min)	30​

The only value which I’ve tested dropping down was d.00, this was initially set to 30, I’ve lowered it to 15, and unfortunately the cycling still persists.

I hope I’ve provided enough info/insight, I’d appreciate some advice. Thanks

Dean

 

[dinzi91]

I thought I'd provide a video (with audio) to understand what's going on better.

Boiler has been idle for an hour. Drayton Digistat RF1 set for 20c (17c currently in the house).

Timeline below if you'd rather not watch the whole 20 mins.

0:00 - Ignition fires up, yellow light, flow begins
10:00 - 55c target flow temp reached, ignition cuts out
13:00 - Within this 3 minutes, light fan/pump noise?
16:00 - All quietens for this remaining 3 minutes
16:20 - What sounds like the ignition firing up, maybe me making noise
16:40 - Ignition fires up, yellow light, flow begins again
19:10 - 55c target flow temp reached, ignition cuts out

Vaillant TurboMax Plus 828E CH cycling

This is "Vaillant TurboMax Plus 828E CH cycling" by Dean on Vimeo, the home for high quality videos and the people who love them.

vimeo.com

 

[Johntheo5]

Anything up to say 6 cycles/hour shoul still heat up your rads.
Are you sure that the boiler is getting away each time it refires after the recycle time has elapsed?.
The Vaillant anticycle time is a lookup table, see below, a set anticycletime of 15 minutes is a actual anticycle time of 6 minutes at 55C, vaillants like all boilers fire at ~ 60/65% of max output, most boilers will then modulate down within 10% or so but Vaillants hold these ignition settings for 60 secs or so which require longish recycle time to get the flowtemp as low as possibl to avoid burner cut out at SP+5C, 60C in your case and multiple recycles before getting away., I would watch the flow temp reading just before the end of this 6 minute recycle time and if its not down to ~ 30C, then increase the aticycle time to 20C which is 8minutes@55C or even 25C which is 10minutes@55C.
Have you considered increasing the boiler target temp to say 65C, it may help but you then require a anticycle time of 25C/30C to give anticycle times of 5.5/6.5 minutes.

 

[dinzi91]

Anything up to say 6 cycles/hour shoul still heat up your rads.
Are you sure that the boiler is getting away each time it refires after the recycle time has elapsed?.
The Vaillant anticycle time is a lookup table, see below, a set anticycletime of 15 minutes is a actual anticycle time of 6 minutes at 55C, vaillants like all boilers fire at ~ 60/65% of max output, most boilers will then modulate down within 10% or so but Vaillants hold these ignition settings for 60 secs or so which require longish recycle time to get the flowtemp as low as possibl to avoid burner cut out at SP+5C, 60C in your case and multiple recycles before getting away., I would watch the flow temp reading just before the end of this 6 minute recycle time and if its not down to ~ 30C, then increase the aticycle time to 20C which is 8minutes@55C or even 25C which is 10minutes@55C.
Have you considered increasing the boiler target temp to say 65C, it may help but you then require a anticycle time of 25C/30C to give anticycle times of 5.5/6.5 minutes.

Thanks for your advice, appreciate your input. I've taken some readings this morning before work, let me know what you think.

Just before it reaches target flow temp of 55c, as it's still burning and just about to cut out.
Reading
d.40
56c
d.41
42c

As target flow temp of 55c has just been reached and ignition has just cut out / yellow light just gone off.
Reading
d.40
45c
d.41
43c

At the end of the 6 minutes cycle time, about 10 seconds before the ignition ticks and boiler fires up again.
Reading
d.40
44c
d.41
44c

A second before the ignition goes off, fires up and yellow light switches on.
Reading
d.40
41c
d.41
41c

 

[Johntheo5]

The burner shouldn't cut out until SP+5C, (55+5) 60C, with your settings, see below.

That boiler has a minimum output of 10.4kw (at least the 2E has, can't find MIs for the E model) ), Once the heat demand falls below 10.4kw then the flow &return) temp start to rise and when the flow temp reaches SP+5C, 55+5, 60C in your case, then the burner trips, the circ pump continues running and when the anticycle time has elapsed (and as long as the flow temp is SP-5, 50C), then the burner will refire at ~ 60% of the boiler's rated output, so 28*60%, refires at ~ 16.8kw output, if the flow temp on refiring is 41C and the SP is 55C, a dT of 14C, then the circulation flow will have to be 17.2LPM for a boiler output of 16.8kw (for up to 1 minute), its very unlikely IMO that the flowrate is this high, if you can get the flowtemp down to say 35C before refiring, this gives a dT of (55-35), 20C, so "only" requires a flowrate of 12.04LPM, which is far more likely IMO to be your actual rad circulation rate with all the TRVs opened up. I would increase the anticycle time, as suggested, to get the flowtemp down to 35C or less and see how you get on. Also once it does get away after refiring, time the on /off cycle times, that will give a good idea of the actual heat demand.

 

[dinzi91]

The burner shouldn't cut out until SP+5C, (55+5) 60C, with your settings, see below.

That boiler has a minimum output of 10.4kw (at least the 2E has, can't find MIs for the E model) ), Once the heat demand falls below 10.4kw then the flow &return) temp start to rise and when the flow temp reaches SP+5C, 55+5, 60C in your case, then the burner trips, the circ pump continues running and when the anticycle time has elapsed (and as long as the flow temp is SP-5, 50C), then the burner will refire at ~ 60% of the boiler's rated output, so 28*60%, refires at ~ 16.8kw output, if the flow temp on refiring is 41C and the SP is 55C, a dT of 14C, then the circulation flow will have to be 17.2LPM for a boiler output of 16.8kw (for up to 1 minute), its very unlikely IMO that the flowrate is this high, if you can get the flowtemp down to say 35C before refiring, this gives a dT of (55-35), 20C, so "only" requires a flowrate of 12.04LPM, which is far more likely IMO to be your actual rad circulation rate with all the TRVs opened up. I would increase the anticycle time, as suggested, to get the flowtemp down to 35C or less and see how you get on. Also once it does get away after refiring, time the on /off cycle times, that will give a good idea of the actual heat demand.

I forgot to mention at the start of this thread.

The whole radiators temperature going luke warm/hot frequently, stemmed from me watching videos on how to balance and me being ready to check flow/return of each radiator to balance them using an IR gun and small pilers.

This in turn brought my attention to the boiler, watching it frequently cycle (every 6 minutes), so by the time I presumably got to the 5th/6th radiator, the boiler has already cut off and gone into cycling (I haven't adjusted any lockshields yet).

What would I like to achieve from these adjustments?

Maybe a longer period of firing/burning and if the radiators are going to go luke warm, maybe try to get them to a minimum of warm instead of luke warm (as to not lose too much heat). Also, use up less gas, so less frequent cycling/constant firing up.

I've used the IR gun and pointed it at the top of the radiators upstairs (last on the chain), they get 54c but not for long. The radiators downstairs nearer to the boiler stay consistently nice and hot.

 

[Johntheo5]

The main thing is to get the boiler away after one recycle, then monitor the cycle times, ie on time/off times, if rads still too cold then you may have to increase the flow temperature (and anticycle times) to get the flowtemp down to ~35C before refiring.