Curious behaviour of my Wallstar boiler

I've probably bored all of you to tears with my ongoing saga over the Wallstar 15/20 oil boiler, but now I've discovered an interesting facet of its behaviour.
The lockouts ONLY occur approx 20 to 30 minutes after first switch-on! AND THEN NEVER HAPPEN AGAIN while there is a "call for heat"!
The Danfoss programmes were set to: 04:30 to 07:30, 16:00 to 17:30 and 21:00 to 22:30.
I have kept a careful record of the boiler lockouts since October.
While reviewing this record (about 12 sheets of A4 by now), it became obvious that the lockouts only happen (and NOT always) after the boiler has come on from stone cold.
Here is a summary:
05/Dec/12: Started at 16:00. Locked out at 16:30. Reset pressed. Ran fine to 17:30 Ditto 06/Dec/12: Started at 16:00. Locked out at 16:20. Reset pressed. Ran fine to 17:30 Ditto 06/Dec/12: Started at 21:00. Locked out at 21:20. Reset pressed. Ran fine to 22:30 Ditto 07/Dec/12: Started at 04:30. Locked out at 05:00. Reset pressed. Ran fine to 07:30 Ditto 08/Dec/12: Started at 16:00. Locked out at 16:25. Reset pressed. Ran fine to 17:30 Ditto 10/Dec/12: Started at 04:30. Locked out at 04:50. Reset pressed. Ran fine to 07:30
So yesterday I had the brainwave (well, I thought it was!) of switching the Danfoss to permanently ON (it's a CP15 and has the settings ON, OFF, AUTO, ALLDAY), figuring that I'd only need to press the reset button the once after the first 20 - 30 minutes and thereafter the boiler would continue to run.
And this is exactly what has happened since yesterday morning at 07:30!
Yesterday morning I switched the Danfoss to ON (i.e. 24/7) and the boiler started. True to form, it locked out at 07:55, i.e. about 25 minutes later. Then I pressed reset and the boiler has been running EVER SINCE!
I have adjusted the temperature of the house by use of the Honeywell TRVs. So right now, at almost ten to seven on Friday morning I have a lovely warm house and the boiler is still running fine. Not a single lockout since that first one yesterday morning at 07:55. It's been running without problem for roughly 23 hours.
Now, which one of you can possibly diagnose why it only locks out after the boiler starts up the first time from stone cold and comes to temperature?
Beats me. Beats my heating engineer. Beats even HRM Wallstar, who have been consulted by my heating engineer several times (he knows several engineers there personally).
It's a puzzle and no mistake.
MM
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It might need a new fuel jet? Bad fuel atomisation leading to marginal conditions/instability of the flame until the boiler warms through. Being hot helps the fuel to vapourise better.
Unless the fuel jet has been recently changed.
Is it possible to view the flame and has it's appearance changed?
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On Fri, 14 Dec 2012 00:44:45 -0800 (PST), harry wrote:

Or the wrong one fitted re spray angle and/or fuel rate.

In half an hour it's going to be more than "warmed through" it it well hot, which to me indicates possible overheat but that is a seperate manual reset themostatic trip not a control box lockout. B-(
Half an hour is quite a decent length burn. Pretty much the only thing that can cause a lockout at that stage is flame failure so (in no particular order) water in fuel, fuel starvation (anywhere from tank to jet), wrong/faulty/worn jet, false flame failure detection (dirty/faulty photocell), intermittent wiring (photocell/oil valve).
'tis a puzzle.
--
Cheers
Dave.




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On Fri, 14 Dec 2012 09:57:12 +0000 (GMT), "Dave Liquorice"

But why only locking out once in a "call for heat" cycle and always about 20 to 30 mins after the boiler starts from stone cold?

Yep, the separate boiler overheat thermostat reset button is inside the white casing on the INside of the garage. This has never tripped.

Okay, but yo can set your watch (almost!) by the time to lockout after starting from stone cold. If any of those were a problem, why would further lockouts occur? Remember that my test run yesterday till this morning was 25 hours continuous operation with no lockout apart from the first one 25 minutes in.

You're no kidding. HRM have even offered to the engineer to soak test my boiler on their test rig for a couple of days at their cost (for good customer relations), but that won't be feasible until the weather turns milder in March/April.
MM
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On Fri, 14 Dec 2012 00:44:45 -0800 (PST), harry
Had one at last service in March.

Dunno. Looking at the boiler, which is a very compact design, I'd say not without any special tool. I'll mention all these points to said engineer in due course. I'm not going to bother with it any more before the Christmas week because I'm going away and it looks like the temperature in this part of the world (Boston area) will stay above freezing. And I'll leave the heating on low anyway 24/7, since once it's locked out the first time, it doesn't do so again until the next time the boiler starts up from stone cold and runs for about 20 to 30 minutes. http://www.theweatheroutlook.com/forecast/uk/Boston,Lincolnshire
MM
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<Snip>
Not bored, facinated (though i'm sure you are frustrated!)
How does the boiler now behave (ie how often is it running (I presume the orange light is now permenantly on?)? How long is it (the burner) on/off for at a time?
While it's good to be warm, it could be expensive if it keeps firing for short periods, stopping and firing again.
I think you have said in the past that there isn't a room stat on this system? I presume there is a cylinder stat on the hot water tank?
Chris
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wrote:

Frustration ain't the word for it! What p***es me off is the lack of decent diagnostic tools. If oil boilers are so temperamental, why don't they have a USB connection to a PC running a test/diagnostic program? I worked in the IT industry for many years and if we had produced such unreliable, undiagnosable kit, we'd have all been fired (!) years ago.
It's not just Wallstar boilers. My engineer tells me he's been to Riello boilers, Worcester, Danesmoor, you name it, with similar knotty problems and it seems to me that the manufacturers just don't place enough attention on the fact that their ruddy "design marvels" (as they must think they are) do go wrong and often at the coldest part of the year. My engineer had 23 emergency calls last week. Bloke must be working 12 hours a day.

Yes, the orange light is on as long as the Danfoss is calling for heat.
The boiler runs constantly as long as the initial lockout is dealt with by me going outside, removing the cover and pressing the reset button. Thereafter it doesn't lock out again. Yesterday's test was over **25** hours, no lockout! (Of course, the boiler itself switches off and on every 4 - 5 minutes as it comes to temp, then cools down a bit.)

See (A) or (B) answer below:
(A) If you mean what I referred to in that last sentence, it varies depending on the setting of the temperature knob on the white casing INside the garage. This has MAX and MIN positions. When at MAX, the boiler OFF period is only about 2 minutes. When at MIN it can be off for up to 10 minutes. I've just completed another hour's test on hot water only (manual override button), and jotted down the on/off times as the boiler came to heat, then cooled down etc: ON 14:41, OFF 15:08, ON 15:12, OFF 15:13, ON 15:18, OFF 15:20, ON 15:26, OFF 15:28, ON 15:36, OFF 15:37. Then it didn't come on again as the one hour call for heat period had expired by then.
NB: During that last one-hour test it did NOT lock out after 20 - 30 minutes. It didn't lock out at all. As I've said elsewhere, the lockouts ~mostly~ happen, but not always.
How do I check the on/off times so accurately? Well, I have a Thomy wireless baby monitor next to the boiler and the parent unit is placed where I happen to be in the house (kitchen, computer room etc). It's easy to tell the difference between the comparative roar of the boiler when it starts and the almost complete silence when it stops.
(B) If, however, you meant how long is it off between calls for heat, the Danfoss programmes are currently set to: ON 05:30, OFF 07:30, ON 16:00, OFF 17:30, ON 21:00, OFF 22:30. The same settings are used for Monday through Sunday.
By the way, as I type this, I have to keep breaking off to turn to my scratchpad and jot down the latest ON or OFF time as I listen to the parent unit! If I don't get an ON within the expected period, I know it will have locked out. Then I pop outside, press the reset button and it then continues to run with no further lockout.

I'm not really all that worried about the cost right now. Preventing the pipes from freezing when I'm not here for several days is far more important to me. Also, I don't have any of the oil-filled electric rads on, so I'm saving a fair bit on leccy. (Normally, I use the heating minimally and use the oil-filled standalone rads to heat just the room(s) I occupy.)
Now the house is indeed nice and warm and it IS a bit of a luxury, but, paraphrasing that old line from Terry Christian's The Word ("I'll do anything to get on TV..."), I'll do anything to stop the pipes from freezing!
The "Firing Rate" stated in the boiler handbook is 1.9 to 2.35 litres per hour, depending on output in kW (16 to 18).

Correct. There is no room stat, only the Honeywell TRVs, except on the towel rad in the bathroom, which my builder said must never be switched off. There is a Danfoss stat on the hot water tank that is set to 60 deg C. But note that the cylinder will only be warm-ish most of the day/night as I only heat enough hot water for a bath or washing up (or both!). The boiler is mainly used for CH.
MM
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Hmmm.....
Maybe it would be worth having the Engineer wire the boiler correctly (with a permenant live as well as a "Call for heat" live). and see if that cures all your problems (Though why this should suddenly be an issue when it hasn't been during the life of the system so far, I don't know).
Have Wallstar been advised of the incorrect wiring and asked for their opinion as to what effect it might have (I did email Wallstar's technical address myself to ask this question, but didn't get a reply)?
Chris
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wrote:

All I know is that the engineer has had close contact with several of the Wallstar engineers and has consulted them several times over the past few weeks, which is how long the problem has existed.
As for getting anything out of Wallstar as a *householder*, fuggeddaboudit! ;) I sent them a *lengthy* email some weeks ago, detailing my problem. Never got a reply. Not even an acknowledgement. Nevertheless, you may know from my other posts in e.g. uk.legal that I don't take these kinds of things lying down, which is why I am keeping a careful record of the boiler's behaviour. This is for the New Year, however.
MM
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How long does it take to get up to temperature from a cold start? During the period it's warming up, it will be generating condensation. I'm not familiar with oil boilers, but with gas, this normally dries up pretty quickly (except in condensing boilers). Could it be that some condensation is running somewhere it shouldn't?
--
Andrew Gabriel
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On Fri, 14 Dec 2012 10:39:56 +0000 (UTC), snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

Heating: Approximately 20 to 30 minutes. This is when the lockout, if it's going to happen, happens. (It doesn't *always* happen!) What I mean is, the boiler comes to temperature, switches off, waits a few minutes while the temperature falls, and then is supposed to come back on. It's at that point that the lockout occurs. When it occurs (and I've stood many a time in front of the boiler with the cover removed listening intently) there is NO SIGN of anything happening whatsoever. No click, no initial fan, nothing, zilch. The red light on the control box just comes on = locked out!
Hot water: The coming to temp is usually much quicker, say about 10 minutes.

Now that could indeed be something else to put to the engineer! I'll note this down. Thanks! There just has to be something magic about that 20 to 30 minutes figure.
MM
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Ah, at first re-ignition after the cold firing.

So thinking miles ahead with insufficient evidence to back it up...
Is there a flame detection electrode (might also be the ignition electrode)? If the support/insulation for it is getting wet from any cold firing condensation, it will conduct to earth when there's no flame. This can't be detected whilst the flame is on (as the flame does the same thing), but the control unit will probably check for no flame before trying to light up, to make sure the flame detection electrode is working and not shorted to earth.
--
Andrew Gabriel
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On Fri, 14 Dec 2012 20:42:14 +0000 (UTC), snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

First *attempt* to re-ignite after the cold firing, coming to temp and switching off, yes.

Okay, that sounds like another excellent point to raise, and logically sound. I don't myself know whether there is such a device in my boiler. I know there is a photocell, because I have kept the old parts and I'm looking at it right now.
If you look at page 38 in http://www.wallstar.co.uk/content/pdfs/wallstar.pdf there is a detailed exploded view of the Sterling burner with all the parts identified.
Further observation since yesterday: It doesn't ~appear~ to lock out IF the boiler was NOT stone cold on initial start-up! That is, I allowed a heating cycle to proceed, say, for 2 hour. Then after the Danfoss had switched off, I waited half an hour and repeated the exercise. It did not lock out again. It seems that as long as the boiler DID NOT start from stone cold, the problem of lockout is avoided.
Of course, in normal use, whehn the Danfoss is set to AUTO and calls for heat according to the three set programmes, then the boiler is going to be stone cold every time the next programme starts. At least, it will with my settings because there is a 8.5 hour gap from the first to the second and a 3.5 hour gap from the second to the third.
This question of condensation (and throwing it open to everybody in the thread), is it a recognised ~general~ problem with these types of oil boiler?
Thanks for your feedback.
MM
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Looking at that, the electrodes are not obviously (to me anyway) in the right position to double up as a flame failure detector, but I have no experience of oil burners.
--
Andrew Gabriel
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On Sat, 15 Dec 2012 13:48:51 +0000 (UTC), Andrew Gabriel wrote:

Oil burners normally use optical means of flame detection. A sooted up photocell is a common failure mode but easy to sort out.
--
Cheers
Dave.




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On 14/12/2012 06:50, MM wrote:

If the boiler runs continuously for the first 20 -30 min I would say that that is quite a long burn.
If say you reduced the temperature, the initial burn might be shorter.
My guess is some sort of oil feed problem. Is the tank above or below the burner?
--
Michael Chare

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On Fri, 14 Dec 2012 23:59:13 +0000, Michael Chare

The tank is below the boiler exactly as per the Wallstar installation instructions.
If there was an oil feed problem, why only in the circumstances I described? Why not at all during the 25-hour test run on Thursday/Friday, after the initial lockout and reset?
I have tried setting the temperature control knob on the white casing inside the garage to MIN, to MAX and to mid-way between MIN and MAX, and although this does alter the burn and rest (that's rest, not reset!) times, it makes no difference to that initial lockout when the boiler started up from stone cold.
MM
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