HRM Wallstar Oil Boiler - Advice please

[SJB060685]

If you have a weak spark then increasing the gap is likely to give problems, also a way of testing to see if the spark is weak. As always adjust to mi's

 

[Simonvr46]

Left heating engineer a voicemail. Burner wouldn’t start this morning took numerous attempts just kept going lockout. Gave up trying, left it for 10mins pressed reset and it started 🤬🤬🤬🤬 I just don’t get what’s causing it. It can be switched on for 6 hrs and it’ll run perfectly, it’ll stop when it gets to temp etc then restart every time. It’s just seems to be on the initial start up.

 

[SJB060685]

Hopefully the engineer will get back to you and you can mention everything we went through last night.

 

[Simonvr46]

Hopefully the engineer will get back to you and you can mention everything we went through last night.

Hope so.....
Spoke to HRM this morning, they said it could be electrode or could be to do with the air in the oil line and advised against fitting tiger loop. The way he was explaining the lockout that I’m having doesn’t appear to follow a normal pattern that you would expect for either air or electrodes.

 

[SJB060685]

I'm under the understanding that a tigerloop would void the warranty from new but your boiler is past warranty anyway. A tigerloop not only lifts fuel, it pre heats it and removes any gas bubbles in fuel supply. Having said that the danfoss pumps are more than capable of drawing fuel up to about 2.5m, even modern Riello pumps can draw fuel a certain distance. The engineer needs to thoroughly check electrode position going by the book, spark quality and whether or not its intermittently sparking elsewhere ie around porcelain protectors or HT lead. If after a number of attempts he is happy all is well then I would move onto checking atomization of fuel at nozzle, this again needs to be done safely and properly.

 

[John.g]

I assume its going through a normal pre-purge and 5 sec ignition before lockout, most burners do a 12 sec pre-purge followed by the oil solenoid energising and the ignitor/electrodes firing for another 5 secs, if no flame established after this 5 secs, 17 in all, then lockout.?
To completely rule out oil pressure problem on start up could you fit a oil pressure gauge and monitor this after failure, you can then concentrate on something else. Also after the 12 sec pre-purge you will hear a distinct "click", I don't know if this is the noise of the solenoid opening or the sound of the electrodes sparking but SJB will know this.

 

[SJB060685]

You are correct to a degree John. This is a Satronic control box so the timing sequence for ignition function and everything else is slightly different. The ignition is on from the start of pre purge and stays on till about 15 seconds after ignition. Putting a gauge on pump will tell you if you have pressure from the start. These Danfoss pumps have operating pressure from the word go, unlike Riello and some Suntecs which have a wash pressure. However the pump has been replaced so I shouldn't be the problem. If it was air in the fuel line I'd be expecting the pressure to be fluctuating up and down and not a solid 8 bar for example. Obviously if the inlet port to HP line was completely air locked then you'd have no fuel at nozzle, one of the reasons I said what I did above.
Yes solenoid have the very distinctive click when opening and closing

 

[Simonvr46]

I'm under the understanding that a tigerloop would void the warranty from new but your boiler is past warranty anyway. A tigerloop not only lifts fuel, it pre heats it and removes any gas bubbles in fuel supply. Having said that the danfoss pumps are more than capable of drawing fuel up to about 2.5m, even modern Riello pumps can draw fuel a certain distance. The engineer needs to thoroughly check electrode position going by the book, spark quality and whether or not its intermittently sparking elsewhere ie around porcelain protectors or HT lead. If after a number of attempts he is happy all is well then I would move onto checking atomization of fuel at nozzle, this again needs to be done safely and properly.

That’s basically what the guy at HRM was saying with regards to the electrode. He said to make sure that the diffuser plates in the blast tube are correct distance away from nozzle/electrodes as that can affect the nozzle pattern.
If the HT leads and electrodes are replaced then that’s everything apart from motor and blast tube.

 

[SJB060685]

That’s basically what the guy at HRM was saying with regards to the electrode. He said to make sure that the diffuser plates in the blast tube are correct distance away from nozzle/electrodes as that can affect the nozzle pattern.
If the HT leads and electrodes are replaced then that’s everything apart from motor and blast tube.

Yes the brake plate needs to be at correct position as well as like you say this will affect spray pattern, too close to nozzle outlet and it will affect its ability to ignite, or delayed ignition. MI's says 3-5mm but I'm sure I've mentioned this before?

 

[Simonvr46]

Hi john,
If you go back through these posts on here you will see a video of our burner going into lockout.
It’s just bizarre that it isn’t every time.
If it continually went to lock out and wouldn’t start i would be happier. I’d be even happier though if it started every time lol.
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Yes the brake plate needs to be at correct position as well as like you say this will affect spray pattern, too close to nozzle outlet and it will affect its ability to ignite, or delayed ignition. MI's says 3-5mm but I'm sure I've mentioned this before?

Yeah I did check these when it was mentioned before and they all seemed ok to within the tolerances specified in handbook.

 

[SJB060685]

With all the parts you've had engineers randomly change you could of bought a new burner. That's another option, many decent engineers have spare burners for problem child situations like this. Maybe if they have a sound Sterling that could be fitted for a week, at least then you'll know if it's a fuel or burner problem. If that's not an option then they need to go through what I've said to rule out possibilities. If I attended and couldn't find the fault first time, after replacing the pump as you said was then I shouldn't be charging you for return visits

 

[John.g]

Any remotely operated fire valve in the oil supply that maybe throttling it?.

Oh yes, I see you had it replaced.

 

[Simonvr46]

left heating engineer a voicemail on Monday morning and tried ringing him during the week. Not heard anything. Haven’t paid anything yet so I know he’ll get back at some point.
Boiler still playing up.
Yesterday morning it wouldn’t start, tried several times ended up bleeding oil line and it started.
Yesterday afternoon wouldn’t start, again tried several times. Tried bleeding oil line again but still wouldn’t start even with 2 inch air bubble. Left it 10mins and it started.

 

[John.g]

Think you will have fit that oil pressure gauge and monitor after cut out.

 

[SJB060685]

The pump has recently been replaced and I'm assuming the coupling along with it and seeing as it's the same problem before and after I'd suspect neither are the issue. Obviously all air needs to be removed from the pump for reliable ignition, a gauge usually fluctuates with air in pump. The motor is running and assuming the coil is sound and clicks then atomization of fuel at nozzle needs to be checked along with spark. If the pump is producing operating pressure and coil opens but no fuel out of nozzle then it could be a dodgy nozzle, a blocked/partially blocked HP line or a dodgy NRV (although I'm not sure if the Sterling has one). If you have neat fuel out of nozzle next check is spark.

 

[Simonvr46]

Never did get to the bottom of this issue.

Decided rather than spend/waste money on trying to fix it.

We’ve gone down the route of having a new boiler, I purchased Worcester Greenstar heatslave II through staff discount scheme we have where I work and then paid an accredited Worcester installer to install and commission boiler.

It’s been installed 11 days and no problems at all. Starts every time and we now have constant hot water.

 

[SJB060685]

Thanks for updating us. Im sorry to hear you made that decision, although it does suggest the problem was never fuel related and was within the burner, unless the installer rectified a proper when installing.
Not a fan of combi boilers personally but if I remember correctly there's just the two of you and they are decent boilers.

Again thanks for updating us.

Many thanks, Simon

 

[Simonvr46]

Thanks for updating us. Im sorry to hear you made that decision, although it does suggest the problem was never fuel related and was within the burner, unless the installer rectified a proper when installing.
Not a fan of combi boilers personally but if I remember correctly there's just the two of you and they are decent boilers.

Again thanks for updating us.

Many thanks, Simon

Hiya, only things that have changed regarding the fueling are that the boiler is now sat on the floor rather than it being in the wall so that the pump doesn’t have to lift the oil up and the fire valve has been replaced with new one instead of the HRM version with non return valve. The installer let me take off all the parts that had been replaced, which I thought was decent of him as he could have kept them and used them.

I think we will use less oil especially during the summer as both of us are at work and we have boiler set to only come on in morning and evening to give us hot water When we need it, instead of it being on all the time and keeping the heatslave tank at constant temp.
Thanks for all your help.

 

[John.g]

Thanks for updating us. Im sorry to hear you made that decision, although it does suggest the problem was never fuel related and was within the burner, unless the installer rectified a proper when installing.
Not a fan of combi boilers personally but if I remember correctly there's just the two of you and they are decent boilers.

Again thanks for updating us.

Many thanks, Simon

SJB, you may have a few comments to make re Stored combi boilers output and flow rates, there are numerous queries on here re gas combi flow rates as well.

I am looking at a brochure for a Firebird C35 combi boiler and to quote "D.H.W. Guide Performance in litres/min (120 litre draw-off at 40C deltaT) 20". It has a primary store of 40 litres heated to 78C.
Do you know if this guide performance is typical for oil fired combis? and also how is this number of 120 litres arrived at?
My simple calc shows that if one assumes cold water at 10C, then with a deltaT of 40C the stored cylinder will give a volume of 40*(78-10)/(50-10), 68 litres at 50C (which should give 20 LPM but only for 68/20, 3.4 mins, the burner should kick in at 73C and then the 35kw boiler will give a continuous flowrate of (35*860)/(40*60), 12.54 LPM.
My main query is this 120 litre figure?, the flow rates are simple to understand IMO.

 

[SimonG]

120 litres to fill a bath. They want to give the idea that you can fill a bath before the store gives out. It doesn't last though.

 

[SJB060685]

Its to do with the amount of stored energy in the thermal store. 120 litres is what can be provided at that delta until the store depletes.
Gas is different, they ramp up to full output and can modulate down for the lower load of CH.
Because up until recently domestic oil burners are fixed rate they have to use a store to aid in HW production.
If my understanding and maths is correct then 20 litres per minute at a delta t of 40°c would require an input of roughly 50kw but as said above if there was no thermal store and you had a nozzle size and pressure to input 50kw for HW then the CH side will also have the same input, obviously being massively oversized.
Perhaps when fully modulating oil burners take off there will be no need for a thermal store.
Thats my understanding, if I'm wrong then please correct me.

 

[John.g]

My calcs show that a 70 litre store would be required to give that 120 litres, the store is definitely required as you say because of the fixed boiler output and if you only needed a flow rate of 4 or 5 LPM then the boiler would be constantly cycling on/off. A continuous 20 LPM at a deltaT of 40 requires 56kw, the more normal quoted deltaT of 35C would require 49kw.

 

[SJB060685]

Can you break down your calculation method.
Bare in mind as the store temp decreases the burner will engage and supply additional energy, until a certain point where the input cant match the output.

 

[John.g]

OK, you are mixing cold water (at say 10C, but you can use your own number) with hot water at 78C (stored water temp) to give a mixed temp of 50C so every 1 litre of water at 78C will give 1*(78-10)/(50-10), 1.7 litres at 50C, so a store of 40 litres at 78C will give 68 litres at 50C. Additional energy will be supplied when the store reaches 73C but store will just about be depleted then and a 35kw boiler will then have a flow temp (to the store) at 20 LPM, of ((35*860)/(20*60))+10, 35C. The only way to get a sustained flow rate at 50C after the store is depleted is to reduce the flow rate to 12.54 LPM (35*860)/(60*(50-10).

 

[SJB060685]

How are you reaching your mixed temperature?

 

[John.g]

I presume the Firebird has a mixer to reduce the temp to ~ 65c and then the shower or whatever will reduce it to 50C but it doesn't matter as the stated conditions are water from a stored temp of 78 to water at 50C (from 10C) so the ratio is 1.7:1.

Thinking back again to the burner re firing at a store temp of 73C, if the probe picks this up very early in the draw off then you could be adding in energy early on so that will have the effect of increasing the thermal store so the 120 litres may actually be not too far off the mark as it would only need a additional ~ 2.5 kwh to achieve this but needs a bit more thought.

 

[SJB060685]

So have I done the maths correct.
Say we have a store of 50 litres with a temperature of 80°c and we want a delta t of 35°c and an incoming temperature of say 12°c
So 1 litre will provide 80 ÷ 35 = 2.28 litres, so 50 × 2.28 = 114 litres?

 

[John.g]

Not quite, the calc IMO is 1 litre will provide (80-12)/(47-12) or 1.942 litres @ 47C so 50x1.942= 97 litres. I will show the actual "long" calc when i return in ~ 2 hrs.

 

[SJB060685]

yes I slipped up. Your figure is correct.
Yes please show me later and also explain where you got this method from and how accurate it is mate please.

 

[John.g]

The following is the heat balance method, I just use a shortened (my own) version above but it is 100% accurate.

L Litres = volume of cold water that must be added to 1 litre of hot water to give you the required mixed water temperature.
So: (1*80)+(L*12) = (1+L)*47
80+12L = 47+47L
33 = 35L
L = 33/35 or 0.942 litres
So 1 litre of hot water at 80C will give 1.942 litres of mixed water at 47C from cold water at 12C.

 

[SJB060685]

Thanks John. Yet again you've provided me with an equation or method for calculating something I didnt know before.

 

[John.g]

I presume the Firebird has a mixer to reduce the temp to ~ 65c and then the shower or whatever will reduce it to 50C but it doesn't matter as the stated conditions are water from a stored temp of 78 to water at 50C (from 10C) so the ratio is 1.7:1.

Thinking back again to the burner re firing at a store temp of 73C, if the probe picks this up very early in the draw off then you could be adding in energy early on so that will have the effect of increasing the thermal store so the 120 litres may actually be not too far off the mark as it would only need a additional ~ 2.5 kwh to achieve this but needs a bit more thought.

Think I may have finally come up with a reasonable calc for the above but is based on the boiler firing up almost immediately. The 78C high temp flow rate from the store will only require a flow rate of 20/1.7, 11.76 LPM from the store until it has fully depleted its 40 litres, the 35 kw boiler will also be heating the water to almost 53C at this flowrate so by the time the 40 litres at 75C is depleted then the store will be full of water at 53C = 43 litres at 50C, so 68 litres at 50C after mixing from the 78C store plus 43 litres at 50C with a little mixing gives a total of at least 111 litres at 50C?.

 

[SJB060685]

I'm going to trust your maths and judgement and say you could be correct.
Most oil combis state a maximum draw off at 40°c delta t, so there will come a time I assume and as I said above where the HW output temperature will start declining until the store is recharged.

 

[John.g]

It certainly will fall off because if the demand is kept at 20 lpm then once the first store is drawn off then the second store flow rate will rise to 20 LPM (practically no mixing) and once this is depleted (at 50C) the 35 kw boiler will only give a steady temp of 35C (35*850/20/60)+10), the flowrate must be reduced to 12.54 LPM, (35*860/40/60), to give a steady temp of 50C. In other words a flowrate of 20 LPM @ 50C will only be maintained for 5.5 minutes, 111/20, and the temp will then fall to 35C if not throttled in., I suppose that really isn't too bad as it will (almost) fill a bath or give a super power shower of 20 LPM for over 5 minutes. The key to the increased (temporary) flow rate is the burner cutting in almost as soon as there is a flow demand.

 

[SJB060685]

When there is a demand at a HW outlet the flow switch and PCB do their thing and the burner and pump should engage straight away anyway.