Incorrect burner head?

Wearb

I am servicing a Grant 50/90 outdoor modular oil boiler. (That is what the label says) The manual gives dimensions for this boiler that doesn't agree with any dimensions that I measure on this unit. In fact none of the boilers in the manual have even close dimensions. Last time I serviced this boiler, I also had worries about nozzle angles and contacted Grant, but I was not satisfied with the answer I got which stated that it was labelled wrong and that I should go by the manual. The Manual give a 60degree nozzle and the label 80. I am inclined to believe the label as it is a square combustion chamber.

To confuse matters even more, about 5 years ago a plumber took away the old burner and fitted a second hand one which is now the one still fitted. I am wondering if he replaced the burner with one with too long of a head. I attach 2 images, though my main concern is the length of the burner head.

jimf

what condition are the baffles in what burner is actually fitted at the moment the spec I have for this boiler states 80000 btu .75x60s nozzle at 7 bar pressure for kero using an rdb with ld3 head

Wearb

Its a Riello 40. Baffles are good, in fact the performance isn't (or wasn't) suffering. I have now put in a .55 80 s nozzle and have managed to set it up to good combustion efficiency. (It had a .60 60s) It seems to be a very forgiving boiler.
My main concern is that the burner head seems to be projecting too much into the combustion chamber.

As I already said, this boiler doesn't correspond to any of the boilers in the manual. It is a different shape to the 50/90 in the manual and as you can see the label doesn't even correspond to any of the manual reconsiderations.

Billy Bunting

The 50/90 comes out of the factory set at 20.5kw/70000btu with a .60/60oS set at 7bar using a LD3 blast tube. But at the end of the day if you have a botch job but the FGA reads good then why sweat over it, away ya go.

jimf

Billy Bunting wrote: »

The 50/90 comes out of the factory set at 20.5kw/70000btu with a .60/60oS set at 7bar using a LD3 blast tube. But at the end of the day if you have a botch job but the FGA reads good then why sweat over it, away ya go.

is it not 9 bar billy maybe im wrong

esox28

that blast tube dosent look excessively long imo, for a 50/90

is that a g3b model reillo 40?

they usually set 60* jet and 8bar pump pressure at the factory.

you were right to change with a 80* as in case of flame detachment, during ignitions at low temperatures, espesally when retro fitting to existing boiler.

esox28

oh no 3 conflicting preset pump pressures

Billy Bunting

jimf wrote: »

is it not 9 bar billy maybe im wrong

9 bar if setting up for 80,000, but comes, or MI states comes from factory at 7bar 70,000.

Billy Bunting

esox28 wrote: »

oh no 3 conflicting preset pump pressures

When there is conflict trust the FGA. :cool:

esox28

CODE MODEL TYPE
20030780 G3B 437T50

Kerosene fuel

8 bar: the pump leaves the factory set at this value.

jimf

esox28 wrote: »

CODE MODEL TYPE
20030780 G3B 437T50

Kerosene fuel

8 bar: the pump leaves the factory set at this value.

sorry esox28 was referring to current mi specs for rdb burner

jimf

Billy Bunting wrote: »

9 bar if setting up for 80,000, but comes, or MI states comes from factory at 7bar 70,000.

but using a .75x60s nozzle by my bible billy set at 7bar for 80000 btu

Wearb

esox28 wrote: »

that blast tube dosent look excessively long imo, for a 50/90

is that a g3b model reillo 40?

they usually set 60* jet and 8bar pump pressure at the factory.

you were right to change with a 80* as in case of flame detachment, during ignitions at low temperatures, espesally when retro fitting to existing boiler.

Yes a G3B. The boiler must have been either an early or late model 50/90. None of the dimensions or boiler label correspond to the manual data. Grant wasnt able to help either. I have diagrams for nozzle sizing with reference to combustion chamber size and boiler output, but how do you decide on which head to use?

Wearb

Billy Bunting wrote: »

The 50/90 comes out of the factory set at 20.5kw/70000btu with a .60/60oS set at 7bar using a LD3 blast tube. But at the end of the day if you have a botch job but the FGA reads good then why sweat over it, away ya go.

Thanks. I understand what you are saying Billy. I suppose I am just too fussy sometimes.

shane0007

Nothing wrong with that blast tube length.
Shorter blast tubes create a reduced static head pressure which is generally not enough to overcome the combustion chamber resistance pressure & the result is a slightly sooted tube end. Boilers such as the HE WF have snub nose blast tubes & the air must be reduced to very low limits to overcome this.
If you notice on adjustable tubes, there is always a test port on the side of the burner head. This is to measure the resistance of static head pressure in mbar. Usually around 4mb plus the chamber resistance of about 2mb.

So basically, it's the correct length tube. The fin pattern is another that is not shown.

Wearb

shane0007 wrote: »

Nothing wrong with that blast tube length.
Shorter blast tubes create a reduced static head pressure which is generally not enough to overcome the combustion chamber resistance pressure & the result is a slightly sooted tube end. Boilers such as the HE WF have snub nose blast tubes & the air must be reduced to very low limits to overcome this.
If you notice on adjustable tubes, there is always a test port on the side of the burner head. This is to measure the resistance of static head pressure in mbar. Usually around 4mb plus the chamber resistance of about 2mb.

So basically, it's the correct length tube. The fin pattern is another that is not shown.

I attach a photo of the fins. This burner hadn't been serviced for 20 months, but as you can see from the combustion chamber, it was fairly clean, except for slight soothing on the surface opposite the burner head.

Billy Bunting

jimf wrote: »

but using a .75x60s nozzle by my bible billy set at 7bar for 80000 btu

In mine its 90000. :eek:

My bible version is outdoor manual 12/04 - 1231A, if its dodgy i'll be looking for a full refund from DGOBS.

shane0007

Wearb wrote: »

I attach a photo of the fins. This burner hadn't been serviced for 20 months, but as you can see from the combustion chamber, it was fairly clean, except for slight soothing on the surface opposite the burner head.

That's not bad for 20 months. This is the result of poor burner head pressure. Fina are correct.
What CO2 was it set to? If as per MI, it's slightly wrong as they are for SEDBUK bettering results!

Billy Bunting

Wearb wrote: »

I attach a photo of the fins.

Looks like a LD2XS that is normally on the 50/70

shane0007

Billy Bunting wrote: »

In mine its 90000. :eek:

My bible version is outdoor manual 12/04 - 1231A, if its dodgy i'll be looking for a full refund from DGOBS.

Think he may ask to see your receipt....

Wearb

See attached FGA readings. Amazingly, I managed to get similar reading 20 months ago with a 60degree nozzle.

shane0007

I'd be very happy with that set up. As I said, not a bad chamber after 20 months.

Wearb

Billy Bunting wrote: »

Looks like a LD2XS that is normally on the 50/70

Longer than that. Looks more like a T3

esox28

Billy Bunting wrote: »

Looks like a LD2XS that is normally on the 50/70

yea billy's right its an ld3 tube for the 50/90 you have the ld2xs shouldnt make any difference but would explain slight soot up in fins, what readings are you getting from the fga?

esox28

sorry but what fga are you using? my sprint v1 dosent have pressure read out!

Wearb

esox28 wrote: »

yea billy's right its an ld3 tube for the 50/90 you have the ld2xs shouldnt make any difference but would explain slight soot up in fins, what readings are you getting from the fga?

V2

jimf

Billy Bunting wrote: »

In mine its 90000. :eek:

My bible version is outdoor manual 12/04 - 1231A, if its dodgy i'll be looking for a full refund from DGOBS.

don't know what version mine is billy no cover on it

shane0007

esox28 wrote: »

but would explain slight soot up in fins

There are 2 important pressure readings with combustion, namely static head pressure & combustion resistance pressure. The latter is the resistance of the combustion chamber from routes, baffles, flue, etc. it is measured in mbars. Usually circa 2mbar but it may vary from boiler to boiler.
The static head pressure is the pressure behind the blast tube fins to the back of the blast tube. This pressure is used to hold the flame in front of the fins. Adjusting the fin position will increase or decrease the static head pressure, lifting or bringing back the flame to the nozzle face. This pressure is usually about 4 - 6 mbar. When testing the two pressure must be added to be set as the total pressure must overcome the resistance path to flue terminal.

Next time you are on a commercial boiler, you should see a test port on the combustion chamber door & one on the burner head. Along with MI's you can adjust the SHP to suit the installation, then adjust the CO2 to suit.

A sign of incorrect settings is slightly blackened fins but a fairly clean chamber. Most domestic boilers SHP's cannot be adjusted. Many CI boilers can though as the resistance with those plays are larger role.

esox28

I've seen the test nipples on certain burners never knew you could put a guage to test. Know a small bit bout com burners just from reading mi. Have booked into com course and looking forward to it.

shane0007

You will really enjoy it. Give Freddie a hard time though.

The Anton Sprint V2 has differential pressure ports which are suitable. Best is a dedicated pressure gauge. Anton also do a nice one.

esox28

Friddie doing the com. Good stuff bit of crack to be had.

Been thinking bout a v2 for a couple of months now, my v1 is 5 years old or more at this stage and going like a clock, spent 200 \ year also on calabratio so just reluctant to get into more money, maybe when im on the course see what dodgy deals are available.

shane0007

The new Evo is snazzy. No purge unless you are going into FGA. It goes straight into gas seeking, pressure, etc. I haven't upgraded yet but am changing my probe to the Evo one for my V2. Changing my case for the the Evo one too.

esox28

shane0007 wrote: »

There are 2 important pressure readings with combustion, namely static head pressure & combustion resistance pressure. The latter is the resistance of the combustion chamber from routes, baffles, flue, etc. it is measured in mbars. Usually circa 2mbar but it may vary from boiler to boiler.
The static head pressure is the pressure behind the blast tube fins to the back of the blast tube. This pressure is used to hold the flame in front of the fins. Adjusting the fin position will increase or decrease the static head pressure, lifting or bringing back the flame to the nozzle face. This pressure is usually about 4 - 6 mbar. When testing the two pressure must be added to be set as the total pressure must overcome the resistance path to flue terminal.

Next time you are on a commercial boiler, you should see a test port on the combustion chamber door & one on the burner head. Along with MI's you can adjust the SHP to suit the installation, then adjust the CO2 to suit.

A sign of incorrect settings is slightly blackened fins but a fairly clean chamber. Most domestic boilers SHP's cannot be adjusted. Many CI boilers can though as the resistance with those plays are larger role.

Put the monometer on two burners today, servicing an 50/90 utitily with bf and got 1mbar.

The other a commission wf k120 with a t5 short tube and got 5mbar, funny enough with this one as I decreased the air pressure it fell from 6mbar to the final position of 5.

Is there any reading on static resistance pressure as I haven't come across it. Also no mention in mi.s as far as I read.

shane0007

You will generally just get the air damper setting in relation to nozzle output. The greater the nozzle, the greater the head setting.the smaller nozzle/power output requiring a lot less static head pressure to keep the flame in the correct position.
Smaller domestic combustion pressures will be upto 1mbar. Larger non-domestic around 2mbar.

Once you play around with them in conjunction with a FGA, you will see more of their affect & importance.

Froststop

This might help: pages 6, 10, & 13 charts.

http://nakco.com/Heating_Tip/Nozzle%20Knowledge.pdf

shane0007

Very useful document but nothing in it for combustion & static head pressures. Just all to do with nozzle selection & nozzle calculations, patterns & fuel flow rates. Danfoss do a similar document.