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Vertical Boiler - blower?

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mick H14/03/2019 09:26:44
728 forum posts
21 photos

Am I going over the top fitting a blower to the vertical boiler I am building? I don't recall ever seeing one elsewhere or on plans.


fizzy14/03/2019 09:38:46
1734 forum posts
116 photos

all depends on what your firing it with - gas=no, coal=definately. Ive never seen any coal fired boiler without one...and ive made and seen a few.

mick H14/03/2019 10:22:47
728 forum posts
21 photos

Thanks Fizzy. It is gas fired. It comes up to steam well with an external steam raiser down the smokestack but the fire (ceramic burner) can be a bit sluggish when there is no exhaust from the motor to gee things up a bit. I suspect also that there is incomplete combustion judging by the smell when the motor is not running. When the motor is running I could not ask more from this littIe boiler which is only 2.5 in in diameter. have had the same experience with gas fired loco.


GordonH14/03/2019 16:47:09
16 forum posts
3 photos

If you need the fan to get a decent flame and without it you suspect incomplete combustion, I'd suspect you may have insufficient air supply to the burner, or insufficient chimney area.


Howard Lewis14/03/2019 17:15:18
3627 forum posts
2 photos

As well as ensuring that there is adequate air supply to the burner,and chimney area, is the chimney long enough?

With the other mods, a slightly longer chimney may encourage a better draught of air through the burner.


fizzy14/03/2019 19:53:49
1734 forum posts
116 photos

Incomplete combustion is something we see with small burners, just put a CO meter near one, be they ceramic, mesh or brass. All three have different burn characteristics. I use solid brass in my commercially availible boilers as they produce the most heat, they are quiet fierce compared to ceramic. I only use ceramic in the twin flue 5" boiler as their sublime nature makes for much easier firing of both flues at the same time. A well designed burner needs no chimney as all of the combustion products are supplied from outside the burner. You will see slits in the sides of PSB burners but these have absolutely nothing to do with the combustion process. Invariably if you have your gas mix too rich a blue flame will be seen where it exits the chimney - check with lights off as it can be difficult to see. Whilst a more stable flame is seen when a chimney is present I can produce effective boilers without a chimney. An option is to have the steam return plumbed into the chimney but this is for authenticity rather than efficiency and i have not noticed any improvment in output.. My advice exit steam through chimney but there should be no reason to add a stand alone blower, especially in a boiler so small.

mick H14/03/2019 21:36:49
728 forum posts
21 photos

Thanks for the interest gents. I do run the exit steam up the chimney and everything goes well when I do so. It is when I stop the motor and there is no exit steam going up the chimney that I have noticed that the fire seems to burn less enthusiastically. On a loco. it is at this point that I use the blower to stimulate the fire until the steam to the pistons is turned on again whereupon the blower is turned off. I only use the steam raising fan when first starting the boiler from cold. Primary air enters through the holes in the No.5 gas jet tube and there is plenty of secondary air available to the burner which burns with a stable blue flame. I am overall very pleased with the situation but just wondered whether results would be worth the effort of including a blower for use when the motor is turned off. It may be that reducing the gas supply when the motor is turned off will achieve the same thing.


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