Powerflame Burner Control

elfie

have recently evaluated heating needs and related it to burner control specs



this is a 15 section cast iron steam boiler with a burner range of 1.9m - 4.6million btu's per hour.  the boiler is rated for 3 million btu's per hr.



however, the radiator capacity is 750 btu's per hour (clearly an oversized boiler).  I was hoping to reduce the burner settings but it seems that the low end of burner range is 1.9m btu's per hour.  even if the burner is manually set to lowest point (and abandoning all the modulating controls that exist), its still a major oversize problem.



not sure if burner can be surgically modified to achieve a reduced range. it would be preferable to have a burner output range of 300 to 1.0 million btuh, and this means that a new burner would be needed and the boiler size would need to be reduced (probably half the sections of steam boiler would need to be removed to accommodate a smaller burner)



curious on thoughts/ideas about these burner related issues.



thanks

icesailor

Missing Equation:

Somethings missing in this equation. A 3,000,000 BTU steam boiler with the Power Flame burner to match it is mucho dinero. I find it unusual that the load  of 750,000 BTU's had a boiler as big as that to handle it. Someone isn't telling you the whole story. I'd be asking some pointed questions. 

There's a limit to how much you can down-fire a boiler with the existing fuel utilization equipment.

IMWO

Steamhead

Agreed- we need more info

what make and model are the boiler and burner?



What modulating controls are used? Are they currently set up to lower the firing rate as far as it will go? Have you done a combustion test to verify that the air/fuel mix and stack temp are OK?

The Steam Whisperer (Formerly Boilerpro)

That oversized doesn't surprise me.....

I replaced a 3.2 million input boiler that only has a 350,000 btu load. I've seen 12,000,000 btu boilers feeding only 3 million btu loads.  Most steamers I see are about double the size they need to be when sized by radiation plaus pick up factor.  Most burners are designed to drop to a minimum of about 1/3 maximum fire when retuned...Which would bring you to about 1.5 million input...Which is a whole lot better than what you have now.  Do those air hanndlers have to heat outdoor air for ventilation.  If they do, doubling the load is very likely.

elfie

burner controls

hi Steamhead



i spoke to manufactured (HB Smith - a good co) and they said that the min level that should be used is 50% of max amount.  so for this boiler with a 1.9m to 4.8m burner range, it should be set no lower that 2.4m btu's - otherwise there may be uneven heating,etc.



for our situation, whether its manually set to the lowest point of 1.9m or 2.4m it is still an issue.



most of the time, the load is in the 300-400 btu range.  the extra radiation is helpful to accelerate the heat up.



presently, it appears it is costing twice as much everytime the boiler is used (not continuously used).  this boiler may last 30 yrs and spending $2-4k additional per yr (and higher if rates increase) is troubling.



my thinking is maybe a new 1m btu steam boiler could be installed (and assuming it costs $25k; plus 10k to dispose of other boiler, it may be worthwhile)



thanks for any feedback

Charlie from wmass

If you get the boiler tuned

and it to down fire as low as you can while maintaining stack temp you can save alot of fuel. If it gets to pressure quick it can be shut off by proper setting of the pressuretrols. Exact model numbers of boiler and burner would mean we could give more specific answers. The point of the blowers using outdoor air is an important question that could effect answers.

Dave in QCA

As I recall....

Elfie,



As I recall, your boiler has a modulating burner with a manual override.  If you turn the switch to manual and turn down the potentiometer, it will put it into low fire and hold it there.  That may reduce your short cycling and your costs.  Perhaps  you are already doing that, as this was discussed last year I believe.



Also, I am curious when you report the BTU of the radiation load, are you including the load of the fan coils and air handlers?  As I recall, you have at least one blower unit and I think I also recall that there were more than one.   Do I recall correctly that part of your building is heated with circulation hot water?  Is that heated from the same boiler?  If so, is it heated from a steam/water heat exchanger?  If it is, have you included that load as well?



I suspect that as you have reported before, you have a building with lots of different portions, that have different types of heating systems, all running off of this one large steam boiler.  It appears that the use of the building is occasional, at least not daily, and that when the building is in use, perhaps not all of it is in use. 



I have looked at the literature for your boiler and the numbers that the factory gave you are consistent and their advice of not greater than a 50% turn-down is consistent with good firing practices.  However, your reports of the current firing rates are not clear.  Have you actually clocked the meter, or are you simply looking at the data plate on the burner.  The burner is rated for many applications besides your boiler.  It is capable of a wide firing range, but the actual set up would not necessarily be for that range as indicated on the plate.  It should, and likely is set up for the maximum firing rate to match the boiler's rated input and hopefully, if it was set up right, the lowest firing rated is 50% of that.  The only way to know for sure is to check it. 



This forum is a great place for finding solutions to specific problems.  There are a large number of pros and a bunch of dedicated volunteers who come here to help people the best they can.  However, this forum is probably not the best way to solve facility issues that are more global in nature.  There is no way for anyone to do this without getting a good understand of the entire system, with all of its various components and operating parameters.   My advice is to get on-site service and evaluation from a qualified steam specialist.

elfie

great comments

thanks



its important to get a very good understanding of the heating environment and equipment so that when a boiler firm visit occurs more can be accomplished.



most firms have no clue what the loads are and only focus on cleaning the boilers (and doing a combustion test)



frankly, great service can be elusive and require vigilant efforts to ask the right questions and encouragement during a visit.   we have a good commercial firm.

RobG

Boiler size

If I remember correctly from some previous post, that looks like a Mills boiler. Could you knock off some sections and down fire or install a smaller burner? Certainly not cheap to do, but if you can match the load you will save money in the long run.

Rob