burners

Fred Cotton

Does anyone have any thoughts about on/off vs. low/high/low vs. fully modulating burners?
My own impression, from the standpoint of mid-size apartment buildings, is that buying a burner without full modulation is like buying an automobile without accelerator and brake pedals. If there's no other traffic on the road, you can drive down the road by turning the ignition on and off. You can even wire the speedometer into the ignition so as to automatically turn the engine off whenever the automobile exceeds a preset speed. It's not an efficient way to operate any piece of heavy machinery.

J.C.A._3

Fred...

> Does anyone have any thoughts about on/off vs.

> low/high/low vs. fully modulating burners? My

> own impression, from the standpoint of mid-size

> apartment buildings, is that buying a burner

> without full modulation is like buying an

> automobile without accelerator and brake pedals.

> If there's no other traffic on the road, you can

> drive down the road by turning the ignition on

> and off. You can even wire the speedometer into

> the ignition so as to automatically turn the

> engine off whenever the automobile exceeds a

> preset speed. It's not an efficient way to

> operate any piece of heavy machinery.

J.C.A._3

Fred...

Too many questions!

Give some specifics...Gas/Oil..How many units?

Boiler size /sizes....hot water options?

On/Off isn't the way to run ANYTHING these days...but to give you some input...we need something a bit more specific.Capise? Chris.

Ken_40

I suspect it was more of a comment,

Than a question.

His logic seems solid to me.

How many days has it ben now since the last puff?

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Brad White

I am with you, Fred

Your accelerator analogy is spot-on in my opinion.

Commercially, I think you have found, that single-stage (on-off) burners are the norm up to about 300 MBH oil boilers and non-condensing conventional gas boilers. The next best would be low/high/low staged control, then of course, modulation. As an interim between on-off and staged control would be two or more boilers set up as stages feeding into a common system, the modular boiler approach. Fine and dandy if you can deny flow to unused modules.

I am designing a performance hall now that has two (2) 5.5 GPH oil burners and Low-High two-stage fire is the best I can do. Just above that, maybe two sizes, I can go to modulation.

What a shame that full modulation cannot reach down to the residential and smaller commercial markets! That has to be where a tremendous percentage of liquid dinosaur goes at the national level- in systems that would most benefit from being properly sized or be able to track their loads.


From what I hear from manufacturers is the limitation of their ability to modulate the air-side down in parallel with the fuel side. Put another way, it is their limited ability to do that at a competitive price.

With Gas-Fired Mod-Con boilers, the technology exists to well below 100 MBH input. The oil side may have some offerings and I would love to know where they are. I have asked and can only hope that day is soon around the corner.

[Deleted User]

Riello's RL 28

can be wired for lo-hi-lo by installing a controller between T6 & T8 in the Siemens LAL Control. Minimum lo fire 2.6 gph. Hi Fire 4.5-9.0 gph.

Strangely enough, Riello does not offer modulating oil thru their RL 130. On dual fuel pieces, they modulate gas, but not oil. Their folks told me several times they don't see any reason to modulate oil.

Jim Davis_3

Car accelerator perfect example of why modulating doesn't work

If anyone ever checks the miles per gallon they get in the vehicle it is on the highway at high speeds. Speeding up, slowing down, speeding up, slowing down does not save energy. I compare Low-Fire/High-Fire to heating up a piece of metal with a torch and then trying to keep it warm with a match. Anytime equipment is not at its maximum firing rate it is using more fuel. This is a fact that has been proven in the field for over 25 years. 100% of all equipment saw reduced energy consumption when Low-Fire was eliminated except for Light-off or Modulation was minimize.

We still need Lo-Hi-Off burners and Modulating burners on bigger equipment. Over 500,000 btu input, Lo-Fire light-off creates quieter ignition but then the burner kicks right to Hi-Fire until satisfied and then off. Somewhere around 2,000,000 to 3,000,000 shutting off in Hi-Fire sounds at little rough. Unfortunately Lo-Hi-Lo-Off burners seem to create excessive CO going from Hi to Lo because of the Spring action motor used most of the time. This is where a modulating burner is needed to create a smoother Lo-Hi-Lo-Off operation. The burner is run in Hi-Fire but Lights and Shuts off in Low fire.

From 1978 to current I have seen a 25%-40% reduction in fuel bills on larger equipment 100% of the time when Lo-Fire run time was eliminated or minimize. Today we see the same thing on 2-stage equipment. This fact not an opinion.

Steamhead (in transit)

We switched one of our customers

to lo-hi-lo, and he saved 40% on his gas consumption. This is on a large Broomell Vapor system.

Not sure what you were working on, but on this system it worked great.

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Jim Davis_3

Two reasons they are saving is because the old burner was running bad and the new burner spends more time in Hi-Fire.
If not he can still save another 25%.

60% of heat transfer from a burner is radiant transfer. A small flame does not and cannot radiate anywhere near the same amount of heat as a large flame that is closer to the heat exchanger and covers more area. Most commercial combustion courses teach that you get 7 to 8 times more heat transfer from the flame than the gasses.

Fred Cotton

burners

The efficiency would also be affected by the fuel-to-air ratio. My understanding is that the modulating burners are adjusting both the fuel and air intake, but that the lo-hi-lo burners are only adjusting the fuel intake.

Steamhead (in transit)

We didn't change the burner

it's a W-M LGB that comes stock with lo-hi-lo, which had never been hooked up. We hooked it up, with a Vaporstat to control the firing rate.

Same thing happened on a Carlin 1150FFD, lo-hi-lo that had never been hooked up, on a church steam system. I don't have the numbers on that one with me though.

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Steamhead (in transit)

Depends on the burner

lo-hi-lo on atmospheric gas typically controls only the burn rate. On most larger oil burners like the Carlin 1150FFD referenced above, both the air and fuel are controlled.

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[Deleted User]

Fred.

Most lo-hi oil burners only change fuel input. When an oil burner is listed as lo-hi-lo, it changes fuel & air.

Lo-hi-lo ex: Carlin 701CRD, 702CRD, 801CRD, 1050 & 1150 FFD. Rated hi fire inputs start @ 6 gph & top out @ 35. Beckett CF1400, CF2300, CF2500, & CF 3500. Inputs from 4 to 35 gph. Webster, Power Flame, Gordon-Piatt, & Riello, are other oil burners w/ lo-hi-lo for mid range applications.

Full modulation requires more sophisticated controls than lo-hi & lo-hi-lo burners. That's one reason we seldom spec full mod below 20 gph. High $$ up front & higher $$ parts replacement cost.

Most oil & gas-oil burners still modulate to a fixed boiler temperature or pressure set point. Wouldn't use for reset systems unless temps are reset thru a mixing valve. Even then, short cycling happens in shoulder months. And. Even w/ newer computerized servo programming, setting up full mod adds $$.

Jim Davis_3

Did you tune these burners with an analyzer?

> it's a W-M LGB that comes stock with lo-hi-lo,

> which had never been hooked up. We hooked it up,

> with a Vaporstat to control the firing rate.

> Same thing happened on a Carlin 1150FFD, lo-hi-lo

> that had never been hooked up, on a church steam

> system. I don't have the numbers on that one with

> me though.

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 367&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

Jim Davis_3

Did you tune these burners with an analyzer?

Underfiring in a piece of equipment with a certain heating surface can't be done as efficienctly as full-fire. That would violate the laws of physics and heat tranfer. If firing in low-high-low reduced consumption then something was really wrong with high-fire. I have seen many steam boilers where the flue temperature was lower than the steam temperature in low-fire but the combustion analyzer says it is 84% efficient. That is impossible!! For too long it has been accepted that combustion analyzer can calculate efficiency with just 2 readings and a lot of assumptions. It is hard to measure pounds of steam per cu.ft. of gas on steam boiler, but in every situation when actual output of air or water was measured, the equipment was considerably more efficient at its highest mechanical firing rate. This has been verified by energy auditors in just about every type of process possible.

Would like to know your steam pressure, O2 & Flue Temp in both firing rates.

I don't doubt you saved your customers money, I just know it can't be attributed to running on low-fire. It is so simple I just can't figure out why so few understand.

This is always a good conversation because I really hope people will go out and test and measure real results. We could cut this countries consumption of fuel 10%-25%.

Steamhead (in transit)

Of course we did!

We test everything. I'm sure the results are in the file somewhere.

The only thing I can remember off the top of my head was the Vaporstat on the LGB trips at about 2 ounces. By then, the system is full of steam, the pickup factor is satisfied, and the boiler just simmers along- a nice long burn with minimal starts and stops. This mimics the old coal fire.

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Jim Davis_3

I am guessing using your analyzer and skills is where the real savings were gained and that does make a difference. But, not low-fire.

Yep, keep my car idling in the parking lot so the engine doesn't have to warm up when I leave. Keeps it from starting and stopping. Just like feeding your horse while it was tied up in the old days.;)

Again with steam it is hard to measure actual btu's going into the steam but with hot water and air it is easier. Actual btu's per cu.ft. of gas drops well below 60% efficiency in low fire. Also when maintaining steam pressure on a heating system, I believe the closer zones will overheat unless good zone controls are used. Higher pressure moves slower versus letting it throttle back down. Actually solved some heating imbalance problems without having to add zone controls on real old systems letting the steam pressure drop all the way down before bringing it back up.

These are my personal experiences and I only want to share them with others as potential options that have shown to work every time. Not criticizing the good work you do.

Fred Cotton

burners

1. If the flue temperature was lower than the steam temperature, wouldn't that mean that most of the heat from the flame was absorbed by the boiler?

2. What is low fire? A turn-down ratio of 1.7:1 is 60% of high fire. A turn-down ratio of 5:1 is only 25% of high fire.

3. About 10 years ago, I attached some data logging equipment to a fully modulating boiler to see how the L91 controller was working. It maintained a constant pressure; but much to my surprise, it did so by constantly driving the motor back and forth all the way from low fire to high fire. It never stopped moving.

Fred Cotton

burners

oops 5:1 is 20%, sorry for the typo.