Steady State Explanation?

Mark R.

I am a homeowner not a professional. I have heard passing reference to "steady state" operating conditions. Can someone help me understand what this means. I have a W-M WGO-3 oil fired boiler and it runs about 20% of the time when it is about 32 degrees. I would appreciate any help.
Thanks Mark R.

Craig_8

when you are driving your car on the highway with the cruise control on, your car is running at steady state, you are not accelerating or decelerating. You will get the most gas milage, and the car will last the longest when opperating at a steady state. city diving is the opposite. the engine's load is constantly changing, it's temperature is fluctuating, and the transmission is shifting frequently. the lack of a steady state operation results in the car not lasting as long.

the same thing is true for a heating system. a steady state is reached once the boiler reaches operating temperature, metal is not expanding and contracting, condensation is not being formed (unless its a condensing boiler) and basically all the parts are not exposed to the wear and tear of frequent warm-ups and cool downs

don_55

different interpretation;

Mark,

What you may have seen is the comparison between
AFUE and "steady state" combustion efficiency.

While the stated AFUE for a WGO-3 is 85.3 this is a
consideration of other factors, standby losses, insulation,
etc.

A properly cleaned, tuned and balanced system, by a
good oil guy with all the right gear might get a
"steady state" efficiency of 87.3, mas o' menos.

The "steady state" term has to do with the completeness
of combustion as measured by, draft, air - fuel ratios and combustion residuals, excess O2, CO, CO2, NOX, etc., or simply energy conversion.

Look up "Stoichiometric".

hope that helps, don

Constantin

Hmmmm....

How cold does it get around your parts? I wonder simply because if the boiler is running only 20% of the time at 32°F, then I suspect it is oversized. I would like to have the pros here confirm this, but here is a bit of back-of-the-envelope math:

• At 32°F, you have 33 heating degree days (HDD) on your hands (65°F-ambient temp).
• At -15°F, with 80 HDD, your boiler would probably not run more than 50% of the time. -15°F; is about as cold as it gets in most of the US on a design day.
• If my math is right, your boiler is sized sufficiently to sustain your house through -100°F or so (160HDD). However, I will presume that the heat-emitters and the piping in your home will be a limiting factor...

As others have stated, steady-state efficiency is what it's all about. Small, low mass systems like condensing gas boilers come up to temperature so quickly that almost their entire operating cycle can be characterized as steady state, particularly if they also modulate.

Your cast-iron boiler will take much longer to get up to temp. This means that you'll benefit from longer burn times, if it's possible to re-rig your boiler to do so.

eleft_4

Steady State

Simply put: The stack temp. is at it's highest point and stays.

al

Mark R.

Thanks for you help !

I appreciate all your help. I guess I can relate to the cruise control comparison best. Constantin you are right on the money with your prediction that the boiler is slightly oversize. The contractor did a heat load on my house and said that a WGO-2 would be just right, but I was planning a small room addition so I moved up to a WGO-3. I am downfiring the WGO-3 very slightly and it works fine. I am running a .75 gph nozzle instead of the .85.
Thanks again, Mark R.