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[chaikwa]

Pump speed or water flow has very little to do with wood consumption...

I've read enough of your posts to trust your advice, but I'm wondering if the pump speed was too low, and the water returning to the OWB was cooler than with a fast pump speed, would more wood be burned trying to heat up the cooler water?

Also, what exactly, (in terms an idiot like me can unnerstand!), is 'delta T'?

[farmboythegreat]

yea  what  is this  delta t

[Scott7m]

Its about boiler protection...  if return temps are allowed to drop below 140 it can cause condensation inside the fire box that allows it to mix with ash and cause a premature failure of firebox

No it wont use more wood

Delta t is simply the difference between the water in ur supply line vs the temp of water in your return line

To measure turn on anything in house that uses heat and.check the differences in temp at your supply and return on back of stove.   

[Sprinter]

yea  what  is this  delta t

These are the spoon fed variety.   With just DT I can determine how many btu's your consuming, GPM flowing, and how efficient your wood is.

If you watch any of those videos or search it, you will learn way more than us just saying its the difference in temp between 2 points. Whether it be supply n return, or from stove to inside house on the same line.

Btu =DT x GPM x 500

The bumblebee I think is accurate in flow measurement. I thought it might just be a set programmed number for each wattage, but I have seen several GPM displayed for the same wattage.  Balancing valves show up.

[martyinmi]

yea  what  is this  delta t

"Delta" means change, "T" stands for temperature.
If you measure 195* water going into your water to air heat exchanger and 175* water coming out, your "Delta T", or "change temperature" would be 20*.
On this site "Delta T" is a term used for thermodynamic change in a given area of a hydronic system.
The term is also used in reference cooling systems too.
Whenever you read it here, just think "temperature change between two or more defined points in a hydronic system".

[martyinmi]

yea  what  is this  delta t

  With just DT I can determine how many btu's your consuming, GPM flowing, and how efficient your wood is.

My DT across my water to air heat exchanger is 19*. My DT from the inlet of my sidearm to the outlet is 6*.
1) How many BTU's am I consuming?
2)  How many GPM's am I flowing?
3)  How efficient is my wood? ()

[Scott7m]

 

[ST98]

To figure wood usage would delta T be figured at the boiler? Instead of a heat exchanger?

[Scott7m]

To figure wood usage would delta T be figured at the boiler? Instead of a heat exchanger?

If someone tells you there delta t, it is impossible to figure there wood usage or whatever based off of that number.  Like marty said, he gave him all his delta t's and explained it in detail.  But there are so many more variables

[ST98]

I'm figuring my wood consumption by how much wood actually goes into the boiler.  The rest of it seems a bit complicated for me.  I was just wondering where you took that measurement from.

[Sprinter]

Ok now you guys are being facetious, but I did type "with only DT" so I guess its my fault for not being more specific enough, or exacting for those who like to pic posts apart.

Knowing the BTU = GPM x DT x 500 formula you would need only two of the three variables to figure the unknown. With additional formulas common in hydronic books you can get very accurate estimates.

GPM = BTUh / DT x 500

DT = BTU/ GPM x 500
Now let's say you have a pretty good idea from monitoring over a set time of your btu output. You can use that to ESTIMATE how many pounds of wood you should be using IF you know the efficiency of the stove. Or compare the calculated lbs to the actual lbs you used, to tell you how much btu your getting from the wood minus the stove efficiency. OR if you have been measuring the moisture content of a known specie of wood or pounds of wood over moisture content , you can calculate some very close numbers. There are pages and pages of enginerds/wood boiler owners that do this to a T. Literally. Its real world versus the lab. And it sounds silly but some take it pretty serious. Kinda like that link to live monitoring of that boiler. Homemade lambda controls and boilers that come with them, just like fuel injection system on a car. The EPA is gonna push so far that all boilers or stove will require cats, oxygen sensors and idling will be illegal as it is in Europe,  just like it is for diesel trucks in some states.
Going thru some of this can give you piece of mind or you might learn something, or you might be able to show someone that your properly run OWB is more efficient and cleaner than the neighbors new propane furnace that never had a heat calc or combustion test done when installed.  Least of all you just might laugh so hard that someone would do all this. But why is burning wood so mezzmorizing or addicting.

Sorry if I got somebody worked up, but here's your spoon feeding for the day......hahahahah

[martyinmi]

Facetious- "treating serious issues with deliberately inappropriate humor".

Not being facetious in any way, shape, or form, my fellow Michigander. Nothing but love coming from the center of our states Lower half.

There are many more variables involved in calculating heat loss/btu's spent in a hydronic system that employs outdoor wood boiler as it's heat source-
radiant losses from the OWB, dew point and ambient temperatures both inside and out, earth temperatures, thermal transfer to the earth from insulated pex, plenum intake temperatures, plenum insulation, etc. to name a few of the obvious.

The point I'm trying to illustrate is that it would be very difficult to come up with a simple mathematical formula for determining either GPM or btu's solely based on a change in temperature in a given area of a hydronic system that employs an OWB. We would need more controls in place beforehand to aid in eliminating or reducing some very pertinent variables (knowing what the variables are that are precipitating said changes) . It's not as simple as calculating horsepower from an internal combustion engine: HP=(rpm x torque) divided by 5252).

Rest assured, you did not get me worked up, my friend.

Sometimes in this life we have tendencies to make tempests out of teapots. Other times, just the opposite.

[Sprinter]

Glad you are an easy going, and understanding guy then. Sure there are lots of variables, but an experienced serviceman can get some very accurate estimates with some simple math. Enough to point you in the right direction or eliminate possibilities. Exact numbers do require more defined criteria or monitoring.