Thoughts on Weighing Loads

[brant2000]

I just got a little digital luggage scale to start weighing loads and was hoping to get some input from others who have/do this. I just started weighing each load the other day and found that my 24 hour consumption was 220 lbs. That would give me an estimated monthly consumption just over 6,500 lbs and about 1.5 cords. Most of what I burned for the day was a mix of hard maple, cherry, and red oak that probably had moisture levels averaging in the higher 20's.

For those of you that have been doing this, are there any tips/pointers that you've found to help to dial in your load weights? I was thinking that I would try to be diligent about collecting these readings for a few days and compare my recorded values to local HDD values to come up with a good estimate of the number of lbs needed per HDD. I know that there can be a large difference in the heating value of wood species, but when you factor in the mass density and are really just concerned about Btu/Lb, have you found there to be much of a difference between species?

 

[goosegunner]

This is my 4th year weighing loads. Wood species doesn't matter much but quality does. In the shoulder seasons I have been using the oak wilt wood that is of lesser quality. It burns well but does seem to take a little more to hit desired storage temps. The trees were past prime when cut down. If they hold their bark while standing they decay kind of strangely while standing dead.

I have a spread sheet that I made for my iPhone that calculates how much would to hit desired storage temp.

Typical winter day I use 140-160lbs. Sub zero days I occasionally go over 200lbs.

It seems like a lot of wood at times when looking at splits. But to put it in perspective I dried and weighed a piece of cherry that was;

13" diameter and 17" long.
green 69lbs
20% 44lbs

So usually less than the equivalent of 4 rounds of wood that are 13" diameter and 17 inches long. That would barely begin to cover the bottom of a Central boiler 6048 or Heatmor 400.

gg

 

[BoiledOver]

Last heating season I weighed and recorded every burn and will do so again this season. My projections based on previous propane usage is pretty close to what is going on now. At this point the consumption is 11% down from last season.

I will continue to weight each burn but probably will not record those numbers after this season. The primary reason for me in weighing the wood is to reach the desired btu load into storage without going over or under. I made a spreadsheet and just enter the storage readings for the answer to pounds required to hit the 1.5-1.6 million btu's.

 

[jebatty]

I've been a bit of a champion of weighed wood burns, mostly because doing so tells you a lot about your system. This year I am not doing weighed wood burns unless I really need to load the storage to maximum because I will be gone for more than two days. I now know very well how much wood to load to achieve a desired outcome.

As I am sure you have read in various posts, all wood (with minor differences) has 6050 btu/lb at 20% MC (well seasoned) and 400F stack temperature (fairly typical). By weighing your wood you know the total btu input to your boiler. Make some reasonable assumptions, like maybe 10-20% loss from the boiler to the surrounding air and through the plumbing before the heat gets to where it needs to be. With that assumption and known temperature and weather conditions, you can compute the heat loss for your home or other heated space. Useful info. If you have storage, you also can compute how much wood to burn to load storage to your desired temperature. And with weighed wood burns you can load your boiler to greatly or completely eliminate any idling, if that is your goal.

Yesterday (pine is my wood of choice) I burned wood to bring my storage up to 193F top, 191F middle and 185F bottom. In the past I actually have achieved a uniform 193-190F top to bottom, no idling. For my boiler and 1000 gallon of storage I know I need about 17 lbs of wood to raise storage 10F, assuming no system draw. I also know that a typical system draw for the radiant floor in my shop drops my tank temperature about 10F, so during a burn I can add another 17 lbs of wood if I expect a call for heat during the burn.

What I have learned from weighed wood burns makes operating the boiler to achieve desired results very simple.

 

[hartkem]

I would like to see what you guys are using to weight your wood

 

[goosegunner]

Here you go! I weigh it on scale and place it in shopping cart, push next to boiler and load. I know about what it takes depending on weather so when I am gone working 24 hour shifts I set up the cart and tell my wife to burn whats in the cart. She will sometimes need to burn a little more.

Got the scale off craigslist for $50

Shopping cart for $10

Wood carts for $35 each, I can roll them through my double door.

 

[brant2000]

I just got a very inexpensive luggage scale on eBay for about $5. I happened to grab this heavy, cracked plastic tote from work, which is the exact width and length of my firebox. It is rather crude, but seems to work fine.

 

[jebatty]

luggage scale and a cradle I made.

 

[hartkem]

Here you go! I weigh it on scale and place it in shopping cart, push next to boiler and load. I know about what it takes depending on weather so when I am gone working 24 hour shifts I set up the cart and tell my wife to burn whats in the cart. She will sometimes need to burn a little more.

Got the scale off craigslist for $50

Shopping cart for $10

Wood carts for $35 each, I can roll them through my double door.

View attachment 150822 View attachment 150825 View attachment 150826

Nice setup you have there goosegunner

 

[goosegunner]

Nice setup you have there goosegunner

Thanks, it gets easier to use every year as we gain experience with the system and how it runs best. The biggest change I have made was starting to use bigger splits,especially on the top of load. I can load much more wood initially without any puffing incidents. With the Econoburn I have found the playing card split is too small to have a large quantity in the firebox on start up, especially with very dry wood like I get from those rolling carts.

gg

 

[Pologuy9906]

Never thought of weighing the wood. I think I will experiment with this. I just loaded my boiler half way to achieve a +20-30° on 1000 gallons of storage. Nothing like dialing your machine in for optimal performance

 

[hartkem]

Well I just weighed my first full load of wood into the eko. I put a mixture of walnut and honey locust in. Total weight was 114lbs. Im curious to know what others can get into there unit with a full load. Average day I would load once in morning and again before bed. Below 15 degrees with wind its 3 loads a day. My house is large at 3500 and sits on an open windy hill. We have been warm and I let my storage go cold. With no load today I'll try to calculate how many BTUs actually make it into the tank.

 

[brant2000]

In case anybody is interested, I started building a spreadsheet to track and calculate my next load weight. You could tailer it to suit your system by adjusting the parameters up top. I size/calculate everything based on the house temperature...for those of you with large storage tanks, you may need to adjust things to size off of your storage temps, instead.

 

[hartkem]

My burn finished and my 500 gallon tank went from 100F top and 70F bottom to 180F top and 180F bottom. Boiler went into idle at the very end with a bed of coals left. If my math works out this is about 55% efficiency of heat transfer into storage. My boiler was cold at 55 degrees at the start of the burn. This doesn't sound horrible but it could be better

 

[BoiledOver]

It may be a little better or worse than that, depending on actual moisture content and beginning btu's. Stratification can be anywhere, just inches above or below a sensor.

Was there any call for heat going at any zone?
Which Eko do you run?

The 25 would only take 60 lbs. max if loaded like sardines. I am thinking that 70% is attainable with an Eko boiler.

 

[hartkem]

I have an eko 40. No load during the burn. I had no fire for 4 days because it was so warm and I just let the propane take over.