Help! Selecting a wood boiler

HardDrinkin'Lincoln

New Member
Nov 2, 2019
44
WA
It looks easy enough. I just want to make sure my wife can handle lighting without an issue. My next question is to size the unit I need. I currently use propane 170KBTU max, 7 zones hydronic/forced hot air. My house is 5500 sq/ft heated, and my external garage is 1250 sq/ft (625 sq/ft per floor). The garage is unfinished but I would like to heat it in the future. How can I estimate the unit size (BTU output) for my current needs? I also have questions on the unit operation. If I fire up the unit but my storage is at temperature does the unit shutdown/smolder until the water temp drops?
Answers to some of your questions can be found in the Vedolux boiler manuals which you can download here:

https://smokelessheat.com/wp-content/uploads/2016/01/VEDOLUX_350_2012-10-09_Smokeless.pdf
https://smokelessheat.com/wp-content/uploads/2016/01/VEDOLUX_450_2012-10-09_Smokeless.pdf
https://smokelessheat.com/wp-content/uploads/2016/01/VEDOLUX_650_2012-10-09_Smokeless.pdf

Here is the section of the manual describing the over-temperature protection features of the Vedolux boilers.

1611359521521.png


It might be helpful to calculate the expected temperature rise for each Vedolux model for various storage tank volumes. We start with the number of BTUs in a cubic foot of wood. In my case I burn a 50/50 mix of Ponderosa Pine and Douglas Fir.

one cubic foot = 120,000 BTUs assuming moisture content less than 16%.

Then we can calculate the expected temperature rise. We will assume that the firebox volume can really only be filled to about 80% capacity with wood and a boiler efficiency of 74%.

1611360048223.png


These temperature rise numbers are added to the starting temperature of the storage tank to establish the expected final temperature when a burn has been completed. For example, if the tank temperature at the start of a burn is 120°F and the expected temperature rise of a Vedolux 650 is 75° in 800 gallons, the final tank temperature may reach 195°. This will exceed the 194° maximum temperature limit of the boiler control and will trigger the boiler protection described above.
 
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Woodman1

Burning Hunk
Jan 15, 2018
135
Michigan
If your heat load is as large as described, that 800 gallons of storage isn't going to last that long. I didn't look where you are from, but if it is in a cold climate I wouldn't expect much more than 10-14 hours depending on how low you can heat with.
 

Bad LP

Minister of Fire
Nov 28, 2014
1,428
Northern Maine
My concern was geared to the design temp of the system you’re planning on installing the coil into.
The change over from one to the other is easy and 100% seamless. No need for any human interaction outside of feeding it wood.
 

HardDrinkin'Lincoln

New Member
Nov 2, 2019
44
WA
How can I estimate the unit size (BTU output) for my current needs?
When determining the size of the wood boiler you have to know the actual heat loss rate for your house. How many BTUs per hour does the house require on the coldest day to maintain 70°F inside? Once that's known you have a number which describes the houses heat reqirement in terms of BTU per hour per °F difference between inside and outside temperature.

In my case my 1,875 sq. ft. house requires 37,500 BTU per hour when the outside temperature is 0°F. That gives a heat loss rate of 536 BTU per hour per °F. Without knowing your heat loss rate we can guess at a number (and it's only a guess) by multiplying my heat loss rate by 3 to approximate what a 5,000 sq. ft. house might look like. That rate is 1,607 BTU per hour per °F.

The next thing to know is what does the outside tempereture look like during a typical winter in Dandbury CT. For that we can find the data we need here.

https://www.climate-charts.com/USA-Stations/CT/USC00061762.html

The data we need is the heating-degree-days (HDD). This number comes from the daily average outside temperature minus 65°F for each day and added together for a monthly total.

1611419674945.png


We will use the 1,165 January value for HDD since this is the coldest month of the year. With this number we can quickly calculate the total number of BTUs required for the month of January.

Total BTUs = HDD x (1,607 BTUs per hr. per °F) x (24 hrs. per day)

Total BTUs = 44,931,720 BTUs

If you divide the Total BTUs by 31 days you get the daily BTUs.

Daily BTUs = Total BTUs / 31 days

Daily BTUs = 1,449,410 BTUs

We can now compare the daily BTU number with the BTUs generated with each firing to determine the number of loads we will burn each day for each model of Vedolux.

1611419732167.png


Keep in mind that this daily amount was based on a monthly average. In reality there can be much colder days requiring more frequent firing.

Here is where storage volume comes into play. If you want to minimize the number of times you relight the stove during a 24 hour period you size the tank to store the energy required, for example, for a 24 hour period and refill the stove as necessary before the fire goes out.

You need to be able to store 1,449,410 BTUs at a tank temperature that does not exceed the high temperature limits of the boiler. 180°F would be a good maximum. The minimum tank temperature, the temperature at the start of a burn, is the temperature that is required by the heating system on the coldest day of the year to maintain the desired inside temperature.

For this example we will assume that the minimum tank temperature is 120°F to satisfy heating requirements. So with 120°F as a minimum and 180°F as a maximum we can calculate the tank volume to store the daily BTUs with a 60°F temperature rise.

Tank volume = Daily BTUs / 8.3 lb. per gallon / 60°F

Tank volume = 2,910 gallons

That's a big tank for holding 24 hours of energy for your house. A 1,500 gallon tank would hold 12 hours of energy. The 800 gallon tank you have would hold 6.6 hours of energy before having to reload.
 
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Woodman1

Burning Hunk
Jan 15, 2018
135
Michigan
Don't forget to size the boiler large enough to supply heat to the house while still charging storage. That goes back to the importance of not undersizing your underground line set. Another option would be to move the storage next to the boiler, if possible.

Does the OP not have access to natural gas? Back of napkin math shows this is going to be hard to justify the cost of this system
 

HardDrinkin'Lincoln

New Member
Nov 2, 2019
44
WA
The data we need is the heating-degree-days (HDD). This number comes from the daily average outside temperature minus 65°F for each day and added together for a monthly total.
Actually, this needs to be corrected. It should read:

The data we need is the heating-degree-days (HDD). This number comes from 65°F minus the daily average outside temperature for each day and added together for a monthly total.
 

S.Whiplash

Member
Oct 28, 2012
102
Make sure you do your homework, the only Econoburn that has tested to the EPA standard is the EBW200-170 model, the rest do not qualify because they have never been tested. New standards again this year, so check the latest EPA list.
 

3fordasho

Minister of Fire
Jul 20, 2007
981
South Central Minnesota
Make sure you do your homework, the only Econoburn that has tested to the EPA standard is the EBW200-170 model, the rest do not qualify because they have never been tested. New standards again this year, so check the latest EPA list.
No model of Econoburn boiler is on the current 2020 list: Woodstove Database | Burnwise | US EPA

They could be in the process of getting approval, best to call and find out.
 

hyfire

Minister of Fire
Aug 3, 2013
695
Ont, Canada
If you ever watched what you have to do to clean an ecoburn you may want to change your mind, it did for me. You have to tear it all apart almost, i was shocked what you have to do!
duct tape insulation, etc
 

salecker

Minister of Fire
Aug 22, 2010
1,322
Northern Canada
Cleaning an Econoburn is relatively simple.
Takes about 10 minuets to have the turbulators out and about 15 minutes per flue tube.
Two hours start to finish if i leave it too long
 

3fordasho

Minister of Fire
Jul 20, 2007
981
South Central Minnesota
Cleaning an Econoburn is relatively simple.
Takes about 10 minuets to have the turbulators out and about 15 minutes per flue tube.
Two hours start to finish if i leave it too long

My Attack has a lever attached to a mechanism to move the turbulators up and down. Since the turbs are not a real close fit to the ID of the exchanger tubes, it really does not clean them that well. I removed the lever and attached mechanism, now to clean I just pull off the top sheet metal cover (no tools required), two thumb screws and the cast iron cover over the HX tubes is off, pull each turbulator out (7) and brush. I attach my brush to a drill and once through and back out with the brush spinning and that tube is done. Can't take me more than 15mn start to finish complete. Pulling the turbs out with the mechanism in place was much more involved so bye bye it went.

The Varms seem to be the easiest to clean but a comparable Varm was a good $4-5K more than what I paid for the Attack.
 
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salecker

Minister of Fire
Aug 22, 2010
1,322
Northern Canada
I tried a brush for cleaning,leaves hard deposits on the flue tubes.
Tried a tool from McMaster Carr that was supposed to work...anyone want it?
Made my own which works the best, cleans the tubes back down to steel
If i used a brush i would be done in less that an hour,but only the ash would be gone.When i finish the tubes are clean like it left the factory.
The Econoburn has a leaver for moving turbulators as well,dosn't really do anything the fit is too loose between the turbulators and flue tube to actually clean anything.
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,048
NE Ohio

salecker

Minister of Fire
Aug 22, 2010
1,322
Northern Canada
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hyfire

Minister of Fire
Aug 3, 2013
695
Ont, Canada
I'm talking about the yearly cleaning you need to gut the whole unit and cut all the insulation out of it and re tape it all take all the metal off looks like a full days work, silicone gasketings etc.
 

salecker

Minister of Fire
Aug 22, 2010
1,322
Northern Canada
I'm talking about the yearly cleaning you need to gut the whole unit and cut all the insulation out of it and re tape it all take all the metal off looks like a full days work, silicone gasketings etc.
WTF are you cleaning yearly the outside skin to remove the insulation?
I remove the rear panal,no silicon it has flat gaskets. 5 miniuets from starting the turbulators hit the floor and i start the flue tubes,15 min each if dirty.5 minuets gets the turbulators back in hooked up and 2 nuts to tighten the panel back on.
So again WTF are you cleaning?
 
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hyfire

Minister of Fire
Aug 3, 2013
695
Ont, Canada
Watch the video then see what I am talking about. I am sure its a good unit but this amount of work to clean is just beyond me..
 

GENECOP

Minister of Fire
Jan 31, 2014
724
Ny
Watch the video then see what I am talking about. I am sure its a good unit but this amount of work to clean is just beyond me..
That cleaning process is insane..lol I guess Salecker has a bigger job ahead of him this year
 

salecker

Minister of Fire
Aug 22, 2010
1,322
Northern Canada
The problem with that video is YOU DO NOT HAVE TO CLEAN IT LIKE THAT!
I have been using my boiler for 11 years.
You should listen to someone that uses their boiler and cleans it instead of watching a video made by someone who hasn't used the boiler for years and learned the tricks to doing the job smarter not harder.
The back plate with the flue does not have to come off,just the top plate that is held down by 2 nuts.
I ditched the bolts the work the turbulators and replaced with hitch pins.That was a tip from a member here that i used,remember the work smarter not harder thing.
Like i said before it is a dirty job but doesn't take more than 2 hours unless you are a slacker and can't actually work and accomplish a task.
The first time i did it was while the boiler was clean,because it looked like it could be a pain in the ass.
So i did a bit of reading and found a few tips and tried them.And low and behold there was an easier way.
I saw that video as well,doesn't mean you have to do exactly as they do.
But go ahead and spread misinformation without knowing what you are talking about.
 
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cumminstinkerer

Burning Hunk
Feb 2, 2016
153
central iowa
@salecker I am with you, I just did mine on saturday morning, didn't need it but it was misbehaving, not burning right, come to find out it was the air flap that prevents back drafts was stuck shut, anyway I started the cleaning at 8:30 and by 9: 30 I had it all done and a fire lit. I may cheat a little too, I don't have the nuts on that hold the top rear skin onto the sides so i can just lift the skin off.
 
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