I have real world BTU numbers, now what?

[JP11]

I put an hour meter on my oil boiler to get some real data on how many BTUs it takes to run my house. I've kept a log so that I can crunch numbers a bit. For instance.. I know it's about 1.2 hours per day of boiler time in the summer for my DHW use.

Anyway.. been waiting on a cold day for max usage. -9 this morning when I woke up.. so I guess that qualifies. I took a reading last night at halftime of the Pats game. Burner has been on constantly. 9 hour run.. and still going. I always thought I was a little under sized on the boiler. I can't blame the plumber, as I am running a biodiesel blend which is 118k BTU per gallon VS heating oil at 129k or so.

Anyway.. Not that it matters much for buying a boiler... as I'm already convinced I want a 200K BTU boiler to feed 1000gal storage (vigas 60kw) I guess it's just a matter of piping size.

On the curiosity front... I was wondering how the net transfer stacks up between the two boilers. In other words.. I am probably at about 120k BTU per hour input with my fuel mix on oil. So how much of that is really going into the house? Losses in the boiler, losses in the transfer. I'm guessing 75%

But it's really irrelevant isn't it.. as the wood boiler is going to have similar efficiences, and the same hot water losses right?

I've been motivated on the wood gathering front. Dad and I made some pallet "U's" with some bracing top and back. I've got 6 of em filled up from yesterday. Hope to never handle the wood again. Tractor moves em good, just gotta go slow (and trade my 3' forks for 4 footers)

Anyway.. just curious of your thoughts. I know next winter I won't be burning a GALLON an hour of fuel!

JP

 

[woodsmaster]

I used to live in a metal sided trailer with 2 x 3 walls. When it got below 0 with wind the propane furnace would never shut off.
I used to lay awake in bed for houres just hoping to hear it shut off. Sounds like you could get away with a 40 except on
the coldest nights you might need some supplamental with a 40kw, but probably not with storage. The way the weather has been
This winter I kinda wish I would have went with a 40Kw I could probably keep a contiious fire going most of the time, but with
the 60 Kw I do batch burns. I've been doing 1 fire a day up untill recently. With the colder weather here I now do 2 fires a day.
I would have saved about 1,200 going with the 40Kw between the boiler price and being able to go with a size smaller piping.
It is nice to be able to charge storage while also pulling a load all on 1 load of wood. Another reason I went with the 60
is It has a longer firebox. 30" long on mine, but most spliters only go to about 24 -25 ".... So hope you make
a decision that works well for you.

 

[TCaldwell]

tale your bio diesel at 120kbtu/hr, adjust down to accomodate boiler effiency, say 75%, the real btu/hr you are achieveing is 90kbtu/hr. as you mentioned there are simular losses for your proposed wood boiler, this is combustion effiency. overall or total system effiency is driven by your emitters and associated house piping losses,there are prior threads on the forum that document in detail on this topic, if i remember correctly, system effiency for a ''average'' baseboard house is about 55-65% regardless of fuel source. I think nofossil was the primary author.

 

[DaBackBurner]

He, he I can remember the excitement of not burning any propane. Heck it is still exciting...especially since the temperatures have dropped to near normal! Sounds like your getting your ducks in a row with the wood collection, good for you. I was behind in that area for the first year and suffered more wood consumption as a result...but it was still better than paying for propane. Every year they kept jacking the price up, this year being no different. My payback is getting shorter and shorter, lol.
The distribution piping that's in the house or an area that's wanted to be heated is not really a loss per say, as those btu's are going towards heating that space. The combustion efficiency is another story and losses do to distributions that aren't in a heated or wanted to be heated space. Just think...no more oil truck...what a great feeling! Keep filling those 'racks' sounds like a great system to reduce the wood handling. Only one more time now...to put in the boiler, NICE!

 

[timberr]

JP,

Are you saying that your house is 100% air tight and your boiler can't keep up? My house was the same way. This past summer I replaced all the windows on the first floor. An d I can't believe how much warmer the house is. Lastnight I had to put a fan on low because we were a little to warm. Last year I would have to feed the boiler during the night and keep the wood stove running to keep the house comfortable, the bedroom was boarder line cold. Last night I started the boiler at 9 PM went to bed at 12:30 (was really excited about the Pats Win!) and the boiler was 75% through it's burn and I let it go (storage 184*). I got up at 7:30 it was -8 storage was at 164* and I never got the wood stove going. Now I won't claim that the circulator heating the house got a lot of rest last night.

My point is it is easy to blame the boiler, if BTU's are heating the outside because of air infiltration getting a bigger boiler is one way to solve the problem. A properly size boiler and weatherization could save on the install but will payback every year is less wood consumption.

 

[JP11]

I think my oil boiler is JUST big enough. I'm handicapping it by using my homeade fuel... but heck.. I'll take 119k btu's for a BUCK a gallon vs 129k btu's for 3.50 but that's just me.

Boiler would probably run 7/8ths of the time at 10 below IF I were only burning dead dinosaurs. House is well insulated, and boiler shut off this morning as soon as the sun came up and it got to -2 or so. I get a lot of solar with lots of windows.

I would prefer to have fewer fires a day, and want to "catch up" on storage while feeding load. So I guess at 175 or so btu's per hour (just rounding down.. not sure how generous vigas numbers are) It sounds like I'll be able to just about half the burn. Half going to storage, half to the load.

Of course.. not every day is 10 below!

I am enjoying putting up the wood. supports on the U's of pallets make a good spot to write year to burn with a lumber crayon. The red oak is getting 13/14 written on it. dead standing I've taken and hemlock is for next year.

JP

 

[Armaton]

Correct me if I'm misunderstanding! Your heat loss is in excess of of 120kbtu per hour, since your biodiesel is approx that. And the furnace never cathes up to house demand, since it never shut off. So even with a 200kbtu furnace you will be burning flat out at least 13 hours a day at max burn, which is virtually impossible so more like 16 hours or more! If this is indeed the facts you probably need to increase house efficiency more than boiler! Just my 2 cents.

Brandon

Ooops was posting when you put in your last comment! So numbers will be different, even so thats a lot of heat loss.

 

[Clarkbug]

I put an hour meter on my oil boiler to get some real data on how many BTUs it takes to run my house. I've kept a log so that I can crunch numbers a bit. For instance.. I know it's about 1.2 hours per day of boiler time in the summer for my DHW use.

Anyway.. been waiting on a cold day for max usage. -9 this morning when I woke up.. so I guess that qualifies. I took a reading last night at halftime of the Pats game. Burner has been on constantly. 9 hour run.. and still going. I always thought I was a little under sized on the boiler. I can't blame the plumber, as I am running a biodiesel blend which is 118k BTU per gallon VS heating oil at 129k or so.

JP,

I was always under the impression that heating oil was 142,000 BTU/gallon, or close to it.

At any rate, any chance you could put a larger nozzle in your oil burner to help you get some of the output back up for those really cold nights?

 

[JP11]

I've seen numbers from 145k to 129k for Heating Oil. I think bio is in the neigborhood of 120k.

I guess I don't see a problem.. as it's not all that common that it's -10 outside. I would think that over the course of a day.. I would have about 16 or so hours of boiler time. House is heated space of 6k SF.

So a -10 day would mean I need about 2 Million BTUs. That's 10 hours of running time on wood. Three fires. I expect to need three fires on a day where it's -10 outside.

I COULD go with a bigger nozzle.. Guess I could try it at the next cleaning. I do my own tuning. I'll have to see how it works.

Do you guys have way bigger oil boilers? I guess the plumber kept me in the smaller boiler, when the house was really on the edge for the next size up boiler.

JP

 

[Clarkbug]

Naah, its not a problem, just all of us thinking out loud, as seems to be the trend.

That is a LOT of conditioned space.

I dunno what is considered a "big" boiler, but I know mine has a 1.25 nozzle in it right now, and I am trying to keep it from firing as much as possible. Then again, I live in a house that has minimal insulation and is quite drafty...

 

[JP11]

Just an update..

I TRIED the 1gal nozzle. Not sure what those nozzles are rated at.. 100psi?

my furnace says max input 1gal per hour.

Well.. I run 140plus PSI due to biodiesel. Flame was BIG on the 1gal. Too big. It wouldn't stay running. I had air open all the way and it still wasn't burning clean. Think it was just too much fuel for the size of boiler.

I went back to my .85 nozzle. I'm GUESSING that they are rated at some lower pressure. If it is 140.. than my calculations on the heat load of the house are off. Whack 15 percent off. So bio fuel is 119k per gal. Minus the 15percent is near 100k input. minus efficiency.. so what.. about 75k per hour into the house when it's -10 outside. I think that's pretty close. 6k feet heated space. Lots of glass. All radiant.

If I have 1k gallons of storage.. 195 down to 130 or so.. that's what.. 600k BTUs stored? Radiant runs a max of 140 on the second floor. 100 to 105 or so in the concrete. Should be a nice batch burning setup... I HOPE.

Boiler is at the dealers. Waiting on the welder for storage tanks.. STILL.

JP