CANT DECIDE BETWEEN REGULAR OWB OR OUTDOOR WOOD GASSER

[dspoon19]

Nope not an engineer, I don't think they get this easily confused and contradict themselves. Using figures calculated long ago? And all those reasons for not wanting an indoor unit, are almost word for word out of a OWB sales training binder. Hmmmm.... Best gasser OWB overall thermal efficiency 30's% and who knows what will be lost to underground lines. Even a single degree is a few million BTU's over a heating season. Versus many other well proven and documented other options. Indoor or outdoor.....it's OK many cannot see past the initial cheap price. And their counting on it. Good luck either way

8 gallons of propane per day @ 91330 btu/gallon = 30443 btu/hr required

I burn no less 20 MMBTU/cord content wood with low moisture content.

Assume a gasser has an overall eff. of 80% and a regular OWB has 30%.

I would need 1.32 cords/month to feed the gasser. and a total of 7.25 cords for the total 5.5 month heating season.
I would need 1.86 cords/month to feed the OWB and a total of 10.25 cords for the total 5.5 month heating season.

I would save 3 cords per year. Wood is free so I save no $. I only save about 12 hours of time each year and I save the few extra lbs of particulate matter.

Are those overall efficiencies assumptions in the ball park? Am I doing something wrong in my calculations?

 

[hobbyheater]

. Wood is free $. I matter. ?

(broken link removed to http://akroncanton.craigslist.org/for/4322979051.html)

 

[heaterman]

Seriously.......If your heating load is that low why are you even thinking about a wood boiler?

Go with a good heat pump, enjoy the 30% tax credit and never have to lift a finger.
If you want to cut wood just for the sake of exercise go ahead and cut to your hearts content.
Sell it and you'll have the HP paid for with a couple years production.

 

[flyingcow]

Even living where I live, I like the efficiency of the HP's. If i ever rebuild it will be a house with r-40 walls and r-60 ceilings. And more than likely an air sourced HP as my main heat. This wood thing has been fun for a while, but damn it's easy to press a button and be warm....or have A/C. My 18,000btu unit cost about $4200. to have installed.

 

[heaterman]

That's the biggest complaint I hear about HP's also. They do move a lot of air to get the job done. A heat pump, short of a water to water unit running a radiant floor will never be a comfortable as a hydronic based heating system.

Most of the issues I see however are because of three main areas:

1.the person doing the install cheaped out on duct sizing,
2.sized the whole system short of actual heat load or
3.flat out didn't know what he was doing.

 

[dspoon19]

I don't know much about heat pumps. These can be either water or air sourced? They last about 15 years? Any ideas on total cost of system plus average yearly operating cost?

I calc'd it out that electric heat per unit is slightly cheaper than propane @ $2/gallon so I would have to install an electric heat supplement system.

My buddy down the street with geothermal and a similar house has outrageous electric bills because his supplemental electric heat has to help out. Summer cooling for him is real cheap though. He did say that his heat never feels "warm", so he burns in an insert to help out on the weekends to take the chill off.


Are there any smaller outdoor wood burning appliances that would suit my heating requirements?

Is it wise to say that I can add load to the boiler to make it more efficient? Like add a garage loop? or buy a hot tub? Eventually I might use more of the BTU's that the furnace can provide to heat the pole barn I plan to build.

I have been thinking about designing one and sending the prints to the local fab shop for quote. I'd do all the assembly and controls myself. I just don't know if I want to take the chance to throw that kinda money away.

 

[flyingcow]

FYI- this is the ytpe of HP I have. Have had good luck with it, but still new to me. It has a head unit, no ductwork. Took a day or so to get used to the head hanging on the wall, but now don't even notice it. We got a $600 rebate(because it was a Hyper unit) from the power co for the install. Plus a slightly lower Kwh rate from oct to april. This has helped lower my wood useage. When it's not below zero, we use it quite a bit(but it does work below zero). It's in the main living area, and keeps a good dose of heat in that area. Our family enjoys that. I also have a 12k unit upstairs. Basically I'm at a point where the investment in these units was at a time when i can spoil us. BUT, it was also dirven by the efficiencies of these units, plus the ability to heat at a lower outside temp. Until recently, HP's have never been practical up here in the north land, IMO. Just want to clarify what type of HP I have. Fujitsu makes a comparable units.

These are the numbers supplied to me by Mitsu::
for cooling---1270 watts
Heating outside temp @47f----1540 watts
Heating outside temp @17f----2620 watts


(broken link removed)

 

[Clarkbug]

8 gallons of propane per day @ 91330 btu/gallon = 30443 btu/hr required

I burn no less 20 MMBTU/cord content wood with low moisture content.

Assume a gasser has an overall eff. of 80% and a regular OWB has 30%.

I would need 1.32 cords/month to feed the gasser. and a total of 7.25 cords for the total 5.5 month heating season.
I would need 1.86 cords/month to feed the OWB and a total of 10.25 cords for the total 5.5 month heating season.

I would save 3 cords per year. Wood is free so I save no $. I only save about 12 hours of time each year and I save the few extra lbs of particulate matter.

Are those overall efficiencies assumptions in the ball park? Am I doing something wrong in my calculations?

Based on your low heating load, these units will idle quite a bit, either one of them. I think your efficiencies are in the ballpark, but the wood usage will be higher due to cycling and idling losses.

The HPs that Flyingcow mentioned are nice units... Mitsubishi, Fujitsu, and Daikin all make them, some that use a single condensing unit outside connected to multiple head units inside the house. Really nice if you have a main living space or bedroom that never gets quite as hot or cold as you want without making the rest of the house terrible.

I would advise against having your own boiler fabbed, just because if something goes south, you dont have any fix other than dumping more of your own $ into it.

However your roll, really insulate your buried lines, and if you are at all near the limits for the size piping, go a size bigger now.

 

[Mr._Graybeard]

dspoon19,

Seems to me price point is a big deciding factor in your system build, or is there another factor I missed? If that is the case have you check out this site? (broken link removed)


(broken link removed) looks to be the cheapest unit at about $6,200 and prices go up from there. If you bought water storage tanks(propane tanks) at $1,000 the price would be very similar to



I don't want you to think I'm trying to spend your money for you, but I'm vicariously living through your project since you are going to be finished before I even get started. What do you think?

My friend has an Attack DP boiler hooked up to a pressurized storage tank. It is a thing of beauty. The smallest Attack boiler from New Horizon is $4900. Might look at that.

 

[dspoon19]

Based on your low heating load, these units will idle quite a bit, either one of them. I think your efficiencies are in the ballpark, but the wood usage will be higher due to cycling and idling losses.

The HPs that Flyingcow mentioned are nice units... Mitsubishi, Fujitsu, and Daikin all make them, some that use a single condensing unit outside connected to multiple head units inside the house. Really nice if you have a main living space or bedroom that never gets quite as hot or cold as you want without making the rest of the house terrible.

I would advise against having your own boiler fabbed, just because if something goes south, you dont have any fix other than dumping more of your own $ into it.

However your roll, really insulate your buried lines, and if you are at all near the limits for the size piping, go a size bigger now.

Yea I looked into those units after I got back from Aruba. They have those things everywhere but are used for cooling only. I like them a lot.

 

[dspoon19]

My friend has an Attack DP boiler hooked up to a pressurized storage tank. It is a thing of beauty. The smallest Attack boiler from New Horizon is $4900. Might look at that.

ill have to check into those.

what does the pressure typically run on pressurized system? do you have more safety equipment when using a pressurized system? do you have to run storage with a pressurized system?

 

[dspoon19]

I think in Ohio you have to have a certain class of boiler licensure to install or modify any pressurized system. Anyone else know about these regulations?

 

[Floydian]

Hello Derek,

8 gallons of propane per day @ 91330 btu/gallon = 30443 btu/hr required
I burn no less 20 MMBTU/cord content wood with low moisture content.
Assume a gasser has an overall eff. of 80% and a regular OWB has 30%.
I would need 1.32 cords/month to feed the gasser. and a total of 7.25 cords for the total 5.5 month heating season.
I would need 1.86 cords/month to feed the OWB and a total of 10.25 cords for the total 5.5 month heating season.
I would save 3 cords per year. Wood is free so I save no $. I only save about 12 hours of time each year and I save the few extra lbs of particulate matter.
Are those overall efficiencies assumptions in the ball park? Am I doing something wrong in my calculations?

These numbers are not adding up to me.

First we need a realistic number for btu/gal of propane at your furnace's efficiency. Let just say 85%. So 91,330X.85=77,630 Btus/gal

At 8 gallons of propane/day you're looking at 621,040 Btu/day X 30= 18.6 MMBtus/month

Now let's look at how many Btus you get from a cord of 20 MMBtu/cord
Gasser @80% eff: 20 MMBtus X .8 = 16 MMBtus/cord

OWB @ 30% eff: 20 MMBtus X .3 = 6 MMBtus/cord

Now back to the 18.6 MMBtus/month that you need......

With a gasser: 18.6 MM DIVIDED by 16 MM = 1.16 cords/month X 5.5 months = 6.38 cords/year

With an OWB: 18.6 MM DIVIDED by 6 MM = 3.1 cords/month X 5.5 months = 17 cords/year

In your OP you mention(I think) that you are averaging about 5.5 gallons of propane/day. I would guess/hope that that is a more realistic number over the course of winter. In that case the numbers would look more like this:

Gasser=4.4 cords/year.

OWB= 11.7 cords/year.

This math obviously uses some big assumptions that could really change things depending but I'd guess they are pretty close for this purpose.

In all honesty, I am pretty anti-OWB to begin with and these above numbers only make me more so. That's without even getting into the particulate/pollution discussion.

Noah

 

[flyingcow]

Thanks for that Floyd. His math didn't look right to me either, figuring a gasser will use 3 cord less?

 

[dspoon19]

Hello Derek,



These numbers are not adding up to me.

First we need a realistic number for btu/gal of propane at your furnace's efficiency. Let just say 85%. So 91,330X.85=77,630 Btus/gal

At 8 gallons of propane/day you're looking at 621,040 Btu/day X 30= 18.6 MMBtus/month

Now let's look at how many Btus you get from a cord of 20 MMBtu/cord
Gasser @80% eff: 20 MMBtus X .8 = 16 MMBtus/cord

OWB @ 30% eff: 20 MMBtus X .3 = 6 MMBtus/cord

Now back to the 18.6 MMBtus/month that you need......

With a gasser: 18.6 MM DIVIDED by 16 MM = 1.16 cords/month X 5.5 months = 6.38 cords/year

With an OWB: 18.6 MM DIVIDED by 6 MM = 3.1 cords/month X 5.5 months = 17 cords/year

In your OP you mention(I think) that you are averaging about 5.5 gallons of propane/day. I would guess/hope that that is a more realistic number over the course of winter. In that case the numbers would look more like this:

Gasser=4.4 cords/year.

OWB= 11.7 cords/year.

This math obviously uses some big assumptions that could really change things depending but I'd guess they are pretty close for this purpose.

In all honesty, I am pretty anti-OWB to begin with and these above numbers only make me more so. That's without even getting into the particulate/pollution discussion.

Noah

What if the furnace is a Lennox rated at 98.2% eff? Are these numbers on the yellow energy tag on the side of the furnace true?

If they are true then just for round numbers supposed 100% use of the fuel. I would use 730,640 BTU's per day x 30 days = 21919200 BTU's per month.

Your numbers suggest I could cut wood usage by 62.4%. In your calc's, why do you change the heating value of the wood and the propane?

Wood is 20MMBTU.
Furnace is 98.2% eff. (just humor me and round to 100%)
OWB is 35% overall eff.
Gasser is 80% overall eff.
Propane is 91330 BTU/Gallon
I use 8 gallons per day

8 x 91330 = 730640 BTU's/day = 21919200 BTU's per month (round to 22MMBTU)

Gasser: Need 22MMBTU's per month + 20% more BTU's to make up for the loss (100-80 = 20)
22MMBTU + 20% more = 26.4MMBTU's per month.
So I need to burn 26.4MMBTU of wood. Wood is 20MMBTU per cord. 26.4/20 = 1.32 cords/month x 5.5 month season = 7.26 cords per season

OWB: Need same 22MMBTU's per month + 70% more BTU's to make up for loss (100-30 = 70)
22MMBTU + 70% more = 37.4MMBTU's per month.
So I need to burn 37.4 MMBTU of wood. Wood is still 20MMBTU per cord. 37.4/20 = 1.87 cords/month x 5.5 month season = 10.285 cords per season

 

[dspoon19]

Even if you use the simple rule of dividing you number of gallons of propane by 220 I would still use 1.1 cords per month but this is at 100% efficiency which is not the case with either of the wood burning appliances I am looking to get.

Add 20% more for fuel for the 80% efficient gasser and you get 1.32 cords per month.

Add 70% more fuel for the 30% efficient gasser and you get 1.87 cords per month.

.55 diff in cords per month x 5.5 months is 3.025 cords less per year with gasser.

I think my math is correct. I get the same results from 2 different methods.

 

[dspoon19]

Based on your low heating load, these units will idle quite a bit, either one of them. I think your efficiencies are in the ballpark, but the wood usage will be higher due to cycling and idling losses.

The HPs that Flyingcow mentioned are nice units... Mitsubishi, Fujitsu, and Daikin all make them, some that use a single condensing unit outside connected to multiple head units inside the house. Really nice if you have a main living space or bedroom that never gets quite as hot or cold as you want without making the rest of the house terrible.

I would advise against having your own boiler fabbed, just because if something goes south, you dont have any fix other than dumping more of your own $ into it.

However your roll, really insulate your buried lines, and if you are at all near the limits for the size piping, go a size bigger now.

Yeah Can I add load so they don't cycle and idle so much? I mean I can always find a use for more heat. Heat the garage, barn, maybe get a hot tub so I'm not wasting the wood on idling.

If I were to not use storage, what is the "sweet spot" to run a gasser at? 80% of total output? 50%?

 

[hobbyheater]

Really think this one needs a little humor !


ATTORNEY: Doctor, before you performed the
autopsy, did you check for a pulse?

WITNESS: No.

ATTORNEY: Did you check for blood pressure?

WITNESS: No.

ATTORNEY: Did you check for breathing?

WITNESS: No..

ATTORNEY: So, then it is possible that the
patient was alive when you began the autopsy?

WITNESS: No.

ATTORNEY: How can you be so sure, Doctor?

WITNESS: Because his brain was sitting on
my desk in a jar.

ATTORNEY: I see, but could the patient have
still been alive, nevertheless?

WITNESS: Yes, it is possible that he could
have been alive and practicing law.

 

[Fred61]

I can't sit on the sidelines any longer. Perhaps this will close this thread.

Here goes: despoon, you say you're an engineer. Tell us what it's like to drive a train.

 

[dspoon19]

I can't sit on the sidelines any longer. Perhaps this will close this thread.

Here goes: despoon, you say you're an engineer. Tell us what it's like to drive a train.

What the heck does a train have to do with this?!?

 

[Floydian]

Derek,

To me you are going about this all wrong.

A cord of wood with 20 MMBTUs burned at 80% leaves you with 16 MMBTUs, plain and simple.
A cord of wood with 20 MMBTUs burned at 35% leaves you with 7 MMBTUs.

Gasser: Need 22MMBTU's per month + 20% more BTU's to make up for the loss (100-80 = 20)
22MMBTU + 20% more = 26.4MMBTU's per month.

Your method here is wrong. Burning 26.4 MMBTUs to deliver 22 MMBTUs is 83.3% efficiency NOT the 80% you referenced earlier.

Your numbers for the OWB at 35% get really wacky.

OWB: Need same 22MMBTU's per month + 70% more BTU's to make up for loss (100-30 = 70)
22MMBTU + 70% more = 37.4MMBTU's per month.

Burning 37.4 MMBTUs to deliver 22 MMBTUs is 59% efficiency. A vast improvement over the 35% number you mention and it ain't gonna happen with a traditional OWB, IMO.

Now to simplify this. I'll give you 100% eff. on the furnace, no problem.
You feel you need 22 MMBTUs/month X 5.5 months = 121 MMBTUs/year, correct?

So you need 121 MMBTUs delivered.

With the gasser at 80% you have access to deliver 16 MMBTU out of a 20 MMBTU cord. 121 MMBTUs DIVIDED by 16 MMBTUs/cord = 7.5 cords/year

With the OWB at 35% you have access to deliver 7 MMBTU out of a 20 MMBTU cord. 121 MMBTU DIVIDED by 7 MMBTUs/cord = 17.3 cords/year

Now I am thinking you really want the OWB from the little I have read of the this thread. That's fine, it just looks to me like you are skewing the numbers in that direction and I am cautioning you, along with others here, to BE WARE! Or just burn crap tons of wood every year.

Good luck,
Noah

 

[skfire]

What the heck does a train have to do with this?!?

on page 8 this thread will officially be a runaway train and you are the engineer.
Fred....just when I thought I was out.....they pull me back in...ooooofa...

 

[flyingcow]

What the heck does a train have to do with this?!?

Floydian.....RUN, RUN away.......You are in the vortex.........

 

[flyingcow]

What the heck does a train have to do with this?!?

BTW..............................is this (dspoon) thread created by Webbie?????? Please say so.

 

[BrotherBart]

on page 8 this thread will officially be a runaway train and you are the engineer.
Fred....just when I thought I was out.....they pull me back in...ooooofa...

It ain't gonna make it there.