could it be said that the closed units are any less likely to CO leaks?
I guess I was forgetting that it is not the burned air, but the heat 
exchanged off of the block that heats the house.


On Mon, 19 Feb 2007, Dale Leavens wrote:

> When you use an open combustion heating system you are burning the air in
> your building then sending it up the chimney. That air you have been paying
> to heat then running it through the flame and outside.
>
> A closed combustion unit draws it's combustion air from outside, burns it
> with the fuel and then sends it back outside. It never participates with the
> atmosphere in the building. This also means that the inside environment air
> never communicates directly with the outdoor environment through the heating
> appliance.
>
> It takes quite a lot of fuel to warm internal air to say 70F. To then burn
> that air to keep the rest of the air at that temperature is
> counterproductive, particularly if you can burn outside air that you haven't
> already heated. The actual temperature of the air being burned isn't
> important.
>
> Hope this clarifies things.
>
>
> Dale Leavens, Cochrane Ontario Canada
> [EMAIL PROTECTED]
> Skype DaleLeavens
> Come and meet Aurora, Nakita and Nanook at our polar bear habitat.
>
>
> ----- Original Message -----
> From: <[EMAIL PROTECTED]>
> To: <[email protected]>
> Sent: Monday, February 19, 2007 2:18 PM
> Subject: Re: [BlindHandyMan] what to know about replacing your central unit
>
>
>> the only part of this I didn't understand Dale, was the
>> all ready heated air" part. What is the theory behind using cooler outside
>> air?
>> thanks
>>
>> On Sat, 17 Feb 2007, Dale Leavens wrote:
>>
>>> Hi Scott,
>>>
>>> Yes, drilling holes to extract geothermal heat is very expensive. The
>>> water
>>> sort can be open or closed loop, they can draw water from the bottom of a
>>> lake or river then return it when the heat or cold is extracted from it
>>> or
>>> they can be closed loop, water or other virulant is run through closed
>>> pipe
>>> in a water bath like a lake.
>>>
>>> Rather than drilling holes though you can dig a trench 8 to 10 feet deep
>>> depending on your frost line, possibly a little shallower and lay a
>>> closed
>>> loop system into it. That is much cheaper than dropping it down a hole.
>>>
>>> To answer your other question, closed combustion units draw combustion
>>> air
>>> from the outside into a closed chamber where it is burned and then blown
>>> back out. Usually two 3 inch PVC pipes are used, there are limits to the
>>> distance you can run them, up here we usually push them out through the
>>> rim
>>> joist but the exhaust must be some distance from a window or other
>>> opening
>>> just to keep carbon monoxide out.
>>>
>>> There is a fan which comes on to clear any residual gasses from the
>>> system
>>> after which an igniter starts a pilot then the main fuel. Fuel is
>>> circulated
>>> along with the exhaust gasses back through the combustion chamber in ways
>>> to
>>> burn any incompletely combusted fuel and the lot recirculated until what
>>> comes out of the exhaust is about body temperature along with a load of
>>> water which is drained off the bottom of the unit.
>>>
>>> The better gas units or propane units claim something like 98% efficiency
>>> but I understand that there are fuel oil versions these days which are
>>> pretty darn good to, a little more carbon to get rid of I suppose.
>>>
>>> The real advantage is not just the efficiency but you are not burning
>>> already heated room air and you don't have an open flue constantly
>>> withdrawing heat up the chimney. Usually finding a place for an inlet and
>>> outlet pipe is easy no chimney and very cool.
>>>
>>> I expect you could go Propane but it will cost to have a tank, similarly
>>> fuel oil.
>>>
>>> If you have enough soil though, a back hoe up here costs about 50 bucks
>>> an
>>> hour last time I hired one and they shift a load of dirt in an hour if
>>> you
>>> want to consider geothermal. It won't be cheap to instal but it will give
>>> you efficiency similar to what you  might expect with outdoor
>>> temperatures
>>> at a constant 55 or so degrees F. There is the additional cost of running
>>> the circulating pump but that is minimal.
>>>
>>> I have a gas closed combustion furnace in my basement, don't remember the
>>> capacity. I am now having a little trouble with reliability, it is now 16
>>> seasons old. There are a number of sequencing things which have to
>>> happen,
>>> little vacuum sensors and such which detect that all the cycles complete
>>> before heat comes through each demand cycle and we have been having a
>>> little
>>> trouble recently with it. I took it apart last week and found some crap
>>> in
>>> the tip of one of the rubber tubes I think washed down the exhaust vent
>>> with
>>> water, it looked to me like a shard of the PVC when a pipe was cut,
>>> probably
>>> washed down over time with condensation. There are a lot of parts though
>>> which could fail.
>>>
>>> Hope this information is helpful.
>>>
>>> Dale Leavens, Cochrane Ontario Canada
>>> [EMAIL PROTECTED]
>>> Skype DaleLeavens
>>> Come and meet Aurora, Nakita and Nanook at our polar bear habitat.
>>>
>>>
>>> ----- Original Message -----
>>> From: "Scott Howell" <[EMAIL PROTECTED]>
>>> To: <[email protected]>
>>> Sent: Saturday, February 17, 2007 3:42 PM
>>> Subject: Re: [BlindHandyMan] what to know about replacing your central
>>> unit
>>>
>>>
>>>> Now water to air sound really interesting. Gee, wish I had known
>>>> about these when I was getting a new system. I looked into one of the
>>>> geothermal systems and they could install, but I'd need a 400 foot
>>>> hole drilled and man that would have cost some serious cash so I had
>>>> to scrap that plan. Drilling into the ground here wouldn't be easy
>>>> since we sit on a great deal of rock.
>>>>
>>>>
>>>> Scott
>>>> [EMAIL PROTECTED]
>>>>
>>>>
>>>>
>>>> To listen to the show archives go to link
>>>> http://acbradio.org/handyman.html
>>>> or
>>>> ftp://ftp.acbradio.org/acbradio-archives/handyman/
>>>>
>>>> The Pod Cast address for the Blind Handy Man Show is.
>>>> http://www.acbradio.org/news/xml/podcast.php?pgm=saturday
>>>>
>>>> The Pod Cast address for the Cooking In The Dark Show is.
>>>> http://www.gcast.com/u/cookingindark/main.xml
>>>>
>>>> Visit The Blind Handy Man Files Page To Review Contributions From
>>>> Various
>>>> List Members At The Following address:
>>>> http://www.jaws-users.com/handyman/
>>>>
>>>> Visit the new archives page at the following address
>>>> http://www.mail-archive.com/[email protected]/
>>>> For a complete list of email commands pertaining to the Blind Handy Man
>>>> list just send a blank message to:
>>>> [EMAIL PROTECTED]
>>>> Yahoo! Groups Links
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> No virus found in this incoming message.
>>>> Checked by AVG Free Edition.
>>>> Version: 7.1.412 / Virus Database: 268.18.1/690 - Release Date:
>>>> 16/02/2007
>>>>
>>>>
>>>
>>>
>>
>>
>> To listen to the show archives go to link
>> http://acbradio.org/handyman.html
>> or
>> ftp://ftp.acbradio.org/acbradio-archives/handyman/
>>
>> The Pod Cast address for the Blind Handy Man Show is.
>> http://www.acbradio.org/news/xml/podcast.php?pgm=saturday
>>
>> The Pod Cast address for the Cooking In The Dark Show is.
>> http://www.gcast.com/u/cookingindark/main.xml
>>
>> Visit The Blind Handy Man Files Page To Review Contributions From Various
>> List Members At The Following address:
>> http://www.jaws-users.com/handyman/
>>
>> Visit the new archives page at the following address
>> http://www.mail-archive.com/[email protected]/
>> For a complete list of email commands pertaining to the Blind Handy Man
>> list just send a blank message to:
>> [EMAIL PROTECTED]
>> Yahoo! Groups Links
>>
>>
>>
>>
>>
>>
>> --
>> No virus found in this incoming message.
>> Checked by AVG Free Edition.
>> Version: 7.1.412 / Virus Database: 268.18.3/693 - Release Date: 19/02/2007
>>
>>
>
>


To listen to the show archives go to link
 http://acbradio.org/handyman.html
or
ftp://ftp.acbradio.org/acbradio-archives/handyman/

The Pod Cast address for the Blind Handy Man Show is.
http://www.acbradio.org/news/xml/podcast.php?pgm=saturday

The Pod Cast address for the Cooking In The Dark Show is.
http://www.gcast.com/u/cookingindark/main.xml

Visit The Blind Handy Man Files Page To Review Contributions From Various List 
Members At The Following address:
http://www.jaws-users.com/handyman/

Visit the new archives page at the following address
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