Intake/Exhaust Pipe within pipe for furnaces?
David Hoerl
intake/extake pipe where the intake pipe was actually inside the exhaust
pipe (PVC, high efficiency furnace.) This seems like a great idea since
the intake air would be warmed by the exhaust gas, giving you even more
heat retention.
Yet, when I looked at what local builders are doing, they have separated
intake and exhaust pipe.
What do the experts recommend here?
Thanks,
David Hoerl
dfh "at" home dot com (reply address has NO_SPAM_ spam filter)
AARON S BECK
not enter the living space. The question is do you want 1 or 2 holes in the
wall?
-**** Posted from RemarQ, http://www.remarq.com/?a ****-
Search and Read Usenet Discussions in your Browser - FREE -
Emilico
wrote:
>I saw on one of the vendors web pages a recommendation to use
>intake/extake pipe where the intake pipe was actually inside the exhaust
>pipe (PVC, high efficiency furnace.) This seems like a great idea since
>the intake air would be warmed by the exhaust gas, giving you even more
>heat retention.
Actually based on what I've seen the intake and exhaust combined in
one pipe only happens at the last three feet of the run therefore
efficiency gain from that run is increased by a very negligible
amount
>
>Yet, when I looked at what local builders are doing, they have separated
>intake and exhaust pipe.
>
>What do the experts recommend here?
>
>Thanks,
>
>David Hoerl
>dfh "at" home dot com (reply address has NO_SPAM_ spam filter)
***** LA VENGANZA SE SIRVE FRIA *****
HVACMAN
terminating the intake and exhaust separately.
David Hoerl wrote:
>
> I saw on one of the vendors web pages a recommendation to use
> intake/extake pipe where the intake pipe was actually inside the exhaust
> pipe (PVC, high efficiency furnace.) This seems like a great idea since
> the intake air would be warmed by the exhaust gas, giving you even more
> heat retention.
>
Arista Engineering
The concentric vent kit works well in cold climates. In Canada, there is a
problem with hoarfrost forming on the combustion air intake which can kick
out the furnace, as the air switch won't make.
With the concentric kit, it tended to resist hoarfrost down to minus 30C due
to the heat from the vent. I told all of my former customers to check their
intakes during extreme cold weather.
The concentric kit is neater, as it requires a single hole in the wall.
There were two drawbacks.
1) It usually required larger diameter vent pipes, possibly due to the fact
that the fresh air intake area, i.e. the annulus area between the 2 pipes
was more restrictive than say a 2" independent intake. No anus or cunilingus
jokes please.
2) With separate intake/vents the vent termination was usually an elbow or a
tee. Sometimes the terminations had a screen etc. The concentric termination
is a straight pipe which must extend out of the building by whatever
distance the manufacturer said. Some customers would worry that insects,
rodents would get into the vent or that "Kids would put rocks in the Vent".
Don't laugh but I have heard this from several different customers
John Mills
David Hoerl wrote:
> I saw on one of the vendors web pages a recommendation to use
> intake/extake pipe where the intake pipe was actually inside the exhaust
> pipe (PVC, high efficiency furnace.) This seems like a great idea since
> the intake air would be warmed by the exhaust gas, giving you even more
> heat retention.
>
I can't imagine that making any difference in efficiency.
>
> Yet, when I looked at what local builders are doing, they have separated
> intake and exhaust pipe.
Well, the bazooka adds $75-100 to the cost of the job, something few
customers
want to spend for no reason. Also, in many cases, the flue comes out at
ground level and must be turned up then out. Can't do that with a bazooka.
Last winter we had a nice wind-whipped snowstorm. I had to defrost several
of them put too low to the ground. Also had to shimmy across a glare ice
roof,
slide into a 2' snowdrift, dig out one and pour hot water down it to thaw
out
the blockage then cut the intake open in the attic to pull out ice.
HVACMAN
John Mills wrote:
> Last winter we had a nice wind-whipped snowstorm. I had to defrost several
> of them put too low to the ground. Also had to shimmy across a glare ice
> roof,
> slide into a 2' snowdrift, dig out one and pour hot water down it to thaw
> out
> the blockage then cut the intake open in the attic to pull out ice.
I *HATE* when that happens! Worst one I had was when the customers kid
shoved 8 lbs of rocks down the exhaust, thing ran intermitantly and got
the rocks good and wet, cust called me as soon as the rocks froze tight
in the PVC!
doc...@pop.sxfl.uswest.net
between intake air and exhaust? Or are area codes different then listing codes?
Don Ocean
John Mills wrote:
> David Hoerl wrote:
>
> > I saw on one of the vendors web pages a recommendation to use
> > intake/extake pipe where the intake pipe was actually inside the exhaust
> > pipe (PVC, high efficiency furnace.) This seems like a great idea since
> > the intake air would be warmed by the exhaust gas, giving you even more
> > heat retention.
> >
>
> I can't imagine that making any difference in efficiency.
>
> >
> > Yet, when I looked at what local builders are doing, they have separated
> > intake and exhaust pipe.
>
> Well, the bazooka adds $75-100 to the cost of the job, something few
> customers
> want to spend for no reason. Also, in many cases, the flue comes out at
> ground level and must be turned up then out. Can't do that with a bazooka.
>
Owen
<doc...@pop.sxfl.uswest.net> wrote in message
news:37F56FD8...@pop.sxfl.uswest.net...
MechAcc
>
> >I saw on one of the vendors web pages a recommendation to use
> >intake/extake pipe where the intake pipe was actually inside the
exhaust
> >pipe (PVC, high efficiency furnace.) This seems like a great idea
since
> >the intake air would be warmed by the exhaust gas, giving you even
more
> >heat retention.
> one pipe only happens at the last three feet of the run therefore
> efficiency gain from that run is increased by a very negligible
> amount
On manufactured home furnaces: Coleman, Miller & Intertherm double pipe
starts at the furnace breech and out the roof. And it is metal vent not
pvc,
> >
> >Yet, when I looked at what local builders are doing, they have
separated
> >intake and exhaust pipe.
> >
> >What do the experts recommend here?
> >
> >Thanks,
> >
> >David Hoerl
> >dfh "at" home dot com (reply address has NO_SPAM_ spam filter)
>
> ***** LA VENGANZA SE SIRVE FRIA *****
>
>
--
Gary Reecher AKA MechAcc
ICQ # 44165241
Sent via Deja.com http://www.deja.com/
Before you buy.
MechAcc
John Mills <ap...@in.net> wrote:
>
>
> David Hoerl wrote:
>
> > I saw on one of the vendors web pages a recommendation to use
> > intake/extake pipe where the intake pipe was actually inside the
exhaust
> > pipe (PVC, high efficiency furnace.) This seems like a great idea
since
> > the intake air would be warmed by the exhaust gas, giving you even
more
> > heat retention.
> >
>
>
> >
separated
> > intake and exhaust pipe.
>
> customers
> want to spend for no reason. Also, in many cases, the flue comes out
at
> ground level and must be turned up then out. Can't do that with a
bazooka.
>
> Last winter we had a nice wind-whipped snowstorm. I had to defrost
several
> of them put too low to the ground. Also had to shimmy across a glare
ice
> roof,
> slide into a 2' snowdrift, dig out one and pour hot water down it to
thaw
> out
> the blockage then cut the intake open in the attic to pull out ice.
>
>
recommended insualtion on the vent pipes if going through an unheated
portion of the building. You might want to try insulating the vent ,the
combustion air pipe and the concentric portion that is in the attic --
MechAcc
doc...@uswest.net wrote:
> What happens to the code restriction of 2ft space(at outside
termination)
> between intake air and exhaust? Or are area codes different then
listing codes?
On manufactured homes, direct vent furnaces, they have been concentric
venting for years. Then again the HUD rules apply to them and not local
building codes.
On the 2 feet restriction this may apply to furnaces that are not
direct vent (sealed combustion) where the combustion air is dumped into
the mechnical (furnace) room.
Arista Engineering
With the bazooka kit, the exhaust pipe is always 2". Even if the furnace
needs a 3" vent you have to reduce to 2" at the termination. They figure
that the exhaust shoots out like a jet and the chances of re-circulating
products of combustion is negligible.
From my experience, all gas codes require venting in a method stated by the
manufacturer. Part of the process of furnaces getting an AGA, CGA, ETL,
Warnock Hersey approval is that one of these approval agencies has tested
and approved the venting method.
doc...@pop.sxfl.uswest.net wrote in message
<37F56FD8...@pop.sxfl.uswest.net>...
>What happens to the code restriction of 2ft space(at outside termination)
>between intake air and exhaust? Or are area codes different then listing
codes?
>
>Don Ocean
HVACMAN
MechAcc wrote:
>
> In article <37f28147....@news.concentric.net>,
> ees...@cris.com (Emilico) wrote:
> > On Wed, 29 Sep 1999 13:49:28 GMT, NO_SP...@home.com (David Hoerl)
> > wrote:
> >
> > >I saw on one of the vendors web pages a recommendation to use
> > >intake/extake pipe where the intake pipe was actually inside the
> exhaust
> > >pipe (PVC, high efficiency furnace.) This seems like a great idea
> since
> > >the intake air would be warmed by the exhaust gas, giving you even
> more
> > >heat retention.
> > Actually based on what I've seen the intake and exhaust combined in
> > one pipe only happens at the last three feet of the run therefore
> > efficiency gain from that run is increased by a very negligible
> > amount
>
> On manufactured home furnaces: Coleman, Miller & Intertherm double pipe
> starts at the furnace breech and out the roof. And it is metal vent not
> pvc,
>
> > >
> > >Yet, when I looked at what local builders are doing, they have
> separated
> > >intake and exhaust pipe.
> > >
> > >What do the experts recommend here?
> > >
> > >Thanks,
> > >
> > >David Hoerl
> > >dfh "at" home dot com (reply address has NO_SPAM_ spam filter)
> >
> > ***** LA VENGANZA SE SIRVE FRIA *****
> >
> >
>
HVACMAN
not make unless the exhaust and CAI are within the same "pressure
zone"... ie: if they are separated the difference in pressure between
the intake and exhaust could be great enough to prevent the furnace from
running.
Arista Engineering wrote:
>
> The distance between intake and vent is as per the manufacture's approval.
> With the bazooka kit, the exhaust pipe is always 2". Even if the furnace
> needs a 3" vent you have to reduce to 2" at the termination. They figure
> that the exhaust shoots out like a jet and the chances of re-circulating
> products of combustion is negligible.
>
> From my experience, all gas codes require venting in a method stated by the
> manufacturer. Part of the process of furnaces getting an AGA, CGA, ETL,
> Warnock Hersey approval is that one of these approval agencies has tested
> and approved the venting method.
>
> doc...@pop.sxfl.uswest.net wrote in message
> <37F56FD8...@pop.sxfl.uswest.net>...
> >What happens to the code restriction of 2ft space(at outside termination)
> >between intake air and exhaust? Or are area codes different then listing
> codes?
> >
> >Don Ocean
> >
> >John Mills wrote:
> >
> >> David Hoerl wrote:
> >>
> >> > I saw on one of the vendors web pages a recommendation to use
> >> > intake/extake pipe where the intake pipe was actually inside the
> exhaust
> >> > pipe (PVC, high efficiency furnace.) This seems like a great idea since
> >> > the intake air would be warmed by the exhaust gas, giving you even more
> >> > heat retention.
> >> >
> >>
> >> I can't imagine that making any difference in efficiency.
> >>
> >> >
> >> > Yet, when I looked at what local builders are doing, they have
> separated
> >> > intake and exhaust pipe.
> >>
dwa...@reliancebankstl.com
> And, the pressure switch(s) within many condensing type furnaces will not make unless the exhaust and CAI are within the same "pressure zone"... ie: if they are separated the difference in pressure between the intake and exhaust could be great enough to prevent the furnace from running.Arista Engineering wrote:> > The distance between intake and vent is as per the manufacture's approval. > With the bazooka kit, the exhaust pipe is always 2". Even if the furnace > needs a 3" vent you have to reduce to 2" at the termination. They figure > that the exhaust shoots out like a jet and the chances of re-circulating > products of combustion is negligible.> > From my experience, all gas codes require venting in a method stated by the > manufacturer. Part of the process of furnaces getting an AGA, CGA, ETL, > Warnock Hersey approval is that one of these approval agencies has tested > and approved the venting method.> > doc...@pop.sxfl.uswest.net wrote in message > <37F56FD8...@pop.sxfl.uswest.net>... > >What happens to the code restriction of 2ft space(at outside termination) > >between intake air and exhaust? Or are area codes different then listing > codes?> >> >Don Ocean> > > >John Mills wrote:> >> >> David Hoerl wrote: > >> > >> > I saw on one of the vendors web pages a recommendation to use > >> > intake/extake pipe where the intake pipe was actually inside the > exhaust > >> > pipe (PVC, high efficiency furnace.) This seems like a great idea since > >> > the intake air would be warmed by the exhaust gas, giving you even more > >> > heat retention.> >> >> >> > >> I can't imagine that making any difference in efficiency. > >>> >> > > >> > Yet, when I looked at what local builders are doing, they have > separated> >> > intake and exhaust pipe. > >> > >> Well, the bazooka adds $75-100 to the cost of the job, something few > >> customers > >> want to spend for no reason. Also, in many cases, the flue comes out at > >> ground level and must be turned up then out. Can't do that with a > bazooka.> >> > >> Last winter we had a nice wind-whipped snowstorm. I had to defrost > several > >> of them put too low to the ground. Also had to shimmy across a glare ice > >> roof, > >> slide into a 2' snowdrift, dig out one and pour hot water down it to thaw > >> out > >> the blockage then cut the intake open in the attic to pull out ice. > >
I have a concentric vent through the roof that is causing ice on the roof. Not sure what is causing this I can only assume warm air exhause surrounded by cold air intake. Do you think this is a problem and can it be addressed or does it need to be. I thought about wrapping the pipe with insulation but you will still have the cold air intake.
Tony Hwang
2 story house? Any way exhaust can condense when cooled off too much for
long run or cold weather. My house is 2 story and I gave up that idea
opting for shortest side vent thru basement wall. In cold weather
dripping water builds icicles at the vent opening but that's about it.