Real Estate Forum

"HVAC Guy" <HVAC@Guy.com> wrote in message news:478171AB.F600CDB6@Guy.com...
> Zyp wrote:
> 
>
> There are no inspections or permits required by any law for what I
> did.
> 
>
> I made no modification to anything *inside* the furnace.  Attaching
> flex lines to the *outside* of the unit's cabinet does not constitute
> any design change to the system.  I have not restricted or modified
> the design intent of the intake grillwork of the cabinet.
>
> The grillwork of the cabinet was designed to allow air to enter the
> furnace for combustion and draft purposes.  I have not modified that
> functionality.
>
> By ducting those intakes directly to the outdoors, I have actually
> made the furnace safer by preventing the furnace from ever
> experiencing a back-draft situation that might arise if there was ever
> a negative-pressure situation inside the building.
> 
>
> UL and AGA approvals are only needed to SELL products at the retail or
> maybe wholesale level.  Ongoing UL and/or AGA approval do not apply to
> items owned by end-users.
>
> A vendor is obligated to sell or install items to end users that have
> UL and/or AGA approval.
>
> An end user is not obligated to insure that those items continue to
> maintain UL and/or AGA approval.
> 
>
> The furnace's gas valve is variable and allows for a variable gas
> output.
>
> The long, slotted burners respond by generating smaller, slower
> flames.  Perhaps inshot burners would not behave properly with reduced
> pressure, but these burners do.
> 
>
> This furnace is a double-unit (joined side-by-side).  8 burners (4 in
> each side).  Thermostat is 2-stage (the second set of burners doesn't
> come on unless the thermostat thinks there is a need for it).  I have
> 4 round flex ducts (4" diam) going to the furnace cabinet.  One each
> to the primary combustion air intake grills, and one each to the draft
> hood intake.  All 4 intakes have been sealed with a combination of
> riveted metal-work and aluminized duct tape.  The flex ducts are
> (each) about 8 feet long.  They come from a large rectangular duct
> (about 1 sq. ft. cross-section) that terminates at an exterior air
> intake grill.
>
> I think that the only time the second unit comes on is in the early
> morning (7:30 am) when the thermostat set-point changes from 63f
> night-time temp to 71f daytime temp.  So the flue draft is supplied by
> two 4" lines even though only 1 unit is operating during the day.  The
> flue pipes are about 6" diameter and rise straight up from each unit
> for about 6 feet and then connect into a large horizontally-run flue
> pipe (about 1 ft diam).  The large pipe runs about 10 feet before
> entering the chimney.
> 
>
> Please explain exactly how the setup as described is unsafe.

If you created a sealed combustion unit, I do not believe you have enough
air for combustion.  I am new at this so this bare with me.  I believe you
require a certain amount of air per 1000 btu's of furnace power. do you have
enough coming into the furnace. With 8 burners you probably have 160-200,000
BTU's of heat.  Since this is a twinned furnace set-up are both blowers
coming on a call for heat.  I am assuming you have a common return.  What is
your manifold pressure at the outlet of the gas valve.  Why would you have a
12" stack for 200,000 btu's that seems a little bit oversized.  Are their
any other appliances connected to it.  What is the internal diameter of the
chimney which drafts your equipment.  Judging by the adjustments you made it
does not sound like a properley calibrated combustion system.  It seems as
though you have decreased efficiency.  Cold dilution air on a conventional
natural draft furnace does not appear to be right.

Mr Storm would probably be able to give you better answers to your
questions, I am just trying to understand your logic.

I don't think you have provided any scientific answers to any of the true
questions asked of you.

What area of the country are you doing these alterations in.  That may make
a big difference.

I am still trying to learn, and you being an HVAC Guy may be able to help me
understand so I can help out my future customers with their equipment by
your aproach to your equipment.

TIA,

Bob P

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