We currently have a 2-1/2 ton A/C unit and a 2 ton furnace for the
central heat/air
in our 950 sq foot house. We received a bid for adding a 500 sq ft
room.
Included in that bid is $5500 for a 2nd a/c unit and furnace.
The contractors were telling us that the unit(s) we have may not be
sufficient for
the total square footage that we'll end up with after the addition, and

this unit(s) would be just for the new room. I countered by saying
that we paid $3200 for the units that we currently have - and that's
for our entire house...how is it possible that we'd have to pay $5500
for 500 sq ft??? Of course, they didn't really know what to say.
Is our current set up sufficient for less than 1400 total square
footage? I know the "rule
of thumb" is 500 sq ft for every 1/2 ton, which would make our unit(s)
more than
workable. Is it the same rule for heating?
Any advice so we don't get ripped off??

"csonsini" wrote in message ...
We received a bid for adding a 500 sq ft
room.
Included in that bid is $5500 for a 2nd a/c unit and furnace.

I countered by saying
that we paid $3200 for the units that we currently have - and that's
for our entire house...how is it possible that we'd have to pay $5500
for 500 sq ft??? Of course, they didn't really know what to say.

Is our current set up sufficient for less than 1400 total square
footage? I know the "rule
of thumb" is 500 sq ft for every 1/2 ton,

Rules of thumb can be tossed out in many cases. Proper calculation is what
is needed; accept nothing less.

If $5500 high? Maybe, but I can't see what has to be done. How far does
the power (gas? electric?) have to be run? What about ducts? Piping?

csonsini wrote:
We currently have a 2-1/2 ton A/C unit and a 2 ton furnace for the
central heat/air
in our 950 sq foot house. We received a bid for adding a 500 sq ft
room.
Included in that bid is $5500 for a 2nd a/c unit and furnace.
The contractors were telling us that the unit(s) we have may not be
sufficient for
the total square footage that we'll end up with after the addition, and

this unit(s) would be just for the new room. I countered by saying
that we paid $3200 for the units that we currently have - and that's
for our entire house...how is it possible that we'd have to pay $5500
for 500 sq ft??? Of course, they didn't really know what to say.
Is our current set up sufficient for less than 1400 total square
footage? I know the "rule
of thumb" is 500 sq ft for every 1/2 ton, which would make our unit(s)
more than
workable. Is it the same rule for heating?
Any advice so we don't get ripped off??

Edwin is on track.

When I added 900 sq ft I had an HVAC guy do a load calculation based
upon the planned addition. He then calculated the furnace, blower, heat
and a/c requirements for the entire house, including the new, proposed,
addition. We then compared that to the existing system. In my case it
was determined that the current system was not properly sized for the
current house (It was too big). But that it would be just sufficient for
the house with the addition. I then brought him back to measure and make
up all the duct work in his shop (Ridged, insulated, duct work). I
installed it all myself, based upon his design and layout. Worked as it
was supposed to. The HVAC guy was a friend and did it for materials cost
only.

I would suggest that you do something similar. Have an HVAC guy measure
everything up and to review plans and give you a definitive answer.

There may be other reasons to do a separate system beyond capacity.
These could be:
- Proximity to current system and availability of duct chases
- Desire for a separate zone
- Desire to not need to disturb existing structure to accommodate pipes,
ducts, electrical and such.

Good luck and let us know what you decide and how it works out in the end.

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No wrote:

csonsini wrote:

We currently have a 2-1/2 ton A/C unit and a 2 ton furnace for the
central heat/air
in our 950 sq foot house. We received a bid for adding a 500 sq ft
room.
Included in that bid is $5500 for a 2nd a/c unit and furnace.
The contractors were telling us that the unit(s) we have may not be
sufficient for
the total square footage that we'll end up with after the addition, and

this unit(s) would be just for the new room. I countered by saying
that we paid $3200 for the units that we currently have - and that's
for our entire house...how is it possible that we'd have to pay $5500
for 500 sq ft??? Of course, they didn't really know what to say.
Is our current set up sufficient for less than 1400 total square
footage? I know the "rule
of thumb" is 500 sq ft for every 1/2 ton, which would make our unit(s)
more than
workable. Is it the same rule for heating?
Any advice so we don't get ripped off??

Edwin is on track.

When I added 900 sq ft I had an HVAC guy do a load calculation based
upon the planned addition. He then calculated the furnace, blower,
heat and a/c requirements for the entire house, including the new,
proposed, addition. We then compared that to the existing system. In
my case it was determined that the current system was not properly
sized for the current house (It was too big). But that it would be
just sufficient for the house with the addition. I then brought him
back to measure and make up all the duct work in his shop (Ridged,
insulated, duct work). I installed it all myself, based upon his
design and layout. Worked as it was supposed to. The HVAC guy was a
friend and did it for materials cost only.

I would suggest that you do something similar. Have an HVAC guy
measure everything up and to review plans and give you a definitive
answer.

There may be other reasons to do a separate system beyond capacity.
These could be:
- Proximity to current system and availability of duct chases
- Desire for a separate zone
- Desire to not need to disturb existing structure to accommodate
pipes, ducts, electrical and such.

Good luck and let us know what you decide and how it works out in the
end.

Inviato da X-Privat.Org - Registrazione gratuita
http://www.x-privat.org/join.php

Excellent advice by both!
You also got advice from several on alt.hvac - check back there again.
- Darrell

--
Optimizing Air-Conditioner Efficiency
http://www.udarrell.com/air-conditio...ator-coil.html

A new addition is hopefully super insulated with high efficemncy
windows and doors, and perhaps spay foam insulation.

such a addition will add little to the heat cool load.any good
contractor already knows this.

They are attempting to rip you off!!!

Since its so blatant and obvious I wonder how many other things your
being ripped for?

I can perhaps see replacing your furnace and AC with a new unit to go
from 70 to 90 + efficency.as part of the addition....

bend over are they providing KY jelly