Alright here's the question:
I've got a
2800 sq ft house 3 bdr
built in 2005
below ground basement
open floor plan/high ceilings
One stage furnace
Denver, CO

I have heard that I could get a 4 ton 13 seer unit with a 5 ton coil
(trane) or go with a 5 ton 13 seer(rheem) with a 5 ton coil.
Will I get better efficiency with the 4 ton/5 ton coil trane?

Way confused! Thanks

If you have a 4 ton unit, then you only get 4 tons of cooling.
If you have a 5 ton unit, then you get 5 tons of cooling (more
cooling).
Both units are rated 13 SEER, so the efficiency should be the same as
far as energy efficiency is concerned.
Why put a greater capacity coil on a smaller unit? Who recommended
doing that?

As far as design is concerned - how much A/C is actually needed for
this home?
I assume that this is the only unit.
What unit and capacity are you replacing, since it was built last year.

Brian wrote:
I have heard that I could get a 4 ton 13 seer unit with a 5 ton coil
(trane) or go with a 5 ton 13 seer(rheem) with a 5 ton coil.
Will I get better efficiency with the 4 ton/5 ton coil trane?

First you need a heat gain calculation to tell you how many tons (BTUs)
of cooling you need. It sounds like your contractor(s) is/are guessing.

http://www.proctoreng.com/articles/better.html

Once you know the BTU load then the contractor will assist you in
selecting the right size condensor and coil. It is not uncommon to
slightly oversize the coil to get somewhat better efficiency (SEER).
However, you want to be sure that the sensible and latent heat
requirements of the load are met.

Brian wrote:
Alright here's the question:
I've got a
2800 sq ft house 3 bdr
built in 2005
below ground basement
open floor plan/high ceilings
One stage furnace
Denver, CO

I have heard that I could get a 4 ton 13 seer unit with a 5 ton coil
(trane) or go with a 5 ton 13 seer(rheem) with a 5 ton coil.
Will I get better efficiency with the 4 ton/5 ton coil trane?

Way confused! Thanks


Why in the world do you think they put these labels on them, 3 ton 4
ton, 5 ton etc?????

It is so the proper sized equipment outside gets matched up with the
proper size equipment outside.

With a 2005 built house, why in the world are you considering a HVAC
change after only one year????

5 ton compressor/condenser should always be matched with 5 ton
coil/evaporator. Any money you save on purchase costs is likely to be
eaten up by operating costs, and in fact, it may cost you more to
operate as the 4 ton compressor will work harder/longer to cool the
house in summertime.

The only way to know for certain, however, is to have a reputable HVAC
contractor come out, inspect the system and make recommendations.

Robert Gammon wrote:
5 ton compressor/condenser should always be matched with 5 ton
coil/evaporator.

Virtually all manufacturers have certified upsized coils for use with
their condensers.

Evaaporator coil size is a major factor in determining the balance
between sensible and latent heat removal. Larger evaporator coils
normally remove less humidity, because they operate at a higher coil
temperature/pressure ratio --smaller evaporator coils tend to
remove more humidity --because they normally operate at a lower
operating temperature. The SEER is usually slightly higher with larger
coils.

See ARI Primenet for specific ratings.

http://www.aridirectory.org/ari/unitary.html

Travis Jordan wrote:
Robert Gammon wrote:

5 ton compressor/condenser should always be matched with 5 ton
coil/evaporator.


Virtually all manufacturers have certified upsized coils for use with
their condensers.

Evaaporator coil size is a major factor in determining the balance
between sensible and latent heat removal. Larger evaporator coils
normally remove less humidity, because they operate at a higher coil
temperature/pressure ratio --smaller evaporator coils tend to
remove more humidity --because they normally operate at a lower
operating temperature. The SEER is usually slightly higher with larger
coils.

See ARI Primenet for specific ratings.

http://www.aridirectory.org/ari/unitary.html



So in Denver with relatively lower humidity than Gulf Coast locations, a
larger coil MAY be a recommended practice.

Here in Houston, or New Orleans, or Pensacola, or Mobile... humidity
extraction is a big concern as the number of 90+/90+ days is very high.
In these locations a 5 ton coil should be matched with a 5 ton compressor.

Robert Gammon wrote:
Here in Houston, or New Orleans, or Pensacola, or Mobile... humidity
extraction is a big concern as the number of 90+/90+ days is very
high. In these locations a 5 ton coil should be matched with a 5 ton
compressor.

Or use a slightly oversized coil with a VS air handler / furnace, and
achieve the same humidty with a higher SEER.

There are certain matches made with a 4 ton 13 SEER condenser and a 5 ton
evap that will get you a higher SEER. You have to check the ARI ratings


"Brian" wrote in message
ups.com...
Alright here's the question:
I've got a
2800 sq ft house 3 bdr
built in 2005
below ground basement
open floor plan/high ceilings
One stage furnace
Denver, CO

I have heard that I could get a 4 ton 13 seer unit with a 5 ton coil
(trane) or go with a 5 ton 13 seer(rheem) with a 5 ton coil.
Will I get better efficiency with the 4 ton/5 ton coil trane?

Way confused! Thanks

Brian wrote:

Alright here's the question:
I've got a 2800 sq ft house 3 bdr built in 2005
below ground basement open floor plan/high ceilings
One stage furnace Denver, CO

I have heard that I could get a 4 ton 13 seer unit with a 5 ton coil
(trane) or go with a 5 ton 13 seer(rheem) with a 5 ton coil.
Will I get better efficiency with the 4 ton/5 ton coil trane?
Way confused! Thanks


Denver, CO summer design conditions: 91 dry bulb 59 wet bulb!
Approximately 12 to 13% Relative Humidity.
You shouldn't have a latent load which frees up the sensible capacity
handle the sensible temperature load.

In a ultra dry climate, go for an oversized evaporator coil, TXV, and
450-cfm of airflow per ton of cooling.
I hope your supply and return air is at or near the ceiling for the
cooling mode and near the floor for heating.
This will optimize the temperature differentials of the air and the heat
exchangers,
which transfers more heat from a specific amount of a cubic foot of
airflow. (More efficient operation)

Have a competent/trustworthy heat gain calc done, then do more to reduce
the heat-gain and size the equipment accordingly.
I would think you could get the sensible heatload and condenser sizing
down to at least 3.5-ton with a matched 4-ton evaporator coil.
Save needless expenses.
- udarrell

--
Air Conditioning's Affordable Path to the "Human Comfort Zone Goal"
http://www.udarrell.com/air-conditio...tent-heat.html
http://www.udarrell.com/ac-trouble-s...ubcooling.html

udarrell wrote:
In a ultra dry climate, go for an oversized evaporator coil, TXV, and
450-cfm of airflow per ton of cooling.

Have a competent/trustworthy heat gain calc done, then do more to
reduce the heat-gain and size the equipment accordingly.

Excellent advice! Sometimes just the addition of some attic insulation
can reduce heat gain by a half-ton or more.

Thanks for the info....just from the above responses, you can see how
much of a "Science" HVAC systems are if done right!!! I now understand
that an installer needs to do the calculations and take the right time
doing it. Thanks again!