Just having some water cooler talk from a few non-experts here. In
summary, what would be the major difference between these 2 setups?
- 3 ton blower
- 3 ton coil
- 3 ton condenser
- 3 ton blower
- 4 ton coil
- 3 ton condenser
Rumor has it that Setup #2 "may" fish out more cooling during the very
hot days. Reason for going with Setup #2 is that 3 ton blower is
existing and can only accomodate a 3 ton condenser. So to "turbo"
charge the system, a 4 ton coil can be used to give it some extra but's
True or False? Would the operating cost be significantly different?
Which would cost more to run? 3 ton furnace with blower is fairly new
and coil and condenser would be brand new rated at up to 15 SEER. Would
appreciate any feedback.
If you start reading the specs of geothermal heat pumps, you can easily
see that Airfrlow rating has a great deal to do with capacity of the unit.
Airflow must be high enough that frost and ice do not form on the condenser.
Manufacturers attempt to balance several different environmental models
to achieve their recommendations. Some areas need only cooling, others
need dehumidification and only mild cooling,while still others need
intense dehumidification and intense cooling. Striking a balance that
works equally well in Buffalo NY, Palm Springs CA, and Mobile AL is
difficult. So local installer adjust the sizes of components in order
to meet local needs.
I do not believe that the manufacturers are leading people down the
wrong path, but local installers MAY. I believe AC mfgs should be
required to rate their units according to the needs of specific areas of
the country. I live in Region 5 according to www.hvacopcost.com. My
heating and cooling requirements are quite different from a Region 1
Denver Colorado, and installers in my area should know how to adjust the
sizes of the installed components to produce the desired effect.
The only time frost and ice will form on the condenser is during the
winter when the unit is not running. You can prevent this by
covering it with a tarp at the end of the cooling season.
Or did you mean "evaporator" ?
Yes, I agree. It does seem illogical, especially when the
manufacturers are doing everything they can to get the energy
efficiency up. So, I find it hard to believe that you can get anything
worthwhile by going to a larger evaporator than is std for that unit.
Evaporator size and air flow are inter-related. Get a too small
evaporator for the airflow of the fan and ice will form. Get a too
large evaporator for the compressor, and excessive wear on the
compressor will result (I think this is the case as pressures in the
system will be lower than exepcted leading to a higher than normal
charge of refrigerant)
So it looks like consensus is that a bigger coil will increase
efficiency and dish out more cooling due to more surface area for air
But how will this affect equipment life, if any? Through logic, it
would seem that this setup would cost less to run, based on electrical
So costing less = less use in electricity because the coil is more
efficient at cooling the air and less runtime is required to reach and
maintain a specified temperature right?
So if the syetem was say rated at Up to 15 SEER, by going to a bigger
coil, you could potentially be going slightly above the SEER rating?
On 14 Jun 2006 21:42:17 -0700, email@example.com wrote:
I've noticed that those mfg that publish the SEER for different
combinations always seem to favor the huge evaporator coils.
For instance, Goodman always had the highest SEER for the 3 1/2 ton
systems when it had a 5 ton coil (with a TXV Valve).
There are some that will say you should match, but if the installer
has a brain, he can squeeze a few more points using an oversize
evaporator coil with a txv).
Of course, your ductwork may need some extra work with an oversize
No change needed to ductwork as the fan speed and air volume are unchanged.
The temperature of the refrigerant exiting the evaporator will be higher
with the larger coil as there is a larger surface area for heat exchange
with the coolant.
Temperature and humidity of the air exiting the evaporator will be a bit
lower as the coil will extract more heat and more humidity than the
smaller coil (same volume of refrigerant, more surface area in the
evaporator for heat exchange)
I stand by my assertion that the ONLY changes needed are at the
interfaces between the evaporator and the plenum and the furnace.
The fan speed doesn't change, the air flow (CFM) does not change, so NO
change is needed in the ductwork. If the ductwork was designed for a
1200CFM fan, and we still keep that same fan, why to we need added ducts
or larger ducts????????
The only changes needed are those to get a physically larger unit to fit
in the space the the former unit occupied.
Yes the installation expense is HIGHER than simply replacing the old
evaporator with a new evaporator of the same size, from the same mfg as
there is sheet metal cutting, welding, bending, and sealing to be done.
Even on my ten year old system the high pressure line from my outside unit
is barely warm to the touch on a ninety degree day. Maybe if you lived in
Phoenix where it gets to 110 it might make a small difference. I believe
compressor efficiency is the main place where you can save energy.
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