Size of coil, condenser and blower makes a difference?

Just having some water cooler talk from a few non-experts here. In summary, what would be the major difference between these 2 setups?
Setup #1 - 3 ton blower - 3 ton coil - 3 ton condenser
Setup #2 - 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 of cooling.
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You just can't change the laws of physics. If it was true, every AC installer would be doing it.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

True.
Which laws?

Not necessarily. Money is also an issue.
Nick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The ones that involve heat transfer, compressing g asses.

So the major manufacturers of AC equipment intentionally match components that will give less than optimum cooling?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Edwin Pawlowski wrote:

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Robert Gammon wrote:

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" ?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Edwin Pawlowski wrote:

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@optonline.net wrote:

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)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I don't see any need for changes in those laws. In fact, they support the case for more efficiency.

It's a compromise, like many things in life. Bigger heat exchangers are more efficient, but they cost more.
Nick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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 flow.
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 bills?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@gmail.com wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Robert Gammon wrote:

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?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 14 Jun 2006 21:42:17 -0700, snipped-for-privacy@gmail.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 coil.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
DK wrote:

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)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sorry, you are wrong.
Yes, the ductwork will need to be changed.
The 5 ton coil will not FIT!!!
And to make matters worse, the transition is often sheet metal so that is an added expense.
wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
DK wrote:

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.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.