pairing condenser/evap

[John Dirks Jr]

I see HVAC contractors using evap coils that are 1/2 sized (tonnage) larger than the condenser. I understand that the goal is higher efficiency.

What exactly is happening in the physical relation and function between components that makes this a better choice?

[Marc]

I disagree that it's better, unless the alleged 'mismatched' evaporator coil is among those models permitted by the OEM system specs.

Marc

[John Dirks Jr]

I disagree that it's better, unless the alleged 'mismatched' evaporator coil is among those models permitted by the OEM system specs.

Marc

For the sake of discussion, consider its within specs. Why choose the larger evap? What is the action of the relation between the two pieces that makes some people believe a larger evap would be better?

[John Dirks Jr]

Trane 4TTB3030E1000A - 2.5 ton condenser

Trane 4TXCB036BC3HCB - 3 ton evap coil

Is it a match by Trane specs? How would I look it up?

[Marc]

Some tradesman of long ago probably came up with the bright idea that more surface area means greater efficiency and aimed for that kind of mismatch but the variables are more numerous and the actual math far more complex than that.

Marc

[Scottpat]

Contact the Trane technical department and see what they recommend. Go straight to the source!

[rkenney]

Seasonal Energy Efficiency Ratings.

The primary advantage to a larger evaporator is greater dehumidification by virtue of a larger surface area. This is all accomplished on the evvaporator side of the system. Remove more moisture you remove more heat.

Evaporator size (capacity) can not exceed condenser size by much however as you still need to dissipate the heat outdoors.

Obviously this benefit is more useful in humid climates than dry ones.

In the push to reach Govt. mandated 13 SEER many systems were installed this way. Newer systems can have 18 SEER or even higher.

[John Dirks Jr]

Seasonal Energy Efficiency Ratings.

The primary advantage to a larger evaporator is greater dehumidification by virtue of a larger surface area. This is all accomplished on the evvaporator side of the system. Remove more moisture you remove more heat.

Evaporator size (capacity) can not exceed condenser size by much however as you still need to dissipate the heat outdoors.

Obviously this benefit is more useful in humid climates than dry ones.

In the push to reach Govt. mandated 13 SEER many systems were installed this way. Newer systems can have 18 SEER or even higher.

Hmmmm...would the larger surface area of up-sized evap coil also allow better airflow through the coil in heating mode? (gas fired) I know the coil would be idle in heat mode but I'm considering the blower has to push heated air through the idled core.

[rkenney]

When your talking about surface area of an evaporator you are speaking primarily of the combined surfaces of the individual tubes in the coil.

Since most evaporators are an A frame design you can change the pitch (height) slightly to add more or larger coils (base will still be determined by cabinet size), but conversely you would want to eliminate coils to increase airflow (less obstruction).

Can't do both. Best you can do is balance the needs of airflow and surface area to achieve the desired result.

That's for the engineers to figure out.

[John Dirks Jr]

When your talking about surface area of an evaporator you are speaking primarily of the combined surfaces of the individual tubes in the coil.

Since most evaporators are an A frame design you can change the pitch (height) slightly to add more or larger coils (base will still be determined by cabinet size), but conversely you would want to eliminate coils to increase airflow (less obstruction).

Can't do both. Best you can do is balance the needs of airflow and surface area to achieve the desired result.

That's for the engineers to figure out.

That makes sense. Thanks.