Is this the best choice coil for this system?

[john_ertw]

I received model numbers for the system that is being installed next week with all of the model numbers. One thing that I am curious about is if the evaporator coil choosen is the best one for this application.

Goodman GMV950905 furnace
Goodman SSX140301 a/c
Goodman CAUF3743B6A + EEP + TXV evaporator
ARI #3262597 (without furnace)

The reason I ask is that the coil quoted is size "B" (for 17.5" wide furnaces) while according to Goodman's specs the 90,000 btu furnace is size "D" (24.5" wide). Would CAUF3743D6A be a better choice to reduce static pressure? Would the contractor choose this coil because the B size is slightly cheaper than the D size (just a guess)?

[BaldLoonie]

Yes, it would be nuts to put the narrow coil on a wide furnace. Static through the roof, cycling on limit, etc.

Best bet is same width as furnace but if that isn't possible, the next size smaller properly transitioned should do. Don't let them sit it on top of the furnace and blank off a few inches!

[Thebil Illpay]

Yes, it would be nuts to put the narrow coil on a wide furnace. Static through the roof, cycling on limit, etc.

Best bet is same width as furnace but if that isn't possible, the next size smaller properly transitioned should do. Don't let them sit it on top of the furnace and blank off a few inches!

My apologies for jumping into this thread with another, but related, question.

In ARI 'matched' combination where the coil is other than OEM what degree of certainty is there that all factors has been considered?

EDIT: I'm off work this week with a badly sprained finger, hence the frequency of my visits.

[ascj]

I received model numbers for the system that is being installed next week with all of the model numbers. One thing that I am curious about is if the evaporator coil choosen is the best one for this application.

Goodman GMV950905 furnace
Goodman SSX140301 a/c
Goodman CAUF3743B6A + EEP + TXV evaporator
ARI #3262597 (without furnace)

The reason I ask is that the coil quoted is size "B" (for 17.5" wide furnaces) while according to Goodman's specs the 90,000 btu furnace is size "D" (24.5" wide). Would CAUF3743D6A be a better choice to reduce static pressure? Would the contractor choose this coil because the B size is slightly cheaper than the D size (just a guess)?

He might have just wrote the wrong number. That coil also comes in a D size. It also won't change the ARI rating.

[john_ertw]

Yes, it would be nuts to put the narrow coil on a wide furnace. Static through the roof, cycling on limit, etc.

It's the static pressure drop I'm worried about. I looked up the coils on Goodman's spec sheet and only found the CAUF3743 coil in C and D sizes. They have a CAUF3636B coil and its pressure drop is 3 times as much as the CAUF3743D6 coil. I'll call the contractor to see if it was a mistake.

[john_ertw]

I contacted the contractor and he realized that it was a typo. He told me this coil only comes in C and D sizes. He will check on Tuesday if the local supply house has the D size in stock as Monday is a holiday.

Is it worth insisting they order the D size if only the C size is in stock? Here are the differences in pressure drops from the spec sheet:

Heating (1400 cfm - minimum heating speed for my furnace):
CAUF3743C6: 0.183 (dry)
CAUF3743D6: 0.110 (dry)

Cooling (1000 cfm for 2.5 ton a/c):
CAUF3743C6: 0.113 (wet)
CAUF3743D6: 0.089 (wet)

I figured that dry applies to heating since the air is dry and wet to cooling since the evaporator will condense water and be wet.

[beenthere]

Unusual for a coil to have a lower PD wet, then dry.

[john_ertw]

Unusual for a coil to have a lower PD wet, then dry.

You are correct that the PD is higher for wet than dry at any given airflow.

In this case the airflow is lower for wet (1000 cfm cooling) than dry (1400 cfm heating).

[beenthere]

Ooops, missed the 100CFM for wet coil.

Think of it this way.

Would you rather have a TESP of .65" or .723" in heating.