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Parameters for matching furnace and A/C indoor coil.

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alum

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Discussion starter · #1 ·
I just had installed a Carrier 58MVC80-14 furnace with a 24ANB630 A/C and a CNPVU3617ACA indoor coil instead of the matching CNPVU36121ACA indoor coil for the furnace. The installer said it was matched because even though the indoor coil size is 17" instead of 21" the indoor coil tonnage is 1/2 ton larger than the outdoor A/C unit. Is this true? Isn't it the coil width only that determines the match?

Just worried because I've read other threads that indicated a smaller width indoor coil could cause furnace limiting issues; not sure what that means but it doesn't sound good.

Thanks for responses in advance.
 
Discussion starter · #3 ·
how did they transition from furnace to coil.

I assume your asking the orientation of the furnace to the coil.

Please see my picture of the furnace setup.

The return duct enters the furnace at the bottom right and goes up the furnace into the coil which I believe is an up-flow setup.
 
#4 ·
alum said:
I assume your asking the orientation of the furnace to the coil.

Please see my picture of the furnace setup.

The return duct enters the furnace at the bottom right and goes up the furnace into the coil which I believe is an up-flow setup.
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Yikes... a pro would probably tell you to use ahri-directory to determine proper matchup, or the carrier technical data that shows the proper match for that furnace and outdoor unit
 
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Discussion starter · #6 ·
I did a bit more research and found the AHRI tables and they all indicate that the indoor matching coil for the 58MVC80-14 furnace is the 21" wide CNPVU3621ACA.

I would like to know if using a 17" wide indoor coil (CNPVU3617ACA) that is 1/2 ton larger than the outdoor coil (3 tons) is okay.

I know all the data indicates it isn't a perfect match but does it really matter enough to make a fuss.

Thanks for all the replies so far.
 
#7 ·
alum said:
I did a bit more research and found the AHRI tables and they all indicate that the indoor matching coil for the 58MVC80-14 furnace is the 21" wide CNPVU3621ACA.

I would like to know if using a 17" wide indoor coil (CNPVU3617ACA) that is 1/2 ton larger than the outdoor coil (3 tons) is okay.

I know all the data indicates it isn't a perfect match but does it really matter enough to make a fuss.

Thanks for all the replies so far.
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A pro might tell you that a good quality contractor will always use tested, proper AHRI matches while installing both a new indoor and outdoor unit.

BTW Pretty much every single furnace/outdoor unit combo install we do has a AHRI matched coil that is wider than the furnace, and they are usually 30" tall making it necessary to build a bunch of fittings to make it work.
 
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#9 ·
alum said:
I did a bit more research and found the AHRI tables and they all indicate that the indoor matching coil for the 58MVC80-14 furnace is the 21" wide CNPVU3621ACA.

I would like to know if using a 17" wide indoor coil (CNPVU3617ACA) that is 1/2 ton larger than the outdoor coil (3 tons) is okay.

I know all the data indicates it isn't a perfect match but does it really matter enough to make a fuss.

Thanks for all the replies so far.
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It's too bad they didn't use the matching 21" wide insulated cased coil and the flex on the humidifier is another indication they don't care much about a quality installation.
 
#10 ·
George2 said:
It's too bad they didn't use the matching 21" wide insulated cased coil and the flex on the humidifier is another indication they don't care much about a quality installation.
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Coil cases cost a few bucks more and so does the extra 15 minutes it takes to use hard pipe for the bypass...
 
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#11 ·
Ask your contractor for the AHRI certificate. I cannot find it for this match. The certificate will list the efficiency and capacity of the system.
 
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#12 ·
comfortdoc said:
Ask your contractor for the AHRI certificate. I cannot find it for this match. The certificate will list the efficiency and capacity of the system.
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This contractor certainly won't have a certificate for that match, neither will AHRI... I would tell them to put the proper case coil in there.
 
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#14 ·
George2 said:
Oh ya, that's right. Why spend the extra money if the customer will settle for a half a$$ job.
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I was just talking about this with a colleague, if you are a homeowner looking for an hvac contractor to do a quality install good luck... around here 95% of jobs are shamefully hacked, we are one of the few (the only that I know of) that takes pride in their work. Its sad
 
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Discussion starter · #15 ·
LibertyTree said:
I was just talking about this with a colleague, if you are a homeowner looking for an hvac contractor to do a quality install good luck... around here 95% of jobs are shamefully hacked, we are one of the few (the only that I know of) that takes pride in their work. Its sad
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It is sad that these unexpected surprises are the norm rather than the exception.
 
Discussion starter · #17 ·
Norm01 said:
Did you get the Infinity thermostat, if you did what is your static pressure.
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Yes I did get the Infinity thermostat but still not too familiar with all the features. Not sure what static pressure you're referring to because the installation sheets show static pressure for both the furnace and air-conditioner. I attached the service screens for both but neither shows any readings; maybe because nothing is running at the moment but not sure.

I'm being a bit cautious navigating through the menus because I was warned that changing some of the settings could require a service guy to come out and reset things on the circuit board in the equipment itself. Confusing because the manual seems to indicate that the thermostat initially reads the hard settings from the equipment into the thermostat memory and uses it from there going forward which would indicate that nothing should be touched at the equipment circuit boards.

Just curious; why are you asking about the static pressure?

(PS. Sorry about not following-up on my own thread but I've been fighting a bit of a fever.)
 
#18 ·
Run system and re-post picture with readings.

your static pressure will probably be high. Draw a square inside of a square with your coil measurements, then draw a third square inside depicting the condensate drain pan at the base of the coil. 21-17-4= 13 inch wide opening on your coil probably equals air flow restriction and at least poor airflow distribution across the coil.
 
Discussion starter · #19 ·
second opinion said:
Run system and re-post picture with readings.

your static pressure will probably be high. Draw a square inside of a square with your coil measurements, then draw a third square inside depicting the condensate drain pan at the base of the coil. 21-17-4= 13 inch wide opening on your coil probably equals air flow restriction and at least poor airflow distribution across the coil.
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I'll do a 5 min. CHECKOUT test on the A/C when I get home later this evening but it will probably be a bit on the cold side.

I hope running the A/C at those low temps don't damage anything.
 
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