A/C Equipment Sizing Please HELP!

[BulletProof007]

First off, I’d like to say what a great forum and thanks to all the people who contribute.

I am looking to install central air in my 1600 sq foot (front to back split) home. I live on Long Island, New York and for the most part only use the air for 3 months out of the year. The equipment recommended to me is as follows.

Lennox 3-ton Air Handler model# CBX32MV-036-230
Lennox 3-1/2-ton 13 seer Condenser unit model# XC13-042-230.
Lennox Signature Series Thermostat model #Y0349.

Goodman Electronic Air cleaner model# GSAS-11

Please note no manual J was performed but the contractor told me he has done many of the same homes in the area and they are basically the same.

I do have a 16 foot vaulted ceiling in my dining room and may add a 20’ x 14’ extension to the upstairs in a few years.

I guess my question is, does a 3.5-ton unit seem big for my home? Also the reason he suggested 13 seer is because by the time I make the money back from the upgrade to a 15 It will probably need to be replaced.

Any pros or cons to the equipment he suggested? Any Thoughts, Feedback or Suggestions on what to look for would be greatly appreciated.

Thanks in advance for any help!

[tigerdunes]

bullet

surprised someone has not already offered a response.

first how do you heat your home?

you should ask for a load calculation for correct sizing. ask for it in writing.

new ductwork to be installed? if so, recommend at least two returns for good airflow

and you can't put a 3 ton air handler with a 3 1/2 ton condenser. you might ask dealer about this since the air handler mdl has a var spd blower.

I don't much about the Goodman EAC. Why do you want an EAC? The 4-5" pleated air filter cabinets are more than adequate for most homes.

IMO

[beenthere]

Might want to question that coil to condenser match as stated above.
So he has done a lot of houses in your area the same way.
So at least you know if your system is oversized, so are all the other systems he's done in your area. If thats a comforting thought to you. Well.

If your money isn't good enough for him to do a load calc, is there anything else he might short cut also?

[BulletProof007]

tiger thanks for the responce I recently did an oil to gas conversion last year Im not exactly sure which model was installed. (see attached photo)

I currently have NO duct work in the home. I spoke with the dealer this morning and it seems like he has that particular model in stock and told me that since he is installing a VS air handler It wouldn't matter that the unit is a 3.5 ton instead of a three ton unit.

I am new to all this but I try to make educated decisions especially when It comes to this amount of money. From the research I've done It seems like if the unit is over sized It will constantly kick on and off which is less efficiant and also can cause the home to be much more humid. When I addressed this concern with the installer he told me that the lennox unit has a hunidity control on the tstat and with the vs blower that wouldn't be the case.

I also think I will take your advice with the filter It does seem like over kill to use a EAC. I do have a small child in the home which so far (3 months old) doesn't seem to have any allergies or medical reason to need and special air filtration.

At this point I really not sure what to do as far as equiptment goes. Thanks again I need all the Help I can get...

[udarrell]

NYC Central Park; Summer Design 89-F dry bulb, 73-F wet bulb, or 46% relative humidity.

A mere 1600-sq. ft., better have a Manual, J, D, & S done!
You ought to be able to do what is necessary before the manual J is done, so that at least a 2.5-ton would handle the heatload.


I do have a 16 foot vaulted ceiling in my dining room and may add a 20’ x 14’ extension to the upstairs in a few years.

Make sure the ductwork system is properly designed so there will be plenty of airflow through the evaporator coil with returns near the ceiling, "EXCEPT IN THE VAULTED LIVING ROOM, keep them lower their & do NOT use a ceiling fan in the living room."

The add-on would only be 280-sq.ft which the 2.5-ton would probably handle okay.

I cool my nearly 900-sq.ft., first floor old 1937 farm with "a mere half ton window AC." The weather here is about the same as where you are; think about that for a few minutes! That is over 1600-sq.ft., per ton of cooling!

It cools it perfectly under all conditions!
Take a good look at the old farm home on the linked page.

http://www.udarrell.com/airconditioner_current_temperature_btuh_charting.h tml
- Darrell

[BaldLoonie]

Yes, a good load calc should be one. 3.5 ton for 1600 sq ft does sound very big. Our salesman just did a calc on a 2 story townhouse here, inside unit, 1200 sq ft not counting basement, average insulation, sized to 95 out, and came up with 14,000 BTU. I lived in a 1200 sq ft inside townhome my first year in town. Even with upper 90s, it cooled to 70 inside with 1.5 ton A/C.

Now, the trouble with sizing to a future addition is too often they don't happen. It might be wise to size for what you have and get a little unit later for that area.

He may be right, with a short cooling season, you may not get a payback on higher SEER. With the VS blower, you would likely get 14 SEER out of the system anyway.

[BulletProof007]

Just for reference what might be some of the concerns with an oversized unit? Efficiency and Humidity problems?

If the coil and condensers are not matched according to the units quoted.

Lennox 3-ton Air Handler model# CBX32MV-036-230
Lennox 3-1/2-ton 13 seer Condenser unit model# XC13-042-230.
Lennox Signature Series Thermostat model #Y0349.

What are some of the CONS from this type of installation?

Thanks again really appreciate every body’s help.
If anyone needs to know how to catch a striped bass or Tuna let me know I can help but HVAC is not my forte.

[Jack2007]

Just to give some perspective, I had a manual "J" done last year and they came up with a 4 ton two stage unit for a 2600 sq ft home in NE of Philadelphia.
.

[beenthere]

Oversize may cause high humidity and mold. Short cycles. Plus if thats not an approved match by Lennox, you may lose warranty on the compressor.

[catmanacman]

Find A New Hvac Company

[comfortdoc]

Find A New Hvac Company

Given the answers your contractor gave to the questions you have asked, this is the best advice given in this thread.

Man J, S and D are the only way to size and design the system properly.

[gator8]

I have to wonder about matching a 3 ton coil with a 3-1/2 ton outdoor section when this is all new gear. Usually folks go to a 3-1/2 ton coil for a 3 ton outdoor unit to get efficiency and use the variable speed blower to manage the humidity. I guess latent heat removal can be a consideration, but without calculations, who can say? Is this an ARI listed system? What are the design considerations? What does Lennox think about the match? I don't know if they will answer, but you can ask. They used to answer consumer questions if they were brief. Just because old equipment is in inventory at discount is not a good reason to buy it. The labor to install your new gear is half of your expense.

You say you have no existing duct work in your home. Golly, this is the perfect time to get yourself a manual J and manual D calculation done. This step is where all these jobs go bad, even when workmanship is good. It gets lots more expensive to correct this if it's done by rule of thumb, even with a correctly matched coil and condenser.

With vaulted ceilings, you have a more complex ventilation concern. If the return is one grill in the foyer with return air weaping under cut doors, you will be very disappointed. This will need capable design and experience.

I think comfortdoc said it best.

[BulletProof007]

I was able to dig this up and I guess if I’m reading this correctly its ARI listed.(attached picture)

I also called a friend of mine that’s in the business, for a quote and he actually was the first person that said he would have to come over to take some measurements and a few notes he also asked about insulation and said there is NO way he could even guestimate a job with out doing some calculations. He recommends Rheem equipment he said he preferred Rheem because unlike the Lennox stuff its easier to get parts in our area and I don’t need all the bells and whistles because the more stuff you have the more stuff that can break. He also said that the install is the most important part of the job. He told me a story about some old equip that he got free from a job and put in his house that he thought he would need to replace soon after its 15 years later and while it may not be the most efficient stuff it still runs great and it was Bottom of the line stuff.

He should come buy in the next day or two and ill make sure to post his proposal once I receive it.

Any thoughts about Rheem in general? He recommends 13 seer for our area.

Thanks again guys!

[supercool8]

a quick calcualtion: square feet X 0.6 divided by 400= ton rate
the higher seer you go, you might want to go down by half a ton in order to get your efficiency. lennox equipment is really good, just make sure the instalation is of good quality.

[beenthere]

As long as its aan ARI match your good on warranty.
And from that sheet, he proposed a good match.

Don't follow the ROT of sizing posted above.

[kptech]

3.5 ton would be too much. I would suggest a 3 ton condenser with a 3.5 ton evaporator coil. A variable speed air handler would be better for the vaulted ceiling, better temperature control. 13 seer is good, but the higher seer, better operation, especially with variable speed operation.

[teddy bear]

I just used 2 ton/DX valve/VS on 2,300 sqft. No westerly exposure. Needs a dehumdifier to maintain <50%RH during cool wet weather. The ASHRAE sensible/latent load is the same as N.Y. city. If you have exposure to westerly sun, you need more cooling. Regards TB