3.5 Vs. 4 Ton

[bohoops]

I understand the humidty problems with an oversized system, but I am getting confusing info. All 5 Authorized Trane Dealers that came to my house say the optimum size for my house should be 3.5 Ton, but I have been told from 3 of 5 that the 4-Ton XL14i with the variable speed air handler will not cause any humidity problems and will work just fine. I have also been told by 2 of the above that the 4-Ton XL19i will negate any humidity problems because it runs in the 2-Ton stage most of the time. I have so called experts telling me 2-3 different things. I'm in Florida, 1850 SQ Ft. Cathedral Ceilings, decent insulation. Will the 19i cause humidity problems? My other option would be the 3.5 Ton XL14i or XL15i. Thanks in advance for you input.

[HeyBob]

The best way to find out exactly what size equipment you need is by having them do a load calc on your house, without a load calc everyone is just guessing.

Now, my house has a 3 ton XC21 2 stage Lennox with a variable speed air handler and with my stat in precision mode all the time the humidity levels are very low and my house has never been more comfortable. I just installed this system last March.

One other thing, make sure that all the equipment is ARI matched, you can buy a 19 SEER unit and not get 19 SEER out of it if it's improperly matched.

So, get those guys to do the load calc and install what your home requires.

[dash]

In Florida as well,have sold hundreds of two speeds,Carrier brand.Most two speed/stage cooling systems are only made in 2,3,4 and 5 ton sizes.

Installing a 4 ton two stage/speed on a 3.5 ton home is no problem ,as it will run in the low stage/speed the vast majority of the time.So it's not oversized at all.


Now installing a 4 ton single stage on a 3.5 ton house can cause humidity issues but,when used with the proper control system,running at 350 cfms a ton and 80% of that when needed to control humidity,it will probably do okay.Not sure why you would want to use 4 when 3.5 is correct,other then if going to a 2 stage/speed for the great dehumidification controls,like Infinity.

When increasing the tonnaqe ,the Duct System ,in Florida is most likely going to be a problem.Most duct systems here ,are undersized for the existing tonnage,so increasing tonnage almost always requires duct modifications,as does adding any type of "better" filter.

[danglerb]

Since requirements change over the cooling season, getting real "stuck" on 3.5 vs 4 ton seems a bit pointless, a 2 stage system is going to have more comfort, and good control system with dehumidify modes will be even better.

Long season, high humidity, 2 stage cooling seems like a no brainer. The XL19 is three stage?

[bohoops]

Am I correct, that the concensus here is that the XL19i 4 Ton will be fine in a 3.5 Ton dwelling?

[imperix]

yep i have a A/S 18 seer 2 stage unit at my house needs just a hair over 4 tons. I have a 5 ton system 37 to 40 percent humidity in South Fla

[tigerdunes]

Originally posted by bohoops
Am I correct, that the concensus here is that the XL19i 4 Ton will be fine in a 3.5 Ton dwelling?

I would consider the 4 ton XL16i HP or AC condenser. Runs at 66% in low stg and should be a little less expensive than the XL19i.

While I like Trane equipment,Carrier has the superior systems controls in their Infinity line. You may want to look at that.

As mentioned by Dash, you want to make certain your ductwork can handle 4 ton condenser-1600 CFMs or you might have a noise issue.

My opinion.

[dash]

Originally posted by tigerdunes

Originally posted by bohoops
Am I correct, that the concensus here is that the XL19i 4 Ton will be fine in a 3.5 Ton dwelling?

I would consider the 4 ton XL16i HP or AC condenser. Runs at 66% in low stg and should be a little less expensive than the XL19i.

While I like Trane equipment,Carrier has the superior systems controls in their Infinity line. You may want to look at that.

As mentioned by Dash, you want to make certain your ductwork can handle 4 ton condenser-1600 CFMs or you might have a noise issue.

My opinion.


Might be setup,I would,for 350 per ton ,so 1400 cfm total.Now an Infinity when set for 350 per ton can go to 400 ,but it won't happen 99% of the time.

Many Florida duct systems are undersized,so the ducts should be looked at.

[kevinmac]

Thge XL19i if sized correctly will run on the 1st stage, smaller compressor for 95% of the time until the house needs to play catch up where the setpoint cannot be met, usually in those peak hot parts of the day. This will cause the 2nd stage to cycle on until the requirement is met and it will divert back to the 1st stage. When the system is run on the first stage and is coupled to a VS AH, the airhandler will not get any higher than 80% of it's configured CFM. When the second stage is called on the VS AH may go to 100% of the configured CFM. The VS AH running on a lower speed will be doing a good job of dehumidifying. So If your system is setup correctly and your home calls for 3.5ton but since the Trane higher effeciency systems are in 1 ton increments, the 1/2 ton extra coupled to a VS AH will not hurt you in any regard. I would configure the 4 ton condensor with the TWE040E13 VS airhandler, this will give you a max of 47,500BTU total, 34,900BTU sensible running at a max of 1425CFM.