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View Full Version : Help deciding if to oversize a Trane XL16i

dohcser
05-19-2009, 09:09 AM
I know it is almost taboo to oversize a condenser, however I am right at the break point of a 2TON system in my house after a J load calc.

As you are probably aware the XL16i don't come in .5 increments rather 2 or 3 TONS.

Here is my reasoning and let me know what you think.
I figure since the XL16i is a 2 stage unit I will probably be running the 1st stage most of the time, until temp increases and the load in the house increases then 2nd stage kicks in.
In my previous post I stated that I am considering expanding over my garage in about 5 years (maybe), if I do i would hate to have to pull out a 5yr old condenser.

ACFIXR
05-19-2009, 09:11 AM
5 years (maybe), Maybe-3 ton, maybe not 2 ton.

Thebil Illpay
05-19-2009, 09:30 AM
This type situation could be among the reasons that people are cautioned not to focus too much on brand.

Gunnery Sergeant Hartman
05-19-2009, 09:36 AM
This type situation could be among the reasons that people are cautioned not to focus too much on brand.

This statement makes no sense at all.

If this guy wants a 2 stage unit, nobody makes one that is in 1/2 ton increments.

Depending on how much over 2 tons that the load calls for and where you live would determine upsizing to a 3 ton.
If you are closer to a 2 1/2 ton load, go with the 3. If you are closer to 2 tons, go with the 2.

dohcser
05-19-2009, 09:43 AM
This statement makes no sense at all.

If this guy wants a 2 stage unit, nobody makes one that is in 1/2 ton increments.

Depending on how much over 2 tons that the load calls for and where you live would determine upsizing to a 3 ton.
If you are closer to a 2 1/2 ton load, go with the 3. If you are closer to 2 tons, go with the 2.

Yes I am at 1.87 i believe on the J Load calc. The house is calculated at 1352 sq/ft living space.
If I stay with the 2Ton system and expand on my house do you think this will put a load on the condensor that it will be running on 2nd stage more often?
If I go with the 3Ton and expanded the house the system will be cycling more often?

By the way if I expand the house it would be a 20 x 20 addition so we are talking about a "possible" 400 sq/ft extra.

I do understand it is difficult to say without seeing the house, but I am asking for professional experience/advise. Thank you!

motoguy128
05-19-2009, 10:04 AM
Did you check the actual sensible cooling output of the unit with the matched air handler and coil?

Are you in a humid climate?

Also consider that a 3 Ton unit needs larger ductwork to handle the high airflow. 3 tons need 1200CFM, 2 tons need 800CFM. That's a big difference in how much air is being moved.

Other factors... do you tend to use A/C in the "shoulder season" of March-May and October, or do you leave windows open and wait as long as possible to run the A/C?

If you use a large set-back you may want the extra capacity so it can recover faster. If you have high solar heat gains, you may also want the extra capacity.

You might want to look at the XL15i and use the dehumidification features of the thermostat to dehumidify on demand with the VS fan. A 2 speed unit is for comfort and I think dehmidify on demand may function better than a unloading scroll.

From my experience, I have a XL16i that's oversized for heating capacity, and I find it still has fairly long run times even in very mild weather and the Visionpro IAQ keeps it on 1st stage. I also run it at 350CFM/ton and use Comfort-R for added dehumidification in summer and warmer register temps in the winter. That also drops it's overall capacity slightly with only a small reduction in efficiency... according to the data sheets I've seen.

I also may be expanding my house in the future, so the added capacity may come in handy. I think oversizing slightly may work out well for you, but just make sure the ductwork gets sized correctly and the branches get balanced.

dohcser
05-19-2009, 10:11 AM
Wow, great info.
I live in Northern, NJ and so far we had two 80 degree days this year. Other than that I don't think I would run the AC up until maybe May, but even today is cold here.
The contractor who did the J load said a 3Ton would not be an issue to install, so I would assume that he looked at the ducting, but will confirm.
I am also going to go with the VisionPro IAQ as I asked him to match up the XL16i with a TXV coil which I read was better for de-humidification.

I am also looking to have a Trane Cleaneffects and an Aprilaire 400 humidifier put in with this system. What do you think about that setup?
I was told it is better to stay away from the powered humidifiers as they waste water and use power ofcourse, so I am looking at the Aprilaire 400.

udarrell
05-19-2009, 10:15 AM
Yes I am at 1.87 i believe on the J Load calc. The house is calculated at 1352 sq/ft living space.
If I stay with the 2Ton system and expand on my house do you think this will put a load on the condensor that it will be running on 2nd stage more often?
If I go with the 3Ton and expanded the house the system will be cycling more often?

By the way if I expand the house it would be a 20 x 20 addition so we are talking about a "possible" 400 sq/ft extra.

I do understand it is difficult to say without seeing the house, but I am asking for professional experience/advise. Thank you!

It all depends on how air tight & well insulated the garage & house are going to be.

Nothing has to stay the same as the initial load calc.

Depending on where you live, I'm betting right energy saving techniques could make the 2-ton work about right on 1752 sf.

I'm using a Half-Ton window shaker on 1st floor around 900-sf in a 1937 home load with windows & it works perfect even at 104-F Heat Index. I did nothing to reduce the load.

Optimizing: duct airflow + insulation + windows + Reduce Air Infiltration to an acceptable minimum. Two ton will cool a lot of area if everything is set-up & done right.
----------
Home Energy Magazine Online September/October 1993
Raising Standards and Savings

Does 40 billion kWh sound like a lot of energy? Researchers believe that's how much electrical this country "could save by fixing inefficient ducts using current techniques." "Refining those [duct retro] techniques could reap savings of 90 billion kWh" plus 9 billion heating therms! Peak loads would be reduced too. [What about reducing Air Infiltration Infiltration.]

To pursue these tremendous savings, national, state, and utility research laboratories, the U.S. Department of Energy, utilities, and energy service companies are collaborating. Their consortium is called "Residential Energy Efficient Distribution Systems," or REEDS. [Not seen it here!]

Home Air Infiltration can be in some situations 50% or more of the Load.
Image Source: DTI Corp (DTI Corp Catalog) http://dticorp.net/catalog/images/logo.jpg - Darrell

Thebil Illpay
05-19-2009, 10:18 AM
[QUOTE=Gunnery Sergeant Hartman;3354462]This statement makes no sense at all.
QUOTE] It cetainly does if you are a consumer that does not know that until you are told.

beenthere
05-19-2009, 12:50 PM
A 3 ton 16i is is over 2 tons of capacity in first stage. Closer to 2.4 tons then 2 tons.

If you expand out over the garage. Plan on getting a separate system for that area.
That way, if you don't do the addition, your not stuck with an oversized unit, making your home too humid most of the time.

dohcser
05-19-2009, 01:07 PM
i recently got off the phone with the contractor and we went over the options and side effects of doing a 3Ton XL16i. He advised me that I am paying for a 2 stage compressor that will be using only one stage, and if I were to expand I should consider doing a separate unit for the addition.
With that being said I am now considering the XL15i with my Rheem furnace and adding an Aprilaire 4200 air cleaner with an Aprilaire 400 humidifier.

wahoo
05-19-2009, 01:15 PM
As earlier posted, you might want to size the unit to the existing house, especially if putting in the ductwork to the future garage addition will present some problems. Many times we see a garage (or bonus room) that presents some real problems in getting sufficient air flow to it from the existing unit in basement. Putting in a small seperate unit is usually the best solution, but this would be different with each addition. You need an experienced HVAC person look at the future problems, and go with his advice. "Don't listen to the cousin of your brother-in law who is in tech school!":D

wahoo
05-19-2009, 01:16 PM
Sounds like you are doing it right!! Good job!:)

dohcser
05-19-2009, 01:23 PM
good to know, so what do you all think about a:
Trane 802 t-stat
Trane XL15i
Coil not sure yet I asked him to match it up to my furnace and heatpump/condensor so I can qualify for the tax rebate.
Aprilaire 4200 Air Cleaner
Aprilaire 400 Humidifier

Anything specific I should request that would help me get the most out of my system, for instance when I was considering the XL16i I was told to get a TXV coil which is better for humidity control. Anything I should consider like that on the equipment I am going with?

pstu
05-19-2009, 03:28 PM
...
If this guy wants a 2 stage unit, nobody makes one that is in 1/2 ton increments.
...

You might look up Trane 2TTZ9030A1 or its modern equivalent at least in past years that was an exception. However if you look up its sensible and latent capacities compared to the 2TTZ9036 model, things get pretty interesting.

Thebil Illpay
05-19-2009, 03:34 PM
You might look up Trane 2TTZ9030A1 or its modern equivalent at least in past years that was an exception. However if you look up its sensible and latent capacities compared to the 2TTZ9036 model, things get pretty interesting.

Uh, I think this treads into the smart-butt area. I pretty quickly found a 2 stage 28,000 BTU system but wasn't about to mention it at the time. First, it's not actually 2-1/2 ton and second it would have been unneccesarily argumentative.

RyanHughes
05-19-2009, 04:45 PM
The XL19i is on its way out though. The XL20i doesn't come in that same 2.5 ton size. So basically, your options for 2-stage units are full tonnage sizes only.