SEER question

[ducatiduke]

Hi -

I am proud new owner of a a XL19i... The questsion is when you look online it states its SEER rating of up to 19.50... All of my paperwork states 17.5 SEER.

I do relize that there are different parts that make up the system, but why is there a difference... Better yet, what could I have done differently to increase this to have a higher SEER.

Just curious...

[tpa-fl]

Probably one of the best threads on here regarding SEER ratings:
http://www.hvac-talk.com/vbb/showthread.php?t=97980&highlight=%22selling+seer%22

Depending on your climate, a high-SEER system might not be the best option. If you want the best efficiency to get a desired temperature, crank that blower as fast as it can go (and the ductwork can handle.) If you want comfort, slowe that blower down as much as possible to make sure you're removing humidity (at the expense of efficiency.) If you use higher-end controls, you can control this based on the actual environmental temperature & humidity and get the best of both worlds. Also, if you are able to get the humidity (latent heat) down to a reasonably low level (40-45% relative humidity), you'll find that you will be comfortable at higher temperatures, which, can mean setting the thermostat higher and possibly saving more energy than you would with the air conditioner running near its SEER ratings. I've seen 10 SEER equipment, when properly installed, outperform and produce a lower energy bill than 16 SEER equipment improperly installed.

Another article on SEER, 'though I'm not 100% sold on everything they say, but I live in swampy Florida, so humidity removal's the main use of air conditioning in my home:
http://www.advancedenergy.org/buildings/knowledge_library/heating_and_cooling/seer_facts_bulletin.pdf

[ducatiduke]

I forgot to mention in the orginal post that I live in the desert - Cave Creek, AZ (just outside of Phoenix)... so humidity is not a huge factor. We do have our monsoon season in the summer where it is humid for us though... http://www.wrh.noaa.gov/psr/general/monsoon/... I am going to go through this tomorrow... thanks for your reply...

[tpa-fl]

In that case... crank that blower up! Another option is to up-size the evaporator coil inside by 0.5-1.5 tons (depends on the size of the unit). It'll remove less humidity, but will drop the temperature quite well. No use removing humidity which doesn't need to be removed.

[beenthere]

That up to 19.5 is for one size only.

I think its the 3 ton.

[pstu]

Hi -

I am proud new owner of a a XL19i... The questsion is when you look online it states its SEER rating of up to 19.50... All of my paperwork states 17.5 SEER.

I do relize that there are different parts that make up the system, but why is there a difference... Better yet, what could I have done differently to increase this to have a higher SEER.

Just curious...
I got a copy of Trane literature titled 'Split System Cooling Product and Performance Data', it reveals what must be done to get the fabled "up to" SEER of this system. According to this you need the 2TTX9030 model condensor, TWE040E13 air handler (not a furnace), and of course the thermostatic expansion valve TXV-NB. With that you will get 34,400 total cooling BTUH, 27,800 sensible, and 19.5 SEER.

Use a furnace with that AC and at best you will lose a full SEER point. Most combos are in the 17-18 range, still good enough to qualify for the IRS income tax credit.

Use the 2TTZ9036 size AC and you get up to 19.00 SEER, 37,800 total capacity and 29,500 sensible. This is what they call the "3.0 ton" size but I observe it is a bit more generous than the 36,000 BTUH size one would nominally call 3-ton. Larger sizes generally get progressively lower SEER, and the XL19i is no exception. If you could identify your model of coil and furnace, that would make it possible to look up the claimed SEER of your combo. However this is under laboratory conditions and many common things might make anyone's AC perform worse in the actual house -- leaky ducts come first to mind.

The 2TTZ9030 size is called 2.5 ton but it seems so generously sized that other makers might call it a 3-ton with a little hyperbole. A lot of combinations in that size result in 32,000-33,000 BTUH output. Certainly less than 6000 BTUH different between the claimed 2.5 ton and 3.0 ton sizes. Trane even rates them at the very same CFM airflow. That struck me as weird.

Hope this helps -- Pstu

P.S. There is a website where you can look up your 19i with various combinations, and see the ratings: http://www.aridirectory.org/
You can fill in just a few of the fields in the search, leave the rest blank, and get a larger number of results. Then you can narrow it down to your interests.

[ducatiduke]

Great info....

I went to the site and plugged info but did not find my set up...

TUD2D120AFV52A - Furnace
2TTZ9048B1000B - Condendser ?
TXC065S3HPC - Indoor ?
TCONT802AS32DA - Thermostat

[pstu]

Probably a spelling "error", if you don't type the match just the way the program wants. I would help you much more, except my wife has a huge amount of entertainment packed into a weekend starting just a couple hours from now. Can you wait until next week and if still necessary we can work on ARI ratings for your system, or the closest we can find?

One thing never to forget is the importance of duct sealing and design, and how leaky they might be due to indifferent craftsmanship. The ARI number is a lab ideal, your experience may be less.

Best of luck -- Pstu

[tigerdunes]

ducatiduke

Looks like a 17 SEER

Ref #798213

http://www.ceehvacdirectory.org

[ericrocks]

I can't help it, the more I think and read about it the more I doubt the value of the SEER rating for people living in Southern states.

SEER is a kind of averaged efficiency rating for an unspecified location in the US. But it ain't Houston, Phoenix, Miami, Dallas, etc.

I like the EER number better. It gives you the efficiency at a defined situation, e.g 95 F outside temperature. And I recently read an article saying that despite the availability of 'more efficient' HVAC system with climbing SEER numbers, the EER value is stuck around 12.

Why is this important? The efficiency of a given HVAC system (cooling) goes down the more the outdoor temperature goes up. And it's steep.

Cooling conditions in the Summer will be closer to the EER conditions than some type of average (in North Texas: 95..105 F during the day, 80 F in the middle of night).

Cooling costs are related to the outdoor temperature squared!

In the Summer your HVAC system has the lowest efficiency and you need most cooling.
In Spring, Fall your HVAC system has a higher efficiency but you need less cooling.

So for these $$$$ 16+ SEER systems in the South: I don't believe in it. They will cut your April cooling bill nicely from $80 to $50, but reduce your $500 August bill only to $400.

Next time your in the market for a new AC system, tell the Sales guy your looking for a 15 EER system. And 'enjoy' the long explanation that follows.

Of course, if you live in Chicago, please disregard this post.

[lackster]

In that case... crank that blower up! Another option is to up-size the evaporator coil inside by 0.5-1.5 tons (depends on the size of the unit). It'll remove less humidity, but will drop the temperature quite well. No use removing humidity which doesn't need to be removed.

So... for my southern, humid climate, could I assume the inverse holds true? If
I downsized my inside coils I would have better humidity removal, but at what cost to the units ability to cool to the desired temperature? Is this something that is considered by most installers?

[Mr Bill]

Hi -

I am proud new owner of a a XL19i... The questsion is when you look online it states its SEER rating of up to 19.50... All of my paperwork states 17.5 SEER.

I do relize that there are different parts that make up the system, but why is there a difference... Better yet, what could I have done differently to increase this to have a higher SEER.

Just curious...


I would not worry to much about the seer rating figure your eer rating and then see what you have, but be sitting down when you figure it.:eek:

[beenthere]

So... for my southern, humid climate, could I assume the inverse holds true? If
I downsized my inside coils I would have better humidity removal, but at what cost to the units ability to cool to the desired temperature? Is this something that is considered by most installers?

Down try to engineer a system by swaping out different coponets for just one part of the load.

The benifit of the higher SEER units, is that they are 2 stage units.
A 2 stage will usually get you the humidity control your looking for.

Is a 16 SEER that will save you 100 bucks on the hottest monthes of the year worth the money over a 13 SEER? Thats up to the individual.
Will your electric rate go up 30% in the next 5 years?

[tpa-fl]

So... for my southern, humid climate, could I assume the inverse holds true? If
I downsized my inside coils I would have better humidity removal, but at what cost to the units ability to cool to the desired temperature? Is this something that is considered by most installers?

You've got it. In many ultra-humid environments (swamps, bayous, beachfront, etc), this is a pretty good way to go, especially if the structure is super-insulated (foam core, solid-pour concrete) and the sensible heat load isn't all that much. This is the way my beach condo was done (went 1 ton smaller on the coil) and no complaints. Some will say you'll be losing efficiency & spending more money to cool the space, but I find myself turning UP the thermostat because the lower humidity makes warmer temperatures feel comfortable.

Ultimately, the condensing unit is only capable of moving xx,xxx BTUs of heat. Whether that's sensible heat or latent heat (humidity), is up to you. Lennox actually does this (see link below) and offers 2nd very small coil that can be installed with their systems to handle the dehumidification.

Would most installers consider it? Never. I'm sure I'll even get blasted by quite a few members in this forum for even suggesting it. Overall, HVAC in the USA is still a good 20 years behind the rest of the world. We're doing what our fathers did and if you pop open most of the ACs sold in the USA today, they're not much different than what we installed in the 1950's & 1960's. Sure, they've become more efficient, but that's only due to simple changes, such as thinner, larger coils, not true improvements. Everywhere else, ductless (or very short ducts), zoned, inverter-driven compressors are the norm. Here in the US, we still try to move air through leaky ducts, often in hot attics, using single-stage equipment which really is outdated junk. I'm still frustrated with the fact that Trane's variable speed air handlers sold today are no different than the ones installed 7-10 years ago. Not sure about your life & home, but the technology changes in mine over the past 7-10 years have been major. Does the older technology "work"? Depends on your definition of "work." An abacus can be used to do your taxes, or you could use TurboTax...which would you rather use?

You'll occasionally find a "renegade" mechanical engineer who bothers to do the calculations and realizes that a "mis-match" is a better match for the building they're working on than the regular standard match-up. If you think about it, as most ACs are installed today, they install the exact same system (of differing tonnage) for out in Arizona as they do coastal Florida... but the actual sensible & latent needs of these locations is vastly different. So why do we keep selling the same matched systems in both locations?

One other trick which is easier to implement and is an easy retrofit is to adjust blower speeds in response to the amount of latent heat to be removed. This is what some of the higher-end systems out there do. Lennox used to do this (not sure if they still do or are sold on the separate smaller coil for that), Carrier still does. Even on older single-stage non-variable-speed systems, the blower usually has multiple speed taps. Add a TXV, fan relay, and a humidistat, or one of the fancier thermostats, and you'll end up with better humidity removal and better comfort on the cheap. It won't have the same humidity removing performance of a high-end system, but it certainly will be an improvement and might cost less to run if you can get the humidity below 48%. It also won't remove humidity when there is no need for cooling (whereas the Carrier Infinity and I think the Lennox system do.)

If your home's system is relatively new, this retrofit option isn't a bad deal, but trying to find a tech who truly understands this and would be willing to do it is another story. Best bet is to find someone who does commercial work or refrigeration work. There's also the option of adding a stand-alone dehumidifier. The Ultra-Stor systems are quite nice and a huge improvement over the home improvement store units, especially their installed units. Then you'd have TRUE humidity control regardless of room temperature. If your system's 10 years old or more, just get one of the newer variable speed systems which has a dehumidify cycle and you'll be very pleased.

Lennox Humiditrol small coil: http://www.lennox.com/products/overview.asp?model=HD

[chillbilly]

Good information.

As for designs, I can show you effeciency levels which meet or exceed design parameters regularly.
This indicates that the designs work well.
Duct losses/gains? Duct losses/gains are almost a non-factor with the types of duct we use today.
I don't see the designs as primitive at all.
My energy costs are very low compared to other energy mooching appliances in my house.
And when I use the term work, I am referring to efficiency.
One need only to take some simple electrical and mathematical calcs to test how well an appliance uses energy.

I'm not sure why you would think that installers would "never" consider undersizing coils or utilizing other means of heat removal.
I have access to the engineering manuals too and we have used thermidistats and variable speed here for years.
If I need to remove 24K btuh from a structure and I need premium performance, I just use variable speed with the numerous airflow trim adjustments availaible, and I use the dehumidification configuration option and adjust my humidity level to a preset point. No big deal.

But I always size the outdoor section to meet or exceed the BTU design requirements regardless of how I juggle indoor air.

[davidr]

Duct losses/gains? Duct losses/gains are almost a non-factor with the types of duct we use today.


These are actually pretty big factors regardless of materials used if installed in the right area.
The installation of the materials is the place that will make the most impact.

[chillbilly]

These are actually pretty big factors regardless of materials used if installed in the right area.
The installation of the materials is the place that will make the most impact.

I guess you will have to define the term, "big factor" for me then.
I can show you alot of load calcs where the percentages of heat gain through duct in the hottest portion of the structure are 5% or less of total btu content.
I normally view those types of percentages as small in comparison to infiltration, people and glass.
I just completed one that was an attic install using R6 ductboard and flex.
Total heat gain through the duct totaled 4% of the total load.
Hardly noteworthy as far as I'm concerned.

[davidr]

Did you actually measure the 4% loss of that system or are you using the numbers the load calcs printed out?

[ericrocks]

Interesting discussion!
I have a hot attick, >110F in the Summer.
Ducts have a length between 10 ft and 40ft, only R3.
I once measured the temperature difference between a return grill and an output grill with the A/C off, fan on. Output was 2F higher than input.

The A/C creates a 20F difference between input plenum and output plenum.

That means I have 10% duct losses.

Davidr, could you share the parameter settings used to come to the 4%: duct length, attic temperature, duct leakage,...

[davidr]

Davidr, could you share the parameter settings used to come to the 4%: duct length, attic temperature, duct leakage,...

Real simple formula you can use to figure duct loss/gain in the field.
To get this figure you need to take three dry bulb temperature measurements, one at the return of the equipment, one at the supply of the equipment, Then take a few at some of the supply registers & average them up.

With these readings you can get a good approximation of what the duct loss is at that period in time.

(Average supply register temperature - supply plenum temperature) divided by (Delta T through the equipment) = BTU% gain through the supply ductwork.

You can manipulate the formula around to do return side gains also, to do % BTU loss switch the register temperature & supply plenum temperature.

Quick example, say you have a supply plenum temperature of 55º a return temperature at the equipment of 75º & a average supply register temperature of 65º

Plug those numbers into the formula (65º-55º) / (75º-55º) = 50% BTU gain through the supply ducting.
Half of the capacity of the equipment is being eaten up by the supply ductwork in this example.

And yes those numbers & conditions do exist in the real world. :D

[ericrocks]

Davidr my mistake. I also believe that duct losses are far from neglectable. My question should have been:

Chillbilly, could you share the parameter settings used to come to the 4%: duct length and diameter, attic temperature, duct leakage,...