Humidity control vs tax credit?
I've been doing a lot of reading and really appreciate all the wise advice on this site.
I have a 20 yr old 4 ton unit that is still chugging along, but we are planning to stay in the house for another ten so it seems worthwhile to consider a replacement. We have a 2400 sqft one-story house in Houston.
Lennox xc16 (2 stage) 4 ton with CH23-51
Advisor claims that he can not configure a unit that meets the tax credit and adequately control the humidity.
Carrier Infinity 21 (2 stage) 4 ton
Advisor claims that the furnace should be replaced if considering a two stage compressor. This solution would qualify for the $1,500 tax credit and also a $1,000 rebate.
By themselves, I would have trusted both advisors. However:
1. Did Advisor #1 fail to mention that the two stage unit would not work properly with the existing single speed fan/furnance?
2. Did Advisor #2 oversize the furnace to meet the tax credit requirements?
Thanks again for all the advice.
A 2 stage with a standard blower won't give the full benefit of of its humidity fremoval.
#2 may have had to go with that larger furnace to get eh SEER rating high enough to get the tax credit.
So, Adviser #2 did confirm that he had to go with the larger furnace to qualify for the tax credit. He says he did not charge additional for the largest size, so financially it sounds good.
Originally Posted by beenthere
But, are there any negative ramifications with a larger furnace? Does it provide the correct air handling unit?
It will give you the correct air flow.
I'm not familar with Carrier numbers enough to know if thats a 2 stage or 3 stage furnace.
But, it probably won't be going to high stage often, if ever.
You sure aren't gonna get the tax credit XC16 and standard blower. I wouldn't spend the money for that fancy unit without matching variable speed inside.
The ratings for Carrier require the big furnaces to get the tax credit. If you went with a more appropriately sized furnace, the EER wouldn't be high enough.
Gee, we don't put 135K furnaces in 2400 sq ft homes up here and we get -10° out!!!!! But... if you want the credit.
Or look at another brand...
The CVA is a 2 stage VS 80, been.
Originally Posted by BaldLoonie
Thanx. I'm sure it is overkill, but if it does not cause any issues and does not cost more, then no problem.
Originally Posted by BaldLoonie
On another note....
I am leaning towards the Carrier system due to the $2,500 in tax credit and rebate. However, should I be concerned with a 5-ton coil matched to the 4-ton compressor? (Note: the actual model of the coil is CSPHP6012ATA)
Two "other" (American Standard and Rudd) advisers had to go with a third-party coil to qualify for the tax credit, but did not recommend it due to potential quality issues with the coils.
The Lennox adviser said he had humidity issues with a coil that would qualify, so he could not recommend a tax qualified system in the Houston climate.
Don't worry about coil sizes. On air handlers, Carrier doesn't even use a size, it just uses a number. Trane is going to that too. What may be a 5 ton coil for a 13 SEER could be a 3 ton coil for a super SEER.
Actually the industry is going to toughen ratings with 3rd party coils. Just seemed funny a 3rd party coil could get so much more SEER out of a unit than the OEM. In other words, you probably weren't getting what you thought you were.
That third party change is around the corner,ratings on AHRI being dropped soon.
Originally Posted by BaldLoonie
Welcome to the wonderful world of bureaucracy. Just because a system meets or exceeds set standards for efficiency on paper, it doesn’t mean it will be efficient in a particular application. Over sizing a piece of heating equipment to get the necessary blower drive to meet SEER / EER rating is a prime example of how screwed up things are. It all just defeats the purpose of encouraging fuel efficiency and energy conservation.
A good HVAC tech knows how, an educated HVAC tech knows why!
So what do the pros think would be a good rating system?
I wonder if each region needs different test conditions.
Maybe Teddybear can single handedly convince the feds that whole house dehumidifiers can actually save HO money by creating comfort using less energy than overcooling a home.
It would be interesting to see some clear difinitive test data in controlled conditions simulating weather conditions in different regions, showing actual energy use with different type of equipment and combinations. It seems like I've seen some comparison done by some universities, but there wasn't IMO a suitable control, or repeatable conditions. It wasn't a controlled test.
Efficiency should be the energy required to deliver a fixed level of comfort. Meaning how efficiently a system can delivery something like 75F and 50%RH in a space with typcial heat gain and air leaks... then average the results over a range of outdoor temperatures, weighted for hotter weather where A/C is used the most.
On a hot day, a properly set-up a/c maintains humidity without over cooling a properly ventilated home. On a cool wet day, controlling humidity requires a dehumidifier or reheat. All green grass climates have enough cool wet weather that these properly ventilatied homes require supplemental dehumidification. The major problem with high eff. coils is water retention at the end of the cooling cycle. they retain more moisture, 10-40%. Most large cooling coils can remove as much moisture with slightly lower air flow.
A simple high SEER a/c works well when combined with a whole house dehumidifier. This combination has about the same cost as a two speed a/c but provides perfect humidity control without any over cooling or without cooling. Warmer temperature with lower %RH provide lower cooling cost and is very comfortable. More and more a/c manufactures are providing supplemental dehumidification. I work for Ultra-Aire and we are growing dramactically. We supply some of the majors with equipment.
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
I see Lennox has some sort of auxillary indoor coil, that I assume functions as a condensor for efficient reheat, turning the A/C into a deumidifier. Am I understanding it's operation correctly?
Originally Posted by teddy bear
A better or at least more compact design would use a oversized coil for maximum sensible when needed, but be able to switch refrigerant flow on part of the coil to act as a condenser while also improving latent capacity on the evap portion.