How effective is Carrier Infinity dehumidification ?

[Andrew G]

I'm deciding whether I need a separate whole-house dehumidifier (eg, an Aprilaire 1750) to supplement my new Carrier Infinity HVAC system.

My HVAC system will include a 58MVC Infinity variable-speed furnace, Infinity control, and a Performance 24APA7 two-stage A/C. I know that system is designed to control humidty better than other systems, but is it enough to achieve ideal humidity levels during the summer?

Some relevant factors: I live in the Washington DC area (hot, muggy summers), my home is extremely tight (SIP construction), I have an independently-ducted ERV that will run on low speed continuously, and we prefer a relatively high indoor temperature in the summer (77 degrees, day and night).

I'm concerned that achieving an ideal humidity level (~45% RH) with just the Infinity system would force the temperature below the 77 degrees we prefer.

What do you think -- do we need install a whole-home dehumidifier to get what we want? Thanks!

[jtrammel]

i would suggest trying out the ac by itself and if you aren't satisfied with the humidity then you can install the dehumidifier. with little or no uncontrolled infiltration the humidity shouldn't be that bad. I'm not sure what the equipments humidity removal capacity is but it probably will be adequate if the system is properly sized which means it should run almost all of the time. Im not familiar with the D.C. area but in my area, Upstate SC, i do suggest most homes need a whole house dehumidifier but i only suggest this after performing certain diagnostic testing (blower door, duct blaster), www.bpi.org or www.comfortinstitute.org to find a contractor , and data logging of humidity and temperature levels throughout the home. Maybe a senior member can give you more advice. good luck. I would also look into Nordyne's IQ drive system before making your final decision.

[hvacrmedic]

I'm deciding whether I need a separate whole-house dehumidifier (eg, an Aprilaire 1750) to supplement my new Carrier Infinity HVAC system.

My HVAC system will include a 58MVC Infinity variable-speed furnace, Infinity control, and a Performance 24APA7 two-stage A/C. I know that system is designed to control humidty better than other systems, but is it enough to achieve ideal humidity levels during the summer?

Some relevant factors: I live in the Washington DC area (hot, muggy summers), my home is extremely tight (SIP construction), I have an independently-ducted ERV that will run on low speed continuously, and we prefer a relatively high indoor temperature in the summer (77 degrees, day and night).

I'm concerned that achieving an ideal humidity level (~45% RH) with just the Infinity system would force the temperature below the 77 degrees we prefer.

What do you think -- do we need install a whole-home dehumidifier to get what we want? Thanks!

You might want to just give your Infinity the opportunity to prove itself before making any decisions. If you don't want the system to use "Cool to Dehumidify", then either turn that feature off or have it turned off if you don't know how to do that, otherwise it will drop the temperature below setpoint up to 3° depending upon the demand for dehumidification. Make sure also that it's set for "Comfort", which is the default dehumidification setting. These are two different settings in the installers menu.

If indoor humidity is an issue with this system in this configuration, then you might want to search for any sources of unwanted moisture before going any further. A whole-house dehumidifier will work, but may not be necessary. One Infinity customer of ours called and complained of water dripping from his upstairs supply grilles. I traced the problem to a drip from the washing machine hose bib in the upstairs laundry room. Just saying. Also, something to keep in mind is that an air conditioner will not dehumidify at all when it isn't running. Any high indoor RH problems in milder weather are beyond its ability to control. You should find out in a few months whether that's going to be an issue.

[beenthere]

You'll need a portable or dehumidifier whole house dehumidifier for the milder temp days when the A/C isn't running.

[teddy bear]

I'm deciding whether I need a separate whole-house dehumidifier (eg, an Aprilaire 1750) to supplement my new Carrier Infinity HVAC system.

My HVAC system will include a 58MVC Infinity variable-speed furnace, Infinity control, and a Performance 24APA7 two-stage A/C. I know that system is designed to control humidty better than other systems, but is it enough to achieve ideal humidity levels during the summer?

Some relevant factors: I live in the Washington DC area (hot, muggy summers), my home is extremely tight (SIP construction), I have an independently-ducted ERV that will run on low speed continuously, and we prefer a relatively high indoor temperature in the summer (77 degrees, day and night).I'm concerned that achieving an ideal humidity level (~45% RH) with just the Infinity system would force the temperature below the 77 degrees we prefer.

What do you think -- do we need install a whole-home dehumidifier to get what we want? Thanks!

You are presenting a problem that most on this do not understand. You are providing fresh air during the warm, moist time of the year. Add the moisture from the fresh air to the moisture from the occupants adds up to 2-4 lb.per hour moisture during the evenings and rainy days.
I live with the same system that you have. On hot days, properly set-up, it will remove most of the moisture, but evenings and rainy days, nothing. I use a small whole house dehu to maintain <50%RH throughout my home. I setup my t-stat during the day or when I am away from my home. You need a whole house dehu if you want <50%RH. I work for a competitor to Aprilaire. Check out Energy Star ratings for dehus. Honeywell/Ultra-Aire/Rheem etc are much more efficient than most.
Congrats on identifing the need for fresh air in your home during the times of the year when homes do not get enough fresh air. Also to your credit for the need of supplemental dehumidification. This crowd thinks that the a/c will keep you home dry when there is no cooling load. You need 6-8 hours of colling load every day to remove the 3-6 gallons of water on typical summer days to maintain <50%RH. Keep us posted on your results.
Regards TB

[mike_home]

I have two Infinity condensers (24ana7) in 2 ton and 3 ton sizes. The 2 ton cools the first floor (1550 sq ft) and the 3 ton cools upstairs (1650 sq ft).

The Manual J calculation had a heat load of about 2.5 tons for the upper floor. Downstaris came in around 1.7 tons. I was worried the 3 ton unit would be oversized. During the summers of 2009 and 2010 I was able to achieve a humidy level as low as 39%. The cool to dehumify feature works well. It is supposed to go 3 degrees below the temperature set point in order to achieve the humdity level. I never saw temperature drop below my set points (typically 78-79 degrees).

I suggest you try the Infinity first before spending any additional money on dehumidifiers.

[commerce48]

Congrats on identifing the need for fresh air in your home during the times of the year when homes do not get enough fresh air.

This is a SIP house. Builders and buyers of such homes are well aware of the need for fresh air, and depending on climate, dehumidifiers.

[teddy bear]

I should that my a/c gets my home down to 45%RH. But when there no cooling load and the outside dew points are +65^F and I have an air change every 5-6 hours, the inside %RH rises rapidily to +65%RH. Home that are able to stay dry when the a/c is not running hard, do not have any real fresh air change.
Homes with proper air change like an air change 4-6 hours will be dry in the winter and as wet as outside unless enough moisture is removed to offset the moisture in the fresh air. Plus the moisture from the occupants is about .5 lbs.per hour per occupant. The exception is +4 occupants in the winter add 2 Lbs. of moisture per hour which is enough humidification to humidify 70-80 cfm of fresh air. In all other cases, humidification to maintain +35%RH with <20^F winter and dehumidification is needed when the outdoor dew points are +60^F spring-fall. This is ideal for comfort and mold/dust mite free interior.
This is the next step in comfort (+35%<50%RH) and indoor air quality (pollutant free and no mold/dust mites).
Regards TB

[BaldLoonie]

Let's say it is a muggy 72° evening and you are set to 77° inside. The A/C won't run much, even being 2 stage, since low is 75-80% of high in most cases. So if it isn't running, it isn't dehumidifying. I'm betting if you want a dry house, it will take more than an A/C, no matter how fancy the controls are. I keep the house cold so the A/C runs like crazy, even with dehumidify on demand, if really steamy I bet I could not achieve 45% RH. Usually it is in the lower 50s.

Try without but I'd bet to really be dry, it will take a whole house dehum. Or keep it a crisp 68° like I do :D

[luxuryheatingco]

If humidity control is as important as it appears to be, start with the Infinity 21 Air Conditioner. We install Trane and Carrier equipment and we haven't seen anything better at moisture removal than the Infinity 21 - although a Performance 17 is a 2 stage compressor, the Infinity technology at the furnace, control and air conditioner is unparallel.

[Andrew G]

Thanks everyone for your replies!

I think I'll give the Infinity system alone a chance, as many of you suggest. Doesn't hurt, as I can easily add a WH dehumidifier on short notice if it isn't enough (and I'll look at the brands that teddy_bear suggests).

I'm a bit concerned about luxuryheatingco's implication that the Performance 24APA7 won't allow me to capture the benefits of Infinity dehumidification. I thought that since it was 2-stage and Infinity-capable, I wouldn't be sacrificing on dehumidification benefits. Am I mistaken? Sounds like mike_home has the same 24APA7's as I would have, and his work great at keeping humidity low even at relatively high indoor temps. I really would like to avoid spending the extra$ to upgrade to 24ANA1's ($x 2 units).

Thanks again to everyone.

[hvacrmedic]

Thanks everyone for your replies!

I think I'll give the Infinity system alone a chance, as many of you suggest. Doesn't hurt, as I can easily add a WH dehumidifier on short notice if it isn't enough (and I'll look at the brands that teddy_bear suggests).

I'm a bit concerned about luxuryheatingco's implication that the Performance 24APA7 won't allow me to capture the benefits of Infinity dehumidification. I thought that since it was 2-stage and Infinity-capable, I wouldn't be sacrificing on dehumidification benefits. Am I mistaken? Sounds like mike_home has the same 24APA7's as I would have, and his work great at keeping humidity low even at relatively high indoor temps. I really would like to avoid spending the extra $ to upgrade to 24ANA1's ($ x 2 units).

Thanks again to everyone.

The difference wouldn't be noticable. The variable blower speed is the primary mechanism for extra dehumidification.

[teddy bear]

Thanks everyone for your replies!

I think I'll give the Infinity system alone a chance, as many of you suggest. Doesn't hurt, as I can easily add a WH dehumidifier on short notice if it isn't enough (and I'll look at the brands that teddy_bear suggests).

I'm a bit concerned about luxuryheatingco's implication that the Performance 24APA7 won't allow me to capture the benefits of Infinity dehumidification. I thought that since it was 2-stage and Infinity-capable, I wouldn't be sacrificing on dehumidification benefits. Am I mistaken? Sounds like mike_home has the same 24APA7's as I would have, and his work great at keeping humidity low even at relatively high indoor temps. I really would like to avoid spending the extra$ to upgrade to 24ANA1's ($x 2 units).

Thanks again to everyone.

Fair enough. Get a %RH meter like the Acruite wireless with remote meters for less than $40. Includes remotes. Put one in the basement and one outside. Keep the main unit on the counter in your kitchen. Let us know what the home conditions are as the outdoor dew point rise this spring. You find it interesting. As the outdoor dew points rise above 60^F, the indoor %RH in the cool basement will be +70% with a 65^F basement temps. You should maintain <50%RH ideally. When the basement reaches 70% without any cooling load, ask these a/c guys what to do?
If the +60^F outdoor persist as they sometimes do, the basement will get smelling like a basement in a couple years of +65%RH. While maintaining <50%RH will make the basement the nicest space in the home. I Gutted my carpeted basement before I figured this out 15 years ago. Carpetting and all the other nice things without any basement smells is great.
Keep us posted.
Regards TB

[mike_home]

Thanks everyone for your replies!

I think I'll give the Infinity system alone a chance, as many of you suggest. Doesn't hurt, as I can easily add a WH dehumidifier on short notice if it isn't enough (and I'll look at the brands that teddy_bear suggests).

I'm a bit concerned about luxuryheatingco's implication that the Performance 24APA7 won't allow me to capture the benefits of Infinity dehumidification. I thought that since it was 2-stage and Infinity-capable, I wouldn't be sacrificing on dehumidification benefits. Am I mistaken? Sounds like mike_home has the same 24APA7's as I would have, and his work great at keeping humidity low even at relatively high indoor temps. I really would like to avoid spending the extra$ to upgrade to 24ANA1's ($x 2 units).

Thanks again to everyone.

Andrew,

I think it is the opposite as to what you have stated. I believe the 24ANA7 (aka 24APA7) uses a two-stage reciprocating compressor. For the 3-ton size the split is about 58% for the low stage. In comparison the 24ANA1 is a two-stage scroll compressor with a split of about 70% for the low stage. It would seem to me you would get better dehumidification with the 24APA7 since you should be able to achieve longer run time without having to drop the temperature.

You can verify the ratings of these units from the Carrier product data documents.

[Advanced Response]

Mike,

The unit that used the bristol 2-stage reciprocating compressor was the 24ANA7 but the new model is a 24ANA1 that uses the scroll unloading compressor... The new 24APA7 uses the same scroll unloading compressor.. The bristol 2-stage recip is gone in all new carrier units..

The currect 24ANA1 is the true infinity model, whereas the 24APA7 is just a comfort economy model that also has the communicating board installed to make it communicating.. The 24ANA1 is the flag ship unit..

J

[mike_home]

Mike,

The unit that used the bristol 2-stage reciprocating compressor was the 24ANA7 but the new model is a 24ANA1 that uses the scroll unloading compressor... The new 24APA7 uses the same scroll unloading compressor.. The bristol 2-stage recip is gone in all new carrier units..

The currect 24ANA1 is the true infinity model, whereas the 24APA7 is just a comfort economy model that also has the communicating board installed to make it communicating.. The 24ANA1 is the flag ship unit..

J

The Carrier web site lists 24APA7 as Performance series model with a two-stage scroll compressor. I thought Carrier had relabeled the Infinity 24ANA7 as a Performance model and gave it a Performance exterior case. Perhaps one of the Pros who is more knowledgeable can shed more light on this.

The 24ANA1 has been around for a few years. I had an option to buy this in 2009. The only advantage I saw of the 24ANA1 was an 18.0 vs. 15.5 SEER rating. I couldn't justify the add extra cost for the summer temperatures in my area.

[luxuryheatingco]

I apologize if you interpreted my suggestion that the 24APA7 isn't a good system - while it is certainly an upgrade over a single stage unit, the 24ANA1 has the ability to run at lower capacities in first stage and the dehumidification-on-demand is more effective than the 24APA7. For the 3 ton example from mike_home, the ratings for a 24APA736 show first stage at 29,200 b.t.u.'s while the 24ANA136 produces 26,200 b.t.u.'s (this is with the exact same furnace and indoor coil for both ratings). Will 3,000 b.t.u.'s be a night-and-day difference, perhaps not but one additional fact to keep in mind is that if operating sound is any concern, the 24APA7 operates with quite a bit more sound than the 24ANA1. With a two stage air conditioner, you're run times will be much longer (if sized correctly), therefore more operating sound.

Also, the ANA7 was reconfigured / relabeled as the APA7 because of the Infinity cabinet - in order to qualify this model for the tax credits, Carrier couldn't get sufficient airflow across the outdoor coil. By using the new cabinet, they were able to meet the necessary efficiency requirements. This is also why the 24APA7 operates with more sound: cheaper cabinet = more sound.

[Advanced Response]

I deal with carrier on a daily basis.... The 24ANA7 was discontinued..Period.. It was a infinity cabinet with the two stage recip compressor..

When the 24ANA7 was discontinued they developed a economy model two stage scroll unit in the comfort line the 24ACB6 then they wanted to have a basic two stage scroll model that would be infinity capable so they took the 24ACB6 added a communicating circuit board and a compressor jacket and then the 24APA7 was born...

In two stage carrier units.. Totally basic 24ACB6, Infinity control basic 24APA7 then you have the Flagship Infinity 24ANA1... All the units use the Copeland unloader Compressor to achieve 2 effective stages..

The 24APA7 is not a bad unit but it is not in the same category as the 24ANA1 on any level..

J

When the 24ANA7 was still around that was my preferred unit,, I have one in my own home.. Great unit but discontinued..

[tedkidd]

... and in 6 months it'll all be inverter driven.... Can't wait!

In the meantime you have 2 choices: Spend money on a dehumidification system, or wait and see. I was really glad to see TB recommend measuring and tracking and would like to reinforce that advice:


Fair enough. Get a %RH meter like the Acruite wireless with remote meters for less than $40. Includes remotes. Put one in the basement and one outside. Keep the main unit on the counter in your kitchen

It sounds like data logging would be of value to you. Here's a cool logger:

http://www.welserver.com/