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Replacement Trane system opinion

Posted by weaselorlando (My Page) on
Wed, Mar 12, 14 at 12:35

This is a post from another HVAC forum. I was interested to hear if other professionals had the same opinion about Trane's 2 stage HP's and their ability to dehumidify? Please see my original post and BallLoonie's reply

""I am seeking your opinion on a replacement system for my house. I have narrowed it down to a few options. I am in the Atlanta area. This is an upstairs system change only. Attic installation. Approximately 1650'. Most all the ceilings are vaulted or trayed. The company I plan to use did a manual J and to his surprise came up with 2 1/2 ton system. He did identify the need for more return air and possibly more supply. He plans to evaluate the duct system and make adjustments as needed. New line set will go 3 floors (plus attic) down to be level with walk out basement.

System #1

4656619 Active Systems XR15 WEATHERTRON TRANE 4TWR5036G1 *AM7A0B30H21 1165 36800 12.50 15.00 35200 9.00 21800 1 HRCU-A-CB 297

XR15 2 1/2 ton HP
TAM 7 air handler
8kw aux heat in 2 stages
Trane's Perfect Fit Media cabinet
New line set
Tcon 803 tstat
outside air temp

System #2
7039036 Active Systems TRANE XR17 TRANE 4TWR7036B1 *AM8C0C36V31+BAYCC24V 1230 980 37000 13.00 17.75 33200 9.20 21000 1 HRCU-A-CB 252

XR17 2 stage HP
TAM 8 air handler
8kw aux heat in 2 stages
Trane's Perfect Fit Media cabinet
New line set
Confortlink II tstat
outside air temp

A different company suggested the XR17 with the TAM7. However it was recommended to step up to the TAM8 with the Comfortlink II to gain better humidity control. Its about %15 more for system #2 over system #1. Some of that is for ductwork for the anticipated additional supply that will be needed with system #2 and the upgraded tstat. I didn't get a price on xr17 and TAM7

Is each system matched well with the other components. Is there a better tstat you would recommend for system #1? I don't need bells a whistles just to have them, but I do like remote access to the tstat.

I like the idea of the 2 stage cooling and longer run times. Are the stages split 70 / 30? That would make it 2.1 ton for a 2.5 ton area?
What do you think?""

BaldLoonie

"The 2 stage scrolls run between 70 and 80% on low. It varies by system. Worth the extra? Hard to say. In the past some Trane 2 stage units had a rather low latent capacity (dehumidfication) rate on low stage. Is the 8 worth it with the fancy control? Also hard to say. Less so since you aren't looking at the communicating outdoor units. But it does give more control plus the remote access. As for system 1, using a control that can trigger dehumidifcation on demand is great in a steamy climate. It slows the blower 20% if humidity rises above setpoint. It's what the communicating control does. Using a Honeywell Vision Pro with module or the Prestige IAQ will do this. There are other brands, Aprilaire 8910."

This post was edited by weaselorlando on Wed, Mar 12, 14 at 12:47


Follow-Up Postings:

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RE: Replacement Trane system opinion

BL is right. The latent capacity (as a percentage of total capacity) tends to be lower during low stage operation, as is the case in just about all manufacturers' two-stage scroll compressor systems. The primary reason is the larger indoor coil volume with respect to the condenser output capacity. This is offset somewhat with the longer runtimes provided with a 2-stage unit, and the key is that you don't oversize 2-stage units such that they short cycle in low stage. Also, in my opinion as long as the 2-stage unit isn't (grossly) oversized as per the load calc, this issue is a bit less significant with the Trane Hyperion air handlers with the EEV (and the expanded performance data tend to show it, last I looked). The EEV does a good job accurately metering refrigerant flow under a wide array of operating load conditions to get the coil cold rather quickly and ready to dehumidify quite well. As BL also mentioned, with a good control like the Honeywell VP IAQ, you can have the system wired/configured to decrease airflow 20% when humidity is above set point -- this further increases latent capacity.

A properly sized single-stage or two-stage unit should do a fine job dehumidifying. The two-stage unit will likely give you longer runtimes and greater comfort. A smart thermostat (as mentioned) is a great addition.

This post was edited by ryanhughes on Wed, Mar 12, 14 at 14:43


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RE: Replacement Trane system opinion

edited

This post was edited by weaselorlando on Wed, Mar 12, 14 at 15:01


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RE: Replacement Trane system opinion

Weasel

I agree with what Ryan has said.

On the XR17 system, I do not like the idea of a communication air handler paired with a non communicating HP condenser.

Drop the Tam8 air handler and go with the Tam7 042 size.

For either the XR15 and XR17 system, go with HW VP IAQ thermostat and have dealer set system up for dehumidify on demand.

I also would go for the 10 KW heat strip for 3 ton system.

Also just noticed in quote #1, you state a 2 1/2 ton condenser but have a 3 ton listed in the AHRI matching number. Which is it?

How do you filter your return air?

The XR17 system should cost no more than $750-$1000 over the XR15.

IMO


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RE: Replacement Trane system opinion

Tigerdunes

The 3 ton in system is a 2 1/2 ton. He said he clicked on the 3 ton unit by mistake when he sent me the info.

Is there a rule of thumb for heat strips? This is one of the areas that we have had a problem with from when we built this house. Cold in our bedroom in winter with the system running all night!

We have the Trane's Perfect Fit Media cabinet 5" filter planed.

I have a simular thread on another forum that I have seen you post as well. I am going to add your reply there if you don't mind. You can find it here:

http://hvac-talk.com/vbb/showthread.php?1520691-Replacement-Trane-System&p=17902821#post17902821

This post was edited by weaselorlando on Wed, Mar 12, 14 at 20:10


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RE: Replacement Trane system opinion

"Is there a rule of thumb for heat strips? This is one of the areas that we have had a problem with from when we built this house. Cold in our bedroom in winter with the system running all night!"

Assuming system is operating and sized correctly, the problem you describe has nothing to do with heat strip. It usually is one of poor insulation and/or bad ductwork design/sizing. Ask dealer to take a look and make suggestions for improvement.

What size system are you replacing?

For heat strip primer. Heat strips serve 3 functions. Emergency heat, supplemental heat, and to temper the air on defrost calls. I always like to size heat strip to the defrost function if homeowner does not want cool AC air entering their home on defrost calls. For a 2 1/2 ton, a 7-8 KW heat strip. For a 3 ton, a 10 KW heat strip.

Keep in mind, Trane has the great feature of electronic demand defrost over the cheap time/temp feature that most brands use.

I would get pricing on both of these 2 1/2 ton systems, XR15 and XL15i.

5198250 Active Systems XR15 WEATHERTRON TRANE 4TWR5030G1 *AM7A0C36H31 1050 32200 13.00 16.00 30000 9.00 18700 1 HRCU-A-CB 244 646 Yes

5021599 Active Systems XL15I WEATHERTRON TRANE 4TWX5030B1 *AM7A0C36H31 1050 33400 13.50 16.00 30000 9.50 18700 1 HRCU-A-CB 253 612 Yes

IMO

This post was edited by tigerdunes on Thu, Mar 13, 14 at 7:36


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