A/C out - need to decide on new system NOW!! Opinions please

[sparksandfan]

Manual J is considered to already have a safety factor built in.

105*F design temperature instead of 100*F adds a half-ton. Since 100* is the 0.4% point, it is considered an extreme point in terms of time temperature exceeded.

Winter design temperature is normally taken as 17*F.

[beenthere]

A non IQ Westinghouse with VS drive will not dehumidify as well as A 2 stage Carrier 50/100 will with the Infinity control. The carrier will have better blower control.
Thats why it cost more. Plus the Carrier name.

[rhb4321]

You guys are great!! Thanks for all of the advice. My trusted HVAC repair guy came out today and found a small leak in the condenser coil, so dumped in some R22 to get us working again until I can figure out what to do. So I've got a little breathing room, but still need to replace the system asap. SO that means I'm gonna keep asking questions....

My Westinghouse dealer is going to quote an IQ system, so will see how painful that option would be....otherwise, it sounds like the consensus is to go with the Carrier system, even though it's a lower EER (which is what I understand that I should really care about for energy efficiency, being in Dallas). So, help again; is the Carrier more about comfort?? Thanks again!!!

[beenthere]

You set your thermostat to a temp that you are comfortable at, correct.

If you only set it as cool as low as needed so as not to die from heat stroke or exhaustion you don't need a system to provide comfort.

[rhb4321]

Sorry, don't understand your question......

[beenthere]

Are you buying a system just to cool the air. Or are you buying a system to keep you comfortable.

[udarrell]

You guys are great!! Thanks for all of the advice. My trusted HVAC repair guy came out today and found a small leak in the condenser coil, so dumped in some R22 to get us working again until I can figure out what to do. So I've got a little breathing room, but still need to replace the system asap. SO that means I'm gonna keep asking questions....

My Westinghouse dealer is going to quote an IQ system, so will see how painful that option would be....otherwise, it sounds like the consensus is to go with the Carrier system, even though it's a lower EER (which is what I understand that I should really care about for energy efficiency, being in Dallas). So, help again; is the Carrier more about comfort?? Thanks again!!!

Earlier, you indicated the existing duct system was inadequate.
If the duct system was only delivering 2.5 or 3-ton of airflow through the coil that is what your 3.5-ton unit would deliver.

It is extremely important that you are renovating the duct system.

However, I would look at where I could reduce the heat-gain/heat-loss so you could use a 3-ton condenser. You could always do more reductions if it didn't handle it well enough.

I checked the Dallas summer conditions & it indicated 31% Relative Humidity, which means it should deliver a high sensible ratio. I know there are times when humidity will be high.; that is when you need longer run times.

If you chose equipment & contractor wisely, you may save enough to do the reduction in heat-gain which beats paying more for supposedly higher SEER Ratings, etc.

The decision is yours, if it were me, I would thoroughly analyze all the options!
http://www.udarrell.com/airconditioning-sizing.html
- Darrell

[rhb4321]

Absolutely, fixing the ductwork is a must-do to get things working properly. I've been mostly focused on EER, as the SEER rating methodology doesn't fit Texas summer weather. I thought 12.5 or more was a good target, but the Carrier config I have been quoted is only at 11. Is this difference meaningful, or will the 2 speed operation make the Carrier more efficient?