Good afternoon gentlemen.
I am seeking input/advice on my current HVAC situation and replace what I currently have.
2007, 4 ton Goodman, single speed air handler.
Evaporator issues with Goodman...currently leaking as well. Thankfully i am not at a complete breakdown.
Current Avg humidity in home with current system is 40-45%. Daytime comfort is at 76`, evening comfort 9p-6a, 70`.
2008 Home is 1600 sq ft., Asphalt shingle roof, CBS construction, on concrete slab, single hung/payne windows, single floor.
Climate is Ft.Myers FL
.53 static pressure. (.4 return / .13 supply)
Proposed systems from 2 companies:
Option 1--Lennox 3 ton: XC 14-036 (CU), CBX32MV-036, Variable speed. (AH)
Option 2--Lennox 3 ton: XC14-036 (CU), CBX27UH-036, Soft start (AH)
10 yr parts warranty, 1 year labor.
Didnt mention ductwork remediation.
Option 1--Carrier 3.5 ton: 24ABC642A003 (CU), FX4DNF049T00 (AH), high efficiency.
Option 2Carrier 3.5 ton: 24ABB342A003 (CU), FX4DNF043T00 (AH) high efficiency.
10 yr parts warranty, option 1 is 5 yr labor, option 2 is 1 yr.
Duct work remediation offered at additional cost.
Other system proposal provided, but out of budget.
Both companies are NATE certified, high marks on consumer satisfaction.
Both did manual j calculations.
Thank you for your time,
The XC14 is a step up Lennox model, rating at 15.00 SEER and 12.50 EER with the 32 variable speed blower. It does even better with the 27 fixed speed blower with 16.00 SEER and 13.20 EER which gets you the federal tax credit.
The Carriers are builder models. The 642 gets 15.00 and 12.50 with the FX4 fixed speed blower. The 342 gets 14.00 and 11.50 with same blower.
What is the Carrier dealer doing with the ductwork? I assume it is all flex in the attic.
Sizing is interesting, you say both did Manual J's huh?
Help me understand why you're not having the six year new system repaired rather than replacing it? Coil should still be in warranty? Efficiency upgrade perhaps?
Bobster- 3 evaporator coils, all replaced due to leakage of r22. last one lasted appx 3 years, no warranty...I think I've spent enough.
Baldloonie- manual j that's what they said. The difference? I haven't had an opportunity to ask. What baffles me is if my static pressure isn't good, and contractor knows this, why would they use a 4 ton air handler?
Duct work is flex. Biggest issue is accessibility; the is very little room. I'll have to open up the ceiling for another access point. From what was explained to me, I need extra return.
Are Lennox and Carrier evap coils comparable in build and material quality?
I have a friend in the industry and he has stated 3 ton would run excessively, especially for the comfort of 70* at night, not to mention increased power usage.
Thank you for the input , I'm trying to make the best decision I can with the info you guys provide.
The blower in the 49 air handler should be set to the size of the A/C, in this quote 3.5 tons. For a humid climate, you'd run closer to 350 CFM per ton so you won't be moving 1600 CFM.
As for your friend, he's wrong on the increased power usage. A smaller unit running non stop will use LESS juice than a bigger unit cycling a lot. First, the smaller unit uses less juice per hour of running but what really is inefficient is constantly starting & stopping. Usually takes about 10 minutes to get today's units up to full efficiency so if they run more and cycle less, more efficient. Will a 3 ton not keep up? Did he do a load calc (Manual J)? If not he doesn't know. Do you keep it 70 inside? Do the 2 other dealers know this? Industry standard is to size to 75 inside so they would need to adjust their numbers if you want it 70.
The Carrier quoted is a lower line unit than the Lennox. Carrier has the Performance series more like the XC14.
Id be willing to bet no one has even checked the static pressure.
If one adjusts a calc to address 70'F for nighttime, one would also need to negate the insolation heat gain AND
Originally Posted by BaldLoonie
adjust to a night time temperature of ~ 84'F.
____________________________ . .
It's Not Rocket Science, But It is SCIENCE
with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE
Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities
If your current air handler is moving 1600 CFM at the posted static pressures. then a 3 ton system moving 1200 CFM through the same duct work would have a static pressure of .226" return, and .073" in the supply.
Originally Posted by SWFloridaGlades
A/Cs are designed to be able to run 24/7 with no harm to them. Basically, a 3 ton 13 SEER running for 4 hours won't use anymore electric then a 4 ton 13 SEER running for 3 hours.
Guys, just to be clear, the call for 70* temp starts at 10p ends 6a. Then program set to rise to 77* till 7p. 7p till 10p I set for 73*.
Baldloonie- you are close at stating the system turning on & off. When thermostat kicks, at any temp, the most it will run is 11-13 minutes once set temp is reached. However the run time is longer when say 7p /10 p is reached. It runs 45 minutes to an 1- 1.25 hrs. and then 11-13 minutes on and anywhere from 15-30 minutes off. Hope I explained that clearly.
Sbkold-.53 static pressure. (.4 return / .13 supply). Using my current 4 ton system.
Dan sw fl- can you rephrase?
I thought this process would be easier!
Again, thank you for the replies. I can think of no other was to get unbiased info.
Sizing isn't an exact science. Normally you size for the typically hot time of the year - each city has a design temp, usually a bit lower than the hottest day of the year. Then you size to what you want it indoors during the day. So that outdoor temp used might be 95 for the heat of the day and 75 inside. But to size for cooling at night, you really oversize to get it 70 if using 95 out since it won't be 95 at night. So Dan is saying 84 might be a more typical night temp. But sizing to that throws things off as well. So sizing to the normal day conditions then understanding it will take some time to hit 70 at night is likely the best bet.
I keep it pretty cold at night too, usually 68. Crisp! The machine gets a good workout!
Baldloonie- I understand now. Low 80s is accurate summertime nighttime temperature in my zone.
The coolest temp I would ever have daytime is 75. And again I do use a programmable thermostat.
So, I seem to notice a consensus , regarding a 3 ton system being appropriate for the home, given the facts I have provided.
I'm going to speak or email the 3 ton contractor regarding how he reached 3 tons...I'm also going to ask him about the evap coil durability. I guess I'm a bit anxious about coils, given my luck with goodman.
I'm not really thrilled about builder grade anything.
At 3 tons, does it make sense to request variable speed or a fixed speed AH given my current pressures?
Anything else guys?
VS helps more with humidity removal, then a fixed speed.
Lennox- CBX27UH-036, air handler, is a direct drive/ soft start.
How does this compare with variable speed?