Wife's Running Out of Patience

[jcurryfl]

Help! My 12 yr old Carrier unit had a compressor burnout a couple of weeks ago and I'm trying to decide what to do. The cost to repair the existing unit is not cheap so I'm leaning towards replacing both the outdoor unit and the airhandler (which isn't cheap either but it's all relative I guess). I had 4 companies give me qoutes on varies brands and price levels within each band (13-17 SEER, variable speed versus single, 2 stage compressor versus single, etc). Quoted sizes ranged from 3-4 tons. Some of the companies pointed out issues with my existing duct work, some didn't mention it at all. After digesting the various quotes, I think I've settled on one of the companies to do the work based on what I perceive to be the most thorough job of evaluation. There are still 2 areas I'd like help with. 1) The company I've selected is insisting a 4 ton unit is needed based on their calculations but it seems on the high side to me and 2) they've offered 3 options, 2 based on Carrier equipment and 1 based on Lennox (they also carry Trane) and I'm not sure which one to pick.

Info on current system: 1996 date code
Carrier 3.5 ton (38YCB042300)
Carrier 4.0 ton airhandler (p/n FC4BNF048000AEAA)

House Info:
Total sq ft = 3200
Location: Orlando Fl, east west orientation with lots of single pane glass
This A/C unit services approx 1260 sq ft of the total house and includes kitchen, dining room and large great room with high cathedral ceiling. Current return is too small for the existing 3.5 Ton unit and located in the kitchen. The estimator recommend almost doubling the size and moving it 2/3 up the great room to pull the hot air out of the cathedral ceiling area.

Options:

1) 4 ton Carrier Infinity 16 (25HNA648A) with variable speed airhandler (FE4ANB005)

2) 4 ton Carrier Comfort B (25HCA348A) with variable speed airhandler (FV4BNF005)

3) 4 ton Lennox (XD-19-048) with variable speed airhandler (CBX32MV-048)

Both the Infinity and Lennox have a large rebate which makes them very close in cost to the Carrier Comfort B. The Lennox 17 SEER and Carrier Infinity 15.8SEER quoted costs are virtually the same so which is the better value when considering the differences in efficiency and quality / reliability of each brand?

Any advice is greatly appreciated since the wife is over my analysis paralysis!!

[RyanHughes]

4 tons for 1260 sq. ft.?

I see that you are in Florida with lots of glass, but 4 tons still sounds like a lot. Only a load calculation will tell. I can tell you that for my house, which has around 3500 sq. ft. of conditioned living space, 3.5 tons does just very well cooling and dehumidifying. I do have shade, though, and I'm not in Florida. Just trying to give you an idea.

If they did a load calculation, ask to see the results in writing. Looking at ductwork and making proper modifications is important. It looks like this company plans to make some changes for improved performance out of the system. For a 4-ton system, I'd recommend more than 1 return, but that's my opinion.

With your climate, I think the Carrier Infinity or Lennox Signature Series systems would be the better choices. What thermostat is included with the Lennox? The 60% capacity of the Infinity 16 on low stage makes it an attractive choice for your climate and potential oversize.

[jcurryfl]

Ryan - thanks for the response. I'm somewhat concerned anout the size as well since the current unit is 3.5 tons but the company measured all the windows, sq footage, went up in the attic, noted orientation of house and effect of of the great room cathedral ceiling which peeks around 20 ft. The kitchen and dining room are 8 ft ceilings but everything is essentially one big room. I haven't asked to see the actual calc's. Two of the companies (including the one I think I'm going with) noted the current single return is sized for a 2 ton unit. I don't know if they intend to add another return high up in the great room and keep the existing return in kitchen or simply replace the one in the kitchen with a single return in the great room - I'll ask.

Thermostat for the Lennox option was a 7000 digital / programmable.

Thanks again.

[barriehie]

Down the road be aware that repair costs on a Carrier are probably going to be higher than on a Lennox.

Barrie

[jims2321]

JcurryFL,

I feel your pain. As I live in lovely Central Florida also. I have a pair of older (about 10 years old) Carrier units (SEER 10's). Since my home is a split level they did two units 2.5 ton for upstairs (700 sqft) and 3.5 ton for downstairs (1700 sqft). In our area, they tend to oversize to compensate for the near 100% humidity during the summer that really lowers the heat exchange between the air and the heat pump. But I would recommend that if you are still worried about the oversizing, then ask more questions.

Jim

[RyanHughes]

JcurryFL,

I feel your pain. As I live in lovely Central Florida also. I have a pair of older (about 10 years old) Carrier units (SEER 10's). Since my home is a split level they did two units 2.5 ton for upstairs (700 sqft) and 3.5 ton for downstairs (1700 sqft). In our area, they tend to oversize to compensate for the near 100% humidity during the summer that really lowers the heat exchange between the air and the heat pump. But I would recommend that if you are still worried about the oversizing, then ask more questions.

Jim

Oversizing is actually worse for humidity control. The shorter cycles satisfy the thermostat's setpoint before being able to remove enough humidity (latent heat). There are, however, thermostats that are better at controlling humidity and actually have humidity setpoints. Longer run cycles help with humidity removal, and that's where a properly-sized dual-stage unit really helps (running in low stage). That's not to say a properly-sized single-stage unit can't provide adequate humidity control.

[Mr Bill]

Down the road be aware that repair costs on a Carrier are probably going to be higher than on a Lennox.

Barrie

Now how on earth do you figure that?

[RomulanSpy]

Down the road be aware that repair costs on a Carrier are probably going to be higher than on a Lennox.

Barrie

You are Carrier dealer or installer give him a heads up right?

[dash]

jcurry,

3.5 sound high,how did the old system do,run a lot on hot days ,or not?


What tonnage is the other system?

Did they measure the peak of the cathedral?

[t527ed]

not sure on the carrier stuff but the Lennox is a 2 stage unit, if load calc is 3 1/2 ton you would have to step up to the 4 ton unit.

unit is XP-048 not XD

with a v drive blower and proper thermostat it will dehumidify very well.

[RyanHughes]

not sure on the carrier stuff but the Lennox is a 2 stage unit, if load calc is 3 1/2 ton you would have to step up to the 4 ton unit.

unit is XP-048 not XD

with a v drive blower and proper thermostat it will dehumidify very well.

What can the ComfortSense 7000 (L7742U) do to dehumidify? Just curious if it has similar abilities to the VisionPRO IAQ.

[m kilgore]

The Comfortsence will bump up the unit to high stage and leave the blower on low stage on a call for dehumidification. This removes more humidity. The IAQ uses low speed compressor and fan.

[jcurryfl]

Dash - It's funny how you never pay enough attention to these details when things are working. It seems to me the unit ran quite a bit and seemed to struggle when the thermal loads peaked in late afternoon, early evening. So I can't say comfort was ideal. I seem to remember the estimator telling the heat load calc came out around 3.5 tons (a tad over) but the system he was recommending (Carrier Infinity & Lennox XP-19 didn't come in 1/2 ton sizes. He elected to go higher based on the high cathedral ceilings (20 ft at peak). Not knowing HVAC that well (that's why I'm here), it seems as if the 2-stage Carrier would give you the best of both worlds. I have 2 other A/C units. I'm not the original owner but the original floorplan was ~ 2400 sq foot ranch style house with a great room splitting the house into 2 halfs. I assume since there's not a good way to run duct work through the catherdal section they put in 2 separate units. One 3.5 ton and one 2 ton unit for the bedrooms on the other end of the house. Sometime in 90's, the previous owners added on an 800 sq ft master suite and bath. They put in a third unit (2-ton) to handle the addition. So now I have 3 units and a rather large electric bill!

[jcurryfl]

Dash - Funny how you don’t pay attention to these things until it’s too late. From what I recall the unit ran quite a bit and struggled to keep up late in the day when the thermal loads are peaking. Recall that a couple of the estimators believed the return was significantly undersized so I don’t know what effect this would have had. I do remember that the estimator said the load calc indicator the need for slightly over 3.5 tons. I believe he said he went up to the 4 tons because of large cathedral area (20 ft ceilings) and the fact that the Carrier Infinity 16 and the Lennox XP-19 didn’t come in half ton sizes.

The other units (I have in total, ugh!) are 2 tons each. I’m not the original owner but the house is a ranch style built in 1979 and originally had ~ 2400 sq ft. The great room with cathedral ceilings split the house in two and I’m assuming since it was hard to run duct work through the great room that they put in 2 systems. The 3.5 ton cools the kitchen area and great room (~ 1260 sq ft) and a 2 ton cools 3 bedrooms, 2 baths and hall (~ 1140 sq ft). An 800 sq ft master suite and bath was added in the early 90’s. It’s serviced by another separate 2 ton unit. End result I have 3 units (total 7.5 tons) to cool 3200 sq ft.

[smittyii]

i can't see the need for a 4 ton, but maybe the contractor knows something we don't. i also don't see why u need to remove the heat from a cathedral ceiling. does someone have a hammock strung across it for sleeping? high ceilings are dead space unless they have windows (heat gain) in fla. you want living space conditioned.

[smittyii]

Down the road be aware that repair costs on a Carrier are probably going to be higher than on a Lennox.

Barrie

they must have a lennox parts house on every corner in las vegas!

[Freezeking2000]

they must have a lennox parts house on every corner in las vegas!

[/I]

cant buy lennox parts in Ct

[jcurryfl]

Thanks for everyone's inputs. Sounds like I need to have the company run through the load calc's and convince me that 4 tons is the right answer. If I went with the 4 ton Infinity 16 with the 2 - stage compressor, would the unit spend most of the time effectively running as ~ 2 ton unit with the 2nd stage available for peak summer heat loads? Would the Lennox XP-19 operate the same? Still not sure which config is right for my situation.

[RyanHughes]

Thanks for everyone's inputs. Sounds like I need to have the company run through the load calc's and convince me that 4 tons is the right answer. If I went with the 4 ton Infinity 16 with the 2 - stage compressor, would the unit spend most of the time effectively running as ~ 2 ton unit with the 2nd stage available for peak summer heat loads? Would the Lennox XP-19 operate the same? Still not sure which config is right for my situation.

If the unit is properly sized, it should spend a good amount of time in low stage. The XP19 will have more capacity in low stage with the scroll compressor. I just recently learned from someone here that to dehumidify, the ComfortSense 7000 will keep the blower on low and bump the unit outside to high stage to provide more dehumidification. Essentially, they're both good systems. You'll have to weigh all the features and benefits that each has to offer.

[lra]

Everyone has taken all of the good technical replies..so my thunder is gone. All good advice. I'd try to relocate the return in the kitchen though. Kitchens and bathrooms are no places for returns. If your wife cooks like mine, when dinner is burned evey day @7pm, the return let's us enjoy blackened food, with a side of smoke all through the air handler and every room in the house. No return in the bathroom for the same eye burning reasons.