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Advise for Replacement System

Posted by tynman11 (My Page) on
Thu, Nov 8, 12 at 14:32

Hello, I have a 2700 SQ foot 2 story house and our upstairs AC unit is leaking and 12 years old so I've decided to replace it. Upstairs is about 1400 SQ Feet. We have a bonus room upstairs above the garage that has always been difficult to heat/cool.

We use a woodstove so haven't used our furance (other than a yearly check-up) in 3 years so I'm leaning on only replacing the A/C side if possible, but realize that I'd need to replace the furnance in order to get the variable fan benefits. Last year we spend $0 heating the house and $600 in cooling during the summer. I've been told that I'd save around $100-$200 a year by upgrading to a 13 or 14 SEER.

So I've gotten a couple of quotes and have gotten conflicting answers from both of them so I'm looking for advice!

Current System:
Condenser - Ruud 10 SEER 2 ton - UAKA-024JAZ
Furnance - Ruud 50k btu - UGDJ-05EAUER

Replacement System:

Company A (did not do j-calc)
Quote 1:
Condenser - Lennox 14 SEER 2.5 ton - 14ACX-30
Coil - CX34-36A

Quote 2:
Condenser - Lennox 13 SEER 2.5 ton - 13ACX-30
Coil - CX34-36A

Quote 1 is about $450 more than Quote 2.

Company B (did j-calc and it came out to 2.25 tons upstairs)
Quote 1:
Condenser - Lennox 13 SEER 2.5 ton - 13ACX-24
Coil - C33

Quote 2:
Condenser - Lennox 13 SEER 2.5 ton - 13ACX-30
Coil - C33
Furance - Lennox Variable Speed 80% 70k BTU - SL280V

Here are the conflicts I've had:
1. Company B states that I cannot support a 2.5 ton condenser with my current furnance and that if I wanted to go above 2 tons (which is what the J-calc recommends) I'd have to replace the entire system. If that's the case I'm not sure why Company A recommended 2.5. I'm concerned that if I go with a 2.5 ton with my existing furnance that the A/C side will suffer damage down the road. Any opinions?

2. Company A said I would have to change out my copper line going from the coil to the condenser. They said it was 5/16" and should be 3/8". Company B said they could reuse it and that you don't need to go bigger unless you're 16 SEER or above. Thoughts?

3. Company B said that if I increased from 2 tons to 2.5 that I'd have to increase my ducting to accomodate. So they priced in increasing the 2 return lines in our bonus room from 6" to 8" and increasing the intake in the same room from 8" to 10". It sounds good because maybe it would help with heating/cooling that room, but does that make sense?

Any other suggestions/recommendations?


Follow-Up Postings:

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RE: Advise for Replacement System

13 SEER is the govt minimum standard.

If you don't have a var speed blower motor, no need going to any AC condenser but a 13 SEER.

I would not have the ACX series Lennox condenser.

If Lennox is the only brand you are considering, go to the XC13 SEER model with best matching Lennox coil.

Bonus room ductwork size should be evaluated both supply and return, size, and insulation properties.

What is your location?

You should find out what the blower motor rating on existing furnace is in
tons.

What size living area does existing system serve? What problems have you encountered cooling this area?

Refrigerant lineset must be sized correctly to match manufacturer specs.

Post back.

IMO


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RE: Advise for Replacement System

Hi tigerdunes and thanks for the response. The furnace I have is not variable speed. The blower it has is a 1/2 horse power one and the ratings on it show the cfm range between 600 (low) and 1200 cfm (high) with speed settings of low, med, med-low and high. From what I've been able to find that coorelates to a 3 ton.

I asked the dealer about the difference between the ACX and the XC models and was told that the ACX has the same guts as XC, but that XC has a better protected condenser and a quieter fan. And basically the $800 additional cost didn't justify it. Not sure if that's true or not though.

I'm in Atlanta, GA. This unit will service the upstairs of a 2 story house. The sq ft of the upstaris is 1200 sq ft (thought it was 1400, but actually 1200). The bonus room has 1 8" in intake and 2 6" returns. All walls are R13, ceiling is R60 with radiant barrier. Size of the room is about 350 sq ft.

The ducting is as follows:
Master Bedroom - 1 8" supply and 2 6" returns
Master bath - 1 6" return
Bedroom1 - 1 6" return
Bedroom2 - 1 6" return
Spare bath - 1 4" return
Hall - 1 14" supply
Bonus room - 1 8" supply and 2 6" returns

As far as problems, for the past 3 years we've had to have refrigerant added. This past summer we had to do it twice. The system is 12 years old. We've always had problems heating/cooling the bonus room, but haven't noticed any issues with any of the other rooms.

Looked up the specs on the 13ACX and 14ACX and it specified a 3/8 liquid line so that answers that question!

Thanks again for your assistance!


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RE: Advise for Replacement System

Hi tigerdunes and thanks for the response. The furnace I have is not variable speed. The blower it has is a 1/2 horse power one and the ratings on it show the cfm range between 600 (low) and 1200 cfm (high) with speed settings of low, med, med-low and high. From what I've been able to find that coorelates to a 3 ton.

I asked the dealer about the difference between the ACX and the XC models and was told that the ACX has the same guts as XC, but that XC has a better protected condenser and a quieter fan. And basically the $800 additional cost didn't justify it. Not sure if that's true or not though.

I'm in Atlanta, GA. This unit will service the upstairs of a 2 story house. The sq ft of the upstaris is 1200 sq ft (thought it was 1400, but actually 1200). The bonus room has 1 8" in intake and 2 6" returns. All walls are R13, ceiling is R60 with radiant barrier. Size of the room is about 350 sq ft.

The ducting is as follows:
Master Bedroom - 1 8" supply and 2 6" returns
Master bath - 1 6" return
Bedroom1 - 1 6" return
Bedroom2 - 1 6" return
Spare bath - 1 4" return
Hall - 1 14" supply
Bonus room - 1 8" supply and 2 6" returns

As far as problems, for the past 3 years we've had to have refrigerant added. This past summer we had to do it twice. The system is 12 years old. We've always had problems heating/cooling the bonus room, but haven't noticed any issues with any of the other rooms.

Looked up the specs on the 13ACX and 14ACX and it specified a 3/8 liquid line so that answers that question!

Thanks again for your assistance!


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RE: Advise for Replacement System

sry for the dup post. I hit refresh! :(


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RE: Advise for Replacement System

Sorry, wall insulation is actually R19. We also have 7 double pane vinyl windows facing NE, 1 facing ES, 2 facing SE.

Also, again, sorry for the confusion, but I got my calcs wrong and the upstairs is 1400 not 1200!


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RE: Advise for Replacement System

A couple of ideas.

First are you satisfied with the performance of existing furnace? If so you need to determine the blower motor rating in tons. Is it a two ton or three ton? I tried to find it but couldn't. A Ruud orReem dealer should be able to tell quite easily over the phone.

I assume all ductwork both supply and return(s) for the second floor is easily accessible.

You may be borderline for a two ton AC condenser but if you do elect a 2 1/2 condenser, you need a furnace that has a 3 ton blower motor rating.

Again I would not have the ACX series Lennox condenser.

If keeping the furnace, I would get a Ruud or Rheem dealer involved in the new condenser selection.

Lineset has to be right size. Close does not count.

What are you doing about filtering your return air? How any returns do you have on this system?

Post back.

IMO


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RE: Advise for Replacement System

We actually don't use the furnace. We burn 24/7 with the woodstove during the winter. We turn it on a couple of times a year for maintenance, etc. When we have used it we're pulling 105-115 degree heat from the registers.

The fan appears to be rated as a 3 ton fan. It's 1/2 horse and can pull just over 1200 cfm on high. I've contacted RUUD, but the only option was through their site so I'm waiting to hear back. I did contact Company A and asked the specific question yesterday on this and he said it was 3 ton as well which seems to coorelate to the numbers on the fan I just provided.

Some of the ductwork is easily accessible, but some of it is not since we have blown in R60 in the attic. Was hoping to avoid disturbing it, but may not have a choice.

For filtering we have a washable filter at the beginning of the return (not sure of the brand/type) and a filtrete 1900 filter at the end.

For returns we have:
1 14" in the hallway
1 8" in the bonus room
1 8" in the master


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RE: Advise for Replacement System

Well ,if blower motor is actually rated at 3 tons, then no problem going up to 2 1/2 ton AC condenser.

You should only use one filter not 2. Use the one at return end only.

Since the heating portion of the furnace is not being used, just the blower in AC cooling s being used, No need to replace furnace.

Dealer should evaluate your ductwork system to see if it can handle the extra CFMs from a 2 1/2 ton condenser.

I would look into installing a good 13 SEER AC condenser-either Ruud or Rheem.

IMO


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RE: Advise for Replacement System

Thanks tigerdunes, any option on going with 2 vs 2.5 ton? I know it's probably alot more involved than the info I've provided but figured I'd ask.

Thanks again!


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RE: Advise for Replacement System

Not sure I am understand your question. I would say you are in a borderline situation between the two sizes.

Bonus rooms are notorious for difficulty in both heating and cooling. Usually insulation and ductwork design/sizing issues.

Please explain how a wood stove heats the second floor comfortably. Where is wood stove located?

IMO


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RE: Advise for Replacement System

I guess I'm concerned that if I go with 2.5 that I won't be able to dehumidify sufficiently, but if I go with 2.0 that I won't be able to keep up with cooling.

With the wood stove, it has a fan that sucks in the cold air and moves it under, behind and above the stove heating it along the way. Combine that with the radiant heat and it puts out 70k btu. There's an open stairway to the 2nd floor that acts like a wind tunnel to transfer some of the heat upstairs and we also have a couple of chase wall ducts with inline fans help too if it gets too toasty downstairs. Ceiling fans help too.

I also did a sealing job on the house using caulk/foam to seal up as many holes/cracks I could find in the attic, walls, doors, windows, etc plus put in R60 blown in insulation and radiant barrier in the attic. This is another reason why I'm concerned on 2 vs 2.5 ton as the house transfers heat/cold more slowly now.

On a 30 degree day we'll have 78 degree temps downstairs, 74 upstairs and about 70 in the bonus room because it's upstairs on the opposite end of the side of the house.

We save money on heating, we're also more confortable because if we used the furnance there's no way we'd keep it on 78 because of the cost and, for us, it has an ambience factor as well. Alot of work though gathering wood, but it's good excercise! :)


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