Furnace & A/C Replacement in Birmingham, AL

[KyBrewer]

I think I have decided on a contractor to do the work, but I would like some opinions on the setup.

Current Stats:

~1600 sq ft. house, built in 1910. Attic insulation is about 8-10" thick blown fiberglass. Original wooden single pane windows with storm windows. Cellar/Crawlspace with furnace/condenser coil of split system.

Furnace is Ducane, 1999 model, 80% efficient, rated 80,000 BTU output. A/C is Goodman, 1989 model, 10 Seer. Both are in working order so I don't have to be in a hurry.

I went back and forth between getting both vs. only the A/C replaced. It seems a shame to do only do the A/C so I'm leaning toward both. I have been through quotes with 4 contractors and I originally wanted to get a higher end unit but I was told by one contractor that my ducts are too small for the 4-ton unit (currently sized for more of a 3-ton unit) and he recommended replacing them. No contractor has done load calculations, all have recommended replacing with 4-ton unit. At that point I found this site, as well as the HVAC-Calc software, and proceeded to do my own numbers. The software told me that my house is borderline 3.5 ton unit (42,000+ BTUH Gain). As for the furnace, 67,000 BTUH Loss.

Bottom line is I'm having a hard time justifying the cost of a high end system and new ductwork. As an alternative lower end system, I have been quoted the following:

A/C: Bryant 123ANA048000
CC: CNPVP4821ATA
FURNACE: Bryant 340AAV060110

Any comments, positive or negative on this setup?

The specific areas of ductwork he has talked about replacing have some cooling issues in the summer (bedroom with south-southwest exposure, kitchen with laundry adjacent) I tried to use the duct sizing on HVAC calc but I'm having trouble finding the CFM output on this particular furnace. I'm actually having trouble finding much of anything on this particular furnace. He tells me its roughly the older model Legacy Line (equivalent to the 350AAV, which is brand new?).

Also, I am hesitant to use a heat pump due to the age of the house. Is that ridiculous for me to think that way? I don't know that it will every be more tightly sealed that it is now.

Please help, and ask questions if more info is needed. Sorry the post is so long.

[catmanacman]

a low end system with a properly sized duct system will out perform and outlast a high end system with a under sized duct system at 10 years old mabey keep the furnace and do a condensor and evap coil and new duct system also add about 10 more inches of insulation to the attic

[KyBrewer]

That was one of the main reasons I think I'll use this contractor. He told me pretty much what you did with regards to the lower end system and new ducts vs a high end system only. Although, I gathered a lot of that from my own research and just asked questions to test him.

I have some rusted through spots on the existing furnace vent, so it will have to be replaced. My thoughts were with the a/c coil off the top of the furnace and having to replace the vent anyway, why not get a new furnace? Plus I'm told that furnace can vent via pvc out the foundation wall, which I feel is much safer.

I'm struggling with the duct replacement. I've been quoted an amount to "enlarge duct system to 4-ton capacity". I want to make sure that I'm getting the proper sized ducts, or at least very close (if some existing were reused). That's where the cfm info for the blower comes in, which I can't find for certain.

I had a different contractor mention to me that adding a powered attic fan could provide the equivalent of 1-ton cooling capacity. Any truth to that?

[catmanacman]

for attic ventilation get a ridge vent installed if possible also the bryant furnace being quoted is a 5 ton 110000 btu should blow up to 2000 cfm

[KyBrewer]

So if he's quoting a 110,000 BTU input furnace that's more than 90% efficient, I should expect a BTU output of ~99,000 BTU?

If that is the case, and I currently have a 100,000 BTU input furnace that is 80% efficient, I am getting an output of 80,000 BTU.

So is he trying to upsize my furnace? The house heats fine and if that's the case, then I should request he quote a 4-ton furnace with the a/c instead? Or am I missing something? Remember my HVAC-Calc heat loss came back at 67,000 BTUH.

[beenthere]

I miss the part where you said what size your current A/C is.
But it sounds like your getting a larger A/C?

If so, why, isn't your current one keeping the house cool?

[KyBrewer]

The A/C is 4-ton currently. It keeps the house cool, but there are some issues in the back. The contractor I am thinking I will use says the ducts are too small for the 4-ton unit, and has quoted to replace them along with the a/c and furnace. I believe he is speaking primarily of those going to the back. I've been able to semi-confirm this myself using the HVAC-Calc software.

Existing A/C is 20 years old, the furnace is about 10. The furnace vent pipe is rusted through so it would have to be replaced. Rather than have everything apart and replacing the vent line hooking back up to the old furnace, I thought it might be worthwhile to replace the furnace as well. The A/C being 20 years old, I don't want to get caught with my pants down in the middle of the summer.

I don't want a larger furnace or a larger A/C, but it sounds like he might be trying to sell me a larger furnace?

[beenthere]

The one you listed is larger then what you already have.

Ask him to get you one closer to what your house really needs.

Don't fall for that. Well a bigger furnace will recover temp quicker after a set back routine.

[KyBrewer]

Although we live in heat pump territory (Birmingham, AL), I worry that it would be less than adequate in a 100 year old house. There is attic insulation and storm windows, but no insulation in the walls. What are your thoughts on a heat pump in that sort of situation?

[beenthere]

Do you spend a lot of time in the 40 to 65° range.
If so, then a dual fuel would still be a good choice.

If your homes heat loss is 70,000BTUs at 0°F outdoor temp.
Then its heat loss at 40°F outdoor temp should be around 27,000BTUs.
A 4 ton heat pump puts out 37,000 to 42,000 or so BTUs at 40°F outdoor temp.

[KyBrewer]

One more question then I'll leave you alone. I'm not real clear on how furnace sizing works. I think I have to have at least a 4-ton blower capacity to match the A/C sizing? If you are familiar with that line of Bryant, which should I be looking for him to suggest? They appear to have a 74,000 BTU output model, 94,000 output BTU model, and 112,000 BTU output model that I think he has suggested. The model numbers aren't a perfect match but I think they are similar just older or newer versions.

[beenthere]

I think the 74,000 output comes in a 4 ton blower size.

Where yours says 060 it would say 048, and where yours says 110, it would say080

[KyBrewer]

Thanks a lot for the input! I think, especially if I put a few more inches of insulation in the attic, the 74,000 BTU furnace should be plenty.

[Phasewolf]

There is a other way too look at this problem. If you don't want to spend the money to get a larger ac unit and do the ducts you could get a energy audit and look to reduce the air leaks and save a bunch of money no matter what you do.

[KyBrewer]

So the contractor now tells me that he can get the 4-ton furnace at 74,000 BTU output, but it will pretty much cost the same as he would have to order it directly from the factory. He also mentioned some additional ductwork due to size differences between the 4-ton furnace and condenser coil.

I *think* he is trying to sell me the 5-ton unit @ 110,000 BTU output because it is one (possibly among several) older model sitting in a distributors warehouse that is easily available. Possibly the 4-ton unit, 74,000 BTU output would be brand new from the factory. He didn't say exactly that, but I'm trying to somewhat interpret him. They would 'dial down' the blower motor to accomodate the 4-ton a/c?

If I were going to pay the same price for a 5-ton, 110,000 BTU output furnace vs. for a 4-ton 74,000 BTU output furnace, which should I choose?

I'm just wondering the Drawbacks/Benefits to either? He didn't refuse to get the smaller unit, just won't really give me a break on price.

[beenthere]

Newer units need to move more air then older ones did.
So even the new one the same size as the old one will need to move a little more air then your current one does.
A larger one, will need to move that much more.
So I would get the proper sized one so all the duct work does need to be replaced to keep it from being loud.

[KyBrewer]

So to recap, I will be getting the following:

A/C: Bryant 123ANA048000
CC: CNPVP4821ATA
FURNACE: Bryant 340AAV048080 (possibly 350AAV if shipped from factory)

The company is going to replace the supply trunk line to the back of the house (where some issues exist with lack of flow due to 8"x18" existing trunk line supplying 4 rooms). He will replace the return duct to the back of the house (10" to 16" round, there are two other return ducts in the front of the house that will be left as-is). That combination of Furnace and A/C coil will require a transition built due to size differences between them. They will change out the lineset.

Does that all seem ok? Anything I need to look/watch for?

And again, thanks for your input!

[beenthere]

Sounds good.

[KyBrewer]

The Plot Thickens...

So I had a 6th and final quote, and the guy quoted Trane equpiment for a pretty good price.

Through this process I have started to understand the construction of my home a little better. The inside unit is located *near* the center of the house in the cellar/crawlspace. It has a spider duct arrangement except for one trunk line that feeds a bedroom, dining room, kitchen, and a second bedroom. This trunk is 8"x18" with a single 8" round to each room feeding a single register in each room. All "spider legs" appear to be 8" rounds, and none is longer than 15'. The area of the house that is not cooling well is most of that fed by the trunkline, between 15 and 30' away from the furnace/condenser coil. My understanding from the HVAC Calc software is the trunkline is undersized for what it is supplying.

I have had one contractor say he will replace the entire trunkline with a larger size. He will tie in the same single supply ducts to each room.

A second contractor has suggested taking one of the branches off the existing trunkline and tying it in to the air handler as another spider leg. That would leave the trunkline serving 3 instead of 4 rooms and would make it reasonably sized, based on my work in HVAC-Calc. He also suggested adding a second register in the kitchen and bedroom, both served from the farthest extents of the trunkline. Instead of one 8" supply duct to each room, I would have two 4" supply ducts from the trunkline to each room.

Both have suggested resizing a return duct from 12" to 16" round.

Which of these sounds like a better idea?

Does neither option sound good?

Alternate suggestions are appreciated. I will try to upload a photo of existing when I get home.

[beenthere]

2-4" round ducts don't equal 1-6"round duct.

[KyBrewer]

Also, there appear to be dampers on all round supply ducts whether they are a spider leg from air handler or a branch off the trunkline.

[KyBrewer]

There are (I believe) 8" round existing. He is proposing to replace one 8" round to a single register with two 4" round to 2 registers (he is adding a register in each room). He hasn't provided me with his quote yet so I'm trying to remember everything that was said.

I'm waiting for his quote via email.

[beenthere]

There are (I believe) 8" round existing. He is proposing to replace one 8" round to a single register with two 4" round to 2 registers (he is adding a register in each room). He hasn't provided me with his quote yet so I'm trying to remember everything that was said.

I'm waiting for his quote via email.
So each register that a 4" goes to, will only recieve 1/4(at best) as much air as the 8" use to supply.

[KyBrewer]

He may be talking about changing to two 8" rounds instead of the one to each room. I'm still waiting on the quote to be sure, but he's been pretty helpful and if I insisted on something he'd listen.

Would that make more sense?

[beenthere]

Well. Using four inch doesn't.

Wait till you get the contract/quote. And see what it really says.

[KyBrewer]

Fair enough. I'm trying to draw a diagram that will show the layout of the supply, but I'll probably have to get home before I can upload it. Unless this works.

That's existing.

[KyBrewer]

Roughly proposed, from contractor 2. (Still haven't got quote)

[beenthere]

Your second drawing doesn't show any 4" duct.

[KyBrewer]

I am assuming he won't propose it, and if he does, from what you have told me I will tell him I want 8". :D

Does that seem like a reasonable setup, or is it a mess?

Taking pictures now. I know the spider leg thing probably isn't the best, but it's what's existing at the moment. I also don't have the legs located just right looking at it now.

[BhamNewbie]

I have a similar setup as you! Do you mind if I PM you about how you decided on a contractor? I can't figure out how to PM though.

[beenthere]

I have a similar setup as you! Do you mind if I PM you about how you decided on a contractor? I can't figure out how to PM though.
Only Pro Members have PM ability.

[KyBrewer]

I don't mind discussing the process if you have any questions, ask away.

beenthere, what do you think of the proposed diagram?

This company has agreed to that work and is quoting the Trane 4TTX5048 A/C and Trane TUH2C100A9V4VA Furnace. He is going to rewrite to include the evaporator coil model number but has already written "Trane 4 ton" for it on the original quote.

He has also included 10 years parts and 10 years labor, as well as 2 years maintenance (twice each year).

Thoughts?

[beenthere]

It looks ok.

Hard to tell what size spplies you need without knowing what CFM each area needs.you need

[KyBrewer]

Also I may regret this, but here are some photos of current.

Slide 1 is the 8"x18" trunkline as it goes to the back of the house, and existing return duct to back of house.

Slide 2 is where the trunk passes under the kitchen and heads toward a single register in the back bedroom. There is a hackjob return modification that this contractor has quoted to correct.

Slide 3 is the beast in all its glory.

Slide 4 is another photo of the beast.

[KyBrewer]

HVAC Calc has all the supplies to each room needed at either 7" or 8" round. Everything existing is pretty much 8", with dampers.

[KyBrewer]

CFM from HVAC Calc

The total CFM is based on the second stage high setting for the furnace. Worst case scenario I think (max cfm)

[beenthere]

8x18 doesn't supply too many 8" branches.

Looks typical.

[KyBrewer]

Thanks!

So it won't be nominated for wall of shame?

[beenthere]

CFM should be based on the sensible and latent load in cooling, and then the heat CFM to deliver enough BTUs for heating, while staying in allowable temp rise for the furnace heat exchanger.

An 80,000BTU input, 95% efficient furnace, at 1850CFM would only have a temp rise of 38°F.
Not many furnaces have that temp rise as an acceptable rise.

A 4 ton A/C, won't remove much moisture at 1850 CFM. So you better live in an arid area, if you use that CFM for a 4 ton A/C.

[beenthere]

Thanks!

So it won't be nominated for wall of shame?
Depends how it looks after the new system is installed. :D

[KyBrewer]

Fair enough I was just looking at the spec sheet for the furnace and chose the most possible cfm for it. I guess in reality it would be set on low or medium for my area (1400 or 1650 cfm in second stage).

Give me a minute and I'll post CFM from HVAC Calc for those.

[KyBrewer]

other cfms

[beenthere]

What was the sensible and latent load BTUs HVAC CALC gave you.

[KyBrewer]

Loads

We prefer it cool in the house :D

[beenthere]

I doubt your going to need to move 1600 CFM in high stage.

[KyBrewer]

It says 1300-1450 for the low and medium-low settings on high stage. If that is the case, do you think that duct arrangement will work alright?

The goal in the duct work is to take a partial load off that trunkline because the back of the house (kitchen and bedroom 3 in particular) don't get comfortable enough in the summer. There is also too much going to the bathroom, but it has a damper on that 8" round that I probably should close partially. I just don't want to do it until I get the new system in. Which they are supposed to balance when they finish.

Also he quoted

FURNACE: TUH2C100A9V4A
A/C: 4TTX5048
COIL: 4TTXCC049

Do you see any issues with that equipment together?

[beenthere]

The furnace will probably never need to go to high stage. Except on the coldest days, or coming out of set back.

Look up post by key1cc. Read about his oversized system. His oversized 2 stage furnace is locked in first stage.

I think you would have benefited from a 2 stage A/C. Had better humidity control in cooling.

[KyBrewer]

He also proposed A/C 4TTB3048, with the same furnace and evap coil.

I just looked up the combos on AHRI.


With 15 SEER:

EER 11.20
SEER 13.75

With 13 SEER:

EER 11.15
SEER 13.25

Seems like the price difference for the 15 SEER isn't worth it if I go with that furnace. Except we would have to revert to a 5 year parts and labor warranty.

[KyBrewer]

The furnace will probably never need to go to high stage. Except on the coldest days, or coming out of set back.

Look up post by key1cc. Read about his oversized system. His oversized 2 stage furnace is locked in first stage.

I think you would have benefited from a 2 stage A/C. Had better humidity control in cooling.

So with Trane, I would probably need the XL16i, model 4TTX6048B?

[beenthere]

Afraid so.

[KyBrewer]

Ouch $$$$

And I would have to stay with at least this furnace?

That will probably be more than we can afford.

I guess I'll play around with a furnace alternative for the 13 and 15 seer a/c.

He also proposed a 13 seer heat pump with that furnace that we could swing to make it dual fuel.

So I'm thinking one of these:

95% furnace with 13 SEER A/C
95% furnace with 13 SEER HP
Lesser furnace with some combination of the 13 and 15 already proposed.

Any thoughts? Would I be better off with a single speed Furnace, say XT90 TUX1C100A9H41B?

[KyBrewer]

So I figured out that the 15 Seer A/C isn't matched with that 4-ton coil, it should be matched with the 5 ton coil.

I'll have to get him to change that.

[beenthere]

VS furnaces are all 2 stage. And you get much better humidity control with a VS blower.

[KyBrewer]

Due to costs, I am probably leaning toward the quoted arrangement with the 15 seer a/c (after I get him to change the coil to 5-ton). It would be hard to swing the 16 seer unit I think. I'll ask him about it tomorrow, however.

We really prefer gas heat, and the 10 year parts and labor, which is transferrable, will be a good selling point I think. With the 13 seer we would only get 5 years parts and labor. Also, the 15 seer is nominally more than the 13 Seer HP when considering the gas company rebate (gas company did some research I guess)

it's probably asking too much, but tell me I won't regret it beenthere :D

[beenthere]

No guarranties over the internet. :)

Its a good system.

[KyBrewer]

Am thinking we'll probably go with:

Furnace: TUH2C100A9V4VA
A/C: 4TTB3048
COIL: 4TXCC049

Even with the better suited coil, I'm thinking it will take longer than we will be in the house to to pay the difference in consumption savings between the 15 and 13 SEER a/c.

[RyanHughes]

It still may be worth it to get the XR13 a/c instead of the XB13. Little quieter, and if you register with Trane within 60 days after installation, you will get a 10-year warranty on all parts (only 10 years on compressor with the XB13).

[KyBrewer]

Thanks for the tip, he's checking on pricing for me.

Said he is going to provide the 900 thermostat too :D

Easily the best dealer experience so far!

[RyanHughes]

Glad to hear it. I did not know the 900 thermostat could be used without a communicating furnace, but that may be the case. Good to know if it is. Great thermostat to control humidity.

[KyBrewer]

I suppose there will be some features that are not used or unavailable, but I'll let you know. I mostly just want 7-day programmablity. If that's a word :)