Help navigating central AC quotes

[idmd]

Current System: A 15+ year old 3.5 ton unit with a SEER 8 rating - ducts appear to be uninsulated and run through the attic. Simple setup with a 50' main supply duct that runs a straight line down the middle of the house and 10 smaller ducts running from it to vents. Home is a ranch style house with 2500 sq ft. Located in southern CT. Current system is obviously inefficient and needs to run 100% of the time during hot weather but does cool and dehumidify well.


COMPANY 1
Quote includes:
Trane outdoor AC unit
Condenser leveling pad
Trane Hyperion indoor air handler
Watertight safety drain pan and platform
Honeywell thermostat

Scope of work:
Remove current air handler and condensing unit and discard per EPA requirments
Place new air handler in attic with water tight pan/wood platform
Wrap existing supply and return distribution system with R8 duct wrap
Install new R8 flexible duct from existing distribution line to ceiling registers
Place outdoor condensing unit on a approved pad
Replace refrigeration piping/electrical wiring
Complete drain piping.

Efficiency Options:

1. XB 14 SEER OPTION - $X
Indoor unit: GAM5A0C42M31
Outdoor unit: 4TTB4042E1
Combined SEER = 15

2. Xli 15 SEER OPTION - $X
Indoor unit: AM7A0C48H41
Outdoor unit: 4TTX5042A1
Combined SEER = 16

3. Xli 16 SEER OPTION - $X
Indoor unit: AM7A0C48H41
Outdoor unit: 4TTX6048G1
Combined SEER = 17

Honestly all of these quotes seems really high. There's nothing particularly difficult about this change out. Guy is claiming it will take two guys 4 days to complete for EIGHT man days and that this is where the majority of the cost is occurred. Guy was pushing option number 2. Honestly I know very little about HVAC.


COMPANY 2
Another guy came in and said he wanted to install a 4ton Rheem with a SEER 13 rating. Project would include changing air handler, AC, and lines.
Interestingly he said the main supply duct was internally insulated and he was just going to wrap that duct without disassembling it and replace the smaller feeder ducts with new insulated flexible ducts.

His cost for the job $X

My concerns: He said 2 days maximum. He is the only one to mention the "internally insulated duct". Is Rheem a lesser brand? I'm assuming if wants to use a SEER 13 system he's scrapping the bottom of the quality barrel? I was referred by my neighbor and they are perfectly happy but I've called some of their "guys" in the past and they definitely value $ over quality. Should I be afraid of this quote??


I only put the $ amount because they are drastically different but the work isn't apples to apples. Any thoughts or opinions would be appreciated.

[PNW78]

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[udarrell]

NO actual prices allowed!

You can explain the relative position of the bids, but list 'NO' pricing numbers!

[idmd]

Ok....quote 1 is a little over twice quote 2.

[udarrell]

Current System: A 15+ year old 3.5 ton unit with a SEER 8 rating - ducts appear to be uninsulated and run through the attic. Simple setup with a 50' main supply duct that runs a straight line down the middle of the house and 10 smaller ducts running from it to vents.

Home is a ranch style house with 2500 sq ft. Located in southern CT.
Current system is obviously inefficient and needs to run 100% of the time during hot weather but does cool and dehumidify well

.
New Haven CT 2.5% summer design is 84-F dry bulb, 73-F wet bulb or 59% relative humidity.

At 84-F outdoors & 75-F indoors, that's only a 9 degree differential; therefore it 'appears' the A/C could be way oversized with ridiculously poor duct system, both from a standpoint of sizing & lack of insulation, causing long runtimes removing the heat of condensation & not lowering the sensible RM/TH temp enough.

There could very well be a number of other reasons why the old 3.5-Ton didn't cool effectively; compromised refrigerant system during installation & more...NEVER go by your old systems performance, - unless every aspect of its "delivered performance" was tested & verified!

You need a heat-gain calc performed with duct sizing in proportion to the Btuh required to each room. Do enough retro-work on your home to bring the heat-gain calc down to 'perhaps' 3-Ton; airflow & everything will work better, with a much higher % of the Btuh heat being removed from the rooms.

Going up to a 4-Ton unit may compound your problems & your utility costs; NOT an idea I would entertain

Get that new duct system optimally insulated; get the return ducting properly sized along with extra large RA filter sizing for optimal airflow efficiency...

[idmd]

.
New Haven CT 2.5% summer design is 84-F dry bulb, 73-F wet bulb or 59% relative humidity.

At 84-F outdoors & 75-F indoors, that's only a 9 degree differential; therefore it 'appears' the A/C could be way oversized with ridiculously poor duct system, both from a standpoint of sizing & lack of insulation, causing long runtimes removing the heat of condensation & not lowering the sensible RM/TH temp enough.

There could very well be a number of other reasons why the old 3.5-Ton didn't cool effectively; compromised refrigerant system during installation & more...NEVER go by your old systems performance, - unless every aspect of its "delivered performance" was tested & verified!

You need a heat-gain calc performed with duct sizing in proportion to the Btuh required to each room. Do enough retro-work on your home to bring the heat-gain calc down to 'perhaps' 3-Ton; airflow & everything will work better, with a much higher % of the Btuh heat being removed from the rooms.

Going up to a 4-Ton unit may compound your problems & your utility costs; NOT an idea I would entertain

Get that new duct system optimally insulated; get the return ducting properly sized along with extra large RA filter sizing for optimal airflow efficiency...

Thanks for the input. Current system is a 3.5 ton handler with a 1.5 ton A/C outside - totally mismatched. The current DOES cool and dehumidify well enough although it runs 24/7 to do so and my electric bill goes up $500 per month in the summer. Company one did a bunch of measurements and calculations to arrive at 3.5 tons.....guy had his laptop out crunching numbers. I think company 1 would do everything to the letter of the law. I think the second company will "get 'er done" but make compromises.

The real question is will those compromises really have a significant impact when we're talking half the money?

Have three more companies coming out to give quotes - can't wait to hear their take.

I really appreciate your input - thank you!

[udarrell]

Thanks for the input. Current system is a 3.5 ton handler with a 1.5 ton A/C outside - totally mismatched. The current DOES cool and dehumidify well enough although it runs 24/7 to do so and my electric bill goes up $500 per month in the summer. Company one did a bunch of measurements and calculations to arrive at 3.5 tons.....guy had his laptop out crunching numbers. I think company 1 would do everything to the letter of the law. I think the second company will "get 'er done" but make compromises.

The real question is will those compromises really have a significant impact when we're talking half the money?

Have three more companies coming out to give quotes - can't wait to hear their take.

I really appreciate your input - thank you!

Well, the new reality that it is a 1.5-Ton condenser with a 3.5-Ton air handler sheds a new light on the situation.
The evaporator coil may not be 3.5-Ton, it may be a 2-Ton indoor Evap-coil.(?)

The air handler may have needed to be larger to easily handle the heating airflow.

It would appear that your home & duct system are NOT very energy efficient; which results in a large utility bill.

If you could tell us where the windows are in relation to your homes orientation; their size & type plus the insulation factors; walls & attic; someone could run a mockup heat-gain calc that would just be a ballpark view of the heat-gain load factors.
Maybe the laptop guy is doing a load calc...?

The inefficiencies appear to be apart from the 1.5-Ton condenser; however, its Btuh performance would also need checking.

[idmd]

Company one came out to calculate a heat gained/lost. Measured all the rooms and input all the variables and because of one room furthest from the air handler on the southern side of the house with large windows on 3 sides it bumped the requirement from 3.5 ton to 5 ton - he said that room alone (maybe 12x12') requires nearly a ton of cooling itself. Obviously 5 ton would add a significant amount $. He said if he changed the parameters from cooling the house to 75F on a 95F day to 77F on a 95F day the 4 ton works. He said I need to add another air return to do this and that the room in questions would likely be a few degrees warmer. As it is with the current system there could be as much as an 8-10F difference with just that room. I'm thinking after sealing/insulating and upgrading that should be more like 2-3F on the warmest days?
This stuff is really outside my knowledge - what do the experts think?

[idmd]

BTW....company 1 is the company that wants to disassemble sections of the main supply duct to seal and insulate all 4 sides. His feeling is there will be heat penetration on the underside and sweating will be a problem. He showed me an area in my dinning room ceiling that I never notices where the plaster is starting to buckle and sure enough the main supply duct runs above that very area (roof is new with no leaks). Also, he said the quoted price includes adding some runs to some of the larger rooms on the southern part of the house that currently only have one run and need two.

[tipsrfine]

Electric bill going up in Summer is not always the result of the air conditioner. I had a homeowner who thought the same thing, but it turned out he ran a 2 HP swimming pool pump 24/7 in the summer. The pool pump was the main cause of the high bills.

[idmd]

No pool...the only difference between summer and winter is heating vs cooling. The old system ran 24/7 when it was hot.

[tipsrfine]

Your first step should be to have an energy audit done to see how leaky your home is and how well insulated. The home is the primary defense against the weather, and that is the place to start. The better the home's envelope, the less HVAC size you need.

[idmd]

We are half way through an energy audit but it stopped when the AC didn't work. Was going to have them back after fixing but now we're going down the road of replacement.

[BaldLoonie]

If a 1.5 ton cooled and dehumidified well but ran all the time, what in blazes are you doing over doubling the size? You had better be ripping all the ducts and putting over double the duct capacity in too. And increasing the number of supply & return vents.

I can't believe 2500 sq ft in CT needs 3.5 to 4 tons. You'll barely run and have high humidity, even the 2 stage since low isn't much less than high .Then you'll need a whole house dehumidifier.

You likely will never recoup the investment for 16-17 SEER either. Good for the salesman's commission which is likely why Mr. Trane was pushing them. Rheem is good equipment but 4 tons without changing the main duct size???? Wow, you have some real winners up there.

Somebody better find out what you have (if you can post model #s in & out we can tell you, somebody, even you, should do an accurate heat gain, then see what you need. But if you kept comfy with 1.5 ton and only complaint is higher than desired bill, you sure don't need those monsters being quoted. Short cycling and if they reuse that small duct system, you may not see much of a savings.

[idmd]

If a 1.5 ton cooled and dehumidified well but ran all the time, what in blazes are you doing over doubling the size? You had better be ripping all the ducts and putting over double the duct capacity in too. And increasing the number of supply & return vents.

I can't believe 2500 sq ft in CT needs 3.5 to 4 tons. You'll barely run and have high humidity, even the 2 stage since low isn't much less than high .Then you'll need a whole house dehumidifier.

You likely will never recoup the investment for 16-17 SEER either. Good for the salesman's commission which is likely why Mr. Trane was pushing them. Rheem is good equipment but 4 tons without changing the main duct size???? Wow, you have some real winners up there.

Somebody better find out what you have (if you can post model #s in & out we can tell you, somebody, even you, should do an accurate heat gain, then see what you need. But if you kept comfy with 1.5 ton and only complaint is higher than desired bill, you sure don't need those monsters being quoted. Short cycling and if they reuse that small duct system, you may not see much of a savings.

Well every single person has recommended a 3.5-4.0 ton unit. I was incorrect (rather one of the salesman was incorrect) on the outside unit being 1.5 ton - it's 3 ton and the air handler is a 3.5 ton unit. This guy is the only one who did the heat lost/gain and every single neighbor with a similarly sized house built by the same builder in 1953 has a 3.5 to 4.0 ton so I don't find the size shocking. Also, it's a ranch with a very large roof, lots of attic volume and lots of very large unshaded southern-exposed windows.

He said going to a 4 ton from a 3.5 ton that the main duct will be fine (it is slightly oversized for a 3.5 ton system), he will need to add a return (there are already two) and runs may need to be added and sizes adjusted based on cfm requirements of the individual rooms.

Lastly where are you from? Don't discount how hot and humid southern CT can be in summer especially along the Sound where you don't get the ocean breezes - just the added evaporative humidity.

[udarrell]

Company one came out to calculate a heat gained/lost. Measured all the rooms and input all the variables and because of one room furthest from the air handler on the southern side of the house with large windows on 3 sides it bumped the requirement from 3.5 ton to 5 ton - he said that room alone (maybe 12x12') requires nearly a ton of cooling itself.

Obviously 5 ton would add a significant amount $. He said if he changed the parameters from cooling the house to 75F on a 95F day to 77F on a 95F day the 4 ton works. He said I need to add another air return to do this and that the room in questions would likely be a few degrees warmer. As it is with the current system there could be as much as an 8-10F difference with just that room. I'm thinking after sealing/insulating and upgrading that should be more like 2-3F on the warmest days?

This stuff is really outside my knowledge - what do the experts think?

Click on http://hvac-talk.com/vbb/showthread....1#post15583161 and read the post again.

If your 3-Ton ran steady at the worst conditions then it was sized right; though it may not have been delivering to & from the rooms near its Rated Performance. They can't size replacement units by un-performance tested existing units; the existing system may need work to improve its performance!

There is NO way you can go to 5-Ton on that duct system & Return Air Filter sizing, etc., don't even consider it; please don't make any equipment decision until the Home Energy Audit & any needed Retro-work is completed.

Please don't get the cart before the horse; You could make a costly mistake that you will regret for the life of the equipment.

Were it me, I would use a separate system for the distant room that is running the load-calc way up. The design conditions show that humidity is probably the biggest problem not temp; therefore, never oversize the A/C, as it needs long runtimes.

Check the duct system & return Air filter area sizing should be for 300-fpm velocity through a 1" deep fiber glass filter (Manual D, Bet they don't know that); you have to keep the pressure drops low...You make the call, you live with an efficient result or, with a very costly result...

[idmd]

Alright, I have his load form in front of me now.

Total sqft = 2510
Total required cooling 47602 Btuh @1600 cfm
Total required heating 75825 Btuh

The "sun room" in question is 192 sqft (bigger than I thought) and he calculates in needs 276 cfm. Some rooms like the dinning room have too much flow as is and some like the very large living room don't have enough. Interestingly the "sun room" is the most cooling intensive room in the house even compared to the 464 sqft living room that only has one externally exposed wall and one large window.

As always comments welcome.....

[idmd]

Click on http://hvac-talk.com/vbb/showthread....1#post15583161 and read the post again.

If your 3-Ton ran steady at the worst conditions then it was sized right; though it may not have been delivering to & from the rooms near its Rated Performance. They can't size replacement units by un-performance tested existing units; the existing system may need work to improve its performance!


There is NO way you can go to 5-Ton on that duct system & Return Air Filter sizing, etc., don't even consider it; please don't make any equipment decision until the Home Energy Audit & any needed Retro-work is completed.

Please don't get the cart before the horse; You could make a costly mistake that you will regret for the life of the equipment.

Were it me, I would use a separate system for the distant room that is running the load-calc way up. The design conditions show that humidity is probably the biggest problem not temp; therefore, never oversize the A/C, as it needs long runtimes.

Check the duct system & return Air filter area sizing should be for 300-fpm velocity through a 1" deep fiber glass filter (Manual D, Bet they don't know that); you have to keep the pressure drops low...You make the call, you live with an efficient result or, with a very costly result...

The reason the 5 ton would be significantly more is because he said all the duct work would been to be replaced....with the 4 ton he says we can use the main supply and since we're changing out all the runs anyway they can be properly sized.

[idmd]

Here are his calcs

[idmd]

Alright....in the middle of the change out. Air handler (Trane Tam7) and condenser (xl15i - 4 ton) is installed and now they are working on the duct work. Turns out main duct was internally insulated with a 1" fiberglass duct liner. Their plan is to keep this because it was done well and in good shape and then use 3" fiberglass duct wrap. Installer said it should give around an R11.

Any reason to question whether or not internal insulation should be removed?