Replace Home AC Unit Proactively or Wait for it to Die?

[LS6 Tommy]

Unless I am mistaken, the lack of an equipment safety shutoff device in a secondary drain pan above a finished occupied space is not in compliance with the International Residential Code.

Mechanical Code has required it since 2012:

"If you are using a drain pan under the appliance, 307.2.3 paragraph 4 (Auxiliary and secondary drain systems) says:

A water-level detection device conforming to UL 508 shall be provided that will shut off the
equipment served in the event that the primary drain is blocked. The device shall be installed in the
primary drain line, the overflow drain line, or in the equipment- supplied drain pan, located at a point
higher than the primary drain line connection and below the overflow rim of such pan.

"If no drain pan or aux drain line is being used, 307.2.3.1 (Water-level monitoring devices) says:

On down flow units and all other coils that do not have a secondary drain or provisions to install a
secondary or auxiliary drain pan, a water-level monitoring device shall be installed inside the primary
drain pan. This device shall shut off the equipment served in the event that the primary drain becomes restricted. Devices installed in the drain line shall not be permitted."

Tommy

 

[bulletpruf]

Ok, I have details. The HVAC guy came over today and we got estimates and details on everything.

Overview - everything is mismatched, components replaced at different times, most duct work is old, all R-22. Total tonnage for 3,600' house is 8.

Electric bills have been getting ugly, too. June was $234, July $375, August $415, September $325. We keep the AC at 78 during the day and 72 (master bedroom) or 75 (remainder of house) at night.

Company that came out to give estimates is very highly rated/reputable local company. Not a Mom and Pop operation. Guy shows up on time, clean cut, dressed professionally, driving a new company truck.

We will be paying cash for any work done and while we're not stupid rich, it won't put us in a financial bind if we decided to replace everything.

Here's the breakdown that we went over:

1. Main Unit - responsible for over half of downstairs. AC is 1980's vintage Trane (house was built in 1988) 3.5 ton. Furnace (I didn't catch the brand) is 14 years old.
-Deficiencies: 1. There's sludge in drain pan - evidence that oil has leaked. 2. There's a 14" return line coming off a 12" x 24" filter. 3. Older gray ducts.
-Replacing with 16 SEER Trane XR High Efficiency 3.5 ton AC and Trane High Efficiency furnace is $8700. We get a rebate from power company of $455. Estimate does NOT include replacing the complete duct system ($5000!!!) or adding a new return ($400).
-My thoughts - add a new return line and then let it run until it breaks.

2. Upstairs Unit. AC is 2 ton Goodman "builder grade". 5 years old. R22. Ruud Weather King furnace (has Trane coil) is very old; very likely original to house (31 years old). Ducts have been replaced; decent condition.
-Deficiencies: 1. Secondary drain pan filling up, indicating some sort of problem. 2. Single return line, undersized. 3. Primary drain pan (under coil) is rusted; it may be rusted through and leaking into secondary drain pan.
-Replacing with Trane 2 ton 16 SEER XR High Efficiency AC and Trane high efficiency furnace is $8500. Does not include replacing complete duct system ($5000) or adding new return line ($400).
-My thoughts: It needs a fair amount of work. I'm not a huge fan of bandaids or mismatched stuff, so I'm inclined to replace at least the furnace and AC.

3. Downstairs Master Bedroom/Office/Family Room. AC is a Payne (ICP), 2.5 ton unit. Looks old but said to be only 11 years old. Furnace is Payne, also 11 years old.
-Deficiencies: 1. Furnace not working. 2. Older gray flexible duct hoses. 3. Main duct system (or whatever you call the assembly that the ducts and furnace attaches to) is in rough shape - several patches evident, looks to have collapsed in one spot. 4. Return line is too small; needs another one.
-Replacing with a Trane XR 16 SEER High Efficiency AC unit and High Efficiency furnace is $8300. Replacing full duct system is another $5000 and $400 for additional return.
-My thoughts: Replace the entire system - furnace, AC, duct system.

Curious to hear what y'all would do.

Thanks in advance for any input.

Scott

 

[acmikee]

1) main unit sludge in pan can be cleaned evidence of oil leak- if oil leaked the unit would be low on charge is it
2) upstairs unit secondary pan has water due to primary pan leaking probably rusted out it can be replaced or resealed
3) downstairs unit why is the furnace not working?

what type of duct work do you have is it hard duct, aluminum flex or wire flex and what type are they going to be installing
your spending over $40000 without looking at your house its hard to tell how bad your system is. I would get 3-4 more quotes mom and pop shop are not bad

 

[yeldogt]

Costs are relative ... you have three systems running in Texas .. what's the electric rate. I pay .20 ...mine are pushing $600 in the summer.

IMO basic equipment properly sized and installed will work better and run longer vs better equipment sized incorrectly and not properly installed. you will not get the efficiencies out of one speed systems if the ductwork is not correct.

Did he do a load calculation ... 8T is a lot. On a very hot day they should all be running flat out at 2pm to maintain 71. My guess oversized. Was the house built with three systems ?

Properly sized equipment is typically smaller ...making the existing ductwork more in line ... also VS equipment can do wonders in those situations.

W/O a good load .. it's all guess work

 

[bulletpruf]

1) main unit sludge in pan can be cleaned evidence of oil leak- if oil leaked the unit would be low on charge is it
2) upstairs unit secondary pan has water due to primary pan leaking probably rusted out it can be replaced or resealed
3) downstairs unit why is the furnace not working?

what type of duct work do you have is it hard duct, aluminum flex or wire flex and what type are they going to be installing
your spending over $40000 without looking at your house its hard to tell how bad your system is. I would get 3-4 more quotes mom and pop shop are not bad

Need to check the inspection report to see what they found with furnace not working.

I'm kind of burned out on budget contractors. We had a plumber that broke more **** than he fixed, so we hired the top rated local plumbing company to clean up the mess, literally and figuratively. Had a complete fiasco with a mom and pop outfit that did our back patio and they didn't stand behind their work.

Costs are relative ... you have three systems running in Texas .. what's the electric rate. I pay .20 ...mine are pushing $600 in the summer.

IMO basic equipment properly sized and installed will work better and run longer vs better equipment sized incorrectly and not properly installed. you will not get the efficiencies out of one spped if the ductwork is not correct.

Did he do a load calculation ... 8T is a lot. On a very hot day they should all be running flat out at 2pm to maintain 71. My guess oversized. Was the house built with three systems ?

Properly sized equipment is typically smaller ...making the existing ductwork more in line ... also VS equipment can do wonders in those situations.

W/O a good load .. it's all guess work

Good point on load calculation. I'll check.

Almost positive that the house was built with 3 systems but not sure how I would be able to figure that out.

Thanks

 

[Notgrownup]

1700 sq’ house here my last bill was $330, been a fairly hot summer, pool, hot tub, shop mini split. I do run it on 70-72 during the day and 66-68 when we sleep. I don’t think your bill is out of line for 3 units even running them in the mid to upper 70s.
Still old equipment and you probably would be more comfortable with new stuff.
My inexpensive Goodman equipment is 17 years old and would be about $6000 to replace it with Trane.
Hard to pick the hacks out compared to the quality outfits sometimes.

 

[yeldogt]

1700 sq’ house here my last bill was $330, been a fairly hot summer, pool, hot tub, shop mini split. I do run it on 70-72 during the day and 66-68 when we sleep. I don’t think your bill is out of line for 3 units even running them in the mid to upper 70s.
Still old equipment and you probably would be more comfortable with new stuff.
My inexpensive Goodman equipment is 17 years old and would be about $6000 to replace it with Trane.
Hard to pick the hacks out compared to the quality outfits sometimes.

Replacing working old single speed with new single speed of the same size is not going to increase comfort .. nothing has changed -- except the balance in your bank account. It may be quieter ..

A thirty year old unit may be about a 8 SEER .... so installing a new 16SEER in theory should cut the electric cost of running a unit that old in 1/2. A 20 year old unit could be a 13 SEER. How long for the payback? It's a math problem to work out ....

Many houses ... especially those in humid areas -- would benefit from going one step further and getting multi-speed equipment and VS fans. Now you are talking comfort along with the efficiency.

The OP needs a full review -- full load done. Understand why and how there are three units -- can any be combined. The problem for the OP is that the most money is made by the contractor -- replacing three units and doing minor duct work. Figuring out what the house really needs and making it work adds time and that time is not generating as much.

 

[bulletpruf]

When I asked about a load calculation, he said, "After speaking with Mrs. Bulletpruf on my initial visit she confirmed the master side of the house does very well and after running our initial numbers it is in line with what should be serving this side of the house. We can perform a load calculation on the house but we do feel very comfortable with the current sizing."

I asked him to do the load calculation.

As for why there are three units, I think I can answer that. It's a 2 story house, but it's really split in half. As you walk in the front door, you're in the foyer and then immediately in front of you is the family room, followed by the back wall. The ceiling in the foyer/family room is 20' or so, and it basically splits the downstairs in half. One unit services the master bedroom/office/family room/powder room and the other unit services two small bedrooms, laundry room, kitchen, formal living room, and formal dining room. Not sure how you would be able to use one large unit to handle the entire downstairs.

The 3d unit takes care of the upstairs.

Thanks

 

[yeldogt]

It depends on where the units are and how the ductwork operates --

My friends had twin units .. not for from each other. One was 3T and the other 2T .... The 2T did the master and some other spaces and the 3T did much of the house. It really only needed 4T and the heaters were way oversized.

They put a 4T VS unit in and zoned the whole place -- 3 zones. Now they can control the master to what they want w/o doing anything else .... the other two zones take care of the house in a more natural way ... the bedrooms are all together on the 2nd floor as one zone.

 

[bulletpruf]

It depends on where the units are and how the ductwork operates --

My friends had twin units .. not for from each other. One was 3T and the other 2T .... The 2T did the master and some other spaces and the 3T did much of the house. It really only needed 4T and the heaters were way oversized.

They put a 4T VS unit in and zoned the whole place -- 3 zones. Now they can control the master to what they want w/o doing anything else .... the other two zones take care of the house in a more natural way ... the bedrooms are all together on the 2nd floor as one zone.

Ok, I think I see what you're saying. We have two units sitting next to each other - the 3.5 ton and the 2 ton. One for upstairs and one for downstairs. Should I ask if we could potentially use one unit here?

 

[yeldogt]

Ok, I think I see what you're saying. We have two units sitting next to each other - the 3.5 ton and the 2 ton. One for upstairs and one for downstairs. Should I ask if we could potentially use one unit here?

Here is the thing -- better contractors have solutions. There are guys that come out and say -- you don't want that complex **** .. A model T was good enough for my grandfather. They never use VS equipment or do zoning .... so they have not history or experience

Then there are other contractors -- guys that install better stuff all the time. They know and understand the products. It's been my experience that there is very little in-between.

Find a contractor that does higher end work. It all comes down to the house and load. My beach house is a typical east coast "four square" upstairs / downstairs w/ a larger kitchen and family room off the back. It's a three zone 4T Carrier 5 speed. Up/Down and Rear. We never use the whole house the same during the day. Why cool the second floor -- when we are not in it. Why have two systems when one can do it ... and that one is doing it with a better system able to remove all the humidity .. w/o any noise.

Again -- it's all based on doing a load and understanding what each area needs.

 

[bulletpruf]

Here is the thing -- better contractors have solutions. There are guys that come out and say -- you don't want that complex **** .. A model T was good enough for my grandfather. They never use VS equipment or do zoning .... so they have not history or experience

Then there are other contractors -- guys that install better stuff all the time. They know and understand the products. It's been my experience that there is very little in-between.

Find a contractor that does higher end work. It all comes down to the house and load. My beach house is a typical east coast "four square" upstairs / downstairs w/ a larger kitchen and family room off the back. It's a three zone 4T Carrier 5 speed. Up/Down and Rear. We never use the whole house the same during the day. Why cool the second floor -- when we are not in it. Why have two systems when one can do it ... and that one is doing it with a better system able to remove all the humidity .. w/o any noise.

Again -- it's all based on doing a load and understanding what each area needs.

Load calculations came back last night -- according to the math (they sent the report - several pages of specs, input and calculations), the house needs 7.95 tons. I'm sure they can make the figures come out with whatever they want, but they're a very reputable company and we're going to take them at their word.

They're installing all new system today - AC, furnace, complete ductwork. We're considering getting the upstairs unit done as well, but we're going to wait to see how this one goes first.

Thanks for all the input.

 

[Notgrownup]

I’m sure it will give you peace of mind after it’s all over.

 

[yeldogt]

8T -- is a lot for under 4k .. that 1T per 500sf.

My new build is amongst 1/2 that number .... 70 on a 102 day. In my case the AC could have been lower .. but I need the HP output to be a bit stronger.

 

[doubleot]

I've been in the same boat for the last 3 years. My electric bill in the summer is annoying and it's clearly struggling keeping up with the heat. I'm waiting for it to die, I've had it checked up in the last year and the guy said everything looked good and he wouldnt recommend a replacement yet.

Sent from my SM-G950U using Tapatalk

 

[danski0224]

8T -- is a lot for under 4k .. that 1T per 500sf.

My new build is amongst 1/2 that number .... 70 on a 102 day. In my case the AC could have been lower .. but I need the HP output to be a bit stronger.

And the readers know nothing about either home...

Little details like windows and their orientation to the sun will make a huge difference.

 

[yeldogt]

And the readers know nothing about either home...

Little details like windows and their orientation to the sun will make a huge difference.

Yes you are correct -- but when I see number that match common 500sf ... one starts to think ..how was the load calculated.

The OP's house is not all that old ... non shingle roof ... two story vs one long story. Yes in .. TX

 

[danski0224]

Yes, the method used for the load calculation is unknown.

Even HVAC-Calc seems to be accurate, but isn't ACCA approved.

The OP could spend $50 of his own money and get the answers. It's pretty easy to gather the data needed by the software.

Then there's the rest of the system... ductwork (flex-work?), evaporator coil choices, filter choices all impact TESP and how much air (efficiency) is actually delivered.

Really too many variables.

I follow most of these threads just for the humor content.

 

[yeldogt]

Yes, the method used for the load calculation is unknown.

Even HVAC-Calc seems to be accurate, but isn't ACCA approved.

The OP could spend $50 of his own money and get the answers. It's pretty easy to gather the data needed by the software.

Then there's the rest of the system... ductwork (flex-work?), evaporator coil choices, filter choices all impact TESP and how much air (efficiency) is actually delivered.

Really too many variables.

I follow most of these threads just for the humor content.

I have my OCD moments. I spend more than typical on both lighting and HVAC when doing my projects. Somethings -- you do once. Like a big complex shower -- after it was done ..instant regret. Over many projects now ........having good lighting and a really nice HVAC system makes for nicer living. There are things I did once w/o regret .. but never do again -- other items you do and never think of not doing again.

It's not unusual for me to end up having an engineering company runs some numbers for me -- 1.5 hours and $450 bucks on my current project. It actually confirmed one of the contractors was close -- the other two were so far off. Heat load of the spray foamed house came in under 60k -- one guy had a 160k boiler for radiant and indirect and a 100k furnace.

 

[MattT]

That load calc sure looks suspicious. 450 sq ft per ton is on the low end of "rule of thumb". It exactly matching the existing equipment sure is convenient. I can't say for sure that it's been fudged but that's how it looks.

 

[Farmall450]

your plan makes sense to me.

This, run it til it dies. Maybe it'll surprise you.

 

[bulletpruf]

And the readers know nothing about either home...

Little details like windows and their orientation to the sun will make a huge difference.

I didn't realize how detailed a load calculation was; if it was simpler, I would post all the details here, but it's several pages worth of specs and calculations.

Yes you are correct -- but when I see number that match common 500sf ... one starts to think ..how was the load calculated.

The OP's house is not all that old ... non shingle roof ... two story vs one long story. Yes in .. TX

Yep. Two stories, concrete tile roof. Stucco exterior. Built in 1988.

Yes, the method used for the load calculation is unknown.

Even HVAC-Calc seems to be accurate, but isn't ACCA approved.

The OP could spend $50 of his own money and get the answers. It's pretty easy to gather the data needed by the software.

Then there's the rest of the system... ductwork (flex-work?), evaporator coil choices, filter choices all impact TESP and how much air (efficiency) is actually delivered.

Really too many variables.

I follow most of these threads just for the humor content.

I would be more suspicious if the contractor had been pushing their top of the line VS units or if he recommended 10 tons, etc. We're sticking with the same tonnage that we had and he recommended single speed 16 SEER equipment.

I have my OCD moments. I spend more than typical on both lighting and HVAC when doing my projects. Somethings -- you do once. Like a big complex shower -- after it was done ..instant regret. Over many projects now ........having good lighting and a really nice HVAC system makes for nicer living. There are things I did once w/o regret .. but never do again -- other items you do and never think of not doing again.

It's not unusual for me to end up having an engineering company runs some numbers for me -- 1.5 hours and $450 bucks on my current project. It actually confirmed one of the contractors was close -- the other two were so far off. Heat load of the spray foamed house came in under 60k -- one guy had a 160k boiler for radiant and indirect and a 100k furnace.

I'm much more concerned with lighting than I am with HVAC. We lived in Korea and Europe prior to moving to San Antonio - lighting in both places was horrible. We went overboard on lighting the house and garage. Huge difference.

That load calc sure looks suspicious. 450 sq ft per ton is on the low end of "rule of thumb". It exactly matching the existing equipment sure is convenient. I can't say for sure that it's been fudged but that's how it looks.

It's possible that it's been fudged, and I'm sure you can make the numbers say whatever you want them to say, but I'm inclined to give the HVAC company the benefit of the doubt, given their reputation.

 

[nsula_country]

450-500 sqft/ton sounds high. BUT, in the deep south summers are harsh and last 8 months.

Our house is about 2220 sqft, 31 windows (6 ft tall), 5 doors, 10 ft ceilings, 2 story, open staircase, partial foam insulated, hardi siding, pier n beam, 2012 construction.

6 tons. Load calc was done. Sized a little large, but not grossly over. Due to glass surface area its needed in the day time. At night not so much. Extra capacity helps in the winter. Resistive heat ususally only activates when in defrost.

2 systems, 16 SEER single stage Heat Pumps. 3.5T downstairs, 2.5T upstairs. Ridgid duct under house 1st floor, flex in foamed attic 2nd floor. We designed and installed all of it.

CT

 

[danski0224]

I didn't realize how detailed a load calculation was; if it was simpler, I would post all the details here, but it's several pages worth of specs and calculations.

I would be more suspicious if the contractor had been pushing their top of the line VS units or if he recommended 10 tons, etc. We're sticking with the same tonnage that we had and he recommended single speed 16 SEER equipment.

I'm much more concerned with lighting than I am with HVAC. We lived in Korea and Europe prior to moving to San Antonio - lighting in both places was horrible. We went overboard on lighting the house and garage. Huge difference.

It's possible that it's been fudged, and I'm sure you can make the numbers say whatever you want them to say, but I'm inclined to give the HVAC company the benefit of the doubt, given their reputation.

Yes, a load calculation creates a lot of data. If a report including all selections is created with HVAC-Calc, it can be quite lengthy. it would be difficult to "fudge" a report to that level just to fake it. However, improper selections for window type and insulation values can swing the results significantly.

Of course, if your system doesn't have the ductwork to handle the required airflow, then you will not get 4 tons of cooling specified on the load calculation- it might only be delivering 2...

You obviously do not understand how variable speed furnaces (or air handlers) benefit the system (air delivery) or indoor comfort (humidity removal). The same can be said for 2 stage condensing units- although the price difference here can be significant. The price difference between a standard PSC blower motor and a ECM variable speed blower motor isn't much at the wholesale level- but the contractor can mark it up however he/she sees fit (a wholesale price difference of $600-$800 was common about 15 years ago, now it is about $250)... and of course the high end thermostats have the capability to control it (ventilation cycles and dehumidification for example). So, I will not bother to waste any more time on this- it isn't just an upsell to pad the project cost.

Choosing lighting over HVAC? Poor choice. Heating and cooling costs account for almost 50% of the total annual energy expenditure for almost all (typical) homes (Google it- it is 42% last I looked). Then there is the significant cost of the equipment and installation on top of the cost to turn it all on... unless, of course, you have a **** ton of lighting that can be seen from low earth orbit...

 

[bulletpruf]

450-500 sqft/ton sounds high. BUT, in the deep south summers are harsh and last 8 months.

Our house is about 2220 sqft, 31 windows (6 ft tall), 5 doors, 10 ft ceilings, 2 story, open staircase, partial foam insulated, hardi siding, pier n beam, 2012 construction.

6 tons. Load calc was done. Sized a little large, but not grossly over. Due to glass surface area its needed in the day time. At night not so much. Extra capacity helps in the winter. Resistive heat ususally only activates when in defrost.

2 systems, 16 SEER single stage Heat Pumps. 3.5T downstairs, 2.5T upstairs. Ridgid duct under house 1st floor, flex in foamed attic 2nd floor. We designed and installed all of it.

CT

Yep, summers here are rough. Appreciably hotter than it is in Houston, where my parents live.

 

[bulletpruf]

Yes, a load calculation creates a lot of data. If a report including all selections is created with HVAC-Calc, it can be quite lengthy. it would be difficult to "fudge" a report to that level just to fake it. However, improper selections for window type and insulation values can swing the results significantly.

Of course, if your system doesn't have the ductwork to handle the required airflow, then you will not get 4 tons of cooling specified on the load calculation- it might only be delivering 2...

You obviously do not understand how variable speed furnaces (or air handlers) benefit the system (air delivery) or indoor comfort (humidity removal). The same can be said for 2 stage condensing units- although the price difference here can be significant. The price difference between a standard PSC blower motor and a ECM variable speed blower motor isn't much at the wholesale level- but the contractor can mark it up however he/she sees fit (a wholesale price difference of $600-$800 was common about 15 years ago, now it is about $250)... and of course the high end thermostats have the capability to control it (ventilation cycles and dehumidification for example). So, I will not bother to waste any more time on this- it isn't just an upsell to pad the project cost.

Choosing lighting over HVAC? Poor choice. Heating and cooling costs account for almost 50% of the total annual energy expenditure for almost all (typical) homes (Google it- it is 42% last I looked). Then there is the significant cost of the equipment and installation on top of the cost to turn it all on... unless, of course, you have a **** ton of lighting that can be seen from low earth orbit...

We got all new ductwork with our system - plenum, ducts, everything. They added a return line that was the same size as the original line, so we doubled the capacity there.

As for the lighting vs. the HVAC, the lighting is an area where we I felt we had a lot of leeway and much room for improvement. It's also an area where you don't necessarily have the guidelines and infrastructure that you do with an HVAC system, so I felt it was on us to get this right, and we succeeded, both inside and in the garage.

As a reminder, for the HVAC, we went with a very reputable company. The big decision was whether or not to replace the systems. Once that decision was made, it was important for me to understand enough about HVAC to make an informed decision on how to proceed. Had we hired the cheapest HVAC contractor we could find (i.e., someone not necessarily licensed, bonded, experienced, etc), I would have felt the need to be much more involved and informed. However, with a reputable and professional company, brand name equipment (all Trane), and a warranty, I'm comfortable with my level of understanding and involvement.