[red tillman]

When an existing air conditioner needs to be replaced, I have two questions:

1. Why is it important that the outside unit seers be the same as the seers on inside unit?


2. What would happen if I installed a New outside A/C unit (5 ton) with a seer rating of 13 seers and I failed to replace the inside exchanger which has a seer rating of 10?

Thank you,

Red Tillman

[hvac1000]

When an existing air conditioner needs to be replaced, I have two questions:

1. Why is it important that the outside unit seers be the same as the seers on inside unit?


2. What would happen if I installed a New outside A/C unit (5 ton) with a seer rating of 13 seers and I failed to replace the inside exchanger which has a seer rating of 10?

Thank you,

Red Tillman

Start with this

I think most home owners will understand if you give them something they can see.
Show the factory charge on the unit they have, then the charge on the new unit.
Most will read as stated below, I think.
I’m just looking for ways to help justify Coil with condenser. This may help?

Nominal Three Ton System.

A heat pump outdoor unit manufactured in 1995 took a 125oz. Charge of R-22.
A heat pump outdoor unit manufactured in 2004 took a 200oz. Charge of R-22.

On the heat pump outdoor unit alone there is a volume mis-match of 1.6.
Meaning, the volume of Refrigerant held in a unit manufactured in 2004
Is 1.6 times that of a unit manufactured in 1995.

On an indoor coil manufactured in 1995 the face area of a
Coil was 3.8 sq. ft. at 13 fin/inch, 3 rows deep.
On an indoor coil manufactured in 2004 the face area of a
Coil was 4.38 sq. ft. at 14 fin/inch, 3 rows deep.


This is just a part of mismatch.

You can mismatch but the unit will not work correctly,the pressures will be off,energy savings will be lost,manufactures do not warranty mismatched units, suction line sizes can be different, TXV has to be used for a mismatched system or liquid slug back can kill the compressor in the new unit.
There are more than this but I think you should get the picture by now. Only a lazy fool does not install a matching coil with the outside unit.

[aldematt57]

It's not a matter of being lazy nor foolish.
There are other considerations to remember, especially for the owner.
I wonder if those who criticize the practice of "mismatching" would be as critical if they were the ones ponying up the money to retrofit a "match" they don't need just because a mfgr. Or a salesman recommends one.
If the owner does not need an indoor section, why replace it if you can show that the only thing affected is a loss of efficiency with no operational problems?

If you install a 13 seer outdoor section with a 10 seer indoor coil, it's not necessarily going to create any operational problems at all. Most new outdoor sections have enough storage capacity in the accumulator to prevent liquid line floodback.
Correct metering at the evaporator is all that is required.
2 tons is 2 tons, regardless of what the efficiency ratings are.

One way to verify that the system is operating properly is to check system superheat AND subcooling as well as proper airflow requirements.
This will indicate the condition of the refrigerant in each coil and would verify if either coil is starved, flooded or in a normal state.
If the system dials in at required superheat and subcooling, there is no liquid line floodback, no starved coils and no problems. Period.
And I don't care what you've been told.
Look at the PDF file shown at the bottom of the previous post.
It shows capacity and efficiency "losses".
It also shows that a 10 seer mismatch with a 13 seer coil actually increases efficiency by 1.5 seer over the previous efficiency rating.


Would a match be more efficient? Absolutely.
Will there be problems if the coils are not matched?
Not if the installing contractor knows what he's doing.

[hvac1000]

Everyone is entitled to there opinion. I prefer to do the job correctly.
Old indoor A/C coils usually are dirty after all the years of operation so unless you clean the old coil you are doing the customer wrong.
Old indoor A/C coils have a drain pan. Usually on the old coil rust has already taken a toll on the drain pan. What is the good of replacing just the outside unit when in a year or two you will have to return to the customers house to replace the indoor coil anyway because of leaks.

One of the reasons for the required 13 SEER minimum energy standard was to help the customer save energy and lower electric power usage on the grid. By just changing the outdoor unit the system will not meet the requirements

As a few companies in my area have already found out manufactures have started to deny warranty for the outside units unless a matching coil was purchased at the same time. When the contractor goes to get a replacement compressor under warranty for a new 13 SEER style unit they must show or the distributer must have a record of a matching coil that was purchased to go along with the new outside condensing unit or they can refuse to warranty the compressor. If you do not believe this read the fine print on most warrants from the manufacturer.

Customer cost

It will cost the customer more $$ in the long run if you use the old coil.

All of this problem will be over when outside R-22 units are no longer manufactured and this is going to happen soon.

In a experiment at the university we used a new donated 410 condensing unit
And connected it to the same size R-22 coil. During life expectancy tests we found that this set up cost about 40% of the normal life expectancy and the BTU capacity was cut 28%. They will not be hooking R-410 condensers to R-22 coils for long when this is discovered by the general public.

I believe in doing things correctly while some people do not. The ones that do not do things correctly will have to answer to there customers sooner or later.

[aldematt57]

I don't see it as an opinion at all.
I see it as verifying the science and not accepting the status quo because someone says it must be so.
A job done right? LOL I don't worry about warranty claims.
Here's what I'd do for my customer... I'd tell them that I will guarantee that the 13 seer outdoor unit will outlive it's warranty requirements or I'll replace the unit free of charge. How's that for the confidence needed to prove that this supposed mismatch will work properly?


I've already stated that a good tech would ensure that the system operation is normal by using superheat/subcooling to verify the condition of the heating/cooling coils. Please explain how proper superheat/subcooling and airflow are not a "job done correctly".
I would assume that a thorough technician would have already assessed the situation to ensure that the indoor section is in good condition.
If they have not, it will bite them in the butt.

All things being equal, I know that certain "mismatches" will cause absolutely no harm to any operating component because I have verified it through my own field operation tests and experiences.
Furthermore, you talk about costs to the customer and refer to warranty claims as though it's inevitable that there will be a claim due to operational problems with a mismatch.
And to that I say, BALONEY.
I also find it laughable that you would refer to the 13 seer standard as a way to save the consumer money.
How are any savings recognized for the HO who lives week to week when a tech or saleman just tells him that he'll have to pony up thousands of dollars in cash to replace his 5 year old fan coil that runs great, because he needs to think long term energy savings?
The point? Some customers don't have the option and they need to be able to rely on an honest company who won't leech their last dime under the guise of "acceptable standards".

I'm not advocating the practice of mismatching equipment, but I can certainly see the need for it in isolated instances, especially for customers who can't afford a new indoor section they don't need. All I'm saying is that it is an option and while it should be a last resort, it is an option that will cause no harm if done right.

You've already stated that using TXV metering is an acceptable form of allowing a mismatch, right?
If you look at the ARI ratings and matches, they do not allow a TXV to be a disclaimer to use to ensure that a factory mismatch become a "match".
They simply show the factory matches.
Of course, many of us know that a TXV will properly adjust superheat as needed and usually prevent liquid line floodback to the compressor.
With a piston, less accuracy is noted but the job of keeping system superheat within allowable limits is still possible.


Sorry, but I see the "mismatch" propaganda as nothing more than a way for mfgrs. To move more boxes and salesmen to sell more "matches" under the veil of misinformation.

It's a point that's becoming less and less discussed because of the fact that piston metering is becoming a thing of the past with 410-A, TXV's and EEV's becoming the standard.

[hvac1000]

I don't see it as an opinion at all.

Since there is more than on way of doing the job it is an opinion.


I see it as verifying the science and not accepting the status quo because someone says it must be so.
A job done right? LOL I don't worry about warranty claims.
Here's what I'd do for my customer... I'd tell them that I will guarantee that the 13 seer outdoor unit will outlive it's warranty requirements or I'll replace the unit free of charge. How's that for the confidence needed to prove that this supposed mismatch will work properly?

Your customer does not care about science. They just want the job done correctly so it will last and be under warranty just in case you are no longer there to service or replace the unit at no charge. This is why I always say DO NOT accept or buy a warranty from an individual or HVAC company. ONLY accept or buy a warranty backed by the manufacturer of the equipment. Manufactures offer both parts and labor warranties direct from them. This way if the dealer or individual dies or goes out of business the owner can call the factory supplied number for the warranty repair.


I've already stated that a good tech would ensure that the system operation is normal by using superheat/ subcooling to verify the condition of the heating/cooling coils. Please explain how proper superheat/subcooling and airflow are not a "job done correctly".
I would assume that a thorough technician would have already assessed the situation to ensure that the indoor section is in good condition.
If they have not, it will bite them in the butt.

How is the tech going to know if the system is operating normally without installing the new outside unit first? Superheat,Subcooling and air flow are necessary to be within spec for a system to operate normally and the specs for the outside unit will not be as stated because you are using to small of a cooling coil since you did not replace the old one with the new design coil for the new outside unit.
How is the tech going assess the situation without seeing the bottom side of the old indoor coil?
I guess the tech will tear apart the furnace top to see the old coil? If so why just not replace the indoor coil when you remove to old coil for cleaning since after years of use they all need to be cleaned for proper operation and if you have experience in this trade you know they are all full of mold/mildew/rust and corrosion of the aluminum fin areas. How about giving the customer a break from all that nastiness and install a new coil. While you are at it also install a new properly terminated condensate line since many of them are running out on the basement floor or in the crawl space.

All things being equal, I know that certain "mismatches" will cause absolutely no harm to any operating component because I have verified it through my own field operation tests and experiences.
Furthermore, you talk about costs to the customer and refer to warranty claims as though it's inevitable that there will be a claim due to operational problems with a mismatch.
And to that I say, BALONEY.
I also find it laughable that you would refer to the 13 seer standard as a way to save the consumer money.
How are any savings recognized for the HO who lives week to week when a tech or saleman just tells him that he'll have to pony up thousands of dollars in cash to replace his 5 year old fan coil that runs great, because he needs to think long term energy savings? The point? Some customers don't have the option and they need to be able to rely on an honest company who won't leech their last dime under the guise of "acceptable standards".


You should go to work at the factory where they make the new equipment. You seem to know more about the equipment than the engineers that designed it. They do not allow mismatches for a reason but you can teach the factory boys a lesson or two about mismatches. LOL
There is a failure rate for a properly installed system and when you start to play games like you do by not replacing the indoor coils with the proper new coils rated to work with the outside unit the failure rate will go up. The 13 SEER rate is the new standard which will soon be going up to 14 or 14.5 SEER soon. By not using the proper coil the customer is spending more on the electric bill to cool there home than if they had the proper coil. You are not saving your customer money by not replacing the coil you are actually costing the customer money every time they run a inefficient unit. So there goes you customer savings theory. A new indoor fan coil does not cost thousands of dollars unless you are ripping of your customers to start with. Fan coils with electric heat only cost the trade about 500.00 to start with for the inside unit and you stated they cost thousands. It really does sound like you are ripping off your customers to use such a high cost. No wonder those poor people who live day to day and week to week cannot afford to buy a new indoor coil from you. You are probably overcharging them for the outside unit to start with so little is left to do the job correctly.
No wonder some customers have no option left if they are dealing with you and you say you're honest? I do not think so. You are the one leaching the last dime from them under the guise of being honest.
Acceptable standards are in place to help prevent the customer from being ripped off to start with so I see nothing wrong with acceptable standards. Only a crook would feel he could do work that did not meet those standards and call it a good job and saved his customer money. Give us all a break here.

I'm not advocating the practice of mismatching equipment, but I can certainly see the need for it in isolated instances, especially for customers who can't afford a new indoor section they don't need. All I'm saying is that it is an option and while it should be a last resort, it is an option that will cause no harm if done right.


It sure sounded like you were an advocate of the mismatch syndrome in your posts. If you cannot do a job correctly and within the acceptable standards of the day it is best not to do the job at all. Let someone else do it correctly.

You've already stated that using TXV metering is an acceptable form of allowing a mismatch, right?
If you look at the ARI ratings and matches, they do not allow a TXV to be a disclaimer to use to ensure that a factory mismatch become a "match".
They simply show the factory matches.
Of course, many of us know that a TXV will properly adjust superheat as needed and usually prevent liquid line floodback to the compressor.
With a piston, less accuracy is noted but the job of keeping system superheat within allowable limits is still possible.


No that statement is false. I believe I said that a TXV metering device would be the only way you could get a mismatch to perform. It is not acceptable by the equipment manufactures and not in keeping with the standards of today. How many tech's actually know how to set superheat or sub cooling accurately. Not only that but most valves from the manufactures are not adjustable but preset from the factory so that means you will have to buy a very expensive Sporlan or Alco or other expensive valve to be able to adjust the system. Wow there you go spending your customers money that they do not have to start with.
How many times are you going to pump the unit down/recover the refrigerant so you can experiment with piston size changes?
By the time you are done selling expensive valves or playing with piston changes along with all the additional labor you could have done the right thing and just replaced the old coil with the proper new one.

Sorry, but I see the "mismatch" propaganda as nothing more than a way for mfgrs. To move more boxes and salesmen to sell more "matches" under the veil of misinformation.

There you go spreading your propaganda that it is OK to mismatch a system and leaving your customers to suffer the consequences of your bad decisions.

It's a point that's becoming less and less discussed because of the fact that piston metering is becoming a thing of the past with 410-A becoming the new kid on the block.

Yes the advent of R-410 will put many of the hacks in this industry out of business. At least I can say that there is a new generation of tech's getting into this business. I proctor NATE and other certification testing in my area and I see many new young faces that seem to want to do it correctly. You can tell because of the questions they ask and the concern they express about air quality/global warming etc. Many of the same tech's attend my class at the university where I try to instill the idea of doing it correctly the first time so you do not have to go back and do it over again.

Forgot to mention this fact. If you started out with say a older two ton outside unit and you just replace the outdoor unit and not the inside coil you will loose BTU capacity. The newer units are using smaller btu compressors but with the new bigger capacity indoor coils the BTU's are the same two ton. Statistics state that the mismatch can cost up to 4000 BTU's. So not only is the customer not getting a quality job they are also loosing BTU's which on most homes will make the A/C not cool as good with the new outside unit/old indoor coil as compaired to the older outside unit and old coil. That is 1/6th the cooling power being lost by not changing the indoor coil along with higher energy costs.

aldematt57 I know you probably know the basics and beyond by here is a bit of info that could be useful to you. I use this info in my classes.

LONG DL

http://www.hvaccertified.com/docs/co...&%20BEYOND.pdf

[hvac1000]

I did not mean for you to run away from the conversation. No guts no glory.
Come back and we will see just how smart you are. This type of discussion is good for the board. It allows regular people/customers to know just what to look out for when hiring a contractor to service/replace there equipment. Now they will know at least about the problems that can develop by not having the contractor change the inside coil when going to the 13 and above SEER units.

[aldematt57]

Run away? LOL I don't give a good crap whether you're a proctor or a proctologist.
A proctor may or may not be a teacher. I've seen enough of them and most of them were nothing more than test adminstrators, so don't flatter yourself.
I've more than a few "certifications" and licenses myself, but I resist holding them up as an excuse for not dealing in reality.:D

As I've already stated, I've never had a single warranty claim on any mismatches that I've done and I've never seen any significant drop in capacity or any operational problems either.
I've even checked EER on the supposed mismatches and found a significant GAIN in efficiency from the previous costs to operate the system with a factory matched outdoor section of a lower seer rating.


You yourself suggested that a "TXV has to be used" with a mismatch, did you not?
Or do you want me to regurgitate your own post for you so that you can review it?
Here it is...

"You can mismatch but the unit will not work correctly,the pressures will be off,energy savings will be lost,manufactures do not warrenty mismatched units, suction line sizes can be different, TXV has to be used for a mismatched system or liquid slug back can kill the compressor in the new unit.
There are more than this but I think you should get the picture by now. Only a lazy fool does not install a matching coil with the outside unit".

The paragraph above is contradictory and does more to perpetuate a few myths.
Let me at least partially address them...

Please explain why "the unit" will not "work correctly". Will it "work correctly" with a TXV or not? DUH
If system(not unit) superheat and subcooling are normal, how exactly do you conclude that there is an operational problem?
If both refrigerant coils are neither flooded nor starved, then they are normal and no liquid slugging can occur.
Suction line sizes rarely differ when moving to higher seer equipment either, especially with units that utilize TXV's and normally sized coils unless there are long line considerations, so that eliminates lack of oil return.
The problems I've seen with inadequate oil return have everything to do with improper installation techniques and pipe sizing and not a damned thing to do with mismatched coils.

To be fair about the supposed mismatch is to say that there may be a need to adjust the charge for heat mode when heat season comes around after system charge is balanced for cool mode and that is attributed to possibly using piston metering in heat mode.
If a TXV is present outdoors as well, it's usually not even an issue and it's certainly not an issue in a refrigerant circuit during cool mode where the accumulator is nearly as big as the compressor.


In fact, if you read the literature concerning mismatches, they never do say that "mismatches" do not operate properly as you yourself have done.
They simply recommend against them.

You say that a customer doesn't care about verifying the science and that is a fairly derogatory remark to make about present day customers.
They very much want to be informed and they are smarter than you seem to be giving them credit for.
They also seem to welcome straight talk from people who stand behind their work and don't perpetuate myths and "upsells".

[hvac1000]

Here is a great video for our homeowners and undernformed contractors to watch. Kind of tell the tale of the tape on this situation. York and Copeland Compressor reps chime in on the situation.BTW a TXV has to be used when you are trying to make something work that would normally not work in a mismatched system.
They explain here why the mismatches do not work and cost more down the road. What you are trying to do is fight against the industry and that never works. Enjoy

YouTube - 13 SEER

[aldematt57]

So, you are now affirming that a purported mismatch can be a perfectly acceptable match with TXV metering?
If not, maybe you could explain how a Trane 10 seer heat pump matched with a Ruud 8 seer fan coil utilizing piston metering at the indoor secrtion could be in service 22 years after it was commissioned, much to the delight of the homeowner?
Undoubtedly, he and I both are still waiting for the compressor failure that you keep parroting is likely to happen.
I've had great success saving customers money by simply using a TXV when necessary, and it's offensive to me when I hear someone say that the practice of creating a match that works well is "lazy and foolish".
I've been in mchanical trades likely longer than you've been breathing, so I'll refrain from hammering you with the point any longer.

Also note that 10 seer equipment can still be installed provided it is available and THERE IS NO MANDATE FORCING HOMEOWNERS TO USE 13 SEER IF LOWER SEER STOCKS ARE STILL AVAILABLE.
Lots of maybe's and could be's in that piece.

[coolmen]

So, you are now affirming that a purported mismatch can be a perfectly acceptable match with TXV metering?
If not, maybe you could explain how a Trane 10 seer heat pump matched with a Ruud 8 seer fan coil utilizing piston metering at the indoor secrtion could be in service 22 years after it was commissioned, much to the delight of the homeowner??
Undoubtedly, he and I both are still waiting for the compressor failure that you keep parroting is likely to happen.
I've had great success saving customers money by simply using a TXV when necessary, and it's offensive to me when I hear someone say that the practice of creating a match that works well is "lazy and foolish".
I've been in mchanical trades likely longer than you've been breathing, so I'll refrain from hammering you with the point any longer.

Also note that 10 seer equipment can still be installed provided it is available and THERE IS NO MANDATE FORCING HOMEOWNERS TO USE 13 SEER IF LOWER SEER STOCKS ARE STILL AVAILABLE.
Lots of maybe's and could be's in that piece.

GO to school numnutts .

[T-Top]

I'm going to have to agree with aldematt57 it will work. What we need to remember the spec is to cover the manufacture. They are not saying it won't work but for bets results follow my directions. Some times the home owner can't come up with the extra $800 to change the coil out, if you don't have the money you just don't. But all ways tell the owner that the SEER has just dropped on their new A/C unit and why. aldematt57 I see you are a person that works in the field like I and knows if it works or not. Good job keep up the good work and stick to your guns.

[hvac1000]

There was never a mention that it did not work the problem is it is not correct to do this. This goes a lot further than just a loss of SEER points. Look and read up on the amount of refrigerant the new outside units hold. Then calculate exactly what is going on in the system when the TXV slams shut or goes full open on the too small old style coil. One other item also. The TXV is not a floodback control. That is not its design or purpose it is just a metering device. If you doubt that flood back statement just check with your ALCO or Sporlan rep for more info. I worked in the field for many years until I sold my small 37 man corporation. There is a right and a wrong way to do all things. I only look at the correct way of doing a job. I know there are people who cannot afford a new evaporator since they are being charged 2,500.00 just for a outside unit slip in but that does not make it correct to do so. A TXV has limitations and you absolutely need one when the mismatch is with a 10 or 8 SEER coil. Remember I said need one to make it work I did not say it was OK to install a system like that. I do not trust piston/capillary metering devices when a situation such as this exists..

There are hundreds of tricks that most of us learn in the HVAC business but I do not believe that most of them should be posted here. Just like the mismatch situation it can cause the uniformed to actually believe they can do this and there system will work OK. A professional might be able to get it to run and cool but it sends a wrong message to most of the readers here. That is why I have stood my ground on this situation. This is not a professional discussion board but one that caters to mostly homeowners and this kind of information can do more harm than good.

It is also understood that many service techs who have done marginal things before will stand by what they say because they do not want to admit they are wrong. So be it. I could put a lawnmower motor in a Caddy and make it work. That does not mean it will work correctly or perform as intended. Lets face it I look at things from a educational stand point since I would never instruct anyone to mismatch on purpose. I also make sure to tell all the young and old students at the university to make sure the evaporators are on the list of accepted units for the condensing unit they are installing. This is done because it is the only accepted way by the major manufactures to install there equipment and that is what is taught here. Doing it the right way is the only way I can teach it.

One good thing about this thread is that the readers will get to see both sides of the story and then they can decide for themselves what is right or wrong.

[coolmen]

OK so I have a homeowner who's 5 year old systems compressor is shot and fan is shot .Builders grade junk. She wants a better grade condenser and I should just leave the 10 seer evap in its place and sell here a tXV and keep it r-22.. I really should try and sell here a condenser with 410a ,a larger coil, and a line set for the 900 k house. I thought the large condenser and smaller coil may not remove moisture as well as it should. What do I know! I just follow directions.

[hvac1000]

900K in my area is a pretty nice house. I would replace the outside unit and also replace the indoor coil with a match to that outside unit. As I stated before you loose BTU's when you place a new 13 SEER unit on a 10 SEER coil and it could be that that house is large enough to notice the loss of 4000 to 8000 BTU's of cooling power. The new 13 units use a smaller capacity compressor with the larger coils to maintain the given BTU's where as the 10 SEER usually had a full capacity compressor. This is all done so that the new equipment can achieve a 13 SEER rate. If you look up the compressor model numbers on the new 13's you will see what I mean. Usually on a five ton the 13 SEER machine will use a 4.5 ton compressor.

As far as R-22 or R-410 that is a discission you will need to make. Both units are still available and the R-410 units are the future as R-22 units will be discontinued shortly in I believe 2010. If you are going to use the old line set with R-410 I highly recommend a good flush to remove the mineral oil and impurities.

[coolmen]

I formed the homeowner the proper way is to replace both condenser and evap coil as well as the lineset . This is the only way I would have offered it. She will be upgradeing to 410A.

[T-Top]

So you sold the home owner a system with the compressor under warranty. Good job(not).

[hvac1000]

5 year old systems compressor


Hey Ttop how long are compressor warranties anyway? He said it was builders grade junk so I thought 5 years on most systems compressors on the cheap junk. Looks like he did the right thing. At least this way the homeowner will have a warranty again.

[T-Top]

Even with what some call junk may have a ten year warranty on compressor. If the serial numbers on the system said 2003, and its 2008 basic warrant on a compressor is 5 years but some times you need to check and go the extra mile for the home owner. A unit that has the date code of 03 may not have been installed until 04(A half truth is a whole lie). But I'm sure the next reply will be all was checked.

[hvac1000]

Years ago Carrier always extended me the courtesy in case of a compressor failure near the end of the warranty to deduct what the cost would be for the compressor off my normal dealer price for a new unit so I could just install a new condenser for the customer. They would just keep the warranty compressor in stock to sell tosomeone else I used that deal to many customers advantage over the years. Now days they probably would not offer that deal even to the best high volume dealers.