10 SEER to 13 SEER?

[hungryjack]

What is the understanding within this Forum regarding the transition from 10 SEER to 13 SEER? Can a homeowner replace the condenser with a 13 SEER and leave the 10 SEER evaporator in place?

I totally understand that the 13 SEER efficiency is lost if the indoor/outdoor SEER ratings are mis-matched. That is not my question. I am asking if the DOE has mandated that the indoor/outdoor components have the same SEER?

[beenthere]

No, its just not legal for the manufacturer to sell equipment that does not have a 13 SEER match.
You can by a 13 SEER condenser and legally put it on an 8 SEER evap coil as far as the Fed DOE reg is concerned. Local codes may not allow it.

Another thing many people are confused about. Is they think that the 13 SEER condenser will just use more electric to do its X tonnage work. In reality, a 3 ton 13 SEER condenser hooked to a 10 SEER evap coil, may now be a 9 SEER 2.25 ton unit.
You lose capacity, thats why you lose efficiency with those matches.

[tomgeer]

So what was the end result with the 13 seer? Compressors are smaller but coils are larger and this is how higher seer is achieved?

Total dehumidification is less and this is why variable speed and two stage equipment is recommended. Not to mention hole house dehumidifiers or the Lennox humidatrole.

[beenthere]

Unfortunately, the EPA, and DOE only looked at energy usage with tunnel vision.
They gave no consideration to some people having to set their stats lower, to get the same comfort from some of the new units.

[luckyair]

In reality, a 3 ton 13 SEER condenser hooked to a 10 SEER evap coil, may now be a 9 SEER 2.25 ton unit.
You lose capacity, thats why you lose efficiency with those matches.

What is the basis for losing capacity? 25% Loss in Capacity? Where does that data come from?

[beenthere]

That was from a test Bristol compressor did. they used a 3 ton HP. Tested it with both piston, and TXV.
And they tested it in both heat and cool mode. they attempted adjustments to the charge.
Someone posted the results, or a link to them. Just not sure what thread it was in, or who posted it.

[udarrell]

We need to face a lot of reality factors that are not mentioned when talking about SEER ratings.

This is only my opinion based on my experience as an HVAC tech since the mid 1970's.

If you are in a hot high humidity climate you will want a very cold cooling cool coupled with long run cycles.

In my opinion, the optimal return on your investment will probably be in reducing humid air infiltration & other factors that reduce the heatload!

I would always demand that the system have a scroll compressor & a Thermostatic Expansion Valve (TXV) refrigerant metering device. In some cases that requires at least a 14-SEER rather than a 13-SEER system.

"Regarding the 13-SEER condenser using a 10-seer cooling coil, if you live in a 'very hot high humidity climate' & the 10-seer coil has an adjustable superheat TXV refrigerant control;" you could set the Room Stat at 78-F & increase the airflow somewhat to get close to the condenser's BTUH Rating.

With optimal air circulation in the rooms & the low humidity (45%) you would be well within the human comfort zone. (i.e., 50% RH 79-F)

http://www.udarrell.com/air-conditioning-total-heat-enthalpy-latent-heat.html
- Darrell

[ECIndHVAC]

How about this strategy:

Suppose the home owner has a 3 ton 10 SEER system (both coil and condenser). Now, my hunch is that if you replace the 3 ton 10 SEER with a 2.5 ton 13 SEER and use a suction line filter dryer (in addition to doing its job of filtering, it would also help flash any liquid that may be coming back to the compressor into gas), then everything should work out OK. I am, of course, assuming that the original 3 ton didn't run all the time to "keep up", so that the new 2.5 ton will just run a little bit longer to do the same job, and perhaps remove more humidity in the process. Any thoughts on this?

[beenthere]

If the suction drier is flashing liquid to gas. Then the system has a problem, and the drier is restricting. And you don't have 2.5 tons of capacity.

If the old 10 SEER system was moving the proverbial 400 CFM per ton. You now have high humidity, and maybe some mold growing in the ducts, and other areas of the house.
Because the evap coil temp is too high.

And, after mold remediation, you still need a new indoor coil or air handler.

[ECIndHVAC]

beenthere,

Thank you for your response. Now, keep in mind, I'm no "master tech" (more of a "helper"), but I have a few questions about your post.

If I understand what you're saying, the presence of liquid in the suction line would indicate that the system definitely has problems and is not operating to full capacity. This seems obvious enough. My intention with the "extra function" of the suction dryer is to add volume to the suction line to keep ANY of the tiniest drops of liquid from returning to the compressor. And my hunch is that there probably wouldn't even be any such liquid because the coil is 3 ton (albeit a 10 SEER).

But, for kicks and giggles, let's suppose that the capacity of the unit has been reduced to 2 tons (for easy math). So, we now have a 2 ton unit with 1200 cfm moving across it. In general, at least in my area, this never causes too many problems. In fact, common match ups in my area are 75,000 BTU furnaces (with 3 ton blower drives) mated with 2 ton AC units. But, to play devil's advocate, this *new* "2 ton unit" will be running 50% longer than the old 3 ton unit, so my guess would be that, in terms of dehumidification, the longer running time would compensate for the lower degree differential.

Or am I completely wrong? BTW, based on Copeland model numbers, it seems that a new 3 ton 13 SEER unit seems to use more or less the same compressor as an old 2.5 ton 10 SEER.

[TMH58]

I posted that data from Bristol a year or so back. Do not remember the exact thread, but along with the testing results and graphs, it showed up to a 40% loss in cap. in clg., up to 48% in htg., up to 40% loss in efficiency in clg., and up to 60% loss in htg..

[beenthere]

Newer units do use a small BTU rated compressor then 10 or 8 SEER units.
They use large condenser and evap coils to get the BTU capacity.

The furnace may have a 3 ton drive, but what is the actual CFM its moving?

Just for explanation, lets say its moving 1200 CFM. And that the new condenser coil combo is 2 tons TOTAL capacity.

Now, with 1200 CFM, the latent BTU is reduced to 2400 BTUs an hour, instead of the 5400 that is needed. So the house is gaining moisture faster then the A/C is removing it.

So now the new unit is running almost 34 minutes to remove the same amount of moisture as the 3 ton would in 15 minutes. Plus not lowering the temp of the house.

Suction filter driers don't add much to the volume of the vapor line. Unless your putting a drier in that is grossly over sized.

[beenthere]

I posted that data from Bristol a year or so back. Do not remember the exact thread, but along with the testing results and graphs, it showed up to a 40% loss in cap. in clg., up to 48% in htg., up to 40% loss in efficiency in clg., and up to 60% loss in htg..
You mean this one.

[TMH58]

No. Not that one. The one I posted had graphs and was set up as a power point. I still have it but can't remember how to post it. It has been a while since I posted pics and power points. Help me and I will send it to you.

[beenthere]

Wow. Blackmail. If you don't help, I won't send it to you. :)

I don't know how to post a PP file.

[TMH58]

Very funny. You are quite witty Beenthere.. Well, you have the info anyway. I just did not remember how to do it. No biggie. It has been a helpful sales tool by poor saps who can't talk homeowners into doing the right thing. I am no salesman. If I don't like the looks of something, I don't do it. Money is not not worth reputation to me.

[RDrennan]

One thing you are also over looking with a mismatched system unless you have a reciever is flodback to the compressor, so you end up having compressor failure. But you get the efficiency loss due to the fact a 13 seer requires more refrigerent than a 10 seer of the same tonage which usually floods the evap and the cooling occurs in the "changing of state" of the refrigerent in the evap coil. With a properly sized evap it is large enogh to accomodate the additonal refigerent so the change of state" occures within the coil like it is supposed to and everything works fine. As for air flow, too much air and you decrease moisture removal "laten heat" and to little air flow and you decrease sensible heat removal but increase laten heat removal. Typicly air flow is between 350 to 450 cfm per ton average of 400 cfm per ton.:)

[BigJon3475]

If the duct system is designed right

Looking at a 1 1/2 ton unit right now....it's got a 14,000 btu compressor in it....with much larger coils.

TXV would help straight a/c if you must do it....

Heatpumps are a no no.

[beenthere]

Receiver won't help.
An accumilator would help alittle.
But, thats just Mcgievering a crap system though.

[RDrennan]

My bad I got it bass ackward... sorry... was typing faster than I was thinking...:o

[beenthere]

happens to everyone. :)

[ECIndHVAC]

That Bristol report is definitely a good selling point for a penny-pinching customer who doesn't want to change out the coil.

But, on the other hand, say your back was against the wall (eg, height restrictions, etc). Could you put a smaller piston on a 3 ton 10 SEER coil and use either a 2 ton or 2.5 ton 13 SEER unit, and then reduce the blower speed (ie, the "blue" speed instead of the black) to avoid the dehumidification problem that beenthere mentioned (BTW, all this latent/sensible heat stuff makes my head spin!)?

[beenthere]

If the old unit was barely able to keep up.
After down sizing the piston, the new unit won't keep up.

Don't forget.
Their are third party coil manufacturers, that make shorter height 13 SEER rated matching coils for most if not all brands of condensers.

[BigJon3475]

The piston that comes with the unit should be used inside. A TXV would be better.

Up sizing 1/2 ton can add back some of that capacity on a straight a/c system. Your pressures will already be low due to an oversized outdoor coil and an undersized inside coil.....dropping the airflow could be horrible.

As beenthere said unless your MCgiever....


Ill add or Hamburglar...:)

[RDrennan]

then you may have an under sized system if you go with a smaller cond. You really need to just change both the cond and coil and solve the problem and be done.http://hvac-talk.com/vbb/images/icons/icon15.gif

[riderman]

If the old 10 SEER system was moving the proverbial 400 CFM per ton. You now have high humidity, and maybe some mold growing in the ducts, and other areas of the house.
Because the evap coil temp is too high.

And, after mold remediation, you still need a new indoor coil or air handler.

I know this is and an old post, but I think I have proof that BT is correct.

Around 2.5 years ago my 12-14 yr (matched with AHU) 10 SEER 2.5 ton HP OD unit died. I replaced the OD unit with a 13 SEER unit, but left the original AHU installed. It did function, but we were cold on the cold day's and HOT on the hot day's, with huge electric bills.

The entire HP unit was replaced with a half ton larger 15 SEER system 2 weeks ago. The comfort so far is like night and day compared to the old unit.

I have pictures of the old AHU coil. Dried Mold! (according to the installer) 1/4" bubble looking things, black and dried covering return side of the evap coil. I have pictures that I can post, they are gross looking.

The duct's are scheduled to be cleaned!

[beenthere]

Post them.

[riderman]

Post them.


I hope it worked (pic post). These are disgusting. Trust me here, I think we change filters above the average person. We've tried high MERV, rock catchers, and almost everything in between over the years. I just dug up a receipt where this EVAP coil was cleaned 2 month's after the 13 SEER OD unit was installed. So, a little over 2 years of a mismatched system caused this? We are embarrassed showing these pictures! If the wife see's this post, I'm a dead man:)

[beenthere]

I think you got some bypass around your air filter.

[Todd A]

I had this same issue on a furnace installed in 2002 that had a 10 seer coil, with a 37 year old 6 seer compressor that was failing. One contractor said the 13 seer into 10 mismatch was no big deal, another said he'd do it but that the mismatch probably would void the warranty. I decided to get the new coil. Ironically I also decided to go up to 14 seer Goodman because it had a Copeland scroll compressor whereas the 13 seer Goodman model had a piston.

[udarrell]

I had this same issue on a furnace installed in 2002 that had a 10 seer coil, with a 37 year old 6 seer compressor that was failing. One contractor said the 13 seer into 10 mismatch was no big deal, another said he'd do it but that the mismatch probably would void the warranty. I decided to get the new coil. Ironically I also decided to go up to 14 seer Goodman because it had a Copeland scroll compressor whereas the 13 seer Goodman model had a piston.

The matching indoor coil is normally a TXV metered coil.
Did your new coil have a TXV?

Beenthere & others; An Experimental Trial:

I am wondering how a 2-ton 13-SEER condenser would work on an existing 3-Ton 10-SEER TXV evaporator with a relatively high heatload through the evaporator?

If the total amount of refrigerant was close to a match, would the 2-ton condenser produce its nominal BTUH rating?

Of course, you would have to reduce the heat/gain & the latent infiltration load. What would its latent to sensible ratio be?

What would its EER & SEER be?

[beenthere]

Probably very close to the condensers rating with a listed coil match that gives 13 SEER.

Depending on weather or not it has the same fins per inch.

Since its sq ft surface area would be very close to what a listed match would be.

[udarrell]

I haven't looked it up, but believe the 13-SEER evaporator would have more wavy & longer fins per inch & therefore less coil unaffected by-pass air, largely due to its more efficient design, than the 10-SEER evaporator coil.(?)

It would be interesting to see detailed test results at both ARI & ACCA TVA test conditions. Should also be tested at different CFM airflow rates through the E-Coil at those two standard LAB test conditions.

Would like to see other opinions.

Which states, or local codes you guys know of, where it a code violation if the evaporator coil is not an official match?

[RDrennan]

The fin spacing of a 13 seer coil and higher definatly is closer together than that of a 10 seer coil. that is one way that they increase effeciency of the coil. As for the "wavy" fins, they all have this effect to an extent and this only aids to give them stability and rigidity and minimize bending in the force of the airflow. Putting a 13 seer coil on a 10 seer unit only increases the 10 seer unit up to maybe 10.5 seer at best and there is no code violations if that was your concern. Not properly matching a system does not violate codes, it only robs the customer of a properly operating system.






I haven't looked it up, but believe the 13-SEER evaporator would have more wavy & longer fins per inch & therefore less coil unaffected by-pass air, largely due to its more efficient design, than the 10-SEER evaporator coil.(?)

It would be interesting to see detailed test results at both ARI & ACCA TVA test conditions. Should also be tested at different CFM airflow rates through the E-Coil at those two standard LAB test conditions.

Would like to see other opinions.

Which states, or local codes you guys know of, where it a code violation if the evaporator coil is not an official match?

[Todd A]

Re:txv, I dont know, Ill ask my installer. The new coil is an Apen and the condensor is a 14 seer goodman condensor with copeland scroll. they also relocated the condensor closer to the furnace and ran a new lineset which has a shorter run. The old lineset ran through the concrete of my slab house and had some issues. It was alot more expensive than trying to reuse the old 10 seer a coil and lineset, but Im glad i did it.

[beenthere]

I haven't looked it up, but believe the 13-SEER evaporator would have more wavy & longer fins per inch & therefore less coil unaffected by-pass air, largely due to its more efficient design, than the 10-SEER evaporator coil.(?)



Might have more fins on some coils, and not on others.

Some "10" SEER coils, were also made for the 12 SEER that was going to be the min required at one time.

A new 2 ton coil may only have 3.46 sq ft of surface area, depending on brand.
Were a older 3 ton may have 4.86 sq ft. Depending on brand.
Even if it has less fins per inch. I can't see it being that much of a loss.