I am having a new furnace and AC unit installed in my home to replace a 40 year old unit (forced hot air). Is the more efficient unit worth the up front cost? The mfg will be Trane. The Ac unit I am considering will have a seer of 14.
Any opinions out there would help.
Also, any one have experience with the Trane Clean effects filter unit? Is it worth the cost?
Replies
In another five years it'll be pretty much impossible to get your standard hot flue furnace -- they'll all be 90+. For new homes the cost savings of not having a regular flue and the flexibility that provides pretty much pays for the delta cost.
In older homes it's a little harder to make the argument, but the high efficiency units are generally smaller, so you can sometimes regain some of the space used by the current unit. In terms of cost effectiveness it likely depends on where you fall in the pricing structure, but it's not unlikely that you can see a 5-10 year payback for the more efficient unit.
In any event, keep in mind that that 40-year-old unit is probably around 60% efficient, so you'll save a substantial fraction of your gas bill even with an 85% unit.
In terms of filters, the AprilAire paper media filter and their electrostatic unit are both sold under a half-dozen different labels, with only minor variations in price. I don't know much about the electrostatic unit, but even though a bit pricy I think the paper filter unit is worth it in terms of reduced maintenance frequency and lower "back pressure". (You can buy the paper filters in bulk on the net and save a bundle over the one-off cost, BTW.)
If the furnace is properly sized (that means doing a Manual J load calculation, *not* looking at the size of the existing equipment), a 90% efficient furnace is 10% more efficient than an 80% model.
So, if your fuel bill is $100 a month, you will save $10 for the added upfront cost of the 90+% unit and installation. How many months will it take?
A 14+ SEER air conditioner does not exist unless you have a variable speed motor in that furnace.
SEER ratings also take things like duct design and air tightness into account. You will not get 14 SEER with poorly designed or installed ductwork.
You will not get 14 SEER if your air conditioner is not installed to manufacturers' specifications. That means using a micron gauge and setting the refrigerant charge properly- not by feel.
EER ratings are simply btu's per kWH without the S fudge factor.
I would think long and hard about installing a 2 stage 80% efficient model with a variable speed motor with the proper two stage thermostat. The variable speed motor will earn its keep in a few short years because the savings are year round.
Proper installation is key if the goal is an efficient system and long service life.
<a 90% efficient furnace is 10% more efficient than an 80% model.>
Ah - no. It's a bit more than 12% more efficient
Forrest - "lies, dammed lies, and statistics"
Ah - no. It's a bit more than 12% more efficient
Must be that funny math.
90 - 80 = 12???
Yes, some "80%" models may really be 83% (ie: two stage variable speed drive) and some 90% models may really be 90%, 92.5%, 93%, 94.5% or 96%- depends on the manufacturers specifications.
We all know that those ratings are developed in a lab, in perfect and ideal conditions.
The AFUE rating, just like the SEER rating, also takes things like electrical efficiency into account. The variable speed drive blower motors and 2 stage or variable ventor motors effect the AFUE rating. That is why manufacturers are moving to PSC ventor motors instead of much cheaper (for them) shaded pole motors.
High efficiency (like 19 SEER and up) air conditioners have variable drive compressors and condenser fan motors.
The only difference between a standard two stage 93% furnace and the 94.5% / 95% models are the blower and ventor motors.
I would be willing to bet that the efficiency of either class of appliance without proper makeup (combustion) air is less. There are plenty of 90+% appliances out there without an intake pipe- what's the point? Cheap customer or cheap contractor? There are plenty of 80% appliances without a combustion air intake near the furnace, too.
That is just one instance where the installation is not to spec.
In this example, think "what percentage of 80 is the 10 more from 80 to 90?"
It's 1/8 (because it's 10/80), or .125
.125 is 12-1/2%
Check by multiplying - 80 X 1.125 (or 112.5%) + 90
Funny part is, 80 is 11.1% less efficient than 90
Same way - "what part of 90 is the 10 less going down to 80?"
It's 1/9 (because it's 10/90), or .11111 . . .
.111111 is 11.1%
Forrest - just trying to help (supercilious boy)
Guess I should have paid more attention in math class....
10% or 11.1% still equals a very long payback horizon.
>>We all know that those ratings are developed in a lab, in perfect and ideal conditions.Actually, they're developed in a computer, using some basic gas percentage measurements, some assumptions, and some formulas which some contest.
May your whole life become a response to the truth that you've always been loved, you are loved and you always will be loved" Rob Bell, Nooma, "Bullhorn"
"We Live" http://www.youtube.com/watch?v=7kuBgh0VCqI&mode=related&search
And Annie Ross's "Twisted" http://www.youtube.com/watch?v=8lqivrCIRGo&mode=related&search=
If 80% was the denominator, 90% would be 12.5% more but since 100 is, 80% is 10% less than 90%. Use money as the comparison, referenced to a dollar, subtracting 80 cents from 90 cents leaves 10.
"I cut this piece four times and it's still too short."
"If 80% was the denominator, 90% would be 12.5% more but since 100 is, 80% is 10% less than 90%. Use money as the comparison, referenced to a dollar, subtracting 80 cents from 90 cents leaves 10."But the demoniator is not 100.The only place that 100, as deminator, comes into affect is the converting from percentage to a decimal number.Remember that we are computing a percentage CHANGE between two value. And those values just happened to given in percentages.What about this example. You want to replce scooter, A that gets 80 MPG, with scooter B, that gets 90 MPG.What is the percentage increase in milage.And what is the advantage of using a percent CHANGE than the a POINT DIFFERENCE.You replace a 80% eff unit with a 90% eff unit. That is a 10 POINT change or a 11.1 % IMPROVEMENT in eff between the units.Or you replace a 10% eff unit with a 20% eff unit. Also a 10 POINT IMPROVEMENT.But a 50 % increase in efficient.Both that the same POINT change. But which is going to have the largest change in fuel cost..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
"But the demoniator is not 100."In percentages, it's always relative to 100%. Relative to 90%, no. Can you have eight pennies, add one to then have nine and not have added 10% of a dollar? No. You can't cut up pennies and still use them. That's why they're called cents. Century, cent, centavo, percent- all relate to 100. Isn't the efficiency percentage supposed to tell how much fuel is used when compared with an older standard? That standard is 100% of what was used. 90% is 10% more that 80%. 100% is the reference, not 90%. I don't think we'll all agree on this one. Yes, 90 is 1.125x8 and 80 is .888888... of 90 but 90/100 - 80/100 = 10/100.Same as 3 being 1.5x2, or 150% of 2 and 2 being 2/3 , or 66.67% of three but they're not being used as percentages of some whole number, like furnace efficiency.
"I cut this piece four times and it's still too short."
"In percentages, it's always relative to 100%. Relative to 90%, no."You right, the answer is NO!A percentage is a ratio used to show relative changes. A way of ccomparing the numbers that measure different things that have the same units or type of measurement.For example a compnay gives every one a 10% pay raise.So the guy that is assemblying widges getin $1 a unit piece work will now get $1.10.Do that mean the janitor making $10/hr and the supervisor getting $25/hr also get a 10 cent pay raise.No, they are get a 10 PERCENT raise. The percentage chagne represents the relative change.Thus the janitor gets a $1/hr reaise and the suppervisor a $2.5/hr range."Can you have eight pennies, add one to then have nine and not have added 10% of a dollar? No. You can't cut up pennies and still use them"But what good it that. If you only know the percentage of a dollar that you have gained that tells you exactly nothing if the goal is $1. Going from 1 cent to 2 gives you the same change in the percent of a dollar."Same as 3 being 1.5x2, or 150% of 2 and 2 being 2/3 , or 66.67% of three but they're not being used as percentages of some whole number, like furnace efficiency."That is where you are making a mistake. The discussion is not on the eff of the furnaces. Rather it is about the CHANGE BETWEEN TO OPTIONS. It does not matter what those option are. In this case they are effienceies. But in my other example they where MPG.Here is the problem.I have furance A and use $100 worth of gas each month.You propose furacne B. Give me ONE NUMBER that I can use to estimate amount of money that I can save if I replace A with B..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
If your pay is 8 dollars an hour and goes up to 9, have you added 10%?
If your view never changes you're following the wrong leader
OK, answer this- the efficiency is 80% or 90% of what?
"I cut this piece four times and it's still too short."
BTU in vs BTU out."Fortunately, the ideas of individual liberty, private property, freedom of contract and association, personal responsibility and liability, and government power as the primary enemy of liberty and property, will not die out as long as there is a human race, simply because they are true and the truth supports itself."
Hans-Hermann Hoppe
OK, so if the BTU in is 100%, 80% is 10% less than 90% because the BTU in is what everything is being compared to, not that they're being compared to the higher of the two. Is there a math teacher in the house?
"I cut this piece four times and it's still too short."
80% is ten points less than 90%, but...
90/80 = 1.125 or 12.5% more efficient for the 90% vs 80% because now you are NOT using the 100% as the nominator."Fortunately, the ideas of individual liberty, private property, freedom of contract and association, personal responsibility and liability, and government power as the primary enemy of liberty and property, will not die out as long as there is a human race, simply because they are true and the truth supports itself."
Hans-Hermann Hoppe
I said DEnominator and if you're using percentages, the denominator is assumed. Then, you just end up adding and subtracting fractions with a common denominator. Ratios are different because they only relate to each other. 80% compared to 90% is a ratio with a % sign attached because the efficiency rating has one. I think people respond to percentages more easily that ratios- listen to a salesperson when they tell you that one thing is better than another. They use percent better/worse, not .888:1 or 1:1.125. They're the same as 8:9 and 9:8 and they're not percentages but they can be converted to that. Unless the load is extremely high, does? Why not just rate it for heat loss and call it that, or come up with a rating system that leaves no room for debate?
"I cut this piece four times and it's still too short."
When using percentages you can never assume anything. They're the love children of unscrupulous statisticians.
If your view never changes you're following the wrong leader
100% of all divorces are caused by marriage.
I thought it was mother-in-laws.
If your view never changes you're following the wrong leader
I thought it was all rumors and innuendo.
"I cut this piece four times and it's still too short."
"When using percentages you can never assume anything."You have to, or the % symbol and per cent mean nothing. % is exactly equal to /100 or "per 100 and it's just a shorthand method of expressing /100. From Wiki, :http://en.wikipedia.org/wiki/PercentLook at the part about percent increase and decrease.
"I cut this piece four times and it's still too short."
Your pay goes up from $8/hour to $10/hour. What's the percentage increase?
If your view never changes you're following the wrong leader
"What's the percentage increase?"That's my point. Some of us are referring to the difference in percentage and the others are looking at the % increase/decrease.
"I cut this piece four times and it's still too short."
25% increase.
"I cut this piece four times and it's still too short."
Wrong. The average hourly wage is about $17 per hour. If you go up from $8 to $10 you've gone up 2/17, or about 11.8%.It all depends on how you look at it.
If your view never changes you're following the wrong leader
"Your pay goes up from $8/hour to $10/hour. What's the percentage increase?"This was the question. There's nothing at all about average wage and $17/hr has nothing to do with your question. There's nothing wrong with my answer when the question is as asked. You can look at it any way you want but, in the words of one of the MythBusters guys, "I reject your reality and substitute my own".
"I cut this piece four times and it's still too short."
Right, there was nothing wrong with your answer, but there was nothing wrong with mine either. And if you had come up with mine, I could have found yet a third one. Until you define your terms percentages are very slippery to deal with.
If your view never changes you're following the wrong leader
Slippery, not so much but all parties to the issue have to know if it's the difference or change in percentages, in this case. What's the difference between a duck?
"I cut this piece four times and it's still too short."
The efficiency of a furnace is the amount of heat delivered out of the heat exchanger relative to the heat produced by burning the fuel. The remaining % goes out the flue, in the general case.A 90% furnace will extract 10% more heat from a given amount of fuel than will an 80% unit (in theory, at least). In terms of fuel consumption, this means that one now gets 90 units of heat from the fuel that previously produced 80. But the purpose isn't to get MORE heat, but rather to reduce consumption. So consumption is reduced to 80/90 of the previous level -- 0.889. This represents a reduction in fuel consumption of 11.1%.
If your view never changes you're following the wrong leader
"A 90% furnace will extract 10% more heat from a given amount of fuel than will an 80% unit (in theory, at least)."You just agreed with me. 100K BTU in and 90K out is 90%, 80K out is 80%. "But the purpose isn't to get MORE heat, but rather to reduce consumption."Right, Reduce lost heat that could have been used to warm the space. Man, I would LOVE to invent something that uses less than it puts out. I'd be like the Warren Buffet of HVAC. I was gonna say Bill Gates, but everyone would hate me if I was his equivalent.Wanna call it a day?
"I cut this piece four times and it's still too short."
Well, a heat pump DOES put out more energy than you feed in.
If your view never changes you're following the wrong leader
More energy is recovered but it can't create energy.
"I cut this piece four times and it's still too short."
"Well, a heat pump DOES put out more energy than you feed in."NOPE, NEVER !!!!That would violate several natural laws.You get more USEFUL energy out (in this cash interior heating) than you PAY FOR (electrical usage)..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
That's what I meant by "feed in" -- what you have to pay for. The "pumped" energy is free.
If your view never changes you're following the wrong leader
Yes, the variable-speed DC motor saves an enormous amount of electricity vs the standard 1 or 2-speed induction motor. Especially significant if you run the fan all the time.
If your view never changes you're following the wrong leader
Yes, it is definitely worth the up front cost. Make sure your dealer sizes the unit properly. They tend to oversize them which can lead to noisy air movement and short cycling of the unit.
Yes, it is definitely worth the up front cost.
Given the choice between a properly sized 2 stage 80% with the variable speed blower motor and a properly sized "standard" 90% efficient model, I disagree.
People will save more money on energy if the houses are built better than with a fancy HVAC system.
My hvac guy stated that a payback approaching the life expectancy of the unit (10 yrs) is a bad idea.
I agree.
Spend the money on proper insulation/sealing of the duct system."Fortunately, the ideas of individual liberty, private property, freedom of contract and association, personal responsibility and liability, and government power as the primary enemy of liberty and property, will not die out as long as there is a human race, simply because they are true and the truth supports itself."
Hans-Hermann Hoppe
>>My hvac guy stated that a payback approaching the life expectancy of the unit (10 yrs) is a bad idea.10 years? In Tennessee. Shot, there are plenty going after more than 20 years in NW Ohio.I suspect your guy just doesn't want to upgrade his equipment and knowledge base; or perhaps he's seen a few units that had problems (did he really set them up and tune them right?) and is over-generalizing.
May your whole life become a response to the truth that you've always been loved, you are loved and you always will be loved" Rob Bell, Nooma, "Bullhorn"
"We Live" http://www.youtube.com/watch?v=7kuBgh0VCqI&mode=related&search
And Annie Ross's "Twisted" http://www.youtube.com/watch?v=8lqivrCIRGo&mode=related&search=
Our Carrier "Quiet" 4 ton ate its compressor's connection at 10 years... almost to the day. It was a better value to replace the entire compressor than the parts.
We have the t-stat at 80deg during the day and 75 evenings, so we aren't overloading the unit.
I hate to write this, but, the newer units aren't built quite as well as those from an earlier era.
"Fortunately, the ideas of individual liberty, private property, freedom of contract and association, personal responsibility and liability, and government power as the primary enemy of liberty and property, will not die out as long as there is a human race, simply because they are true and the truth supports itself."
Hans-Hermann Hoppe
Well, this guy's current furnace is 40 years old, ours was 32 when we replaced it (and it still worked fine). I'd argue that higher efficiency INCREASES life expectancy by distancing the horizon at which replacement due to inefficiency will be needed.
If your view never changes you're following the wrong leader
Equipment made 30 and 40 years ago wasn't squeezed for every last cent of profit like the stuff made today.
If you have gas hot water which was vented through a common chimney with your older furnace, remember that the water heater should now run through a flue liner added to the chimney.
May your whole life become a response to the truth that you've always been loved, you are loved and you always will be loved" Rob Bell, Nooma, "Bullhorn"
"We Live" http://www.youtube.com/watch?v=7kuBgh0VCqI&mode=related&search
And Annie Ross's "Twisted" http://www.youtube.com/watch?v=8lqivrCIRGo&mode=related&search=
No mathematical discussion here but I did just install two 15 SEER AS/Trane A/C units in our house both WITH Clean Effects - love it so far. Best A/C we've ever experienced. Heating is via boiler (Weil McClain Ultra Gold) and HW hydronic so can't comment on furnaces except that the ones we specify professionally do very well.
Also have AS/Trane ERV (Energy Recovery Ventilator)
Jeff