I didnt know furnaces ran windows. Consumer Reports mag did a poll of about 22000 people years ago, the top results were suprising, you do have CR mag online, right. If I was looking for one it would be stainless steel heat exchanger not treated steel. If you over heat them ive heard they fail fast. Checking the temp just above the exchanger is something you should have set up and do. If it gets humid inside when temps are mild, to mild for normal AC, a Vsdc blower will do alot by running real slow and cycling the Ac only for humidity removal, if its set up right. Vsdc should also save you 15-30% on electric usage overall. The first generation untis failed within 6-10 years, ive heard but they redisigned the electronics so maybe they last now, you still need the longest warranty if you go with the fancy stuff. 10yrs is common and maybe 15yr warrantys are done now. 2 stage or modulating gas valves allow more even heat. With a high efficiency condensing unit you automaticly cut the size of overall btus needed by
10 to maybe even 15%. If you dont run it 24 hrs a day on the coldest days you might cut its size more. But if you do the setback or vacation alot recovery is harder. You could Diy it , save money, have no warranty and maybe be covered on savings. I think vsdc motor is
600, but im guessing on all numbers.
Excuse me, but you've obviously got me confused with HomeGuy. He's the guy that started the Win98 crap that got the thread off track and made the above quoted statement. Perhaps you remember him as the profanity spewing poster you previously engaged with.
I checked there already. They said the problem reports were about the same for all the manufacturers and didn't rate one better than the other. They gave some average price of a furnace information for the manufacturers. But I'm not sure what that even means. Does it mean that the price for a similar furnace from each company? Or does it mean that it's the average price of the systems each company sells? If it's the latter, it's useless, because company A could offer more high-end systems and have a higher average price, while actually being cheaper on the particular system type I want.
Thanks again for the help in the past on that CR stuff. I finally got a subscription.
I was thinking about that. With the current furnace, with an outside temp of' about 28F, it raises the temp from 60 to 70 at about 5F per hour. Current
26 year old furnace is 150K input. So, I'm thinking with 93% or so efficiency new one, 100K should be about the same. It's not close to running constantly on the coldest days here in coastal NJ, which would be about 8F. But any smaller and it cuts back the ability to set it back at night. Right now it's set to go to 60 at 11PM, back to 67 at 5:30AM
I also take maybe 7 trips in the winter where I set it back to 50 and from the above, you can tell it takes several hours to get back to a reasonable temperature. I've though about getting an thermostat that I could control via the internet to set it back up when I'm on the way back.
Would you think it a good idea to go with a smaller one if it means less ability to set it back, even on a daily basis?
As far as the VSDC, etc., I'm going to see what the contractors have in the systems that meet the credit reqts as well as those just below it. I'm thinking I'll probably wind up essentially getting a better furnace for free when you factor in the credit.
Don't joke. Next year they'll be running linux or android.
So post them here.
Yes. Stainless for both the primary and secondary exchangers. Take a magnet with you to the hvac dealer's show room and test the units they have on display.
Correct term for vsdc motors is ECM. ECM motors are a crock of shit. Best you'll save is 100 watts compared to 1/4 hp AC motor, and less if you have 2-speed AC motor. Saving 100 watts at 10 cents/kwh is about $100 (that's 100 watts continuously for an entire year). Now subtract the electricity used by the furnace motherboard, and various other blowers and condensate pump. The extra 100 watts used by AC motors are dumped into the house as heat - which is what you need in the winter (and spring and fall depending where you live) so it's not all wasted energy.
Lifespan of ECM motor is 1/2 to 1/4 that of AC motor, and it's 4 to 8 times more expensive (upfront cost of furnace is higher, repair costs higher). ECM motors create EM/RFI on your household wiring, can interfere with tv and radio reception.
Now tell me how you're saving with an ECM motor.
So where are we?
1) Adding second stage heat exchanger to conventional (70 - 80%) furnaces from 30 years ago gives us condensing furnace (95% give or take) - which is good. I do like that improvement.
2) Using cheap steel for heat exchangers compared to furnaces from 30 years ago is bad. Using stainless is good.
3) Using electronic ignition is bad comprimize from cost/savings point of view compared to standing pilot light. No real need to use electronic ignition in modern condensing furnace.
4) Using ECM motors is also bad comprimize compared to 1/4 or 1/3 hp AC squirrel cage motor. *Actual* or *Net* energy savings don't justify extra cost and reduced longevity.
As a consumer, give me the choice of electronic ignition or conventional pilot. Give me the choice of ECM vs standard AC motor. Give me the choice of mechanical thermostat (in the furnace) to control gas valve and fan motor instead of electronic motherboard. Give me all stainless for the exchangers. If you don't give me ALL those choices, then I say that modern furnaces and the entire industry is a crock of shit.
Beyond the furnace itself, it's time to start ducting winter heat around the AC coils instead of going through them. You want efficiency? It's not efficient to blow air through coils when you don't need to do it during the winter.
It's also time to allow for spring/fall cooling by having ducting and gating that allows the furnace to pull return air from the outside, force it into the house, and gate the interior return air back to the outside. When ever you want the house cooler, and the outside air is cooler than the inside air, then why use your AC when you can draw outside air into the house directly?
The CR survey was notable because it stated Goodman to be less reliable, but I guess you are not looking at Goodman.
Your 150k furnace is likely 82% and 123,000 output, a 100k 94% unit is
94,000 output so its alot less, near 30%. I wonder does it even run in
6 hrs at night on 6f cutback? a load calculation is really needed to know what is needed, or just dont go to much smaller. The only real need I can see for 2 stage or modulating gas valves is if you have uneven heat and need more comfort. Just cutting my furnace size 50% gave me more even heat but I was way oversized. Ecm-Vsdc would help more in winter if heat is uneven but it really makes sense for AC if alot of your climate is near 70 but humid or you need to boost AC. With 7 trips a winter and setbacks you will be colder longer if its alot smaller. I think the main benefit is a cheaper unit, but you didnt say heat was uneven or bad. if your fine now maybe Condensing and no fancy stuff is best. a bit smaller and heat will be more even.
I dont know how to cut and paste yet but its 2008 CR magazine furnace survey
Ecm Vsdc, it can run at 100watts vs 375 for my 1/4hp, thats near 70% saving in slow mode, maybe near 100w less at high speed.
Who in the US pays only 0.10c per Kwh, you must live near a big Dam and get subsidised electric because im .18 and so is the rest of the US, many place are near 0.25 kwh.
You miss the point, its comfort or else you wouldnt even have a heating system. Vsdc can remove in low speed maybe 50% more moisture with minimal cooling so its great in humid areas, great for homes with uneven heat. It is about comfort, but can save the cost of the motor in electric usage over 6-7 years. That was my figure years ago at .
125kwh.
You have to know yearly hours run in heat and AC and a real Kwh cost to make any claim to it not paying back.
Lifespan, are you refering to the old or new redesign motor.
I was thinking the current 26 year old furnace is more like 60 or 65%% efficient. Don't you think 82% is way high? I'd expect that from a more modern furnace, eg the current low cost entry level systems, but not from my ancient beast. If it's 65%, then replacing it with a 100K, 93% one is pretty close.
I set it back to 60 at 11PM and it definitely will run overnight if it's cold weather, probably from the low 20s on down.
The first contractor, Carrier guy is coming tomorrow and I think he's going to do one. But it would seem to me that the actual experience I have with the current one is just as useful, maybe more so. At least for the heating part.
de quoted text -
That's about where I'm headed. The only issue I have now is that it would be good to have more cooling upstairs. Main issue there is the limited duct work originally installed. One thing I want to look into is more blower capacity to help with that. But I think the best solution would be a second AC system for upstairs. I don't think it's enough of an issue though to warrant doing that.
So, I'm thinking get more airflow if possible, and a system that's sufficient in rating to meet the tax credit.
I know boilers have been 82% steady state running for over 110 years, My 1954 Kewanee steam 1.200,000 Btu is 82% running and a 110 yr old style or older, for boilers the reduced water supply is the main advantage today, for steam they are now still only 82% rated. Better controls, flue damper, electronic ignition and holding less water are steam boilers only improvements. For furnaces with the tank style exchanger I think those are less but if its clean, not way oversized, not short cycling, if the burners are burning right 82% is my guess.
1984 isnt that long ago, we went through a energy mess in the mid 70s and I was converting to flourescents as utility prices were going up.Google a bit and see if you can find out what things really were 26 years ago. Your payback might be alot less than you think with a new unit.
I just looked a bit, there were condensing furnaces 26 years ago. Can you find a Btu input-output rating, use that and take off maybe 5%, you might be near 60, or 80.
If you are replacing an existing furnace, one that has been running for years in a given house and presumably giving satisfactory service, then how possible can you remove it and "improperly" install a new one in it's place?
What is meant by improper? That a water line is connected to the gas input line? That the upstairs thermostat is connected to the furnace AC power input? That the return duct and output air plenum are connected backwards?
How does the correct sizing of a furnace impact on whether or not the heat exchanger lifespan is impacted by being stainless steel or regular steel?
Would these be the same ductwork designed and installed by licensed contractors?
Would these be the same ductwork that was original to the homes in question - the same ductwork that somehow didn't manage to dammage or burn out the motor in the previous furnace - presumably an AC motor?
I'm sorry, but if my 36 year-old AC motor didn't burn out because of the size of my existing ductwork, then it's a crock of shit that the same ductwork is the reason why a new ECM motor burns up.
Blame the ductwork. When you have to explain to the customer why his new $4000 furnace is costing so much repair hassles, blame the ductwork.
You need to show you're a man by pointing out exactly which of my statements above are wrong.
I'm right when I say that:
1) ECM motor uses 100 less watts when running full speed compared to 1/4 hp AC motor running at full speed.
2) The extra 100 watts used by AC motor is dumped into the house as heat during the heating months, so it isin't exactly wasted energy from the point of view of the home owner.
3) You can't compare the energy usage of an ECM motor running 1/4 or 1/2 speed against a single-speed AC motor. If you want to compare the costs of multi-speed operation, then you must compare ECM with a 2-speed AC motor, and you must correctly estimate the amount of time (total hours per year) that the fan will be running at fractional speed.
Totally wrong, because you have to factor in the control or drive electronics that's powering the motor, and when you do, you'll end up with burned out transistors.
The efficiency of fractional horse-power ECM motors are (at best) 60%, while a 1/4 hp PSC AC motor will have an efficiency of 40% (if running at full speed). 1/4 horse power is about 186 watts, so an AC motor will use about 465 watts, while an ECM motor will use 310 watts. The difference (about 155 watts) would use 1,357 kw hours given a continuous 1-year run time. If the total electricity cost was 15 cents per kw hour, then that equates to $200 per year.
Now if you consider the case of a 2-speed AC motor compared with a
2-speed (or even variable-speed ECM furnace) and if you factor in that in a typical use-case that neither motor would or could be operating for up to 25% of the time, then the potential savings from using an ECM motor will almost certainly drop to closer to $100 per year.
Now if you factor in that the 155 watts of extra energy being used by the AC motor is given back to the house as heat, then you need to determine what that equates to in terms of cubic-feet of equivalent natural gas and subtract the cost of that amout of natural gas from your electricty bill to get the true additional electric cost by using an AC motor instead of an ECM motor.
While all ECM motors are capable of infinitely variable speed and can be implimented as such by something as cheap and easy as programming code in the controller, furnace makers charge a fortune for anything more than simple 2-speed operation. That is another crock of shit for this industry.
I could argue that a belt-driven fan with an AC motor with bushings is quieter than a direct-drive ECM motor with ball bearings.
Or so you think. There's no way that a home-owner (or even consumer reports) is going to know which units put out RFI, and which units actually give you what you pay for. Models change all the time - too fast for independant testing and analysis to have any effect or be useful for the buying public.
Which equates to 155 watts as I calculated above.
Be a man and tell me where I've said anything wrong.
We're comparing 30 - 40 year-old furnace technology with conventional furnaces. If furnaces cost proportionately more today in terms of % of disposable income then I should expect no less durability or longevity compared to the older furnaces. You seem to be an appologist for the industry by indicating that we should pay more and expect less.
Because standing pilot lights have been used for decades and have proven themselves to be reliable, safe, simple, and cheap.
The pilot light and it's thermocouple switch have proven to be an excellent design in terms of safety, reliability and durability for residential furnaces. Do you disagree? Do you have the balls to disagree?
Removing the electronic ignition and replacing it with a pilot-light and thermocouple does not constitute "removing a safety" device. Get a grip here.
See above. Best case savings is $200 a year, typical savings will almost certainly be less than $100 a year.
Anyone who lives in a climate zone where they expect to use their furnace at least 5 months out of the year will realize less than $100 savings in their combined electric and gas bill just by having a furnace with an ECM motor. Anyone who lives in a more temperate climate zone and runs their fan more often either alone or in conjunction with their A/C unit will come closer to the $200 in electricity savings.
We're talking simply about ECM motors replacing conventional PSC AC fan motors in residential furnaces. Motors that are part of other components (heat pumps, A/C compressors, dishwashers, clothes washers, dryers, etc) are another matter and have different cost/benefit arguments.
The single largest decrease in my energy bill that the furnace industry can give me compared to what I have now comes from the 2-stage condensing heat exchanger. Better airflow design, thinner materials, stainless, possibly better burner design, etc. All of that comes from better thermodynamics and materials - NOT ELECTRONICS.
The addition of electronics - particularly the electronic ignition and ECM fan motor, adds unnecessary cost and complication to the modern furnace with no tangible benefit to the home-owner and comes with additional medium to long-term cost of ownership costs and device down-time caused by component failure.
Screw the contractor. I want a box that will sit there and work year after year. It's no consolation to me that a repair tech is just a phone call away. I'll take reliability and durability any day over repairability. Especially when it comes with lower up-front costs (no electronics). And in this case, I'm not even sacrificing repairability. Low tech = high repairability.
I can install myself any furnace. That's not the point. I'm just bitching about they choices that furnace makers are making when they design / build them.
When you have electronic ignition, you HAVE TO HAVE an array of electronic sensors to make it safe. Having those sensors and electronics comes with a price - a hit to cost, durability, reliability.
When you have a standing pilot light with electro-mechanical thermocouple and gas valve, you don't need sensors or electronics, because it's inherently safe.
We're not talking about the thermost here. I can have the most advanced, computer-controlled thermostat I want upstairs to control my
35 year-old furnace, yet still have no electronics *in* my furnace. Understand the difference?
Can't figure out whether you are serious or pulling our legs about making such comprehensive and radical "modifications" to the modern high efficiency gas furnace. I suspect that anyone following your advice would end up with a system that (1) was substantially less efficient than it could/should be, and (2) was unsafe to the point of probably failing many or even most safety codes for using natural gas furnaces in private residences.
Are you a believer in conspiracy theories that the all the manufacturers of these furnaces got together and agreed to intentionally fill their products with expensive, unnecessary and failure-prone components so that they all could reap larger profits? You would have to be. Otherwise, at least one or two of the companies would leave out many or all the components you advise removing and advertise that their products were equally safe, equally efficient, but much more reliable and less expensive that their competitors that include those components.
I don't know squat about engineering a gas furnace, but your advice just doesn't compute with me.
By having too high of a TESP (total external static pressure.
Older furnaces had a lower CFM rating, hence they have a higher temp rise for a given output BTU rating. Newer equipment for effeciency's sake have thinner heat exchangers (less metal thickness to push the heat through) that can't tolerate the heat without cracking hence they have a higher CFM rating, hence more TESP by trying to shove more CFM through the existing ductwork.
Sometimes, just go to the hvac-talk.com wall of shame and see all the bad ductwork installations, many being a "ductopus" using flex duct.
Yes, and here is why. Your average PSC or split-phase induction blower motor on high runs at a fairly constant speed (a 4 pole motor can only speed up from its rated speed, usually 1725 RPM to just under 1800 RPM @ 60Hz). With a centrifugal blower (squirrel cage) the torque load on the motor is directly controlled by the amount of air flowing through it (ande vice versa), hence as you restrict the airflow (increase the SP) say with undersized ductwork the blower unloads. Less torque at the same speed means less HP (HP=torque in ft-lbs x RPM / 5252) hence less motor watts. An underloaded motor is less effecient but lasts longer. Too little TESP on a system with an induction motor can actually overload the motor, hence why old systems that had belt drive blowers usually has a variable pitch sheave on the motor. The belt ratio hence wheel speed was adjusted to run the motor at full load with a new system. As the ductwork and/or filter got dirty the TESP went up and the motor unloaded some.
Now here is where it gets tricky, ECMs as used on indoor blowers are constant torque NOT constant speed. The shaft torque is held constant hence the airflow is held mostly constant. Increase the TESP on these systems and the blower speeds up either till the torque/airflow goes back to rated or till the motor hits its top speed limit. More RPM X same torque / 5252 = More HP = more watts. More watts x same airflow means hotter electronics hence shorter life. Add in a plugged filter and the poor little motor runs its little heart out at max speed with little cooling airflow till it burns up.
Explained above.
As said this depends on TESP. At high TESP the ECM can use more watts than the PSC.
Electric resistance heat is usually more expensive than gas heat and in the summer it is just more sensible heat load on the evaporator hence more watts still loses.
A while back I came across a study done on the savings of ECM blowers in residential HVAC applications segmented by geographic regions/climates. One key result of that study, which I didn't expect and I believe is reflected in what you say, is that how much energy one saves depends to a large extent on the duct work. The greatest savings came from ideal duct work, ie lowest pressure. Next was good duct work, which also used significantly less savings. Duct work they classified as typical still got savings, but much more modest, maybe 15- 20% in electricity cost. However if you have poor ducting there can be no savings or even a net loss of up to I think about 10%. The energy savings also obviously depends on the climate.
But I think HomeGuy has a vaild point, at least to some extent. Whether you can recover enough in energy savings on an ECM versus the increased upfront cost as well as the real potential for higher repair bills is questionable. I've seen horror stories here of the ECM electronics fried by power surges for example and a $600 bill But I've never heard of a conventional furnace blower failing from a power surge. Also, I think you'd agree that if improper duct sizing can screw it an cause it to fail, it's entirely possible that some contractors who don't know what they are doing will result in the motor failing at some point. And if that point is after the warranty is up, then you're screwed.
This same faulty logic is frequently applied to water heaters with claims that the standby losses from storage tank models helps heat the house. For some reason, they completely forget that for most of us with AC, that gain turns into a loss in the summer.
Not uncommon, actually. Upflow unit replaced with downflow unit ... presto.
Gas fittings / pipe 'held together' with duct tape .....
One of my 'most memorable' discoveries long ago - Imagine a typical kitchen from the 70's. Stainless steel sink, electric
4-burner in-counter stovetop right next to it.
Accidently touch the chrome trim around the stovetop and the sink at the same time - get knocked on your ass.
Oh - house occupied by two old folks in their 80's.
Lift the stovetop to find - a wire burned off the burner connector, so someone ( a PAID 'repairman' ! ) strapped it to the OUTSIDE of the burner element with a worm clamp.
If a power surge fried the blower it would have got the control panel first. With any new unit you should be doubly sure its surge protected and well grounded since you will have alot of electronics. When I got my install they offered to somehow test my duct airflow, thats where shopping for the right pro is important. I heard those motors were redesigned a few years ago to separate the electronics from the heat of the motor, since the electronics were what failed and now the motor and design has finaly matured.
It is quite possible. A belt drive blower could put up with an awfull lot
Not necessarily - but if the installer does not do the temperature rize test and properly set the motor speed, you could get a failure due to improper installation.
You underestimate the difference in efficiency between a standard induction motor and an electronically commutated DC motor, PARTICULARLY with multi-speed AC motors. At lower speeds ECMs can save over 60% of the electricity used by PSC motors. For example, in low speed circulation a typical PSC furnace motor will use 350 to 500 Watts while an ECM will use 75 - 125 W.
You need to read the entire study at:
formatting link
an interesting part is the following - with the same airflow,
"The power use of the ECM and the PSC motor were measured in one-time tests using a Nanovip power meter. The ECM used 16.5 Watts in circulation speed and 284 W in heating speed, while the PSC motor used
350 W in circulation and 490 W in heating. Thus, the ECM used 58% as much as the PSC motor in heating speed, but only 5% as much in circulation. The ECM?s flow rate was almost identical to the PSC?s in heating speed, and was 47% of the PSC?s in circulation speed."
Ditto
The National Research Council study quoted shows 206 watts difference on high speed, and 330 watts less on low speed.
Except when running the AC - and gas is cheaper than electricity for heating.
Or do as the National Research Council did, read the study - very comprehensive testing.
Actually, they are finding the ECM to last at least as long as the AC motor in many tests. (in part because they run cooler). The motor control electronics are the least troublesom of all the controls on modern furnaces. SNIP
I do. I've replaced too many thermocouples on standing pilot furnaces - and NO electonic ignitors so far on the new furnaces. Average lifespan of my thermocouples has been less than 7 years (5 in 22 years on my own furnace, and 5 in 7 years on my friend's gas boiler) I'm on #3 on my water heater as well. This is, I believe, year 8 on the electronic ignition furnace.
SNIP
The blower in my furnace runs at low speed 100% of the time that the furnace is not running on high for heat or a/c. (for air cleaner and overall comfort) If the furnace NEVER kicked on, the ECM saves me 2890kwh per year. (330 watts X 24 hrs/day X 365=2890800 wh).That's $232 at $0.08 per kwh. and that's not counting the savings when the furnace is actually running. And the actual cost of electricity is more than $0.08/kwh here when you add in the distribution charges and everything else, and throw on 13% HST
Actually, IF the condensing furnace is 7% more efficient than the equivalent non-condensing furnace, (97 vs 90) the fuel savings will be about 8%. With my total annual gas bill of $700 (part of which is my water heater) my maximum total gas savings would be less than $56 per year. Not a very attractive payback, particularly if I end up replacing the secondary heat exchanger in 10 years.
The ones I've looked at are rated as BTU input, primarily because they have a fixed operating point (orifice sizes, pressures, etc.) and the efficiency isn't well regulated. The burner efficiency can be measured and the BTU output calculated, though.
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