-snip-
80% is a good number, but you are looking at the steady state efficiency, not the annual efficiency (AFUE).I've checked 15 year old gas fired hot air furnaces that had a 83 to 86% efficiency.
There is a difference.
So why do all the mfg's show an output btu rating that is 80% of the input?
Should it not be > 80% to account for the cycling?
efficiency,
You really want me to think tonight, don't you? I'm not going to get this right, but I'll try.
Here on my desk, I have a rating plate off of a GE furnace. While I can't be sure of the date, I'm sure the furnaces they were attached to were made in the late 1970's. They show an input of 160K and an output of 132.8K,
80%, right? What about the pilot? Then you have to add the efficiency of the blower motor and the 110v/24v transformer. (BTW, that direct drive blower was huge compared to the blower that replaced it) This is what drags down the efficiency.Any better?
Steady State is the efficiency it runs at when warmed to full efficiency, many heavy old units may only achieve this for 50 % of their complete cycle thereby lowering overall AFUE rating. An example ,I have a 50 yr old steam boiler in an apt building it is was a #1 design then and today, a Kewanee Scotch Marine, Today when used commercialy running constantly they reach 82-85%, efficiency , but overall AFUE may be only 50% because It holds 400 gallons to heat, where a new unit will do the same job with 50 gallons. New units have more efficient designs alowing them to reach maximun efficiency sooner, also ' thinner metal" This is also why short cycling, keeping a minimal swing will reduce a units efficiency significanty, it takes time to reach full efficiency. But our new efficient heat exchangers do not last as long, thinner metal is used to increase rapid heat transfer to reach full potential fast, and for highest AFUE at the lowest cost to the manufacturer.
So i've asked a couple times in other threads, trying to find the rated efficiency of my furnace. It claims to be rated for 130K BTU output for water. but then has "AGA" rating of input =218,000 BTU output = 172,800 BTU
Does that mean efficiency is: 172800 / 218000 = 79% or 130000/218000 = 59%
Considering the boiler was installed 50 years ago (estimated) I'm guessing 59%, but I could be wrong.
Please don't make me post to the HVAC group... I hear they're mean. ;)
With what little I know about age and design and a unit I had replaced your unit was 59% is now much less, maybe 50-55%. Modern units with no pilot and a auto chimney damper are 82-83% . no pilot and damper raise efficiency 5-10% Look into a modern condensing unit , they range from
93-99% efficient.Turtle et al.:
Second service call was much better. He actually took apart everything, scrubbed and vacuumed everything and only had to replace one part, the copper wire to the pilot light. Took only an Hour. The bill was 186 bucks:78 for the service call which included 1/2 hour and
70 bucks for for 1/2 hour of additional labor and 25 for one part.He wasn't a crook like the other guy who told me it would take 4-5 hours to take everything apart, and perhaps cost me 1000. I doubted your claims turtle but you were right on the moneyThe second guy quoted 3000 for a new 80 percent furnace. He never even pushed it. He only told me after I asked. I asked him whether he detected any holes rusted through, and he said no, not that he could see with the naked eye, but he would have to turn it on and see what the flames did. He said everything was fine, just old. He even gave me turorial on how the limit timer worked , and explained the reason it didn't work before was the burner was all clogged up and wasn't producing enough heat. Nithing corroded in the lmit timer. All I need now was a 16x25 filter.
Well what a relief. Found an honest service tech. I will actually think about him during Thanksgiving.
Happy Holidays
Keep his number around for the future, and tell your neighbors if they have problems, that he is the guy to call.
Now complain to your city and atty general and call your local newspaper, they may run a story. Ask for your money back from the first crook or stop payment on check or credit card
So are you saying that the pilot + increased CFM = 20% Also, the induced draft motor should be included?
Unit design is what makes efficiency not Cfm
The standing pilot wastes gas and the older motors are less efficient. The numbers are for the Annual Fuel Utilization Efficiency(AFUE). In other words, the annual use of fuel, not the combustion efficiency.
This is Turtle.
if you have a 218,000 btu input and have a 172,800 btu output. You have a 79.266 % Rating of the furnace. Now when you use this figure as to how effecent it is. Your very lucky to get the full rating out of it as stated here for everything has to be perfect to get this rating. 20 years ago or more the rating system was just a estimate at best and what you would hope to get out of it if everything was perfect and brand new. These older unit when they get some age on them will at best get a 55% or 60% in the real world.
You don't need to go to alt.hvac for a lot or most all the ones at alt.hvac that would answer questions are right here answering questions. If you give a question here and I / we can't answer it. I will copy and paste your question over there to have a discussion about it. If you don't get a answer to any normal question here , we will move it over there for a discussion.
TURTLE
This is Turtle.
I just had to mouth off here for it ruffled my feathers to see a scam artist like this do it to the public. Now i will say you need to have it cleaned just a little more than every 20 years. I would say about 5 years being the max. time to go without a good cleaning. Like others have said here. keep his number in your roller dex to call when you have trouble. Also you know who to call when you have trouble now on.
Now if You want Give me his address and Phone number and I will come over there and kick his ass. I can't stand theif's working in this business.
TURTLE
SOme more to chew on. Crook took off the lid to the filter and blower and told me "Look, the filter is stuck to the blower and so the blower needs to be replaced" He didn't even bother to take 2 seconds out of his life to remove the filter to see it wasn't actually irreversibly fused and melded to the blower, to form a bliter, as he claimed. Well, honest guy just took the filter off and told me "This needs to be checked once a month. If the filter does not look like it did when you bought it, replace it. Go to Home Depot or Lowe's and get a
16x25." He meant the filter needs to be replaced, not the entire blower. Very strange. He never mentioned the entire blower needed to be chucked.Also, the crook spent 10 seconds trying to take the burner plate off, but it got stuck so he gave up and told me it would take 4-5 hours and tons of money to clean and replace parts, so might as well spend a lot more for a new furnace.Lazy low-rent Asshole. Honest guy took about 5-10 minutes unscrewing and undoing nuts , shutting off the gas first then unscrewing the pipe with a variety of screwdrivers and wrenches to get the plate out. He wasn't happy but he did it. In the beginning, while he was doing this, I was anticipating lots of things he could rip me off on as he furiously used the various wrenches and screwdrivers and plain old muscle power. Never did. As the hour went by, I dismissed my suspicions .Total Pro.
I'll consider the 143 bucks the crook charged me for doing absolutely nothing in 10 minutes as tuition for learning about crooks and pros.
Happy Holdays
On 11/20/2004 3:27 AM US(ET), NWM took fingers to keys, and typed the following:
Was the good guy an independent contractor, or was he an employee of someone else? If either, I would have given him a nice tip, the amount depending upon the question I asked. I tip everyone who works at, or delivers to, my house. Not only is it a reward for doing a good job, it sometimes helps to move you up on the list the next time you need them. Besides, people are friendlier when they know you tip well.
Co is supposed to be in the flue not the house, blower should have been cleaned and oiled if needed. run on will not hurt anything. Call him back and dont pay to clean the blower
Did I miss something? Where is there any indication, in this or the other thread, that CO is entering the house?
What I am hearing is that the blower is running twice. Most likely it just needs a minor adjustment of the fan switch. Certainly not anything to get excited about.
Gary R. Lloyd CMS HVACR Troubleshooting Books/Software
Nah....at no point was that mentioned...I mentioned that a CO test needed to be done..thats all. Besides, the OP stated that its a Chrysler unit...it REALLY needs a CO test done.
>OP complained he did not test Co in the FLUE.. OK so who does ???
-- nobody...
Answer no one, you test Co in the Room- home.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.