# Current Furnace BTU rating method changed from earlier method!!!!!

I wish I could tell everyone with an oil, or gas?, furnace, but this is a start.
It seems that the current furnace BTU rating method has changed from earlier method, the one used when my furnace was new, 31 years ago!!!!!** Maybe that accounts for many of the people who have installed the wrong size furnace in their house.
**They don't actually *rate* mine as 85,000, but the brochure and the owner's manual refer to Model 58V and specifically 58HV085.
The 4th character V was based on the physical arrangement and could be V, E, H, L or C, for highboy, lowboy, horizontal, upflow, and downflow.
The 5th to 7th characters, 085, 100, 125 are the bonnet capacity, the output K-BTUs. For the horizontal model, this was true for these numbers and also for 150, 200, 250, and 335. The number-suffix of the model and the output are always the same.
So that's why I say my furnace was rated on its output. Is that fair?
Someone here pointed out that if it says 85,000 BTU, that refers to the amount of fuel used, the heat input of the furnace.
And that if the furnace is 90% or 80% efficient, the output is only 90 or 80% of the input.
Since I have now an 85,000 BTU furnace and it's definitely sufficient, and since the blueprints themselves say 85,000 on them, I was looking for an 85,000 btu furnace, but since now that woould be the input, I'd end up with one that was too small. Alas and alack, that would be bad.
Now I'm ignorant, and maybe stupid, and not in the business, but I'll bet even some young pros could make the same mistake. "You have 150,000 now, we'll put in the same thing."
Later another installer says that there should have been a load calculation, because that is his first step, and the homeowner thinks that's the core of the problem, but I wonder how many were first befuddled by this change in rating method.
When did the current method begin?
BTW, I'm glad I learned all this before I saw this ad on ebay today: "This is a used Thermopride upflow 85,000 BTU oil fired furnace. It was installed in November of 2009 and used only four months. The house was 75% heated with a wood burning stove and the furnace was only on during sleeping hours. This unit is excellent condition. We changed over to gas. The return is on the bottom of the unit and as was told that it also can be from the side. The dimensions 24x33x56, model # oh5-85. Webside for the unit is www.thermopride.com. "
The requested starting bid is \$500. The furnace is shiny clean inside. picture 1: http://cgi.ebay.com/ws/eBayISAPI.dll?VISuperSize&item30523771185 It's in driving distance for me, but it's too small for me, but there are occasionally others with such good stories. Do you believe their story?
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I don't know about your specific furnace and it may be different for oil than gas. But I'm sitting here looking at the documentation for my previous NG furnace, a 27 year old Ruud. The first page has the secret decoder for the model number and the middle 3 digits are the INPUT BTUs, eg 075= 75K input BTUs.
That is exactly how the new gas furnaces are labeled and marketed.

Correct, at least for gas

When I was getting estimates, every installer knew about input vs output BTUs. None of them recommended replacing the old 150K with another 150K. Not sure if that's even possible, as the largest I've seen today is 120K. Three recommended that, two recommended 100K, both 95% efficient. I believe either of those would have been OK.

Yes, that's supposed to be the correct starting point according to most of what I've heard too. None of the 5 companies I had did one though. Only two of them measured the sq ft of the house. I can understand why they didn't. The manual J takes a significant amount of time and since they are only giving an estimate, they would be wasting a lot of their time.
Here's my thinking. You already have an excellent reference point. That is the performance of your current furnace, ie measuring how long it runs during cold periods. Knowing that and it's efficieny, IMO, is probably more accurate than doing the manual J, which is a lot of work.
Now we get to another issue, which is how long the furnace should run if it's correctly sized. You will find most "experts" saying it should run close to all the time on the coldest days. That in turn brings up more issues:
What defines "coldest days"?
Lets say we take it to mean the coldest day in the last 20 years. If we size the furnace to run all the time on such a day, what will it do on days when it's 10 or 15 deg warmer than that? There will be a lot more of those days in the years ahead than that single coldest day. It will be running less. But, what about it's ability to recover from a lower set temp? If you set it back at night, as most people do, what happens? Or if you come home at a different time some days and set the heat back up. How long will it take to recover? IMO, if you size it to run 100% on the coldest day, then you're still going to have a very long recovery time on many other days when the temps are 10 or 15 warmer. I don't know about you, but if I come home unexpectedly, I don't want to wait 5 hours for the temp to recover. For example, I go away on trips and set it back to 50. My system recovers at about 5.25 deg an hour. And with that recovery rate, it's only running about 35% of the time during some of the very coldest days. Hence, while a smaller furnace would keep it warm during the coldest days, for recovery issues, I would not want a smaller furnace. If you get a furnace that runs 100% on the coldest day, then you're going to have many days where you effectively can't even set it back overnight to save fuel.
You don't want it so large that it short cycles and only runs for a brief period on moderate days either. It should have enough run time to evenly circulate the air around at least a reasonable amount.

I would investigate further as to how the ratings are done with an oil furnace. My guess is that they haven't changed and this furnace has exactly the same input BTU rating as your current furnace.
As to buying stuff on Ebay, the usual rules apply. Have they sold a lot of similar stuff and have excellent feedback? What was the negative feedback for? Is it nearby so you can go pick it up, inspect before paying? You have to be careful and know what you're doing. But if you do, there are excellent deals on Ebay and I would consider buying a furnace there.
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On Jan 27, 8:42 am, snipped-for-privacy@optonline.net wrote:

I did buy a new furnace off ebay from a company that was selling unclaimed freight. I also see there are some ebay sellers that routinely sell new hvac equipment. Mostly goodman(janitrol). I have some of the goodman stuff that I got locally and it's ok these days. You're usually better off if you can find someone locally that has a license and can buy the equipment from a local supplier like johnstons. I have not seen any bargains on ebay for new stuff and you usually have to add \$100 or more to ship it freight.
Having two houses and a condo totalling 6 hvac systems I'm in the mode of diy when ever possible. I can tell everyone that at least with r22 systems there is nothing wrong with using solver solder instead of brazing the copper lines. You can get small silver solder kits with flux for around \$10. If you solder you don't really have to have a nitrogen setup because you won't create a lot of oxidation. It's just like soldering copper water pipe. A vaccuum pump is still a good idea though. Especially with used equipment as you have no idea it's history. Vacuum all day and install a filter/dryer as well.
I have bought used stuff off craigs list because that gives you the oppportunity to look at it first. I'd only consider used equipment that is a few years old. Installation is a big piece of work and it's silly to install a piece of hvac equipment that is already half way through it's life expectancy.
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On Thu, 27 Jan 2011 06:18:18 -0800 (PST), jamesgangnc

So do you forego the warranty? Even if there was a 5 year warranty and it's only a couple years old?
I thought by having a licensed installer do the final parts of the installation, , measure with the proper gauges, adjust all the adjustments, and also verify everything I had done, I'd be okay on the guarantee. But one company says that no furnace of theirs bought over the internet and sold directly to the consumer is warranted.
So I've already lined up an installer and I thought, well he could buy it for me, but that has its own problems and further down on the warranty page, it seemed to say that just being sold on the internet means no warranty (no matter who bought it, I guess.)
I had never even heard of Comfort-Aire and could find little about it on the web, but then I saw that half of the models the local large heating and airconditioning supply house sells are Comfort-Aire. The other half are Dayton. Surely they couldnt' be selling crap, but I don't konw if Dayton is grade A and Comfort-Aire is their C+ model.
Another problem for me that won't be easy is
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I'd say in most cases, you wouldn't get warranty coverage on used HVAC, at least not through the manufacturer. At least some of them require that for the full warranty the unit must be registered within a few months of it being installed. I'd bet they further restrict the warranty to the original owner only, etc.

I've seen that too. It probably varies from company to company. Some of the HVAC stores selling eqpt online say they will handle and process warrranties for parts. So, assuming they do, you would have warranty coverage through them for parts. But..... that assumes you can wait for the time it takes to probably send them the part, have them send a new one, etc. Not the same as having the local HVAC guy come over and fix it in a day or two. And I think if you buy it online, you're always going to be out the labor, if any. But, given that you can buy a whole new furnace for \$1800, if you save \$3000 over a local guy the warranty issues may not seem that big anymore.

Probably another grey area.
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On Thu, 27 Jan 2011 09:09:48 -0800 (PST), snipped-for-privacy@optonline.net wrote:

Yes, that's the case with alpinehomeair.com . They say they warranty the stuff themselves.

I thought you would say I send the part to them, they send it to the manufacture, and back again in two legs. If it's only one back and forth, that's not so bad.
So far their service has been great. Ordered the little humidifier I needed Saturday night. It came Tuesday at noon. Answered the phone quickly, and were competent on the phone. And they sell, and describe online (very good webpage), all the extra parts needed for installation, plenum kit, filter holder, corners to set the furnace on, high-temp evaporator tray (needed for oil furnaces that burn hotter than gas) etc. (Everything but the elusive flexible duct connector, which someone here showed me where to get. )

I don't know if I would save 3000, maybe 2000, but yes, exactly.
BTW, I had the chimney cleaned Monday, 170 dollars. And that whiff of oil smell at the start of most cycles, I haven't had since then.
I've thought before that it was gone, but never for 3 whole days.
He was slow and thorough and took almost 3 hours, including up on the roof. He didn't say it was "too dirty to clean" like the previous guy, 170
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On 1/27/2011 10:42 AM, mm wrote:

Comfort-Aire is another generic HVAC unit that may come off the same assembly line as other contractor/builder grade equipment. I've installed and repaired a lot of HVAC equipment and the builder grade units all look very much alike on the inside.
TDD
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On Thu, 27 Jan 2011 13:00:18 -0600, The Daring Dufas

So contractor grade means it won't last 32 years like the Carrier, only about 20??
And it will break 1 or 2 more times or more seriously than a grade A brand during that time??
Or what is likely? :)

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On 1/27/2011 1:31 PM, mm wrote:

If you own a cheap car and service it regularly, it will last longer than an expensive car that receives no service. One thing I see with cheap HVAC systems is more corrosion than pricey systems. I worked on a Carrier unit for an old fellow who had purchased it back in the 70's and it was the most expensive unit Carrier produced at the time. It had stainless steel screws and there was no rust on the metal covers and brackets. A more expensive system may have more safety controls than a cheap builder grade system. Safeties that are often missing from the cheaper units are anti short cycle timers, high and low pressure cut out switches and condenser fan cycling controls. I ordered a three phase unit with all the extras including a 3 phase power and voltage monitor and have never had to do anything to it except clean it and change the optional 2 inch thick pleated air filters. One of the things I will install on any HVAC system in a rural area are hard wired surge arresters. This is something I'd like to see as a standard feature because it prevents a lot of damage to circuit boards, fans and compressors.
TDD
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On Thu, 27 Jan 2011 16:29:40 -0600, The Daring Dufas

A lot to think about. I don't live in a rural area, but could I install my own surge suppressor between the furnace and the line, like are sold for computers? Maybe the ones that need replacing after they work.
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Millions of people don't have surge suppresors. It's about the last thing I would worry about. Just about all power supplies have regulators in them these days. Plus a 20% surge at 24vac is 29 vac, hardly likely to "fry" anything..
In most hvac systems just about all the parts are made by a few large manufacturers. A number of the hvac companies actually make many of the brand labels.
I would consider anything from a basic single speed system to the more midrange systems. Stay away from the most effecient whiz bang system there is. It will not have much of a track record and the service guys will not be familiar with it.
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It's not the 20% surge that one is concerned about. It's the 3KV surge that could make it to the service in your house if lightning strikes a nearby electric utility wire, transformer, etc. It used to be you didn't have to be concerned with those at all for a furnace, because all it had was motors and switches, which could survive those short, high voltage spikes. But with more and more appliances being used in the home having electronics inside them, I think it makes sense to add surge protection. But I would not do it for the HVAC seperately. I would add a whole house surge protector at the panel, which you can buy for under \$100. That location provides protection for everything in the house and can be connected directly to earth ground, making it most effective. You can then supplement that with additional plug-in surge protectors on the most critical electronics, eg computer, TV, etc.

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On 1/28/2011 7:04 AM, snipped-for-privacy@optonline.net wrote:

Here in Alabamastan, Alabama Power will install a whole house surge protector that plugs in between the power meter and socket. It's a pretty slick gadget which, of course is replaceable after an attack of God. :-)
TDD
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On Fri, 28 Jan 2011 19:35:52 -0600, The Daring Dufas

Hadn't thought of this. Installation is surprisingly easy.
The instructions for the Leviton model, at least, keep mentioning the use of conduit, either flexible or rigid, including plastic.
If all the other wires in my house are Romex with no conduit, do I still need conduit here?
It also says the suppressor should be as close to the breaker box as possible, but that mean I should use conduit, does it?
It seems the lowest retail price right now is about 180, but that too would be worth it.

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On 1/28/2011 9:25 PM, mm wrote:

I install the cube style surge arresters right on the HVAC unit itself where the electrical power is hooked up. There is usually more than one 1/2 or 3/4 electrical knockout on the cabinet. I get them at the HVAC or electrical supply house and there are several brands I will use.
http://preview.tinyurl.com/4h3qyo5
TDD
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On Fri, 28 Jan 2011 22:28:39 -0600, The Daring Dufas

Thanks. These are pretty good too. This raises a question I should have asked 25 years ago, or maybe I did and I've forgotten: "Ensure that the barbed side of the locknut is in contact with the metal of the enclosure"
Is the barbed side the top of the locknut's "dome" or the bottom of the dome where it's widest?
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On 1/29/2011 5:28 AM, mm wrote:

The barbed side bites into the cabinet keeping it tight and providing for a case ground but the surge arrester case is usually plastic so it doesn't matter. With metal parts you want the teeth digging into the metal. Some lock nuts have serrations on both the wide and narrow side and installing one wide side up can make it easier to tighten it by putting the blade of a flat tipped screwdriver against a lug and tapping the end of the screwdriver handle with lineman's pliers.
TDD
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On Sat, 29 Jan 2011 06:35:35 -0600, The Daring Dufas

Thanks. I looked at that Square-D SDSA1175 and I see I could use two of them on the two legs in my breaker box. That's a reasonable idea, right?
To know when they need replacement, I have to look at the LEDs once in a while, right? No other sign>? (not counting the trees knocked down by lightning)
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You can get an Intermatic whole house surge protector for about \$100.
http://www.intermatic.com/~/media/files/intermatic/products/other/surge%20suppression/ig1240rc%20-%20data%20sheet.ashx
The above is the IG1240RC, which is rated at 20K amp surge per line They also have the IG3240RC, which is rated at 60K per line.
Your choice, depending on how much margin you want. You connect it to the panel using an ordinary double pole breaker, 20 or 30 amp. Because they are made to connect to conduit, that is how I'd connect it, either rigid or flex.
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On 1/29/2011 8:26 AM, snipped-for-privacy@optonline.net wrote:

http://www.intermatic.com/~/media/files/intermatic/products/other/surge%20suppression/ig1240rc%20-%20data%20sheet.ashx
Me and my friends who service HVAC systems don't usually fiddle with the main power for the home so we recommend that the customer get the surge suppressor that the power company installs behind the power meter. We install the separate secondary suppressors on the HVAC equipment itself. The power company will guarantee their power supply in case of damage. Bigger pockets prevail in those situations. :-)
TDD
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