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

I recently replaced my upstairs 2 1/2 ton split ac. It was a bit under a grand for new goodman outside unit and new cased coil. I installed both. I did the 90k gas furnace downstairs with the new, damaged in shipping =3D dented a little on one corner, fridgedare gas furnace for $400 from a freight liquidator, plus $50 or so for bits and pieces. I've got a couple hundred in a set of guages and a bargain vacuum pump. Those have come in handy like when one of my trane heat pumps at our lake house cracked a small copper line. I soldered a scrap of copper over it with silver solder, vacuumed and recharged. Cost to me $50 in r22. So yes warranty is an issue but I've saved so much that I don't care so much about warranty. Besides they hardly ever break in the warranty period. Trane was 6 years old when it broke.

Reply to
jamesgangnc
Loading thread data ...

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.

Reply to
mm

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.

Reply to
jamesgangnc

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.

Reply to
trader4

While I think two stage can be an advantage, at least in some applications, I think dumb two stage, which is what you have is, welll, just dumb, at least for most people.

I come home earlier than expected to a house that is now at 60F. Why should I sit around in the cold while the furnace fires at only

70% of capacity for the first 12 mins? Or how about each night when it has to recover from setback? It takes longer to recover each day because it wastes 12 mins at the lower output. Consequently, each day the setback period is longer than it could be.

To do 2 stage right, you need a 2 stage thermostat. The thermostat, which has all the info needed to make the right decision, then chooses whether to fire at 100% or 70%. Consequently, in the above two situations, it fires at 100%. In periods where it's just maintaing temp and it's moderate out, then it fires at 70%.

But even that isn't enough. You have to make sure that the furnace you buy supports a two stage thermostat. Some do not and work as you described. Some allow you to choose how you want it to work, with 2 stage thermostat or 1 stage thermostat using the time delay method. Some let you set the time delay period to like 6mins or 12mins, etc. IMO a lot of these get installed by lazy installers who are too lazy to run an extra thermostat wire and do it right. OF course there are cases where it could be difficult to do that and the timed option might start to make sense.

IMO, two stage is way over sold, based on a lot of myths. On most days, whether it fires at 100% or 70% makes no difference, yet they get sold on claiming that it will save LOTS of money on energy usage. What usage exactly? The furnace is 95% efficient whether it runs at 70% or

100%. At 70% it just uses gas at a lower rate, but runs longer. In the end, it uses virtually the same amount. But it does run the blower longer, using more electric.

So yours is a good example of where two stage makes sense. Yours is an atypical situation. With a small house, even the smallest furnace at 100% would be over sized.

It goes up about 5 to 5.25 deg an hour here at my house. Big difference. See why I wouldn't want a two stage that spends the first 12 mins at

70%?

I set it back from 67 to 60 and It's about an hour and a half here. And keep in mind, my furnace runs probably 50-60% of the time on the coldest days of the typical winter. You can see why I'm not a believer in the common advice that your furnace should run 100% of the time on the coldest days. If I did that, you can imagine the recovery time.

Reply to
trader4

Fine for new construction. But if I have an existing furnace of a given efficiency and know what percent of the time it's running on the coldest days of the year and how long it takes to raise the house temp during a recovery period, I say that is at least as good as the theoretical calculation.

A calculation BTW, which NONE of the 5 reputable contractors I got quotes from did. Nor did mm.

Reply to
trader4

I'd like to see a credible reference that says a two stage furnace gains a few % in efficiency running at the lower stage, instead of the higher. If that were so easily possible, then they could achieve similar gains with any furnace, by just resizing the burner relative to the rest of the unit. And in the game to increase efficiency in general, you'd think that would be happening, no?

All the gas furnaces I looked at for specs made no distinction in efficiency between the two firing rates. I would agree that there could be some small difference, but I'm betting it's so small that it's close to neglible. Offsetting that is the increased upfront cost of the two stage furnace, additional service complexity, more parts to potentially fail, etc.

Two stages used to be sold more on comfort issues. On moderate temp days, they can run longer, providing more air flow through the house, evening out temp differentials, eliminating hot spots near registers, etc. Somewhere along the way it got morphed into efficiency, and I had contractors standing here telling me that it's gonna save me a lot of money, which I think is pure BS.

It think that's exactly what's going on. They wing it based on experience with similar homes and alwasy err on the side of it being a bit too big instead of too small. How many customers are ever gonna call up and bitch if their furnace runs only 1/3 the time on the coldest days? But if it can't keep the house at 70, you can be sure there's gonna be trouble.

Reply to
trader4

I agree, 2 stage is more a comfort feature than a savings feature. Any differences in total operating cost to keep the house warm will be miniscule. If you don't have a comfort issue with an existing single stage unit then there is not a lot of reason to go two stage. I also agree on the thermostat, if you do two stage then get the two stage thermostat. Stupid not to.

Reply to
jamesgangnc

Well, I called the seller and he told me that the 85,000 referred to output, but because he's the seller, I doubted him. So I looked for Thermo-pride online and I found the manual online and indeed, Model oh5-85 has 85,000 Heating Capacity in BTU/hour. Model oh11-105 has 101,000 Heating Capacity in BTU/hour, but 101 is a lot closer to 105 than the input rate which is 126,000.

In the meantime, Carrier which used to echo the output value in the model number has changed to including the input value!

Very confusing and indeed a possible source for buying the wrong furnace.

None of the guys who gave me estimates sent me written estimates that named the model they intended to install. :)

Reply to
mm

You should ask for the equipment to be listed. Otherwise you have no way to compare estimates. Normally they will provide an equipment list with the estimate. Some wil give you a couple estimates for each of the brands they normally install.

Reply to
jamesgangnc

For a little over 200 bucks I could add a 2 stage thermostat if I thought the extra cost and complexity would buy me anything important.

I figured it was a waste of money, for me.

Nothing to do with lazy installer - they'd GLADLY charge a few hours extra to pull in the 6 wire cable (which my house already has, by the way - 4 wire for heat/cool is minimum)

This is where you are wrong. Particularly with an 80+ instead of a 95% efficient furnace. If a furnace is "too big" it runs short times, and during the warm-up and cool-down it is NOT as efficient as during steady run. As for running the blower longer, mine runs all the time, for the cost of roughly 1 100 watt bulb.

And in MOST houses, the furnace supplied by the builder is oversized. If it will take a house up from setback to full temperature in 5 minutes it is oversized by a minimum of 30%

So you set the damned thing to start the warmup 10 minutes earlier - what's the big deal?????

You should spend some money on insulation, and mabee seal up the cracks around the windows and doors.

The recovery time using a 2 stage would be, at most, 10 minutes longer than what you have right now - and with a properly sized 2 stage, likely less than that - because your low would be lower than you have now, and the high the same or slightly higher.

But hey, it's your house, your furnace, and your money - you can do as you please.

Reply to
clare

Only stupid not to if you regularly need the "high fire" output - which I do not. Everyone is talking about more complexity being a bad thing, more expensive, more trouble prone, more difficult/expensive to repair, yet in the same breath they say I'm "stupid" not to have the more complex thermostat.

Reply to
clare

Reply to
clare

Around these parts, they don't quote furnace installs by the hour. They quote a price for a given furnace, installed. They might call out including a new thermostat, but none of the 4 quotes I got called out the specific thermostat. So, upon figuring out that they were one wire short of two stage happiness, what do you think they would likely do? Run new wiring, or set up the furnace as yours is, to run at the lower stage everytime first, for a given period? In fact, some 2 stage furnaces are of such stupid design, that they always run 10 mins at the low stage, no matter what the installer does.

As for 4 wires, whoopee de doo. That's the minimum you need for a single stage furnace and AC anyway.

What moron would buy a two stage furnace that is 80% in the first place?

Yes, I agree if a furnace is SIGNIFICANTLY over sized for the house, then it will result in short run times which are not as efficient. You basicly have a two stage furnace that runs almost like a single stage, on the low output because your house is too small for the furnace. But that isn't what we're talking about, now is it? We're talking about a furnace that is correctly sized for the house. I'd love to see all these energy savings due to two stages documented. Most people don't understand the simple fact that if you burn 70% of the gas, you wind up burning longer to get the same heat output and consume almost the same amount of gas. They see, wow 70 vs 100, that's a lot I'm saving....

Here's a research paper where they conclude that even the alleged 3% extra efficiency that the DOE tests attribute to two stage is really due to the fact that the test was not designed with two stages in mind. With the new proposed test procedure to correctly test two stages discussed, the supposed savings vanish.....

formatting link
"Overall, the DOE test procedure shows a reduction in the total site energy consumption of about 3% for two-stage compared to single-stage furnaces at the same efficiency level. In contrast, the 2006 ASHRAE test procedure shows almost no difference in the total site energy consumption. The 2006 ASHRAE test procedure appears to provide a better methodology for calculating the energy consumption of two-stage furnaces. The results indicate that, although two-stage technology by itself does not save site energy, the combination of two-stage furnaces with BPM motors provides electricity savings, which are confirmed by field studies."

I'd be happy to see any research that shows two stages are more efficient overall and save any significant amount of money.

Reply to
trader4

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

Reply to
The Daring Dufas

Absolutely. Thanks, and thanks for your other posts in this thread.

Reply to
mm

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.

Reply to
mm

Exactly what I said - I said 4 is the minimum for heat/cool and mine has 6. Learn to read.

I resent that you self righteous fool - I bought the furnace I bought for good reason.Condensing furnaces are much more trouble prone and have, generally, a significantly shorter life span. Also, with my 80+ % furnace costing $700 a year to heat the house (including hot water - so let's be really pessimistic and say the furnace costs $600 a year,) the difference between 80% and 95% is something like $95 per year savings. The difference at the time mine was installed was about $750.That's an 8 year payback. Assuming there is no problem with the furnace. I know LOTS of high efficiency condensing furnaces that have been replaced in under 10 years due to repeated failures. And the 80+% efficient furnace is supposedly running about 85% as installed - so the savings would likely be less, and the payback longer. Going to a DC blower over the standard AC blower saved me close to 4 times that much since I run the blower on low 24/7/52. I'm very happy with the furnace I bought, for the price.

MOST single stage furnaces are significantly oversized for the house they are installed in. I'm not talking McMansions here - I'm talking "normal" family sized homes owned by lower middle class to middle class folks to whom the cost of housing and heating is a significant issue, not "morons" as you would call them who think a big fancy house is an "investment".

Hey, I can give you numbers for my house. It ran 4 hours and 12 minutes on Tuesday, and 4 hours both wednesday and Thursday. It was down to -26C Monday night. It's run less than 4 hours today (it got up to -4C this afternoon) So my total heat loss today is approxemately 4X28000 = 112000 BTU, and my total fuel usage today was about 4*32000= 128000 BTU, or 128 cu ft of natural gas. (equivalent to less than a gallon of #2 fuel oil or Kerosene) (or 10 lbs of coal)

And I'd like to see the figures you base your "moron" designation on for comparing an 80+% to a 95% furnace in my "average" home. Can you show me a better than 8 year payback, and document the probability that the furnace would significantly outlast that payback period, making the purchase of the non-condensing furnace 8 years ago a "moron"'s decision? My furnace is now something like 8 seasons old, and I expect it to last at least another 16 - I don't figure I'll be around when it needs replacement the next time.

Reply to
clare

A quote for a furnace replacement without detailing exactly what equipment is being provided, and what work is being done, should be illegal.

I would never sign a contract that did not spell it all out. Not even for WINDOWS, much less a furnace and/or A/C system.

Reply to
clare

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.

formatting link
TDD

Reply to
The Daring Dufas

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.