One Or Two Words ...which Furnace Do You Reccomend/ Just The Brand

[Bob S]

Which furnace would you install?........Presently an...... Air Ease residential - family dwelling- gas fired- 2 people and a dog. One I have needs to be replaced Now cracked flu 22 years old original \owner. me ...thanks very much for your input . Bob s

 

[Dana]

Before installing any new equipment, run a fuel use heat load analysis, and be sure to pick something that's not ridiculously oversized for the actual heat load. Even with modulating units the modulation range is not infinite- it pays in comfort to size it right, and the existing furnace is a useful measuring tool.

If you can't follow how to do it on that bit of bloggery I can walk you through it here if you can share the exact model number, your ZIP code, and some wintertime gas bills with the EXACT meter reading dates & usage.

Once you have the range of heat output that makes the most sense you can narrow in on which vendors have suitable & reliable models that would work.

 

[Sponsor]

 

[Bob S]

Before installing any new equipment, run a fuel use heat load analysis, and be sure to pick something that's not ridiculously oversized for the actual heat load. Even with modulating units the modulation range is not infinite- it pays in comfort to size it right, and the existing furnace is a useful measuring tool.

If you can't follow how to do it on that bit of bloggery I can walk you through it here if you can share the exact model number, your ZIP code, and some wintertime gas bills with the EXACT meter reading dates & usage.

Once you have the range of heat output that makes the most sense you can narrow in on which vendors have suitable & reliable models that would work.

96 % percent efficient is what we need for this 3200 sq ft -with basement, brands are what i was after, quality for another 20 years. .Ease of repair thanks for the help though bob s

 

[Dana]

Can't make any recommendations without knowing the heat load. A load number derived by fuel-use against heating degree-day calculation takes 15 minutes (or less), and is a better indicator than a Manual-J calculation.

Heat load isn't a function of square footage- it's all about exterior surface area and air tightness, and the thermal performance of the materials that make up the exterior assemblies. A fuel use calculation doesn't care about the details, it's agnostic of the house construction type & condition or even the condition of the ducts.

Getting the size right is a once in 20-30 years opportunity moment. Oversizing by more than 1.4x has a comfort penalty. With condensing gas furnaces even 5x oversizing doesn't have much of an efficiency penalty, but the shorter run cycles, higher air volumes and noise, along with temperature over/undershoots means you don't really want to go there if you don't have to.

Most installed furnaces in the US are at least 2-3x oversized for the design loads, making them sub-optimal. An oversized furnace will heat the place, sure, but if the goal is to keep the humans comfortable, right-sizing is the way to go.

 

[Bob S]

Thank you Dana ...You told me things to ask about,..with my installer.I was just wondering really!... about the.. quality... of different brand furnaces- as opposed to one another in brand names..Which one these fellows here would;say they liked the best in performance and durability. The .....FACTS AND SPECS ....I already .havethanks bob s

 

[Dana]

Don't expect the installer to have a clue as to the real heat load unless the do a formal and agreessive Manual-J calculation without any thumbs on the scale. To do it right takes time, and they would have to charge you for it (typically $500-800 in my neighborhood for a legitimate Manual-J) .

But it takes only about 15 minutes to run the fuel-use heat load calculations once you've figured out how to do it. It'll probably take you as long to read that blog piece on the method than to actually do it, if you know how to use spreadsheet tools. I've walked numerous people through that sort of load calculation on this forum, and others. It's not hard, and it's better than a calculation- it's a measurement.

 

[Bob S]

Don't expect the installer to have a clue as to the real heat load unless the do a formal and agreessive Manual-J calculation without any thumbs on the scale. To do it right takes time, and they would have to charge you for it (typically $500-800 in my neighborhood for a legitimate Manual-J) .

But it takes only about 15 minutes to run the fuel-use heat load calculations once you've figured out how to do it. It'll probably take you as long to read that blog piece on the method than to actually do it, if you know how to use spreadsheet tools. I've walked numerous people through that sort of load calculation on this forum, and others. It's not hard, and it's better than a calculation- it's a measurement.

 

[Bob S]

These calculations were all done in 93 when i bought the ...broken one ...3 BEDROOMS basement kitchen dinette- formal dining room -large living room- and family room the same, as i have now. Nothing has changed in or outside, or basement, which is long--- with ! bathroom down 2 bathrooms up stairs. bob s............ 90% efficient with A/C coil air bear filter lobb humidifier.this help any/

 

[Dana]

How do you know the calculations done in '93 had any bearing on reality? Even now HVAC contractors are WAY too conservative on their assumptions, leading to gross oversizing factors "just to be sure" that they never get the 5AM call on the coldest night of the year from a shivering and irate custmer. It's sad fact that the typical Manual-J done by an HVAC installer is heavily biased toward the high side.

I'd bet they didn't run a blower door test to get a handle on the likely air infiltration losses and made a high-side assumption. I'd also bet the didn't test the duct leakage either, making another high side assumption. Even if they got ALL of the rest of it right they started out more than 40% to the high side, then upsized the equipment from there. Most Manual-Js done by HVAC folks will oversize the load by more than 50% from measured reality, and they then up-size that by another 50% "just in case". In those cases it won't be 5x oversized, but more often than not it's more than 2x oversized. Ideal sizing would be 1.4x oversizing for the load at the 99% outside design temp.

With a fuel use analysis none of the construction or duct details matter. The insulation, windows, duct leakage and outdoor air infiltration are whatever they are. Those loss factors are automatically built into a fuel use derived load, since there is no way to separate them out.

What is your ZIP code (or at least the first three digits, if you'd rather not say)? Barring that, pick the nearest listed city, so we can estimated the 99% outside design temp. The full ZIP code and the exact meter reading dates & fuel use of a couple of mid-winter gas bills would be enough to run the whole calculation, by looking up heating degree day data for those intervals on degreedays.net.

What are the BTUs- in on the furnace? What are the BTU ratings on the AC coil (and condenser)?

I'm going to take a WAG that you have something like 100-150,000 BTU/hr of furnace, serving a 99th percentile heat load that is somewhere in the 45-60,000 BTU/hr range, with something like 5 or even 6 tons of cooling for a real load that's under 3 tons. If they totally botched the load calculations it could be even worse.

If the basement doesn't have foundation insulated and/or the house leaks air like a sieve you'd be on the high end of the 45-60K estimated range. If it's pretty tight and the foundation is insulated you'd likely be on the low end of that range. If it's exceptionally tight and had low-E windows instead of clear-glass double-panes it could even be in the 40K range. But if you won't run the fuel use numbers you'll never know.

 

[Bob S]

I will be talking with them again here soon , double pella windows wood. insulated every where well. I think its 100,000 btu i am in lower mich 229

 

[Dana]

ZIP codes starting with 229 are in Virginia (that's WAY lower Michigan, eh? )

Michigan ZIP codes all start with 48 or 49. I'm going to go out on a limb and guess that you're either in Britton (Lenawee County) or Ecorse (Wayne County), either of which would have a 99th percentile temperature bin in the low to mid single digits, say 3-5F.

Your windows could have U-factors anywhere from U0.28 to U0.50 which is quite a range, but it doesn't matter what it is if you calculate from fuel use measurements. To run a Manual-J you would need to know what the real U-factors are, measure up all of the window, wall, door, attic areas and apply the correct U-factors for each, measure the air leakage (or guess, which isn't an exact science), and measure the insulation depths everywhere, then subtract out 24/7 electrical loads, body heat, etc to come up with a number. With too many guesses the numbers just get fuzzier, less accurate, and it takes time, which is why they would have to charge real money for it. With a fuel use calculation you're using the existing furnace and it's efficiency as a calibrated measuring instrument, and you don't need to know ANY of that other stuff.

A Manual-J is necessary to figure out the ducting to make sure there's the correct proportion of heat in every room, but the ducts already exist, you really only interested in the magnitude of the whole house load, and it's nowhere near 100,000 BTU/hr, it's probably half that or less.

In the time that I've responded to your posts I could have run the calculations for you multiple times if you just spilled the beans on the fuel use, full ZIP code, and meter reading dates.

Having calculated the load before meeting with the contractors gives you a big leg up on the situation. About 8-9 out of 10 contractors will propose something that's more than 2x oversized, then try to snow you that it doesn't matter, because it's a 2-stage furnace. The low fire output of most 2-stagers is about 60% of the high fire output, so if it's 2x oversized at high fire it's still 1.2x oversized at low fire. Ideally you'd be no more than 1.4x oversized at high fire, which means it would cover the load more than 80% of the time at the more efficient low fire range, and would only step up to high-fire after a fairly long run cycle.

 

[Bob S]

49229 is my zip what do you need one of my last paid bills?? bob s

 

[Dana]

ZIP code, exact meter reading dates, and the amount of fuel consumed during between those meter reading dates would do it.

A couple of billing periods is more accurate than one. Mid winter bills are better, since it's affected less by things like solar gain or hot water heating using the same fuel. The wintertime heat load is higher, and the solar gains lower. If you were off on the beach in Belize for a couple of weeks with the thermostat turned down to 50F during that time, use a different billing period.

 

[Bob S]

get them tomorrow for you
bob s