Small ducks , wrong size furnace

[catmanacman]

I'm sure your friend ment well but maybe he was a quack

[vibration]

Check if your furnace is 2 stage before you remove it.

[Dr.phil]

You guy's aren't making fun of the Ducks are you?

[tedkidd]

Since 60 will heat 3500 sf homes in my area I'd say you best get something that modulates down. A multi stage could have the highest stage locked out.

Look for one based on how low it will go. Ie, goodman 45 only drops to 30 whereas carrier 60 will drop to 22.

[lynn comstock]

....Similarly, when people say "duck tape," they mean "duct tape." ...

I guess it is official:

Did You Know?
Duct tape actually emerged from the trenches of World War II. GI's used the government issue sticky stuff to keep boots and ammo boxes dry, calling it "duck" tape for its ability to repel moisture. When soldiers brought the tape home after the war, the housing boom provided them with many uses for it, including holding together heating and cooling ducts. Thats when it became "duct" tape, though Duck Tape survives as a trademarked brand.

This Old House, January/February, 2003, page 20.

[lynn comstock]

.... I had no issue with my heat system, but noise is unbearble. No zoning for two story house.

• A pro might be able to select a lower fan speed and check heat rise to be within design limits.
• It is possible that the noise is whistling caused by air moving across cheap grilles.

[Cooked]

Tom Hanks used it on the Apollo 13 mission to repair the dilithium crystals in the warp drive and return safely to earth.

Maybe, aside from the noise, static pressure issues, air leakage and sweating in cooling season a 100K furnace is not too big if the ducks are uninsulated.

[amd]

Since 60 will heat 3500 sf homes in my area I'd say you best get something that modulates down.

Kind of difficult to believe.

The homes in your area must be very well built in that case.

[tedkidd]

Kind of difficult to believe.

The homes in your area must be very well built in that case.

Nope. 2 x 6 walls. R50 attic. Not a blower door medalist either, 2100. Put a 40 on a 1700 sf MOBILE HOME (goal was reducing equipment noise). Result was far rooms got comfortable for 1st time in 17 years because equipment RUNS rather than cycling quickly off.

People just seem to have no clue what a btu is, or what homes require. 60,000 btu is a LOT of heat. Fear of sailing off some edge of the earth encourages "eh, throw an extra ton at it."

This is made worse by homeowner ignorance. They want their homes heated and cooled, but they want the equipment to NOT run. They want to whipsaw temperatures around like they're driving a corvette rather than a super tanker, (what is thermal mass?). "I want my house to cool in 15 minutes! Hey, why is water dripping off the ceiling?"

Calculations are a great thing, but observations of actual performance can help a LOT. Your ac never runs continuously but some rooms are uncomfortable, therefore add 1/2 ton at replacement? How often do you see that disconnected thinking?

At 2f outside my 3500 sf homeowner (yes, 10 foot ceilings - like that matters - "Oop, better throw another 1/2 ton just to be safe!") reports the house tends to run on medium stage - 46,000.

[motoguy128]

Nope. 2 x 6 walls. R50 attic. Not a blower door medalist either, 2100. Put a 40 on a 1700 sf MOBILE HOME (goal was reducing equipment noise). Result was far rooms got comfortable for 1st time in 17 years because equipment RUNS rather than cycling quickly off.

People just seem to have no clue what a btu is, or what homes require. 60,000 btu is a LOT of heat. Fear of sailing off some edge of the earth encourages "eh, throw an extra ton at it."

This is made worse by homeowner ignorance. They want their homes heated and cooled, but they want the equipment to NOT run. They want to whipsaw temperatures around like they're driving a corvette rather than a super tanker, (what is thermal mass?). "I want my house to cool in 15 minutes! Hey, why is water dripping off the ceiling?"

Calculations are a great thing, but observations of actual performance can help a LOT. Your ac never runs continuously but some rooms are uncomfortable, therefore add 1/2 ton at replacement? How often do you see that disconnected thinking?

At 2f outside my 3500 sf homeowner (yes, 10 foot ceilings - like that matters - "Oop, better throw another 1/2 ton just to be safe!") reports the house tends to run on medium stage - 46,000.

I agree.

Thermal mass is something I'm not sure is very well taken into account in equipment sizing. In winter, design temperatures might only last for 4-6 hours in the morning. In that time, you might only lose 1-2 degrees if you were slightly undersized and the sunshine (the coldest days usually have clear skies) will quickly warm it up by 10AM.

I think many would be suprised at how small of a furnace you can actually use in most homes. AC is a little different because of latent loads and solar heat gain and system capacity can be effected easier by dirty coils, system charge, etc. Hight heat gain conditions can linger within a few degrees of design temps for 8-10 hours, expecially in mid summer when the ground is warm.


I hear all the time how most people believe it's bad for the equipment to run for a long time or even continously soem days. They think it will wear out quicker. Yes it may "wear" quicker, but oversized equipments starts and stops more often and can therefore "degrade" faster or rather wear out in different ways.

Using the same argument, many would think that a tractor trailer should have something like 2000 horsepower.... since with only around 500-700HP, it's working too hard. The reality, is that engines are comparatively more efficient when operating closer to their desing capacity in most cases.

[motoguy128]

Your ac never runs continuously but some rooms are uncomfortable, therefore add 1/2 ton at replacement? How often do you see that disconnected thinking?

Rather than spend $$$ on anothe 1/2 ton and then spend more operaitng it... you could probably throw in a couple dampers or just change out a couple supply registers with less restrictive ones and even downsize a 1/2 ton.

With just 2 new supply registers and 1 damper, I eliminated a 2-4 degree temperature inbalance between 2 sides of my downstairs. Adding 1 supply register, relacing 1 supply register, setting the blower to the correct speed and removing a register damper I cut noise in my upstairs system in half. That's a lot cheaper than replacing an oversized system.

My upstairs furnace is almsot 3X the size needed because they used a rule of thumb or based it on the number of radiators in the old boiler system and didn't factor in inproved insulation and storm windows, compared to the origninal design. Hmmm.. I had 10 radiators downstairs and 8 upstairs and they installed a 100k down and 80k up. Coincidence.... not likely.

[coolwhip]

I like small ducks...they are cute and fuzzy!

[Armis]

My Bryant 350aa is single stage , i believe fan is down to lowest speed for a/c and "middle" for heat.