HVAC Questions? Ask an HVAC Expert for Answers ASAP
Hello, My name is XXXXX XXXXX I will do my best to help you today.
i got three different answers about installing a lennox g61 furnance in my 1600 square foot home 17 years old well insulated and would like to heat 800 square foot basement for living area is the 70000 btu or 90000 btu better it is a two stage 2 contractors said the 70000 and one said the 90000 would be better
They both have aXXXXXblower so either will work it just depends on what type of climate your putting this in.
putting it in michigan just dont want to be oversized or undersized at present it one has a one stage furnance
I would go with the 90,000
that would be better than the 70000 how do you figure out the calculations on that is it because i want to heat the basement and if i went with the bigger one could i add a 14x14 room in the future
The only true way to know exact is to do a manual J on the house. This requires software that is about 2,000.00 or someone who has had classes on how to do one by hand.
most installers do not ever do a manual J they use rule of thumb Technics which get it close.
if you have 2400 sqft total that means you need XXXXXfurnace.
The single stage and 2 stage doesn't matter when considering heating BTU's it just determines how efficiently it provides those BTUS
what isXXXXXforce what furnance g61 70000 or 90000 the 1600 ranch top floor has vaulting in the living area only basement is small want it heating so we could use it for some living space what would you use if its your home
they were going to use 2 1/2 ton air
that would be for the main floor sq/ft
but you said there was another 800 in the basement?
yes main floor 1600 basement is just a basement of 800 square feet we would like to heat and do some finishing on to watch tv etc
If you are goign to tap off the existing system for the 800 sq/ft basement then I would want bigger than 2.5 ton.
unless they plan on power zoning the basement off the system
probably that power zoning the basement i dont know i will talk to them but what about the furnance size
this G61 is a 90+% furnace so going with 70,000 BTU is more than enough
if you where using an 80% furance i would go with 90,000
so the 70000 will be enough to heat the top floor and the basement i know it is two stage but one of the contractors said the 90000 would be better because 1600 is at the top of the 70000
at present the furnance is one stage and only 70000btus
would there be a problem with using the 90000 instead
no none at all
If it short cycles too much you just go down and block off one burner
Having too much heat isn't as big as problem as having too much or too little cooling.
what one would short cycle too much the 70 oe 90
70 or 90
For example here in Georgia for a system that requires 4tons of cooling we could put the smallest possible furnace on 40,000 btu and still have plenty but we can't because the smallestXXXXXfurnace is around 90,000 BTU
So we just put the 90,000 BTU furnace in and then block one or two burners off so it is actually putting out around 60,000 or 50,000 btu
i dont understand what you are saying what would short cycle
The bigger one would cause short cycling if it was too much heat
i see so having too much because the lowest btu it starts with is 66000 mite not be good
But you can always decrease the size of the bigger one. You can't increase the size of the smaller one.
So if in doubt go bigger
If they are power zoning the basement then 70,000 is plenty
If they are just dumping runs to the basement and it gets air anytime the furnace is on for stairs then go bigger
just has runs in the basement with that has air vents on them that you can open and close
so special power runs or zones i just dont know what to do dont want to be to big or be to small and the furnance always cycling i guy came with a computer and put all measurements in and said 70000 but my husband did not tell him about the basement how much is the top square footage that the g61 70000 can heat
70,000 BTU is perfect for the 1600 sq/ft upstairs.
is the 2 and 1/2 ton air conditioner compatible with the 90000
what about the basement
what does exactally mean
if you figure in the basement duct work and sq/ft it really should be at the very least 3 ton with a 90,000 furnace.
I mean what about the basement
when I say exactally
ok so i need to go back to the drawing board i have had differences because of this furnance it is starting to get to me i need to decide by tuesday
All your doing when you take runs off the furnace and stick them in the basement is stealing the BTU needed for upstairs so the upstairs takes longer to heat and cool then it should based on the size system installed. If you are putting in new equipment you should go up in size to accommodated for this extra 800 sf that is now being heated and cooled.
Chances are you currently have a 2.5 ton system with a 70,000 BTU furnace and they quoted changing that system with the exact same size system right?
i had 70000 single speed and i guess that was the same with air everyone says two speeds are different what exactly can the lennox 70000 handle in square footage
man you really have to investigate everything yourself to get a good answer you know what i mean
That system that you have on the house now was designed for the upstairs 1,600 sq/ft only. So while you have the chance you need to up the size of the system to accommodated this extra 800 sq/ft that wasn't there when the original system was put in. And that would be a 4 ton air conditioner with a 90,000 BTU furnace. You could get away with a 3 ton air conditioner and a 90,000 furnace because a basement doesn't really need much cooling in the summer it stays cool.
It's hard to put a number on sq/ft heating BTU. It really depends on the tonnage drive of the furnace.
so when they told me the lennox 70000 could easily handle 1800 square feet they were probably off.
70,000 BTU furance can handle up to a 3 ton a 90,000 can handle up toXXXXX/p>
no I wouldn't say they were off at all. 70,000 btu can handle 1800.
70,000 btu furnace hasXXXXX so at 600sqft/ton that is 3 ton for 1800 sqft
I would't go much more than 2,000 on a 70,000 btu furnace because then you would require a higher ton blower.
but you have 2,400 sqft of heated area with the main floor and basement
so you need a furnace that has aXXXXXblower. furnaces go from 3 ton and then the next size up is 5 ton meaning it handles up to 5 ton.
the 90,000 btu has this size blower.
if this was your house then you would go with the 90 i forgot to tell you the basement is open to the house no door on it we want to put a door on the basement would the 90 over power the home
no it would not
especially in Michigan.
i have to tell you the guys who told me to put in the 70 one said the basement would heat fine after i called him
i just dont want to make a mistake on this investment
it probably would, it probably would heat too much
The upstairs would be what struggles
The thermostat is upstairs so the furnace would run until the upstairs reached temperature. The basement is underground so it doesn't lose it's heat as fast and doesn't require as much to keep it warm.
your taking about the 70 now
So as the upstairs runs to get to temperature and hold it the downstairs just keeps on getting heat it doesn't need.
doesn't matter what size
so what are you saying to do
okay here is what "I would do If it was my home"
I would install a 3 ton system on the 70,000 BTU furnace. I would then go in and power zone the system so that the upstairs and the basement both had a thermostat. These power zones close off the runs to the basement at the furnace if the basement doesn't not want heat or cooling and it closes off the runs to the upstairs if the upstairs doesn't want heat or cooling. This way I can control the environments separately and maintain the temperature I want within 1 degree on both levels.
If I didn't have the money for the extra 3,000.00 that power zoning costs i would put in the 90,000 BTU furnace on a 4 ton air conditioner.
i dont have the extra for the power zoning so i guess i will have to do the 90 and tell the guy the 2 1/2 ton air is too small
and live with the basement being a little warm during the coldest days of the winter when the upstairs takes longer to heat up and a little colder during the summer on the hottest days when the upstairs runs longer to keep up.
why does he think the 2/12 goes with the 90
Make sure you ask him to install a return run for the basement if they haven't already. If you do not zone the system this is the best thing you can do for the system.
the 70 probably would not heat the basement and upstairs correct
90,000 BTU furance can handle up to 5 ton. You can put anything you want on it 5 ton and smaller
you just lower the blower speed down
It would heat it don't get to caught up in heating it up and cooling it down. It is about the time it takes to heat it up and cool it down.
what is the best efficiency
and for the difference in a 90,000 btuy and a 70,000 btu you may be talking 100 dollar a year difference in energy usage it's not that detrimental.
thanks for being patient my husband dont check into this stuff we are 56 and this is the first time i bought a house he had a house when we got married so it is a new experience
so your saying the 90 is the better one for this home
yes if you do not power zone it. Going bigger is better
If later on down the road you feel the system heats up too fast and it is too much BTU for the home you can always have them block one burners and decrease it.
If you go with the 70 and it turns out not to be enough for your liking there is nothing you can do about it
matthew has been great and very gracious
Well thank you. Please tell that to the website when you leave feedback :)
matt i have to say you have explained more to me than anyone i have talked with you have patience i went on earlier and i got some answers but you gave me the confidence i need to make a decision everything you said had a good explanation if i need to talk again will i get you or someone else
Again make sure you ask for a return run in the basement if there isn't one already. This at least will help circulate the air in the basement while the upstairs tries to satisfy the thermostat. If there is no return you will get hot dry air laying in the basement in heat and moist cold air laying around during cooling. With the return at least it circulates the air and pumps fresh in.
this 2 stage furnance i guess it what makes the difference in btu huh
All 2 stage means is that it uses half of it's full BTU for a small amount of time and then kicks in the full BTU after that amount of time is up.
This is so if the thermostat drops 1 degree and the furnace kicks on it can try to heat the thermostat back that 1 degree without using the full gas usage. If after the 1st stage time is up which is normally around 4-6 mins then the full btu kicks in and gets it the rest of the way.
Just regulates the gas usage more than a single stage but you still are using the same amount of BTU furance
i am getting that pure air system and also a lennox air exchanger not the big kind just one to bring more fresh air in that is what my husband and i did not undestand because the 90 starts at 66 btu and the 70 at 45 so he thought the 70 would run more.
the first stage starts at 45btu output and then ramps to 70 during 2nd stage. the 90 starts at 66 and ramps to 90
and the one lennox guy said you will overpower it at 90 and if you get to big that is not good and the duct work cannot handle it
They both are going to run more than your old one that is just the nature of a 2 stage furnace. It is hard for people to understand this because you would think a furnace running longer means it cost more to run but it actually costs less because it's running longer using less gas.
so you can see why people get confused with this stuff
This guy that said 90 was too much was he aware that the basement runs had been taken off the furnace?
no the basement runs are on the furnance they go to other parts of the house you just have to open the vents in the basement but there are only 2
i see what you are saying that the furnance is feeding the basement runs
well we did not tell him we were going to use the basement for tv room etc
Even if you put the 70,000 btu in your home will heat and cool just fine really it will. It just may cost a little more per year then it would to get the same comfort with the 90,000 btu
and like I said why not go up so you have options if it is too big rather than go small and not have any option if it is too small.
yeah your right just dont understand all this stufff one tells you one thing the other another thing better be safe than sorry if i have more questions how can i talk to you
Just come back to the thread it will still be here accept or not it will still be here.
to the thread what does that mean