20 year old home with WeatherKing Furnace/Air Question

House built in 1990. Northern Illinois, Chicago land area. Getting a New Goodman Furnace and Split air conditioning system.

What I have now is a Weatherking Upflow single stage 120,000 BTU and the Air conditioner is 3.5 ton with 3.5 ton evaporator. Not sure of the Seer and efficiency of the Air Conditioner and Furnace? 20 years old maybe 10 seer on the air and 65-70% on the furnace?

Furnace is in the basement and I was told by two contractors that the current return ductwork 24 by 8 inches was too small.

It is a QUad level 75 % Brick home full finished basement 7 feet to drop ceiling 1 foot between the drop and floor. 675 square feet. The top level of the Quad level is not brick but wood from the ground up, why not brick I have no idea?

4 feet drop ground next level 525 square feet. Ejector pump for bathroom on this level.

Ground level 675 square feet.

Top Level 750 Square feet.


Windows up the Wazu!! Ground level has 2 sky lights and 10 windows and of the 10, 5 of them are in a row in the front room.

Top floor has two windows in the master bedroom, 1 window in the John :), 2 windows in the 2nd bedroom and 1 in the 3rd smaller bedroom.

4 foot drop level has the same 5 window in a row, utility room on this same level has one window a door to the outside as well as a door to the built in 2.5 car garage.

Basement has 3 wells each with windows.

The attack does have insulation. House being 20 years ago the windows should be energy efficient??



MY ISSUE IS:

Two contractors said go with what is in there now and the system has been just fine for the last 20 years except the evaporator has decoded to leak which I have controlled for the last two summers but the leak has gotten really bad now. Loses refrigerant in 2 days. I put in the Cliplight Super seal and seem to have the air working again but I am still getting a new system.

Two other contractors said to go with the 3 ton air and 90,000 BTU two stage Goodman. I want to go Goodman and don't want to start any thread on why Goodman now.

WIth some duct work modification in the return will the 115,000 BTU2 stage 80% goodman, 3.5 ton Air by goodman be ok to use?


I was told the air might be ok but the furnace will not bad will cycle on and off too much?

Its not doing any of that now so why would the Goodman unit do that? I am going 5K less BTU.

Basically the contractor that is putting it in is complaining its too much and he won't be responsible if its cycles on and off to the point is shuts down.

The other contractors said if that became a problem I could add another register to the return but would that not be an issue if the hot water heater is in the same room? The gases from the hot water heater would cycle back into the return and that would be too dangerous right?

Anyone can help on this one I would appreciate it greatly

talk to the equiment manufacturers, they may be able to supply a higher performance supply fan, to overcome duct losses and increase system performance, can you vent the hot water heater exhaust outside to get rid of harmfull flue gases.

It is exhausted. My bother is the one who said its possible some residual gases may re-enter.

I can get a 5 ton blower instead would that help things? Also they said to go 1/2 ton more on the evaporator.

The person that is going to put it in who has been doing this for 15 years and a Goodman/Sure comfort authorized dealer/installer said that 115,000 BTU goodman is going to short cycle and I am lost as to why this will happen?

Maybe I can put a return in the basement which has none!! Just vents out no returns.

So if I can pipe that into the main return that will give me more flwo I assume. Its too much work to change the duct work leading leading away from the return and others but I can change the return from the cold air drop from a 24 by 8 inch to a 25 by 10 inch. Would that help some?

I really don't think a 90,000 BTU 2 stage 80% is going to cut it with all the windows and the top level honestly.

Nothing short cycles now and the air conditioning system was running great for 20 years no short cycling their either.

He is ok with the air conditioner but not with the furnace. I cannot run a 2.5 ton on the 90,000 furnace it only allows for a 3 ton evaporator coil so I am stuck on all this because of this shortcoming.

If the 90,000 BTU unit would take on a 3.5 condenser and coil then everything would be ok with me.

I'll get a hold of goodman but just wanted to see if anyone has had similar experience with the 90,000 vs 115,000 80% furnace verus 3.0/3.5 ton air conditioner system.

Sorry about all the spelling my keyboard has wacked out on me.

Quote

"bother"

should be:

"brother"

Quote

"I cannot run a 2.5 "

should be:

I cannot run a 3.5"

Hi hvactech,
Good to here you have ducted the flu gases from hot water heater as they contain carbon monoxide, not nice stuff. Tend to go to sleep and die.
With the air side problem consider the supply air as water, OK the duct is smaller, the heater requires X air flow, your old system is what ever ducting sizes. So in effect you have to punch 'xyz ' up the duct to overcome to total static resistance, with high temperature supply systems the air flow quanity is less than an A/ C system, for the same effect. Back to the water thing, punch water up a small pipe you get zip out the other end with a long pipe. The same applies with air, just that you can not see it feel it. OK the densities and what ever are dramitically different. But same theory applies.
OK, bigger fan required to acheive same / or similar performance, could be noisier in the duct and at diffusers. With the higher air flow , the system should not short cycle so long as you maintain the required air volume over heating and cooling coils.
Check all windows, for thermal insulation effect, double / or triple glassing is a one up cost that can save thousands of dollars heating and cooling effective costs over a short period.

Thanks for the reply and clearing this up.

So the conclusion is I have to make some changes to the ducts to accommodate the new furnace.

So I can make the necessary adjustments and hopefully get away with using this 115,000 BTU model although it is 5K BTU less so I am still not totally clear why I cannot substitute with mostly changes to the return for now.

Hi hvactech,
modifying the return air ductwork will improve the fan performance by increasing suction volume.
Similar when you remove a dirty intake filter, you here the fan noise change.
Do not forget to allow for around 10% air volume as fresh air. Introduces oxygen to sealed homes in winter, partial pressurization as well.

Even with the Duct Mods my Contractor said no more than 90000 BTU at 80%. I was told furnaces today are so much different than what they were 20 years ago and this being a two stage furnace along with some other things that even 70000 could cut it but 90000 is the way. 115000 will short cycle to much.

He said that the furnace I have now has a hi set point of 180 degrees and the modern day units have it around 120 degrees. So he is worried too much about it shutting down from all that I have talked about in my prior postings.

Oh Well!!

The high set point trip is relative to lack of air flow, low air flow equals high off coil temps..,
So my original suggestion was a bigger supply fan, most come with multi speed selection, ie High medium and low.
Did you clarify system and flows and what ever with new system supplier [ manufacturer ], not the brother-in-law.

Yes All set now thanks