Replacement system questions

[tj363]

Background: replacing a 20yo comfortmaker system 100k 80% furnace and 2.5 ton AC which I'm sure has a crappy SEER, house size is 2,500sf located in suburbs of Pittsburgh, PA. Normal gas monthly budget $115 and electric is $125. Winter months stat set at steady 69 and in summer steady 75 (with fan running constantly) have a programmable stat but don't use it. We both work from home so there are always computers/radios/TV's on along with lights most hours of the day.

1) is my current A/C tonnage low for the size of my house? recommendations are coming in for a 3.5 unit.

2) based on my my monthly gas budget is going up to a 95% worth the extra cost?

3) am I misguided that I don't want a 2-stage furnace? (I feel that is just something else to go wrong over time)

4) with my current electricity cost I feel a 13 SEER A/C unit is fine based on today's technology VS 20 years ago.

Based on quotes, to get a high SEER A/C and 95%+ furnace is going to cost me approx $ more than a 'less efficient' one and I don't see breakeven for perhaps 15 years and that is being optimistic.

[Cooked]

They're gonna beat you up over the pricing....but.....$ seems excessive to me. Of course you don't say what they are quoting, 16, 17, 20?

Not enough info to answer #1 IMO. #2 is debatable. As far as #3 you'll experience more comfort with a 2 stage. You'll notice that it won't be "hot" one minute and "cool" the next. In other words much smoother heat. On #4 I'd say you are correct.

[dan sw fl]

Running the blower constantly could cost upto about $35 / month

[tj363]

Running the blower constantly could cost upto about $35 / month

Based on what I was told when the system was installed about running the fan during A/C season 24/7 would cost me next to nothing since the fan was always 'up to speed' my knee-jerk reaction was to say you are crazy.... but after researching what you posted you maybe even on the low side of what it is costing me.... thanks for setting me straight on that myth!

Having said that, after running it 24/7 the last 19 years VS per cycle the first year, it does keep both floors relatively even per se..... so I'd have to say it is well worth the extra money to do so in my case.

PS, what a great forum! I was going to post about what mfg VS another and after using the search feature have learned much by reading other threads.

[Cooked]

Running the blower constantly could cost upto about $35 / month

Yes it can, especially on an old unit. But, there is a tradeoff in that it can in some cases prevent stratification.

[beenthere]

Background: replacing a 20yo comfortmaker system 100k 80% furnace and 2.5 ton AC which I'm sure has a crappy SEER, house size is 2,500sf located in suburbs of Pittsburgh, PA. Normal gas monthly budget $115 and electric is $125. Winter months stat set at steady 69 and in summer steady 75 (with fan running constantly) have a programmable stat but don't use it. We both work from home so there are always computers/radios/TV's on along with lights most hours of the day.

1) is my current A/C tonnage low for the size of my house? recommendations are coming in for a 3.5 unit.

2) based on my my monthly gas budget is going up to a 95% worth the extra cost?

3) am I misguided that I don't want a 2-stage furnace? (I feel that is just something else to go wrong over time)

4) with my current electricity cost I feel a 13 SEER A/C unit is fine based on today's technology VS 20 years ago.

Based on quotes, to get a high SEER A/C and 95%+ furnace is going to cost me approx $ more than a 'less efficient' one and I don't see breakeven for perhaps 15 years and that is being optimistic.

If 2.5 tons has been cooling your house ok, no reason to go up to a 3.5 ton. it will just cost more to use, and end up making your indoor humidity high in the summer.

100,000 BTU 80% furnace evens sounds over sized for heating your house. A 95% in the size range from 60,000 to 80,000 BTU input would probably be far more appropriate. And give you a return on the investment.

It would probably be better if you found a contractor that would do a load alc to know what size furnace and A/C you really need. You already know you don't need an A/C bigger then 2.5 tons if your current 2.5 is cooling the house to set temp ok. And if your furnace is cycling on and off on the coldest days, you know its over sized, and you should have a smaller furnace.


Might want to check our contractor locator map, and see if one of our members is near you.

[tj363]

Thanks for your input all!

Had my final estimator come out today and felt pretty good with his knowledge of the products he was selling and what I need and don't need.

The quote is for a Goodman 95% 2-stage variable speed 90k with a 5 ton blower furnace and a 14 SEER 2.5 ton A/C unit. Not being a HVAC person a 5 ton blower for a 2.5 ton A/C unit raised questions to a layman like myself but I didn't catch it until I was reading over the quote tonight.

I'm going to call him on Monday and get some clarification on that issue but more than likely will give him the install.

Thanks again folks!

[beenthere]

90,000 BTU 95% is actually more heat then you have now. Old furnace was 100,000 in and 80,000 out. New furnace is 90,000 in and 85,500 out. So it will need to move more air then your old furnace, and could make your duct system loud. You need a contractor that will do a loud calc and select the proper sized furnace.

Don't buy into any BS that it won't matter because its a 2 stage furnace.

[tj363]

90,000 BTU 95% is actually more heat then you have now. Old furnace was 100,000 in and 80,000 out. New furnace is 90,000 in and 85,500 out. So it will need to move more air then your old furnace, and could make your duct system loud. You need a contractor that will do a loud calc and select the proper sized furnace.

Don't buy into any BS that it won't matter because its a 2 stage furnace.

F'me ... this is getting too complicated. Too bad there is only "1" "one" "uno" member within an hour of my location where the yellow pages has at least 100! Got to move on and just hope the next HVAC person has some integrity and expertise of what is best for me and just go for it. You folks will make me an insomniac if I keep posting...LOL

[catmanacman]

A over sized two stage furnace is a huge waste of money because it only runs on first stage.tell the bone head to do a lad calc then install the correct size .one of the problems is everyone is getting caught up in the high seer vrs comfort ,some units require a big blower to get that extra 1 seer to get a big blower you get a oversized furnace .a 60000 btu furnace will heat a pretty good sized home and the smaller a furnace is the more it will run and give a more even temperature

[tj363]

In the real world, how many HVAC estimators do a 'true' load calc test before quoting a customer? .... I deleted the rest of this post since I know the factual answer.:censored:

[dan sw fl]

In the real world, how many HVAC estimators do a 'true' load calc test before quoting a customer?

New Construction - the Majority

Replacements - Less.

BLOCK Loads are not time consuming given the appropriate tools and Locale experience.
Load Calc on < 3,000 Sq. foot residence should be performed in < 15 minutes.

Quoting is easy. Signing a contract with real model numbers is not easy.

[beenthere]

In the real world, how many HVAC estimators do a 'true' load calc test before quoting a customer? .... I deleted the rest of this post since I know the factual answer.:censored:

Good contractors are hard to find.

[jpsmith1cm]

hvaclown

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[tj363]

Good contractors are hard to find.

finally found 2 HVAC estimators who actually walked through the house, did measurements, window size, direction of the sun, etc....

long story short they both came in with identical recommendations ... 3 ton A/C, 80k 95% 'single stage furnace' with a fan that will run at full speed when cooling and 1/2 that speed when just circulating the air constantly during the summer months. 'single stage' furnace because the 2nd floor would suffer with a 2-stage furnace.

bottom line is one was selling carrier the other york and the prices were close ... went with the carrier based on the installer giving me 5 years free labor VS the york quote only giving one year.

[dan sw fl]

finally found 2 HVAC estimators who actually walked through the house, did measurements, window size, direction of the sun, etc....

long story short they both came in with identical recommendations ... 3 ton A/C, 80k 95% 'single stage furnace'

'single stage' furnace because the 2nd floor would suffer with a 2-stage furnace.

bottom line is one was selling carrier the other york and the prices were close ... went with the carrier based on the installer giving me 5 years free labor VS the york quote only giving one year.

Sounds lke a winner.

I really don't understand how a 2-stage is not going to provide more even heating throughout the house given Longer run cycles.

[duckman06]

In the real world, how many HVAC estimators do a 'true' load calc test before quoting a customer? .... I deleted the rest of this post since I know the factual answer.:censored:

I do!!! How would you no what to quote without one? Sure you could always go by the current size that is there. The problem I run into down in northeast LA is oversized furnace and a/c units with undersized duct work! Also who is to say that there current system is the actual size of the name plate?

Example: I looked at a Heil system thursday and it was listed on the name plate was a (4) ton but after carfull review found the original comp. Was only a 42,000 btu. My point is looking at the system size on the nameplate is not always accurate. This was a system that I looked at 2 years ago but she called me back out to revise the estimate. An even though I had my load cal. From 2 years ago. I reran to ensure her that when we install her new system
It will be proper sized.

I have gained a lot of customers from doing this and also lost some because no matter what they have another company or several telling here them that it needs the same size system or bigger. When really they needed a proper sized system to deliver what the duct system can handle and return. It is sad this day in time with all the tech. We have and a load can be done in matter of mins. That most don't do it.

Just my 2 cents on this.

[tj363]

Sounds lke a winner.

I really don't understand how a 2-stage is not going to provide more even heating throughout the house given Longer run cycles.

both contractors had concerns about the first stage of heat being able to push air to all parts of the house evenly. they thought that two of our 2nd floor bedrooms could have issues.