Upgrade from 92-95% and adding variable valve/speed-Worth it?

[heartmd]

I currently have TWO 80% 20 year old Tempstar 150K BTU furnaces, one for each floor in my 4600 sq ft home (2300 in each floor) (built in 1989).

Due to some situation, the builder will be replacing both furnaces with new Trane 92% furnaces FREE. He says that per his calculations TWO 120K BTU furnaces will be enough for my home (I am adding R30 cellulose insulation to my attic)

I have to pay extra if I need TWO 95% furnaces instead and extra if I want TWO variable valve and variable speed ones (all from Trane)

I use $2288 worth of gas each year to heat my home and operate the hot water heater and drier each year.

Questions:

1.
Am I right that I will save 3% on my gas bill with the extra 3% efficiency? That means I will save $60 each year and for the lifetime of the 95% furnace which is 20 years, I will save $60X20=$1200 for both furnaces ($600 for each furnace). So anything more than $600 extra for each 95% furnace will not be cost effective

2.
What is the gas savings with the variable valve and variable speed.

3.
Do variable valve and speed furnaces make any sense financially and even comfort wise in a 2 furnace home?

[amd]

The real world difference between 92 and 95% is negligable; however, upgrading to a variable speed blower is worth while.

Having a 2-stage (or modulating) gas valve will not save fuel but it will dramatically improve comfort.

If you run the blower full time, the more efficient blower motor will easily save at least $200 of electricity per year. (per furnace, 0.10 per kwh or higher assumed)

120k BTUs for each floor excessive - was a load calculation performed?

R40-R50 attic insulation is recommended these days. (In ontario minimum code is now R40)

If you get multi-stage furnaces, insist on 2-stage thermostats. (Note: new wires will have to be pulled)

[2old2rock]

Are you sure you need 2 - 120,00 btu furnaces? Did you have a load calculation?

[t527ed]

where are you located, thats a lot of heat for a house that size.

[Sleuth]

It might be a good idea to ask your builder/contractor the warranty on the parts and labor for repairs on the high tech/high eff equipment,

I would want to know the cost for replacement of a variable drive not covered by warranty.

[beenthere]

I would want to know the cost for replacement of a variable drive not covered by warranty.

But how will the builder know what a VS blower motor replacement will cost 5 years from now?

The more common, VS blowers become, The less they cost for repair when/if needed.

[beenthere]

OP.

As others have stated. 120,000 90%+ for each floor sounds over sized.
You might want to ask to see this supposed load calc that says you need that size equipment.

If he can't/won't show you. You might want to do your own. Since over sized furnaces, on under sized duct tends to make for high heating bills. And it sounds like you would like lower heating bills.

HVAC Calc

Did/do your current furnaces run 24/7 when its at your coldest outdoor temps?
Strange how 80% of 150,000 = 120,000

[Sleuth]

The OP states for some "reason" he's getting free replacements for his 20 yr old furnaces.

The high tech equip available, which he's inquiring about, has pros and cons.
Sizing, reliability & repair costs would be good points to be considered.

OEM ECMs out of warranty will make your jaw sore.

[beenthere]

OEM ECMs out of warranty will make your jaw sore.

Most ECM motors are replaced when there is nothing wrong with them.
Its more often the module that is bad. And the module is not that expensive.

[sktn77a]

95% furnaces will get you an aditional $1500 in Federal tax credit. Does that change the equation?

[sheltermonkey]

Just put a 96% var Trane in my house yesterday. Can't comment on the two stage gas heat-just going to use 1st stage. Original poster could always just lock these 120,000 monsters in 1st stage heat and buy that 10 year warranty.
Don't forget about a more efficient A/C with humidity control which the guy might also need if his Air conditioners are also over sized. OP might already have the 1500 tax credit covered with attic insulation.

I think it was worth it now, but then again I have to justify it all to myself right now. Come tax time I might be happy too.

[amd]

Original poster could always just lock these 120,000 monsters in 1st stage heat and buy that 10 year warranty.

What's the point of having an expensive singe stage furnace?

Why oversize and not utilize the equipment to it's potential?

[Quig]

As you may have gathered from previous posts, we are all quite suspicious of the load calculation on your home. In my estimation, you must live somewhere near santa clause or in cardboard box.<<<<(joking obviously). Theorietically, your math is accurate, but more than math is involved here. First of all, the addition of R-30 on top of whatever you had previously will negate your figure for annual gas consumption, which by the way seems like quite a large number but then again, you have two large and relatively inefficient furnaces. If I were in your shoes I would
1. Verify the validity of the load calculation. Was it a manual D type load or rule of thumb stuff.
2. Having determined the sizes i need, i would always go with a two-stage variable over the single. Here's why: the lower, quieter, slower heating of the first stage tends to be more comfortable which, in my opinion, tends to lend itself toward savings b/c of less t-stat adjustments and happier occupants.
Its very difficult to put a number on comfort factors. I also agree that you will see electrical savings with the variable IF you run the fan constantly, which is recommended b/c it helps keep more even temps throughout the home, thus comfort, thus savings. I am obviously a huge fan of variable gas and variable speed based more on comfort than savings. Two furnaces sounds wild, but we obviously cant see the situation.
Im not a tax pro, but make sure you are covered with the incentives.

[sheltermonkey]

What's the point of having an expensive singe stage furnace?

Why oversize and not utilize the equipment to it's potential?

Cause I can't get a smaller furnace with variable speed and want the ECM capabilities. OP has a different situation.

[Freezeking2000]

It is very rare to have a head load in a home that size be more than 100K for both floors. I have done at least 50 calcs in homes that size and have NEVER seen a load that would require that size furnace. Most likely the second floor can use 60-80K unit depending on the blower requirements for cooling. The first floor the same.

[heartmd]

Zip code:
60045, Lake Forest, Illinois (Northern (Lakeshore of Lake Michigan) suburb of Chicago)

Heat load:
The heating contractor came in a half day and measured the home. He also took the architect's plan of the home with him and came back the next week. He took measurements of all the windows.
He then called and said that I currently have TWO 150 units and all I need are TWO 120 units. He told me that the excessive glass casement windows and huge front door with semicircular glass above it was the cause for the excessive heat load. These are thermopane but not the gas filled type.

Costs:
The builder told me that the heating contractor is installing the TWO 92% 120K furnaces for $5200 for TWO furnaces, installed and he will pay him the $5200. Recall that I have to pay for any upgrades to 95% or any variable valve and variable blowers.
The upgrade to TWO 95% which will cost me$1551 for both the furnaces. Please remember that I get the TWO 92% 120K furnaces installed for free.
The variable valve and blower with TWO 95% units cost $3840 for TWO furnaces ($1920 each furnace) plus an additional $ 868 for 2 Thermostats and for running new wires to them ($434 each thermostat).
The variable valve and blower with TWO 92% units cost more than $4000. So they were not considered.

Questions:
1.
What would you do if you were me? I do not want to throw my money away.
2.
Does a variable blower make sense in a TWO furnace home?
3.
Some below have advised going for the 92% with variable valve and blower but that option is more costly than 95% with variable speed and blower and was not considered. See above.

Thanks for all the replies below.. I appreciate your input.

[beenthere]

I REMOVED the prices you posted.


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[hvac n-j-near]

The other posts are right on regarding the unit size and comfort from variable speed. Here is how to look at the math:

Total gas bill is roughly $2300 per year including dryer and water heater. You need to subtract these since they are not changing. Look at a summer bill which should be only water heater and dryer. Say it’s $50 a month (just a guess but simplifies the example), multiply by 12 months to get $ 600 total. Subtract that from the total to get the heating bill with old eqp. $2300 - $600 = $1700. Now since your old furnaces were 80% efficient multiply $1700 x 80% to get the $ worth of gas it takes to heat your house. $1700 x 0.80 = $1360. The other 20% ($340) is lost to inefficiency. Now with the new systems divide the total $ worth of gas required by the new efficiencies. Therefore, 93% efficiency would be $1360 / 0.93 = $1462 and 95% efficiency would be $1360 / 0.95 = $1432 (all rounded off). Therefore the 92% furnace will save about $238 per year over the 80% unit. The difference between the 95% and 93% is $1462 - $1432 = $30 per year in savings. So unless the upgrade is less than $600 total ($300 per unit) it will be hard to justify from a cost savings perspective.

Now I am sure many will point out that the variable speed blower will use less electricity and many other minor flaws with my math, but the point I am trying to make is compared to the 80% unit there is very little difference in 93% or 95% furnaces.

[heartmd]

1.
I am incorrect in stating in my first post that the gas bill is $2288 per year in 2008-9. It was $2262.54 in 2001 when the heat was set at a constant 68degrees in the daytime and 63 degrees at night.
If one says that the price of oil in 2009 is double that of 2001, then one extrapolate that the heating bill if heat is used to maintain 68degrees in the daytime will be $4512 per year Sorry, I don't have values for years 2003-2009 as the heat was not used continuously.

With this added info, which furnaces do I choose? The free TWO 92% without variable valve/blower OR
just 95% without variable valve/blower OR
95% with variable valve/blower?

2.
Trane is giving a 5 year parts warranty and the heating contractor is giving a 1 year workmanship (labor) warranty.

Thanks for all the replies so far. All of you have been helping me make up my mind.

[commerce48]

1.
I am incorrect in stating in my first post that the gas bill is $2288 per year in 2008-9. It was $2262.54 in 2001 when the heat was set at a constant 68degrees in the daytime and 63 degrees at night.
If one says that the price of oil in 2009 is double that of 2001, then one extrapolate that the heating bill if heat is used to maintain 68degrees in the daytime will be $4512 per year Sorry, I don't have values for years 2003-2009 as the heat was not used continuously.

With this added info, which furnaces do I choose? The free TWO 92% without variable valve/blower OR
just 95% without variable valve/blower OR
95% with variable valve/blower?

2.
Trane is giving a 5 year parts warranty and the heating contractor is giving a 1 year workmanship (labor) warranty.

Thanks for all the replies so far. All of you have been helping me make up my mind.

I'm not a professional, but I've been looking at these issues for my own house for the last two months. I think there is no doubt that you will be happier with an ECM blower (often referred to as a variable speed) and a multi stage or modulating furnace. Quieter and better comfort. Energy cost will be somewhat reduced, mostly in the electric cost to run the furnace. There are some small benefits cost wise to having longer run times that the modulating furnace will give you.

You should be able to get a federal tax credit of 30% off of the extra they charge you for the upgrade. Your local utility may have an incentive as well. That should make it a no brainer. Don't oversize it for the best benefit.