Should I Upgrade?


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Old 11-25-07, 10:48 PM
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Should I Upgrade?

I've come into a situation where I'm thinking it might be a good idea to upgrade my furnace, but I'd like to have some more educated opinions. I've been biking lately with a guy who owns an HVAC business, and he's offered to do the work at a discount. That, along with winter coming and my friend noting that I have a 136,000btu furnace and I only need 75,000ish has pushed me to seriously consider an upgrade.

The house is a 1600sq ft (not counting the 1000sq ft basement) home built in 1946 with relatively poor insulation in the walls (the attic is well insulated). It has a 135,000btu 80% Lennox Gas furnace from 1990.

My friend is offering a scratch and dent 75,000btu for $1500 installed. He said he could do the AC as well for a bit under $3000. (my AC unit is from 1978, so it needs replaced).

Questions:
1) Is the deal above a good deal?
2) About how much would I be saving going to a smaller/more efficient furnace? ( we use from 12-341CCF/month and our bill averages $130/month over the course of last year).
3) Is 75,000btu appropriate? The home's lack of insulation concerns me, but my friend thinks it is oversized and noted that the ducting is for a smaller furnace since it gets very hot when the furnace runs.
4) Would electric or a heat pump be a good option, or cost more?
5) Any other suggestions?
 
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Old 11-26-07, 11:22 AM
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You haven't given enough information for anyone to make a legitimate answer to your questions.

The first thing that you need to do is to perform a heat loss calculation on your home. This will give you the needed size of a furnace.

1. When I had my new furnace installed in April of 2006 it was a Lennox 80% two-stage variable speed unit and the cost was $2800. Your quoted cost of $1500. MAY be a good buy or it may be just a bit under the going rate depending on many, many factors.

2. If your present furnace has an AFUE of 80% and the proposed new furnace also has an AFUE of 80% then the savings you may realize will be more from longevity than anything. If your proposed new furnace also is a two-stage variable blower speed then you will save on electricity and some on fuel. The amount is difficult, if not impossible, to predict.

3. The ONLY way to determine what size furnace is appropriate is to do the heat loss calculation. It is POSSIBLE that your friend has done enough calculations and furnace installations, and is also familiar enough with the local weather patterns along with typical house construction in your area to make an educated guess but that is all it is, a guess. It is also unfortunate, but very true that undersized ductwork is often installed so the mere fact that the ductwork is not appropriate for your current furnace is not a good indicator of the proper size furnace that needs to be installed.

4. Whether or not a heat pump or resistance electric heat is a good option depends on your local climate, the cost of the electricity and other fuels and what your finances will allow for the capital costs of a new system. You must also factor in how long you plan to stay in this house.

Your present furnace is now about 17 years old. Normal expected life of a forced-air furnace is about twenty to twenty-five years so your current furnace is definitely in middle age and fast approaching old age. Depending on the items I have listed and a few others it may make a great deal of financial sense to seriously consider replacement.
 
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Old 11-26-07, 09:27 PM
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Thanks for all the info Furd.

1) The unit he recommended was a scratch and dent 90% Lennox. He said they still retain their warranty and I could care less if my furnace has cosmetic damage.

2) I don't know if the new one would have a two stage variable blower. Is this feature common or more of a luxury feature? The reason I ask is he's looking for scratch and dent for me...and asking for particular features may make his search tougher.

3) My friend was a tech for 13yr and started his own business last year...all in Indiana. That being said I'd bet our old home is less efficient than most any newer home. Is there a resource to do your own heat loss calculations, or does it take special equipment?

4) I think your link in the other thread of mine answered this.
 
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Old 11-27-07, 11:32 AM
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If you use a two-stage furnace it is not quite as important to have an exact heat-loss calculation. Because most of the time you do not need the full output of the furnace the two-stage option makes for much better overall efficiency, greater comfort and longer equipment life. I would never suggest anything but a two-stage furnace except in those cases where a person was replacing a furnace just to allow them to sell the house.

The variable speed blower option has a few niceties but is not an absolute need.

I'm pretty sure that this link will get you to a heat loss program. You will have to register and I suggest that you use "student" as your business.

http://www.heatload.com/
 
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Old 11-30-07, 09:33 AM
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Originally Posted by BQuicksilver View Post
I've come into a situation where I'm thinking it might be a good idea to upgrade my furnace, but I'd like to have some more educated opinions. I've been biking lately with a guy who owns an HVAC business, and he's offered to do the work at a discount. That, along with winter coming and my friend noting that I have a 136,000btu furnace and I only need 75,000ish has pushed me to seriously consider an upgrade.

The house is a 1600sq ft (not counting the 1000sq ft basement) home built in 1946 with relatively poor insulation in the walls (the attic is well insulated). It has a 135,000btu 80% Lennox Gas furnace from 1990.
Like excess electrical capacity, excess heating capacity is used when called for, i.e., when weather circumstances demand additional heating. Your 135k BTU heats the house more quickly than a smaller furnace would.

If the walls of the home are not insulated, a smaller sized furnace may actually be inadequate. Are your window units insulated?

Not wanting to deprive you of a bargain, or your friend of work, you might be better off foaming the wall cavities of the house with low expansion foam (check Dow's www.greatstuff.com web site for the professional foam kit dispensing from a tank).

Increasing the R value of walls pays off with greater savings due to lower demand for heating and cooling. It also provides the added benefit of less wear and tear on H & A/C equipment due to reduced service demand.
 
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Old 11-30-07, 11:46 AM
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Are you saying that you think his estimate is low, or are you just playing devil's advocate? I know you can't see the house, but you have some idea what we're dealing with (1946/no wall insulation/attic well insulated/1600sq ft). Wouldn't the idea be to keep the temp well regulated that to want something that heats at a quicker rate??

Window units?? Do you mean my windows?

The walls of the home are plaster, so getting into the studs would be a major PITA. I'm just not nearly as comfortable with plaster as drywall.

I'm not wanting to be rude, but I was a bit confused by your reply since I couldn't tell if you're a pro or just some guy saying "more R is better" of course... Saying that you'd want a bigger unit to heat faster and presumably run lots of short cycles seems to go against what I've read as being correct. I'm just a DIY'er, so my opions may be way off base...but let me know if they are. I just want to do this right.
 
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Old 11-30-07, 11:12 PM
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Originally Posted by BQuicksilver View Post
Are you saying that you think his estimate is low, or are you just playing devil's advocate? I know you can't see the house, but you have some idea what we're dealing with (1946/no wall insulation/attic well insulated/1600sq ft). Wouldn't the idea be to keep the temp well regulated that to want something that heats at a quicker rate??

Window units?? Do you mean my windows?

The walls of the home are plaster, so getting into the studs would be a major PITA. I'm just not nearly as comfortable with plaster as drywall.

I'm not wanting to be rude, but I was a bit confused by your reply since I couldn't tell if you're a pro or just some guy saying "more R is better" of course... Saying that you'd want a bigger unit to heat faster and presumably run lots of short cycles seems to go against what I've read as being correct. I'm just a DIY'er, so my opions may be way off base...but let me know if they are. I just want to do this right.
You asked for "other suggestions" so I offered some.

Short cycling equipment from an over-capacity unit makes for short periods of operation. It means the fan runs less.
It also means the unit wears out more slowly, breaks down less often, etc. If you put in a unit too small to handle the requirement, it runs all the time, breaks down more often and operates less efficiently, regardless of what the ratings are on the label. Remember, modern high efficiency heaters were/are designed to go into modern, well insulated, thermally efficient houses.

My experience is 16 years as a managing general contractor specializing in total renovations and change-of-use projects ranging from single family dwellings, multi-unit residential and large commercial projects.

If your goal is saving money, gaining an additional 12.5% efficiency (from 80% to 90%) by spending $1,500 will barely make back your investment over the next ten years ($130.00 x 12 = $1,560 / yr. @ 12.5% = $195.00 / yr savings) if you don't count the cost of throwing away the remaining use in your 1990 furnace AND if you have no other gas appliances in the house (water heater, stove, dryer, etc.). If you have other gas appliances contributing to your monthly $130.00 gas bill, your savings will probably never return your $1,500 investment.

The suggestion made by Furd to calculate the heat load requirement is valid. Not knowing your actual needs makes specific comments difficult and speculative at best.

If you don't have thermally efficient insulating windows (a.k.a. window units) you might be better off starting with gas filled, low-e coated windows.

On the other hand, if you already have dual pane insulated windows in the structure (you did not say in your description) adding low expansion foam insulation to the walls (poke and shoot method) would give you year round gains in heating and cooling efficiency, because those nice plaster walls are then able to heat up or cool off and retain the thermal energy provided by your heating/cooling equipment.
BTW, dealing insulating plaster walls is easy... drill holes, inject proper foam materials, patch holes, touch up patches.

You did not say whether your present furnace is broken, not working or otherwise. In many cases the best plan is regularly maintaining good equipment (Lennox is good equipment), making proper repairs when necessary, and replacing when repairs are no longer feasible.
 
 

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