An out-of-town friend has a two-story condo with an old gas, forced-air fur= nace in a pantry off the kitchen. She wants to replace it with a high effic= iency furnace, taking her from 80% efficiency to 95% efficiency,for the fue= l savings.=20
A contractor came to estimate the job and said that she couldn't put a high= efficiency unit in that space but didn't give a good reason, at least not = one that she understood. One complicating factor is that she thiks that the= re is just one chimney outlet on the roof which is shared by the two adjoin= ing condos but I haven't actually seen the unit as it's hundreds of miles a= way.=20
Does anyone have any ideas about all this? It seems that you should be able= to just remove the old unit and put in a new one unless the high efficienc= y units are somehow larger, hotter or whatever.=20
Check with other contractors, and get estimates for their installation of a high efficiency furnace. The chimney should not matter, as high efficiency furnaces don't need one. The location may be in a difficult location making it a problem to install the plastic exhaust pipes as they are limited by length and location, or maybe she will need to get someone to clear a path and then cover the pipes once they are installed. The original contractor probably didn't want the job or he is incapable of explaining the problem in lay-man's terms, which means you don't want him either.
Tell your friend that given the low price of natural gas, it will take
50 years for the cost of the new furnace to equal the savings in natural gas used.
And new furnaces are a repair nightmare compared to older ones. More sensors, delicate electronic motor.
High efficiency furnaces don't exhaust the combustion gas through the chimney. You have to run a new exhaust pipe (made of plastic) through a wall to the outside. The layout and current location of the furnance must mean that it would be a bitch to run this new exhaust pipe.
furnace in a pantry off the kitchen. She wants to replace it with a high efficiency furnace, taking her from 80% efficiency to 95% efficiency,for the fuel savings.
efficiency unit in that space but didn't give a good reason, at least not one that she understood. One complicating factor is that she thiks that there is just one chimney outlet on the roof which is shared by the two adjoining condos but I haven't actually seen the unit as it's hundreds of miles away.
just remove the old unit and put in a new one unless the high efficiency units are somehow larger, hotter or whatever.
While it's true that a high efficiency furnace will lower your gas bill by 10%, I'm not sure it pays in the long term. Here's why:
High efficiency furnaces are more complex than regular furnaces. Since they have more parts, they tend to break more often. About 30 days after your warranty expires, the draft inducer motor/fan assembly will fail. Total cost for that with labor is $500.
A year or two later, a safety vacuum switch will fail as well. With labor, kiss another $150 good bye.
And by the time the furnace is 15 years old, it will likely be torturing you with repair bills...mostly related to the high-efficiency safety devices.
Add up all the repair bills and the the initial higher price of the furnace and you'll find you won't really save any money.
I know you don't have to have a chimney but why couldn't you use an existing chimney anyway? It doesn't seem like it would hurt anything, but I really don't know much about them; I have an old fashioned hot water radiator/boiler system.
"> Add up all the repair bills and the the initial higher price of the
That is the same story I was told 26 years ago when I installed a high efficiency furnace in my house. At that time I could have purchased a cheap low efficiency furnace, but I went with a high efficiency one. I have had only one part replaced in the 26 years, that was the exhaust fan, it didn't fail but the metal housing started rusting out. While others have a gas bill of $1,000 to $1500 per year, my bill is about $600.00 per year for heating of a 2000 square foot bungalow, water heating and for cooking. Admittedly, my water heater is also high efficiency, and that keeps the bill down as well. I have saved the cost of the equipment several times over in the past years so don't believe the "old wives tales". My current furnace has a 12 year warranty for parts and labor, it will probably outlive myself. Also many parts such as the exhaust fan can be replaced by most people who read this newsgroup, which would keep costs down when the warranty expires.
High-efficiency units can't exhaust upward because the exhaust gas isn't warm enough to rise that far- they use a fan to blow the exhaust pretty much horizontally and out through a wall.
Hey, that sounds like my furnace! I replaced the draft inducer fan, last year.
Other reason, might need two furnaces to keep the existing chimney warm enough to draft.
Christopher A. Young Learn more about Jesus
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While it's true that a high efficiency furnace will lower your gas bill by 10%, I'm not sure it pays in the long term. Here's why:
High efficiency furnaces are more complex than regular furnaces. Since they have more parts, they tend to break more often. About 30 days after your warranty expires, the draft inducer motor/fan assembly will fail. Total cost for that with labor is $500.
A year or two later, a safety vacuum switch will fail as well. With labor, kiss another $150 good bye.
And by the time the furnace is 15 years old, it will likely be torturing you with repair bills...mostly related to the high-efficiency safety devices.
Add up all the repair bills and the the initial higher price of the furnace and you'll find you won't really save any money.
The 90 percenters, the exhaust isn't cold enough to naturally rise. The cold exhaust (also a lot of humidity) would not dependably exit the building.
Christopher A. Young Learn more about Jesus
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I know you don't have to have a chimney but why couldn't you use an existing chimney anyway? It doesn't seem like it would hurt anything, but I really don't know much about them; I have an old fashioned hot water radiator/boiler system.
ing chimney anyway? It doesn't seem like it would hurt anything, but I real= ly don't know much about them; I have an old fashioned hot water radiator/b= oiler system.- Hide quoted text -
If by use an existing chimney you mean just route the PVC exhaust pipe to the chimney and tie it it, no you can't do that. A chimney relies on hot gas to create a rising air current. A condensing furnace has air that is barely warm. A related problem is if you have a gas water heater on the same masonry chimney as a gas furnace and then replace the furnace so that the chimney is left with the orphan water heater. That leaves a chimney too big for just the water heater alone. In winter in cold climates the gas will condense and the acid formed will destroy the chimney over time. That can be solved by putting in a chimney liner.
If by using the existing chimney you mean routing the PVC pipes from the new furnace up, inside it, essentially using that as just a conduit, that might be possible, if nothing else, eg gas water heater uses the chimney, but I've never seen it done. Every one I've seen uses PVC that is run as short a distance as possible to the outside, which is usually easier done directly.
For the condo in question, the essential question is what the path would be to run two PVC 3" pipes to the outside via either a wall or through the roof. They also have concentric termination kits where the two pipes can be combined into one where they go through the wall if that makes it easier.
There are also restrictions on how close the exhaust can be to a window that opens, a door, another appliance exhaust, an overhang above, etc. For details, you can pull up the install manual on any one of the commonly available furnaces and they will have diagrams and rules.
Also the poster that claimed a high efficiency furnace will only lower your gas bill by 10% is wrong. Let's compare two furnaces, one at 80%, the other at 95%.
I put 100 units of energy into the 80% one and get 80 units out. To get that same 80 units with the 95% furnace I need to put in 84 units. That's a savings of 16%. And that assumes that the old furnace is indeed operating at
80%. If it's 25 years old and not in great shape, it may be less.
That depends on a whole host of factors not placed into evidence. Like the location. Georgia and Michigan are very different. And you have to factor in rebates, utility credits, etc that can offset the cost. But that can and should be done to get an idea on the payback. Also, if the existing furnace is 30 years old, there is also the question of how luck you feel. Many would prefer to replace it when there are rebates, incentives, tax credits, good deals available as opposed to having to do it in Jan in a crisis.
If you want. you can buy many high efficiency condensing furnaces that have a simple PSC motor, just like the existing furnace.
You would think that if that were the reason, the contractor could have explained it. The fact that the contractor couldn't give an explanation suggests the need for a new contractor.
furnace in a pantry off the kitchen. She wants to replace it with a high efficiency furnace, taking her from 80% efficiency to 95% efficiency,for the fuel savings.
efficiency unit in that space but didn't give a good reason, at least not one that she understood. One complicating factor is that she thiks that there is just one chimney outlet on the roof which is shared by the two adjoining condos but I haven't actually seen the unit as it's hundreds of miles away.
just remove the old unit and put in a new one unless the high efficiency units are somehow larger, hotter or whatever.
Hi, Hi efficiency one has different fresh air intake and venting. Also it produces condensated water from near perfect combustion needing drain. It is not just a simple swap out. I observed it when ours was upgraded.
furnace in a pantry off the kitchen. She wants to replace it with a high e= fficiency furnace, taking her from 80% efficiency to 95% efficiency,for the= fuel savings.
high efficiency unit in that space but didn't give a good reason, at least = not one that she understood. One complicating factor is that she thiks that= there is just one chimney outlet on the roof which is shared by the two ad= joining condos but I haven't actually seen the unit as it's hundreds of mil= es away.
able to just remove the old unit and put in a new one unless the high effic= iency units are somehow larger, hotter or whatever.
The contractor that talked to the OP obviouosly did not tell the OP the whole story in an understandable manner. All the comments made about the venting situation for the new furnaces was exactly correct.
Other factors come into play. Last year, at work, we replaced a
1970's boiler with a new one. With the old boiler, the heat would come on and make my office nice and comfy. Then the heat would go off and I'd feel the cold air down my back until it cycled on again. With the new boiler, it circulates lower temperature water for a longer time and I never feel the draft. An outside temperature sensor helps to determine the proper water temperature.
My forced hot air furnace and air conditioning is variable speed. It doesn't go on and off. It adjusts to whatever level is needed to mainatin the set point temperature.
There is (or was) nothing stopping you from adjusting the gas-valve (or thermostat) on the old boiler so that it too would have circulated lower-temperature water, giving you the same result.
I do exactly the same thing with the 36-year-old furnace in my house. I adjust the gas dial-valve in the furnace (the electrically-operated valve that has the pilot-light setting and the "ON" setting) and instead of turning it full-on, I adjust it much lower (just like you would on a barbeque). This has the effect of putting out less heat and results in a longer run-time for the fan - and better "comfort" in the house. Probably gives better efficiency as well (less waste heat going up the flue).
Send me $4200, and in 60 days I'll send you a $4,000 rebate.
Christopher A. Young Learn more about Jesus
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Other factors come into play. Last year, at work, we replaced a
1970's boiler with a new one. With the old boiler, the heat would come on and make my office nice and comfy. Then the heat would go off and I'd feel the cold air down my back until it cycled on again. With the new boiler, it circulates lower temperature water for a longer time and I never feel the draft. An outside temperature sensor helps to determine the proper water temperature.
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