buying a used furnace

fix what? · 10-06-2012, 10:20 AM

i had it with my 25 year old rusty gas furnace

i had 2 service calls so far this year and many last year
and seems the darn thing keeps breaking down on me, like now it's dead
due to my income and credit, theres no way i can afford to buy a new one
i see a lot of used furnaces on craigslist for a good price that are not that old
and this i would have to install it myself but have someone else do the gas and electrical connections
my furnace is a con aire 100000 btu up draft
my 1920 home with new windows and doors is 1100 + square feet
we converted the attic into a bedroom and will run a heat duct up there but i don't know if the attic is included in the 1100 + square footage or do i need to add more square feet to the 1100
i do know the furnace is over powered for my home as they tell me
any help guys ?
i forgot to mention that we live in upstate new york

DangerMouse · 10-06-2012, 11:10 AM

When we got our new 95% eff. furnace, I sold the old (5 years old is all, 75%) on Craigslist for $350. It worked fine, we just wanted more eff. and to use less propane, which this one does. Funny thing though..... the guy called me like a MONTH later and asked me some questions on how to hook up this and that and vent it properly. I had to laugh!

DM

Missouri Bound · 10-06-2012, 11:22 AM

In your area 50 - 55 btu's per sq. ft. is the "average" requirement. Of course this is with appropriate insulation, caulking and weatherstripping.

DangerMouse · 10-06-2012, 11:59 AM

I should add though that I DID assist him on the phone, and later he called back and said it was working perfectly and Thanked me.

DM

REP · 10-06-2012, 12:01 PM

Quote:

Originally Posted by Missouri Bound

In your area 50 - 55 btu's per sq. ft. is the "average" requirement. Of course this is with appropriate insulation, caulking and weatherstripping.

I don't know where you got that average,but he is not heating a sauna,he's heating a house.
If he has new window's and added insulation he would need around a 40,000 90% furnace that would be around 3.75 btu's per cubic foot or in your world where all ceilings are 8' high,30 btu's per sq ft.

funfool · 10-06-2012, 12:19 PM

Is 2 decent looking updrafts for sale here in Albuquerque, a 125k btu for $100, they upgraded to another type of system.
I paid $50 for my 75k btu.
I would say it would be good chance the physical dimensions may be different.
Means you will have to modify or make some sheet metal to connect to existing ductwork. I have a question below yours about sizing ductwork.
I am no expert.

Something else I would be concerned about is venting. Furnaces are sized to venting.
Example, My 75k btu has 4" b-vent, I had a chance for free 5" b-vent.
I was told the larger pipe could allow the exhaust to cool and condensate in the pipe, running back into the furnace and cause it to rust out.
So physical size and venting are just 2 ideas I have for you when shopping.

**beenthere** · 10-06-2012, 12:27 PM

Quote:

Originally Posted by funfool

Is 2 decent looking updrafts for sale here in Albuquerque, a 125k btu for $100, they upgraded to another type of system.
I paid $50 for my 75k btu.
I would say it would be good chance the physical dimensions may be different.
Means you will have to modify or make some sheet metal to connect to existing ductwork. I have a question below yours about sizing ductwork.
I am no expert.

Something else I would be concerned about is venting. Furnaces are sized to venting.
Example, My 75k btu has 4" b-vent, I had a chance for free 5" b-vent.
I was told the larger pipe could allow the exhaust to cool and condensate in the pipe, running back into the furnace and cause it to rust out.
So physical size and venting are just 2 ideas I have for you when shopping.

A furnace with a 4" vent has no problem being connected to a 5" b vent. Someone mislead you. Unless your vent runs outside for 35 foot.

**beenthere** · 10-06-2012, 12:32 PM

Quote:

Originally Posted by Missouri Bound

In your area 50 - 55 btu's per sq. ft. is the "average" requirement. Of course this is with appropriate insulation, caulking and weatherstripping.

Doubt it comes out that high.

Missouri Bound · 10-06-2012, 01:13 PM

Rep and beenthere.....I am throwing out my old BTU map as we speak...

and thank you both.

funfool · 10-06-2012, 01:24 PM

beenthere,
Thanks for setting me straight on that, I do not want to mislead others.
And depending how old the furnace being replaced, it could actually be a 8" vent.
So in op case is something to consider.

I actually bought my b vent off craigs list used, was a hvac contractor cleaning out his storage yard.
He advertised the b vent and other connectors I needed for $1 each, not exactly free, had a $10 minimum.
When I called him, he said he sold all his 4" and only had 5" left. and told me what I just repeated here.
He called me back the next day and said he found enough 4" pieces to make it worth me coming out.
For $10 dollars I got all the 4" including rain cap and storm collars, and same for 3" I need for my new gas water heater to replace the electric.
Guy really was a flake, he wanted to be sure I got everything first trip, He said and I quote, Frankly I do not want you calling me back to buy more.

So maybe a warning about the people you will meet on craigs list is also not a bad idea.

**beenthere** · 10-06-2012, 01:24 PM

His areas design temp is only around -10. I did work in his city many many years ago.

**beenthere** · 10-06-2012, 01:29 PM

Quote:

Originally Posted by funfool

beenthere,
Thanks for setting me straight on that, I do not want to mislead others.
And depending how old the furnace being replaced, it could actually be a 8" vent.
So in op case is something to consider.

I actually bought my b vent off craigs list used, was a hvac contractor cleaning out his storage yard.
He advertised the b vent and other connectors I needed for $1 each, not exactly free, had a $10 minimum.
When I called him, he said he sold all his 4" and only had 5" left. and told me what I just repeated here.
He called me back the next day and said he found enough 4" pieces to make it worth me coming out.
For $10 dollars I got all the 4" including rain cap and storm collars, and same for 3" I need for my new gas water heater to replace the electric.
Guy really was a flake, he wanted to be sure I got everything first trip, He said and I quote, Frankly I do not want you calling me back to buy more.

So maybe a warning about the people you will meet on craigs list is also not a bad idea.

As there are all kinds of people in the world. You will meet all kinds of people on craigslist, or any internet site.

how · 10-06-2012, 03:17 PM

Good luck on trying to find an inspector that will approve a second hand furnace.
Most don't want to validate a second hand furnace when they are not sure of the exchanger integrity.

techpappy · 10-06-2012, 07:42 PM

I know that's not their job however, any inspector, worth a grain of salt, should be able to tell if there is a cracked heat exchanger or signs of a cracked heat exchanger within 5 mins of start up. I have found many from major to very minor and was right every time. Other than that I seem to remember that it was against code to install used fittings but, not sure about furnaces. Like it has been said.people change out slightly used furnaces for many various reasons so, why not take advantage of the opportunities.

BTW..seems like a 65 - 80 btuh should work...hpowever, best to get an estimator to do calculations even if you have to pay them $100. Probably well worth it.

Missouri Bound · 10-06-2012, 08:38 PM

How much would you spend on a used furnace? There are a lot of online retailers that will ship you a furnace with no shipping charge. The warranty coud be an issue if you install it yourself, but if you are already considering used the warranty must not be an issue.