Gas and Oil Home Heating Furnaces - Replacing Gas Furnace
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jv457
02-18-09, 02:21 PM
I started researching this about a month ago, and everything I have seen so far, says get a professional to install, but it doesnt seem that hard.
I just want to know what is involved in replacing a single-stage 80% upflow unit, with a multi-stage 95% upflow unit. To be more specific, my current model is a Lennox and I want to replace it with a Goodman. I know the higher efficiency units can be directly vented through the side, but this model can installed as an upflow. I figure if I keep it as an upflow, the installation will be a bit simpler since I can reuse the existing supply plenum.
I just want to get a better idea of what exactly is involved from the pros out there. More details along the way.
I'm going to have my friends father, who is an experienced hvac technican, check the installation.
I just want to know what is involved in replacing a single-stage 80% upflow unit, with a multi-stage 95% upflow unit. To be more specific, my current model is a Lennox and I want to replace it with a Goodman. I know the higher efficiency units can be directly vented through the side, but this model can installed as an upflow. I figure if I keep it as an upflow, the installation will be a bit simpler since I can reuse the existing supply plenum.
I just want to get a better idea of what exactly is involved from the pros out there. More details along the way.
I'm going to have my friends father, who is an experienced hvac technican, check the installation.
furd
02-18-09, 03:03 PM
Generally speaking, when you self-install you get no manufacturer's warranty. If that doesn't bother you (and in my opinion it should) and if you are handy with sheet metal working along with electrical and gas piping then go ahead.
Be sure to get the required permits from your local Authority Having Jurisdiction (usually the building department of your town or city) before starting the installation and follow precisely all the manufacturer's instructions and local code requirements. Have the permits closed by the necessary inspections.
Be sure to get the required permits from your local Authority Having Jurisdiction (usually the building department of your town or city) before starting the installation and follow precisely all the manufacturer's instructions and local code requirements. Have the permits closed by the necessary inspections.
jv457
02-18-09, 03:30 PM
I guess let me rephrase. We can discuss warranties, permits, and just about everything else that could go wrong doing anything yourself.
I just want to know if anyone is willing to discuss installing a furnace doing it yourself. As with anything technical, I am very interested in the process, so any ideas for my particular situation. I know there are a lot of variables too consider, so thats why I want to consider the simplest install possible.
What's the easiest system to replace. I would think going from a system that is the same size, same specs, wouldnt be too difficult. With using the existing ducts, no custom sheetwork needed.
I just want to know if anyone is willing to discuss installing a furnace doing it yourself. As with anything technical, I am very interested in the process, so any ideas for my particular situation. I know there are a lot of variables too consider, so thats why I want to consider the simplest install possible.
What's the easiest system to replace. I would think going from a system that is the same size, same specs, wouldnt be too difficult. With using the existing ducts, no custom sheetwork needed.
furd
02-18-09, 04:02 PM
First you really should do a heat loss calculation on your house to determine the proper size, BTU wise, you need in a furnace. More likely as not your present furnace is oversized and it could be vastly oversized.
Second, going from a single stage 80% AFUE unit to a two-stage 90+% AFUE unit is definitely going to be in a different "case size" from your present furnace and this WILL require custom ductwork to fit. There are various ways of dealing with the ductwork issue and most of them, from a DIY viewpoint are either a pain in the rear or quite time consuming.
You can purchase really thin sheetmetal from a big box mega mart home center in sizes up to about 36 by 48 inches I think but it is really thinner than desired for any but the smallest duct transitions. Or you can find a local sheetmetal shop that will sell you the proper gauge (thickness) in larger sheets but you will still need a way to bend it and make the seams and connections.
A furnace installer will almost always have a mini sheetmetal shop in the truck he uses to bring the furnace and this will include a shear, bending brake and Lockformer tool at the minimum. The installer will be proficient in using these tools to bend up the sheet metal in one try, skills that a DIYer probably doesn't have. Even if the installer doesn't have the tools in his truck he does have the skills necessary to make the correct measurements and then go back to the shop (or a contract sheetmetal shop) and have all the ductwork bent up in one stop.
Of course there is nothing stopping you from contracting with a sheetmetal shop to bend your ductwork, the problem will be getting the correct measurements and unless you have a fair amount of sheetmetal experience the likelihood of you getting the measurements correct are not so good.
It is quite possible that the inlet and outlet flanges on the new furnace will have different dimensions than your existing ductwork so that involves not just new ducts but duct size transitions. These can get really tricky in the measurement and layout before even cutting and bending the sheetmetal.
The rest of the installation is fairly straightforward. You need to supply electricity, maybe need a few feet of armor-clad cable or flexible conduit with separate wires inside to connect from the furnace to the existing junction box. You also need to pipe the gas supply and your local code may require this to be hard-piped or maybe done with flexible pipe. Of course you need to use the proper threaded joint sealants (usually not common Teflon tape) and test the joints for leaks after the piping is finished. Then you need to run the combustion air and exhaust piping, 90+% furnaces using PVC piping and usually requiring the piping to run through a wall rather than up and out a chimney. Thermostat wiring needs to be done and if you install a two-stage furnace you really should also install a two-stage thermostat.
And although some installers don't do it, the manufacturer usually calls for combustion tests to be done and to measure the gas flow to the furnace on both high and low fire settings. You should also do a temperature rise across the heat exchanger test to be sure the fan settings, combustion rate and ductwork are all in compliance.
This is why that I, with thirty plus years of experience in the heating field, with sheetmetal, electrical and piping experience decided I wanted my furnace installed by a pro. Yes, I could have done it myself but it probably would have taken a week and looked like a cob job since I don't have access to the proper sheetmetal tools. The professionals were done in about four hours.
Second, going from a single stage 80% AFUE unit to a two-stage 90+% AFUE unit is definitely going to be in a different "case size" from your present furnace and this WILL require custom ductwork to fit. There are various ways of dealing with the ductwork issue and most of them, from a DIY viewpoint are either a pain in the rear or quite time consuming.
You can purchase really thin sheetmetal from a big box mega mart home center in sizes up to about 36 by 48 inches I think but it is really thinner than desired for any but the smallest duct transitions. Or you can find a local sheetmetal shop that will sell you the proper gauge (thickness) in larger sheets but you will still need a way to bend it and make the seams and connections.
A furnace installer will almost always have a mini sheetmetal shop in the truck he uses to bring the furnace and this will include a shear, bending brake and Lockformer tool at the minimum. The installer will be proficient in using these tools to bend up the sheet metal in one try, skills that a DIYer probably doesn't have. Even if the installer doesn't have the tools in his truck he does have the skills necessary to make the correct measurements and then go back to the shop (or a contract sheetmetal shop) and have all the ductwork bent up in one stop.
Of course there is nothing stopping you from contracting with a sheetmetal shop to bend your ductwork, the problem will be getting the correct measurements and unless you have a fair amount of sheetmetal experience the likelihood of you getting the measurements correct are not so good.
It is quite possible that the inlet and outlet flanges on the new furnace will have different dimensions than your existing ductwork so that involves not just new ducts but duct size transitions. These can get really tricky in the measurement and layout before even cutting and bending the sheetmetal.
The rest of the installation is fairly straightforward. You need to supply electricity, maybe need a few feet of armor-clad cable or flexible conduit with separate wires inside to connect from the furnace to the existing junction box. You also need to pipe the gas supply and your local code may require this to be hard-piped or maybe done with flexible pipe. Of course you need to use the proper threaded joint sealants (usually not common Teflon tape) and test the joints for leaks after the piping is finished. Then you need to run the combustion air and exhaust piping, 90+% furnaces using PVC piping and usually requiring the piping to run through a wall rather than up and out a chimney. Thermostat wiring needs to be done and if you install a two-stage furnace you really should also install a two-stage thermostat.
And although some installers don't do it, the manufacturer usually calls for combustion tests to be done and to measure the gas flow to the furnace on both high and low fire settings. You should also do a temperature rise across the heat exchanger test to be sure the fan settings, combustion rate and ductwork are all in compliance.
This is why that I, with thirty plus years of experience in the heating field, with sheetmetal, electrical and piping experience decided I wanted my furnace installed by a pro. Yes, I could have done it myself but it probably would have taken a week and looked like a cob job since I don't have access to the proper sheetmetal tools. The professionals were done in about four hours.
seabee570
02-18-09, 06:29 PM
like furd said,you need to do a heat loss calculation on house.modern furnaces(80-92+) cannot be slapped in like the old ones were.The newer furnaces have thinner metal in the heat exchanger and can be damaged easily the first time you start the furnace.the btu's must match the ductwork,and it must mach the specified temperature rise of the unit.failure to do all of these things can cause severe problems.As far as goodman,they are not the best brand around,I would try another brand.In the old days you could just rip a furnace out and install a new one,but they were made with a heavy heat exchanger.good luck
dun11
02-18-09, 06:42 PM
:bad poster:First you really should do a heat loss calculation on your house to determine the proper size, BTU wise, you need in a furnace. More likely as not your present furnace is oversized and it could be vastly oversized.
Second, going from a single stage 80% AFUE unit to a two-stage 90+% AFUE unit is definitely going to be in a different "case size" from your present furnace and this WILL require custom ductwork to fit. There are various ways of dealing with the ductwork issue and most of them, from a DIY viewpoint are either a pain in the rear or quite time consuming.
You can purchase really thin sheetmetal from a big box mega mart home center in sizes up to about 36 by 48 inches I think but it is really thinner than desired for any but the smallest duct transitions. Or you can find a local sheetmetal shop that will sell you the proper gauge (thickness) in larger sheets but you will still need a way to bend it and make the seams and connections.
A furnace installer will almost always have a mini sheetmetal shop in the truck he uses to bring the furnace and this will include a shear, bending brake and Lockformer tool at the minimum. The installer will be proficient in using these tools to bend up the sheet metal in one try, skills that a DIYer probably doesn't have. Even if the installer doesn't have the tools in his truck he does have the skills necessary to make the correct measurements and then go back to the shop (or a contract sheetmetal shop) and have all the ductwork bent up in one stop.
Of course there is nothing stopping you from contracting with a sheetmetal shop to bend your ductwork, the problem will be getting the correct measurements and unless you have a fair amount of sheetmetal experience the likelihood of you getting the measurements correct are not so good.
It is quite possible that the inlet and outlet flanges on the new furnace will have different dimensions than your existing ductwork so that involves not just new ducts but duct size transitions. These can get really tricky in the measurement and layout before even cutting and bending the sheetmetal.
The rest of the installation is fairly straightforward. You need to supply electricity, maybe need a few feet of armor-clad cable or flexible conduit with separate wires inside to connect from the furnace to the existing junction box. You also need to pipe the gas supply and your local code may require this to be hard-piped or maybe done with flexible pipe. Of course you need to use the proper threaded joint sealants (usually not common Teflon tape) and test the joints for leaks after the piping is finished. Then you need to run the combustion air and exhaust piping, 90+% furnaces using PVC piping and usually requiring the piping to run through a wall rather than up and out a chimney. Thermostat wiring needs to be done and if you install a two-stage furnace you really should also install a two-stage thermostat.
And although some installers don't do it, the manufacturer usually calls for combustion tests to be done and to measure the gas flow to the furnace on both high and low fire settings. You should also do a temperature rise across the heat exchanger test to be sure the fan settings, combustion rate and ductwork are all in compliance.
This is why that I, with thirty plus years of experience in the heating field, with sheetmetal, electrical and piping experience decided I wanted my furnace installed by a pro. Yes, I could have done it myself but it probably would have taken a week and looked like a cob job since I don't have access to the proper sheetmetal tools. The professionals were done in about four hours.
Think he got it ?
Second, going from a single stage 80% AFUE unit to a two-stage 90+% AFUE unit is definitely going to be in a different "case size" from your present furnace and this WILL require custom ductwork to fit. There are various ways of dealing with the ductwork issue and most of them, from a DIY viewpoint are either a pain in the rear or quite time consuming.
You can purchase really thin sheetmetal from a big box mega mart home center in sizes up to about 36 by 48 inches I think but it is really thinner than desired for any but the smallest duct transitions. Or you can find a local sheetmetal shop that will sell you the proper gauge (thickness) in larger sheets but you will still need a way to bend it and make the seams and connections.
A furnace installer will almost always have a mini sheetmetal shop in the truck he uses to bring the furnace and this will include a shear, bending brake and Lockformer tool at the minimum. The installer will be proficient in using these tools to bend up the sheet metal in one try, skills that a DIYer probably doesn't have. Even if the installer doesn't have the tools in his truck he does have the skills necessary to make the correct measurements and then go back to the shop (or a contract sheetmetal shop) and have all the ductwork bent up in one stop.
Of course there is nothing stopping you from contracting with a sheetmetal shop to bend your ductwork, the problem will be getting the correct measurements and unless you have a fair amount of sheetmetal experience the likelihood of you getting the measurements correct are not so good.
It is quite possible that the inlet and outlet flanges on the new furnace will have different dimensions than your existing ductwork so that involves not just new ducts but duct size transitions. These can get really tricky in the measurement and layout before even cutting and bending the sheetmetal.
The rest of the installation is fairly straightforward. You need to supply electricity, maybe need a few feet of armor-clad cable or flexible conduit with separate wires inside to connect from the furnace to the existing junction box. You also need to pipe the gas supply and your local code may require this to be hard-piped or maybe done with flexible pipe. Of course you need to use the proper threaded joint sealants (usually not common Teflon tape) and test the joints for leaks after the piping is finished. Then you need to run the combustion air and exhaust piping, 90+% furnaces using PVC piping and usually requiring the piping to run through a wall rather than up and out a chimney. Thermostat wiring needs to be done and if you install a two-stage furnace you really should also install a two-stage thermostat.
And although some installers don't do it, the manufacturer usually calls for combustion tests to be done and to measure the gas flow to the furnace on both high and low fire settings. You should also do a temperature rise across the heat exchanger test to be sure the fan settings, combustion rate and ductwork are all in compliance.
This is why that I, with thirty plus years of experience in the heating field, with sheetmetal, electrical and piping experience decided I wanted my furnace installed by a pro. Yes, I could have done it myself but it probably would have taken a week and looked like a cob job since I don't have access to the proper sheetmetal tools. The professionals were done in about four hours.
Think he got it ?
thermofridge
02-18-09, 08:41 PM
If I may add a comment, Goodman used to be low end , cheap equipment. The new furnace they have out is definitely a better machine. There have been even more improvements the last year and I am extremely impressed. Just 5 years ago I wouldn't even consider installing one and now dare I say it might be the best value out there.