Horizontal Flue

[nena+lyn]

I live in Illinois, Peoria County, Radnor Township, City of Dunlap. I am getting a new furnace and found that the old one has a long horizontal flue. The company said there are no codes for a flue in my area, just the furnace manufacturer's recommendations. When I asked for them in writing, he said he can not find them. I am getting a Goodman GMH95-70, 2-stage, multi-speed, gas, 70,000 BTU furnace. He said they will use 2" PVC pipe with 1/4" incline per foot of length to the outside. It will go up 3 ft. and 16 ft. across to the outside. It is located in the center of a full basement with proper clearance. They are using union installers. Is this safe? I want it properly done and up to code. I had never heard of or seen a horizontal flue before. Our home inspector never even said anything before we bought the house 9 years ago. Please advise me what is correct. Also, thank you for your web site!
Nena Lyn

[Jerry Peck - Codeman]

[Jerry Peck - Codeman]

Hi Nena,

Goodman sent a copy of the installation instructions to me, the following are some of their requirements for installation:

-> ATTENTION INSTALLING PERSONNEL
- -> As a professional installer you have an obligation to know the product better than the customer. This includes all safety precautions and related items.
- -> Prior to actual installation, thoroughly familiarize yourself with this Instruction Manual. Pay special attention to all safety warnings. Often during installation or repair it is possible to place yourself in a position which is more hazardous than when the unit is in operation.
- -> Remember, it is your responsibility to install the product safely and to know it well enough to be able to instruct a customer in its safe use.
- -> Safety is a matter of common sense...a matter of thinking before acting. Most dealers have a list of specific good safety practices...follow them.
- -> The precautions listed in this Installation Manual are intended as supplemental to existing practices. However, if there is a direct conflict between existing practices and the content of this manual, the precautions listed here take precedence.

-> TO THE INSTALLER
- -> Before installing this unit, please read this manual thoroughly to familiarize yourself with specific items which must be adhered to, including but not limited to: unit maximum external static pressure, gas pressures, BTU input rating, proper electrical connections, circulating air temperature rise, minimum or maximum CFM, and motor speed connections.

There is a section on page 16 which states "Vent/Flue Pipe Lengths and Diameters" which lists some specifications regarding the installation of the vent/flue. I have attached that section below. The following information is from that section.

The table shows your model, 070, with two versions, one a 070_3 and one a 070_4, with three different configurations in number of elbows and length of pipe. This table is for Non-Direct Vent installations.

The 070_3 shows a pipe size of 2 inches, and the following number of elbows/lengths of pipe, the termination elbow is included, so the number of elbows allowed in the run would be the number stated less one: 2 elbows/68 feet of pipe; 3 elbows/65 feet of pipe; 4 elbows/62 feet of pipe; 5 elbows/59 feet of pipe; 6 elbows/56 feet of pipe; 7 elbows/53 feet of pipe; 8 elbows/50 feet of pipe.

The 070_4 shows a pipe size of 2 inches, and the following number of elbows/lengths of pipe, the termination elbow is included, so the number of elbows allowed in the run would be the number stated less one: 2 elbows/46 feet of pipe; 3 elbows/43 feet of pipe; 4 elbows/40 feet of pipe; 5 elbows - 6 elbows - 7 elbows - 8 elbows shown as NOT RECOMMENDED.

The 070_4 shows a pipe size of 3 inches, and the following number of elbows/lengths of pipe, the termination elbow is included, so the number of elbows allowed in the run would be the number stated less one: 2 elbows/68 feet of pipe; 3 elbows/65 feet of pipe; 4 elbows/62 feet of pipe; 5 elbows - 6 elbows - 7 elbows - 8 elbows shown as NOT RECOMMENDED.

The table also shows a minimum length of 5 feet and 1 elbow.

You said "He said they will use 2" PVC pipe with 1/4" incline per foot of length to the outside. It will go up 3 ft. and 16 ft. across to the outside."

The pipe is required to slope 1/4" per foot when installed horizontally, which they said they will be doing - that is good.

The combined length of the pipe the stated is 19 feet, which exceeds the minimum length of 5 feet - that is good, and is within the maximum length of 43 feet with 3 elbows, even within the 40 feet with 4 elbows (using worst case from the table).

There is another table with lengths for Direct Vent (Dual Pipe) installations, the Standard installation dimensions are the same, however, if they use the Alternate installation method, then the pipe lengths are shorter. That said, the worst case shown on that table with 3 elbows allows 30 feet of pipe and with 4 elbows allows 27 feet of pipe.

With the limited information you have given, if the installer installs it as such, that should all work out within the installation instruction requirements and allowances.

Back to another question regarding your original installation: Yes, horizontal (1/4 inch per foot slope minimum) installation were allowed, and depending on the code and the manufacturer of the vent, the TOTAL horizontal offset (distance) was allowed to be either 75% of, or 100% of, the TOTAL vertical height above the draft hood.

Looks like your installation would be good to go is they do what they say, make sure it is carefully inspected by the city. After the new furnace has been installed, I would call the installation company and ask the owner of the company (preferably the owner, if not, then the highest up person you can get) to come out and inspect the installation *before* the city does, after all, the owner of the company IS RESPONSIBLE for the work of his workers, and have them "sign off" that the installation meets the requirements of the code and the manufacturer's installation instructions. Then have the city inspect it.

Hopefully, some of the above information will be of assistance.

Codeman

[nena+lyn]

Thank you for your diligent work on my concerns. You have worked faster than the owner in answering my questions. I will do exactly as you have suggested. Again, thank you!
Nena Lyn

[Jerry Peck - Codeman]

Hi Nena,

Thank you and hopefully it works all out for you.

I called Goodman to try to get some additional information not shown (at least I did not find it) in the installation instructions, information such as maximum vertical height, maximum horizontal offset-to-vertical height ratio, etc., but so far have not been able to get those answers. Those answers may be "it does not matter as long as the maximum length of pipe/number of elbows is not exceeded" - but I don't know that.

Logically, it would seem that a horizontal distance under fan power could be longer than a vertical height under the same fan power, simply pushing air up takes more force for the same distance than pushing air horizontally does. However, so far, no additional information.

I will post any additional information I get here, if I get any.

Codeman