Page 1 of 4 1234 LastLast
Results 1 to 13 of 45
  1. #1
    I had a new furnace put in today. Its a frigidaire 80,000 BTU force hot air unit. I was told by the installer that my gas line (3/4") is not big enough and that the line needs to open up to 1 1/2" after the main. I guess I am confused because main gas line coming up through the ground is only 3/4" so how would opening up to a 1 1/2" pipe increase flow. The main has a T connector on it with one (3/4")line going to another thermopride unit which works fine and the other 3/4" line going to my hot water heater and new furnace. The hot water heater works fine. I have no other appliances using the gas. The gas man said I had 8 something or other coming from the main which is more than enough. Anyone know what is going on here.

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,194
    How far is it from the meter to the furnace/water heater area? And the only thing on this 3/4" line are those 2 units? How many BTUs is the WH?

    Coming in from the street, the gas is at a higher pressure so the pipe can be small. At the meter it is reduced and yours apparently is 8" water column in pressure. That's fine. Allowing for .5" drop, 30' still gives you capability of 200,000 BTU. Even at 60' you are still barely OK if you haven't got a big BTU WH.

    Tell him 1 1/2" gas line at house pressure allows OVER A MILLION BTUs of capacity at 30' and you don't need that unless you are heating 1/2 the neighborhood

  3. #3
    Join Date
    Mar 2006
    Location
    tex
    Posts
    477
    8 inches Water colume is it nat gas or lp? 3/4" should be big enough if it is less than 50'. did your old furnace work on that same line?

  4. #4
    its natural gas...The water heater is 40,000btu. Just to calrify my gas main has a T connector on it. ONe line goes to a 100,000 BTU thermopride heater. The line is about 25' and is 3/4". This unit runs fine. The other line coming out of the t is a 3/4" line as well and runs approximatly 35' supplying gas to my 40,000 btu water heater and my new frigidaire 80,000 btu gas furnace. But I feel like someone isnt telling me something.

  5. #5
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    i could see him wanting to change the line to 1 inch to hold more volume and less chance of the pressure pulling down. 1/12 is totaly over kill for 120,000 btu

  6. #6
    hes saying now that he cant get the furnace to work because the line isnt big enough.

  7. #7
    Join Date
    May 2006
    Location
    Philadelphia, PA
    Posts
    1,391
    What size is the main off the meter. Depending on the length any pipe common to all appliances may need to be larger than 3/4 (between meter and T), but each 3/4 off the T sound like they are large enough for their connected loads. 1" is likely large enough for the common pipe.

    Did he measure the gas pressure? What are inlet and outlet pressures?

    Ask the gas company to evaluate the distribution system in the house. Some utilities are very easy to work with and will do this for you.
    Climate Control Solutions for your Home or Office

    Serving Northeast Philadelphia and Surrounding Areas

  8. #8
    Join Date
    Aug 2006
    Location
    SW, Michigan
    Posts
    160
    Was this install done on a quote? I think proper size gas line to feed a furnace is part of installing it unless there was some reason he could't know ahead of time.
    GOD knows if you did your best! <><

  9. #9
    the main going into the meter is 3/4" and the line coming out of the meter is 3/4" the T is Right at the meter.

  10. #10
    hankmcneil
    he qouted me 2800 for everything. This is the system and electrical. But he SAW the old furnace AND 3/4" line going into it. He shoulda said something then. I inly gave him half and its all installed (just not running)

  11. #11
    Join Date
    Aug 2006
    Location
    SW, Michigan
    Posts
    160
    Other Pro's:
    I'm a service tech, am I off base here???
    GOD knows if you did your best! <><

  12. #12
    Join Date
    May 2006
    Location
    Philadelphia, PA
    Posts
    1,391
    I don't have capacity charts in front of me. Someone please correct me if I'm wrong here.

    The common between the meter and T should be 1". This pipe has to carry 220 mbh. Then when it T's 3/4 will carry the appliances on each connected branch (100 mbh @ 25' and 120 mbh @ 35').

    To clarify - the common pipe size should only be a problem when both furnaces are running. Otherwise the 3/4 is fine for either one.

    If I missed this I would just fix it and bite the bullet. If it was alot of material needed I might ask the customer to help out with material cost. Depends on the entire situation though. Mistakes do happen.

    [Edited by comfortdoc on 10-16-2006 at 09:45 PM]
    Climate Control Solutions for your Home or Office

    Serving Northeast Philadelphia and Surrounding Areas

  13. #13
    Join Date
    May 2006
    Location
    Philadelphia, PA
    Posts
    1,391
    I will also add that pressure readings with the appliances running will verify the need to increase pipe size.
    Climate Control Solutions for your Home or Office

    Serving Northeast Philadelphia and Surrounding Areas

Page 1 of 4 1234 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event