Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

Texas Boiler Requirements

KentB Member Posts: 6
We will be replacing an existing 325MBTUh atmospheric, hydronic heating boiler. On Friday, I talked with a manufacturers rep to make sure I was calling out the correct model with all the correct options. He told me we could NOT replace the existing boiler with a similar one because of new Texas boiler requirements. He said he would fax all the information to me on Friday so I could get the spec out before Monday. Must of slipped his mind because I didn't get the fax. He said that the new boiler would have a draft inducer so it could no longer share the flue vent with the water heater. Looking at the shape/size of the new boilers, there will be many other changes required - reconfigure the entire mechanical room, new roof penetration, etc. This is NOT what I wanted to find.

I have looked through the Texas Boiler Law on the internet, nothing appears applicable. However, a change may be efficiency or polution related so it may not show up in the Boiler Law (which almost exclusively safety oriented). I need to see if there is a grandfather clause that would allow a replacement of an existing boiler with a new boiler of similar size, shape, venting, etc. I will be able to get answers to these questions during the work week, but I'm trying to get the bid spec out Monday morning early. Can anyone help here? Maybe point me to a copy of the applicable law/requirement?


  • Joannie
    Joannie Member Posts: 95
    Texas Low NOx


    I tried to email you, but the address came back as undeliverable.

    I believe the requirement you have run up against is the recently-adopted Low NOx requirement.

    You didn't mention which boiler you were trying to replace, and with that information, the manufacturer of the boiler may see it here on the Wall, and may be able to help.

    I work for Laars Heating Systems, and I know people from other manufacturers also join in on this site. Laars makes a model 325, so if it's our boiler that you are replacing, I can help you, and you most likely will not have to change the venting system.

    Let me know if I can help, or post the information on the boiler, so others may be able to help.

    Joannie Mishou, Laars Heating Systems
  • KentB
    KentB Member Posts: 6
    Lo NOx and common venting

    Joannie was exactly right, the 'new' Texas requirement is that boilers under 2,000,000 BTUh have to be Lo NOx. Lo NOx appears to only be available with a draft inducer on the vent. My problem is now how to vent that into a combined vent with a domestic water heater. There may be some simple solutions, but I'm having trouble sorting through the catolgs to get the combination I need.
  • KentB
    KentB Member Posts: 6
    Email address

    There was a mixup on the email address in these postings. I went back and change the email address on the previous postings. The email address is now shown correctly. Sorry for any problems this may have caused.
  • Joannie
    Joannie Member Posts: 95
    Kent - I can't email you

    Hi, Kent. I hope you get this. I tried to reply to your email, and I am getting failures. It's the same address you corrected here. Maybe it's on my end. Please either call me, so we can talk 603-335-3600 x558 or email me your fax number. I have a couple options for you.
  • John Miles
    John Miles Member Posts: 2

    I beleive that Texas has adopted a very similar standard to Southern California. I don't know if they require the separate 3rd party testing certification that SCAQMD do but it is a low NOX standard

  • National Fuel Gas Code allows

    natural draft equipment with fan assisted into the same flue. That is NFPA 54/ANSI Z223.1

    There are charts and table for sizing. If it is metalbestoes double wall you can use the SElkirk Metalbestoes manual.

    That is unless your Texas code forbids that being done.

    I also have a guide available out of our catalog showing the sizing and set up.
  • joel_14
    joel_14 Member Posts: 116

    The Vitogas 100 is very low nox and atmosphereic i don't know it's exact rate but Iknow it's down there.
  • KentB
    KentB Member Posts: 6
    Fan assist combined with natural draft venting

    Combining the natural draft venting with a fan assisted is not prohibited by local codes. However, it raises a lot of eyebrows and concerns. If the inspector takes a quick look he will red tag it first an wait for the Contractor or Owner or Engineer, etc. to show him why it is safe.

    I think the inspector is smart to do this. He needs some level of assurance that the installation was thoroughly investigated and will vent properly. Now that I've run into this potential problem, I will have the supporting data waiting for the inspector. I don't think I will have a problem now.
  • KentB
    KentB Member Posts: 6
    3rd Party testing

    From what I have seen, Texas accepts the manufacturer's statement of NOx emissions. The ruling seems a little strange to me since it only applied to small boilers, under 2 MMBTUh.

    The NOx requirement is not a law, but a rule by the Texas Natural Resource Conservation Commission (known by the accronym TNRCC - usually pronounced 'Train Wreck'). That explains why I didn't find it in the Texas Boiler Law.

    The new rule can be met but as with anything new it will cause some headaches until everyone is comfortable with it.
This discussion has been closed.