1. ATTENTION returning members. If you are coming here from the old forum for the first time, you will need to reset you password. However, we had an email problem getting password reset links set out to a lot of the email addresses. That problem is temporarily rectified but IF you still have an issue, email me direct at info@thebuildingcodeforum.com and I will give you a temporary password.
    Dismiss Notice
  2. Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by clicking here: Upgrades
    Dismiss Notice

electric tankless water heater UL 499

Discussion in 'Residential Plumbing Codes' started by Flexo, Jul 10, 2018.

  1. Flexo

    Flexo Member

    Joined:
    Jan 28, 2018
    Messages:
    9
    Likes Received:
    1
    Are you or your jurisdiction requiring P&T valves on electric tankless water heaters? We use the 2012 codes,
    P2803.1 in the IRC requires all residential water heaters to have P&T relief valves. UL 499 allows for no P&T relief for electric tankless units meeting the UL 499 standard. I know that the IRC would preempt the UL and that the most restrictive regulation shall govern. Does your jurisdiction require a P&T relief valve in this instance?
    Thank you.
     
  2. Pcinspector1

    Pcinspector1 Platinum Member

    Joined:
    Oct 28, 2009
    Messages:
    2,297
    Likes Received:
    202
    The ones I've inspected so far have been installed, did not know that there was a UL 499 exemption.
     
    Francis Vineyard likes this.
  3. ICE

    ICE Sawhorse

    Joined:
    Jun 23, 2011
    Messages:
    7,260
    Likes Received:
    520
    I've never inspected one. It may come down to the volume that the heater can contain. For example, pool heaters are seldom equipped with a TPR valve but the volume of the coil qualifies the heater as a storage capacity heater and as such requires a TPR valve.

    Gas fired tankless water heaters always have one. A reasonable assumption is that the coil holds enough water to be classified as a storage capacity water heater.
     
  4. Rick18071

    Rick18071 Sawhorse

    Joined:
    Nov 28, 2009
    Messages:
    1,339
    Likes Received:
    80
    I saw a few the said right on the unit that a P&T is required, that is the only time I required it.
     
  5. Francis Vineyard

    Francis Vineyard Sawhorse

    Joined:
    Jan 1, 2010
    Messages:
    2,973
    Likes Received:
    364
    Don't recall all the complexities of how the fuel-fired tankless system works but my understanding is the fuel burns at one temperature and therefore has the potential to exceed the temperature for the flow of water to be heated and require a PTR valve. Whereas electric has a duty cycle (on/off) and better control the heat the water to the set temperature.

    An example of a manufacturer's installation guideline of an whole house electric tankless unit invites

    NOTICE.JPG

    A code change proposal:
    RP54-13 P2803.1, P2803.2 (New)
    Revise as follows:
    P2803.1 Relief valves required.
    Storage water heaters and hot water storage tanks shall be protected against over-pressure and over-temperature conditions by one of the following methods:

    1. A separate pressure-relief valve and a separate temperature-relief valve

    2. A combination pressure- and temperature-relief valve.

    P2803.2 Instantaneous fuel-gas fired water heater relief valve.
    A fuel-gas fired instantaneous water heater shall be protected against over-pressure conditions by a pressure relief valve. The valve shall be located on the cold water inlet piping to the heater at a point that is downstream of all external valves except where the heater manufacturer’s instructions require the valve be located elsewhere.

    Committee Action: Disapproved Committee Reason: This proposal doesn’t address small tankless water heaters. The manufacturer’s instructions take precedence. https://www.iccsafe.org/wp-content/uploads/10-IRC-P.pdf

    R102.4 Referenced codes and Standards.
    The codes and standards reference in the code shall be considered part of the requirements of this code to prescribed extent of each such reference and as further regulated in Section R102.4 and R102.4.2

    Exception : where enforcement of a code provision would violate the conditions of the listing of the equipment or appliance, the conditions of the listing and manufacturer’s instructions shall apply.

    R102.4.1 Conflicts. Where conflicts occur between provisions of this code and referenced codes and standards, the provisions of the code shall apply.

    R102.4.2 Provisions in referenced codes and standards.
    Where the extent of the reference to a referenced code or standard includes subject matter that is within the scope of this code, the provisions of this code, as applicable, shall take precedence of the provisions in the reference code or standard.
     
    #5 Francis Vineyard, Jul 10, 2018
    Last edited: Jul 10, 2018
    ICE and Pcinspector1 like this.

Share This Page