# electric tankless water heater UL 499



## Flexo (Jul 10, 2018)

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.


----------



## Pcinspector1 (Jul 10, 2018)

The ones I've inspected so far have been installed, did not know that there was a UL 499 exemption.


----------



## ICE (Jul 10, 2018)

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.


----------



## Rick18071 (Jul 10, 2018)

I saw a few the said right on the unit that a P&T is required, that is the only time I required it.


----------



## Francis Vineyard (Jul 10, 2018)

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




*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.


----------



## HForester (Jul 20, 2018)

The proposal's reason statement:

"A question that is often asked is whether existing Section P2803.1 applied to instantaneous (“tankless”) water heaters as it is impossible to install a temperature relief valve (in accordance with Section P2803.4) as there is no tank!  A new section is added to cover gas instantaneous (“tankless”) water heaters. The fuel gas-fired instantaneous water heater industry is waffling about whether a pressure relief valve is required and most have in their instructions “ it’s up the local code official or jurisdiction”. Many questions come up about this and code officials are not sure what to do. We need to settle the debate by simply requiring the pressure relief valve at least for the gas-fired tankless water heaters. Note that electric instantaneous water heaters are exempt from having a PRV by the UL listing for those products. While the code could be written to require PRVs for electric tankless water heaters, it is impractical to install PRVs for the small electric units (think of the one fixture, under the cabinet type) and then the issue is where to route the discharge pipe. Generally, the gas instantaneous (“tankless”) water heaters are for the whole building and are installed in a basement, garage or other location (outside) where routing of the PRV pipe is no more difficult than it is for a storage tank water heater."

It seems to me that if UL doesn't care about a pressure relief valve for electric tankless water heaters (of any size) why should the code be worried? An overabundance of caution will only lead to complications (where to route the discharge?) that will virtually eliminate anyone choosing to use small [electric] tankless units.


----------



## sharoncynthia (Feb 5, 2019)

Before hiring any water heater installation expert ask referrals and then askthem about their work. Company with poritive feedback must be chosen for your heater repair.


----------



## steveray (Feb 5, 2019)

Required....as long as it does not void the listing....

P2609.2 Installation of materials. Materials used shall be
installed in strict accordance with the standards under which
the materials are accepted and approved. In the absence of
such installation procedures, the manufacturer’s instructions
shall be followed. Where the requirements of referenced standards
or manufacturer’s instructions do not conform to the
minimum provisions of this code, the provisions of this code
shall apply.


----------



## HForester (Feb 5, 2019)

It doesn't make sense to try to install a _temperature_ relief valve on any tankless unit because it can't be installed in accordance with the listing: The probe must be located withing the top 6 inches of the storage tank.


----------



## steveray (Feb 5, 2019)

Deleted......


----------



## leonoro (Mar 9, 2019)

I want more ideas. Anyone help me ?


----------



## Flexo (Mar 9, 2019)

Thanks for all of your answers. The gas fired instant water heaters that I have inspected have all had provision for P&T valves. In several instances where there the P&T was missing, upon re-inspection it was installed. My question was generated due to an electric instant water heaters that had no provision for a pressure and temperature relief valve, this surprised me, so I learned more regarding UL 499. I certainly respect all of the collective knowledge here, so I thought that I would inquire how you handle this conflict between the code requirement and the UL listing.
Leonoro, what do you need to know. Be specific.


----------



## jar546 (Mar 9, 2019)

I am glad that this has been resurrected.  I see a lot of these installed in high rise condo's but I am not inspecting the plumbing end anymore.


----------



## leonoro (Mar 10, 2019)

leonoro said:


> I want more ideas. Anyone help me ?


----------



## Builder Bob (Mar 11, 2019)

Might be time to ask ICC for a formal interpretation..... what a quandary


----------



## MikeC (Mar 11, 2019)

IPC 504.4 specifies "storage water heaters" when requiring a relief valve.  Tankless water heaters are not storage water heaters.

IRC P2803.1 requires a relief valve on appliances used for heating water or store hot water - so this required here, except maybe by R102.4 in the exception where it states the conditions of the listing shall apply if the code would violate the listing.  So list leads to the question of - would an inline relief valve violate the listing?  I doubt it would.  Now, as it has already been stated, while a pressure relief valve may be installed inline near the appliance, the temperature relief valve is required to be installed in the tank which is impossible due to the lack of a tank.  This brings up the question of - if one is required by code and it shall be installed in the storage tank, can you require the installation of a storage tank when there is a water heater present?  I would never do this, but the code does lead you in that direction.

So, my take on this is:
Structures built under the IRC require a relief valve for all water heaters & hot water storage tanks.  If there is no provision for a temperature relief valve on the appliance and no instructions on how to install one, only a pressure relief valve is required.
All other structures only require a relief valve when there is storage of hot water.
This wording has followed through into the 2018 I-codes


----------



## MikeC (Mar 13, 2019)

Okay, I feel the need to add one thing to my post above. IF the appliance is not a listed appliance - the code is enforced 100%.  There is way too much crap for sale on ebay & amazon that doesn't meet any standard and, IMHO, shouldn't be installed anywhere.


----------

