Central vs Point of Use Mixing Valves

[Codeman2020]

For a commercial building with hot water only being used for sinks, can the water heater be set (by the thermostat on the heater) at 140 and only use point-of-use mixing valves at each sink (that lower to the required 110F)? If that is allowed, would that be preferred over a central mixing valve that limits to 110 F since legionella growth in the lines would be a concern? I've seen a central valve used to limit the supply temp to 140 and then point of use valves to lower the sinks to 110, but using both types of valves seems like overkill if there are only public lavatories being supplied.

 

[linnrg]

yes, In health care facility we are seeing this specified. The problem is the installation instructions for some of the newer water heaters are specifying them at the heater. If you don't put them there does the water heater manufacturer my not warranty it!

 

[TheCommish]

is the system piped as circulating hot water or dead ends? consider the energy codes nd water waste waiting for hot water at the tap

 

[Codeman2020]

is the system piped as circulating hot water or dead ends? consider the energy codes nd water waste waiting for hot water at the tap

It was a hypothetical system, but lets assume circulating hot water. If the manufacturer doesn't require a central valve by the water heater, it is code compliant/good practice to only use point of use mixing valves?

 

[TheCommish]

I am not sure about the code, as a circulating system the mixing valve should be at/near the point of use or the return temperature will be lower than intended

 

[mark handler]

I would say no, because a temp control on a water heater does not conform to this:

Plumbing Code 2015 of Pennsylvania
416.5 Tempered Water for Public Hand-Washing Facilities
Tempered water shall be delivered from lavatories and group wash fixtures located in public toilet facilities provided for customers, patrons and visitors. Tempered water shall be delivered through an approved water-temperature limiting device that conforms to ASSE 1070 or CSA B125.3.

 

[Codeman2020]

I would say no, because a temp control on a water heater does not conform to this:

Plumbing Code 2015 of Pennsylvania
416.5 Tempered Water for Public Hand-Washing Facilities
Tempered water shall be delivered from lavatories and group wash fixtures located in public toilet facilities provided for customers, patrons and visitors. Tempered water shall be delivered through an approved water-temperature limiting device that conforms to ASSE 1070 or CSA B125.3.

The point of use mixing valve under each lavatory would be an ASSE 1070 valve. Just curious if that's enough or is a ASSE 1017 valve required too, although I think I just answered my own question. Seems like a 1070 central/source valve IS required even with point of use 1070 valves per 613.1.

613.1 Temperature-Actuated Mixing Valves

Temperature-actuated mixing valves, which are installed to reduce water temperatures to defined limits, shall comply with ASSE 1017. Such valves shall be installed at the hot water source.

 

[mark handler]

For a commercial building with hot water only being used for sinks, can the water heater be set (by the thermostat on the heater) at 140 and only use point-of-use mixing valves at each sink (that lower to the required 110F)? If that is allowed, would that be preferred over a central mixing valve that limits to 110 F since legionella growth in the lines would be a concern? I've seen a central valve used to limit the supply temp to 140 and then point of use valves to lower the sinks to 110, but using both types of valves seems like overkill if there are only public lavatories being supplied.

Miss read your post... I will change my answer to yes.