Emergency Eye Wash Tankless Water Heater

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bradbb2005

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South Carolina
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Electrical Designer
Hello,

We are in the process of designing a Mechanical Room inside another building with an existing service. We have utility data per 220.87 for determining existing loads. Now, we are getting into the actual demand of this room. The eyewash looks to need an 18kW (208/3/60) tankless hot water heater which significantly adds to the load. No, this will not be running much, if not all in its life. Where could I find a way to apply a demand factor to reduce the loading?

Thank you in advance.
 
There isn’t anything to directly reduce the loading that I’m aware of. I would suggest to them to use a mini 2.5 gallon tank. It won’t be too much bigger (physically) then the instant water heater and it will be more reliable. Those tankless heaters have control boards that are prone to failure.


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I doubt a 2.5 gallon hot water heater would do it. If it is just eyewash it needs to run for 15 minutes at 0.4 gpm. That's about 6 gallons. I suspect the heater can't recover fast enough to keep the water warm for the entire 15 minutes.
 
A lot of eye washes offer the hot water as an option however it’s not actually “hot” water, it’s more like tempered water (around 90ish).


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A lot of eye washes offer the hot water as an option however it’s not actually “hot” water, it’s more like tempered water (around 90ish).


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I think the rule is not to exceed 100 deg F. I never quite understood why there was a minimum temperature requirement though.
 
I doubt a 2.5 gallon hot water heater would do it. If it is just eyewash it needs to run for 15 minutes at 0.4 gpm. That's about 6 gallons. I suspect the heater can't recover fast enough to keep the water warm for the entire 15 minutes.

Well if it’s only 0.4 GPM then an 18kw water heater wouldn’t be required. EEMAX makes water heaters specifically for eye washes. Assuming a 60 degree temp rise is required and 0.4 GPM, then only a 4kW heater is required.


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Thermon has a trace calc program that may help. You also have to check OSHA for the water temperature, but I cant recall the standard.
 
I think the rule is not to exceed 100 deg F. I never quite understood why there was a minimum temperature requirement though.
Just from experience a desired temp as near body temp is most desirable as much lower or higher can cause enough discomfort that it can make adequate rinsing difficult or impossible.
 
Our Mechanical Engineer is selecting the WH. We have had issues with the smaller EEMAX so he is going with one rated at 3.0GPM. I just get the loads and tell them they will work or not and complain a little. I was just hoping to reduce the possible sizing of the feed to this room. The new Mech room already exceeds the building's historical power consumption. SKM is calculating around 164 Amps for this new equip pushing the total load on this building to ~320A on a 150KVA xfmr and unknown main panel breaker and service conductors. Government jobs are fun.
 
I don't believe that the code has any provision for a demand factor for an infrequently used (emergency and testing only) water heater.

With that said, you might have some wiggle room if you argue that while the 'nameplate' rating of this water heater is 60A, the actual load is the heated water so if the eye wash fixture has a maximum flow of less than 3 GPM you could make a strong argument that the actual load is less than 18kW. (Just as a transformer can be larger than the load served without increasing the load.) But code doesn't say this; you would need to argue the point to get a variance from the code.

Jon
 
I don't believe that the code has any provision for a demand factor for an infrequently used (emergency and testing only) water heater.

With that said, you might have some wiggle room if you argue that while the 'nameplate' rating of this water heater is 60A, the actual load is the heated water so if the eye wash fixture has a maximum flow of less than 3 GPM you could make a strong argument that the actual load is less than 18kW. (Just as a transformer can be larger than the load served without increasing the load.) But code doesn't say this; you would need to argue the point to get a variance from the code.

Jon

I think that will be a tough sell (even though it makes sense).
It’s kind of like calculating a motor load based on what it’s connected to, mechanically.
 
I think the rule is not to exceed 100 deg F. I never quite understood why there was a minimum temperature requirement though.
Even with your eye full of acid, it's tough keeping your face in the water to get the eye flushed out if it's at 40-50F. Ask me how I know.
 
Gee, hot and cold water available, as well as probably a drain. Any chance someone will install a sink later?
 
Gee, hot and cold water available, as well as probably a drain. Any chance someone will install a sink later?
Not sure about sink but I know one place I worked we had to have not only eye wash but also a shower station as well for emergency if chemicals spill on you, we used both heavy caustic and acids. We avoided using both at same time, but occasionally it would mix in drain and not enough water flushed in between each and would result in a temp evacuation of the plant or section of plant until fully ventilated.
 
Not sure about sink but I know one place I worked we had to have not only eye wash but also a shower station as well for emergency if chemicals spill on you, we used both heavy caustic and acids. We avoided using both at same time, but occasionally it would mix in drain and not enough water flushed in between each and would result in a temp evacuation of the plant or section of plant until fully ventilated.
In my experience, there is a combo eyewash/safety shower station typically installed. The shower head goosenecks over the eyewash basin. There's a large push paddle to activate the eyewash, and a triangular pull handle to activate the shower.

C1967107_main-1.jpg
 
Those combo stations require lots more available water than just an eye wash. 3gpm wouldn't even come close.

-Jon
I did a quick Google and found this.

KEY REQUIREMENTS FROM THE ANSI Z358.1-2014 CODES:

  • Shower shall deliver minimum of 20 gallons per minute (Sec. 4.1.2) and provide a column of water 20 inches wide at 60 inches above the surface floor of user. (Sec. 4.1.4)
  • Eye/Face wash equipment shall deliver minimum of 3 gallons per minute of water for 15 minutes.(Sec. 6.1.6) Eyewash shall deliver minimum of 0.4 gallons per minute for 15 minutes. (Sec. 5.1.6)
 
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