emergency shower heating

Jellis

Howdy folks,
needing to provide a water heater for a emergency eyewash station. 20gpm of 90°F water for 15 minutes is required.
Looking to provide a storage tank but I am second guessing myself with sizing.

Spirax sarco offers a calculator for mixed water
20GPM required at 90°F

storage at 140°F
mixed to 90°
9.5GPM hot water
10.5GPM cold water

9.5GPM for 15 mins= 142.50 Gallons.

So if i have 150 gallons stored at 140 then i should be good?

I keep hearing my high school math teacher laughing...
I was looking for a good formula to use...

Jamie Hall

Nothing wrong with your math. My high school math teacher gave me odd looks from time to time, too.

EBEBRATT-Ed

Sounds right. You could store at a higher temp and reduce the tank side

ratio

I see many emergency eyewash stations fed from demand water heaters around here. Silliest looking one had 4-6 electric heaters (bigun's, too) ganged together, but that was an industrial building so maybe their requirements were different.

mattmia2

20 gpm at 90 f can take a whole lot of energy depending on what your supply temp is so having to gang several electric instantaneous units to get that flow and temp isn't out of the question.

Jellis

I like the on demand option much better as well since these are emergency stations and will not see regular use. the cost of storing water for rare use seems very silly to me!
I will be pushing on demand options.
Thank you everyone

dopey27177

Try connecting to the building domestic hot water supply with a mixing valve to lower the water temp, 90 degrees.

That is relatively cheap compared to electric heaters or electric boiler and or storage tanks.


Jake

Jellis

dopey27177 said:

Try connecting to the building domestic hot water supply with a mixing valve to lower the water temp, 90 degrees.

That is relatively cheap compared to electric heaters or electric boiler and or storage tanks.


Jake

No can do,
the DHW is provided peace meal around the building. mostly basic electric storage tanks to serve break rooms bath and locker rooms.

plus at 20GPM not many DHW heaters could keep up.

Jamie Hall

It's a rare domestic hot water system that can cope with the flow demand of an emergency eye wash station -- never mind an emergency wash down shower!

ratio

I'm sure that's why there were so many ganged together on that job I mentioned. They were big 3 phase models, like 2'x3'. Expensive to operate, but as opposed to storing 100's of gallons of hot water for the one time you really need it...

Jellis

Eemax is just one company i've looked at that makes a heater for safety showers, electric on demand capable of 50° rise at 20gpm which is enough.
however they are 600v 3 phase and use 1ga wire. not to mention they cost as much as a 2 year old corolla...