I do have other hot water requirements and the first thing I did was size the storage for the additional load of the emergency equipment. However, the architect is not giving me any floor space for water heating even though this is a huge warehouse/office/processing application. She wants me to put water heaters on a platform above the janitor's closet. The combined weight of the equpment using stored hot water is over 5000 lbs. I can go that route, but that's a hefty platform. I need to weigh the cost of the structure and storage heater against the instantaneous multiple heaters, beefed up gas supply, etc. I have never designed emergency equpment with instantaneous but it makes sense to me if I can get it to work at reasonable cost. It is weird that all of the hits I get when I google this are electric heaters with about 180 KW (no, we do no thave that extra capacity in the building) or steam converters.
The mixing valves I have looked at so far are Leonard TM850 with minimum recommended inlet temperature of 120 deg. F., Guardian G3700 with minimum hot water supply temperture of 140 deg. F., and Powers ETV200 with MAX hot water supply of 180 deg. F (no minimum listed, I have contacted them for more info).
I have considered lowering the final tepid temperature to 65 degrees F, however even though it meets the requiremts it's pretty cold to stand in for 15 minutes. My understanding is you want the injoured person to stay in the flushing fluid long after they think they need it which is why they went with the tepid requirement in the first place.
I am trying to find an ASSE 1071 valve with a delta T of about 20 degrees or less so I don't have to waste so much expense and energy to heat the water way above the set-point of the valve discharge. It seems these valves are adjustable to a wide range of temperatures, making the delta T of 20 degrees above the highest adjustment of the valve. In other words, if the valve is adjustable to 60-100 degrees F output, the minimum inlet temperature would need to be 120 degrees to make a Delta T of 20 above the highest set point of 100. I will call some of these manufacturers today to find out if that's the case, or if I can realize a delta T of 20 above MY set point of 65 or 70.