Instant Hot water heater under the sink Bradford model EFT-28000-4-T-10 208 volt single phase. Draws close to 140 amps. Theres 45 units that theses are POSSIBLY going to be installed. As far as I see it each one must be rated for condutious duty(X125%)45 x 6075x125% aprox 760 amps ??? Anyone know of any derateing ect in this case?? Seem like a lotta power for Hot water??? Yoopersup
Yooper, I might see a few errors in your thinking.
These are single-phase 'whole house' water heaters. I assume that means that these will each be going in a different residence, and different panels.
Does the load seem high? Sure - that's the price you pay for 'instant' heat.
When you do the load calcs for multiple dwellings, there's a multiplier for your "diversity factor." The effect of this is, whether you use the 125% figure or not in each individual panel, I don't think it will change the final total service needed.
Looks like you need 3 two-pole breakers - and they;ll need to be mounted next to each other, so they can be considered as disconnects 'grouped together.'
I called the Company your right, Three 2 pole 40 amp breakers for each unit . and thats the Minimin size they say would be required to feed a, Shower, Bathroom sink, Kitchen sink combo. Becta there not going in!!!.
It's insane how much power it takes to heat water on demand, isn't it? I would have had to upgrade my service to put in an in-use hot water heater for my home. Gas isn't much better- the size gas like you need for even a 1-shower-at-a-time tank line that is obscene, too.
It doesn't really take more energy to heat the water; it's just that you're trying to heat it in seconds instead of minutes. If you think about the gas versions, you're using 30 minutes worth of a gas flame in a few seconds. That means that the flame will look more like a welding torch than a stovetop burner.
My electric one takes (4) 30 Amp 240V circuits, but it doesn't really show up as a noticable amount on my bill; so I'm not using a LOT of energy, I'm just using the same amount very very quickly.