Electrical question

larry merlau

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Location
Delton, Michigan
how much amperage would i need to run 3-50 gallon water heaters.. am going to run them in series so they can be partially shut down when consumption is low. as i understand it i will have 3 separate circuits for this to work and the plumbing makes the choice on how the water source is.
 
A lot depends on the exact water heater purchased but as I have a plumbing, HVAC/R, and electrical background I'll work through the theory:

Three WH seems like a LOT, especially at 50 gallons each. If you have a fossil fuel available to use it seems a tankless such as Navien might be a better choice. That's what I use for my home on propane.

If you want to use three in series, you're going to want the last one set at the desired temp with the preceding tanks set at lower and lower temps so they preheat the water to increase the recovery time of the third. You are going to have substantial pressure drop across a 3 tank run.

To answer your question, the standard elements in a 50 gallon water heater are 4500-5500 watts each and there are two of them. Using the heater as factory wired USUALLY results in only one element operating at a time BUT most heaters allow for use of an increased or dual circuit wiring so that both elements can operate at the same time approximately doubling the recovery rate. Each element at 240 volts will consume up to ~23 amps which is why most are wired with a 30 amp 2-pole breaker.
 
Know what size the elements are in each? 3500W? 4500W? 5500W?

Divide watts by voltage to get amps so probably looking at 20 to 30 amps each depending on the wattage. Get the model numbers and we can figure out what you need. Also what distance does the wire have to go from the panel?
 
It's easy to figure out, Larry. The hypotenuse of the co-linear hyperbole is equal to the inverse of the hemoglobin aperture. Except on Tuesdays. Simple, really. :rofl:

(Sure is handy having guys like Robert and Darren around, huh?) :thumb:
 
As someone who just recently replaced a water heater, I'm interested in what you are going to do with that much hot water. Seems interesting.

I was wanting to go tankless, but my calculations indicated I'd need way more than the 30 amps I've got wired to the water heater closet to make tankless work, since I don't have gas out here.

If I did have propane or gas, I sure would have considered going tankless.
 
It's easy to figure out, Larry. The hypotenuse of the co-linear hyperbole is equal to the inverse of the hemoglobin aperture. Except on Tuesdays. Simple, really. :rofl:

(Sure is handy having guys like Robert and Darren around, huh?) :thumb:

The formula for wattage is VERY easy for me to remember! :rofl: P=IE and I just happen to love PIE!! P for Power (measured in watts) equals I for current (from current Intensity measured in amperes) times E for voltate (from EMF for ElectroMotive Force measured in Volts)

Another good formula from Ohm's law is the Eagle flies over the Indian and the Rabbit:

E
-------
I | R

So same symbols as PIE but add R for Resistance (measured in Ohms) Cover up any variable you don't know and use the rest i.e. E=I*R , I=E/R, R=E/I. This works for resistive loads. Might be useful for someone someday. :dunno:
 
thanks for the help on this folks and yes vaughn our group mix is very helpful.. i sent the check yesterday for consultation fee's..

back to Mr Johnson here is my reason on having 3 water heaters.. this is a camp that has summer time kids and during the wknds they have weddings and such and rent out rooms.. the bathrooms also have showers for the kids which get used a lot during the summer... they now have a 70 gallon htr that uses oil but they state has told them they need to get it out of there no oil!!! they dont want to re-plumb a gas tank to get a gas system because of venting costs.. so electric is there choice.. the power source Darren is less than ten ft from where these tanks would go.. so i am thinking 3-30 amp circuits and separate disconnects inside the heater room to turn them off for service or to eliminate the third one during slow times..
 
Gotcha - good info to work with there. If there is gas on site and an exterior wall then tankless might still be the best option as they make an outdoor unit as well as one that direct vents through an exterior wall. If not, scrap that idea. As for Brent's application, electric tankless SUCKS so never do that unless it's a small point of use system for an isolated sink or other odd application.

Recovery rate is something you might consider addressing rather than volume of storage. The preferred method of piping heaters is always parallel, not series. This helps with the pressure drop issue I mentioned as well as equal use of the tanks vs one or the other bearing the majority of the work. You can still use isolation valves for each tank so they can be changed or worked on without interrupting hot water that way as well.

I really think you're going to be disappointed with three tanks in series. Either one 80 gallon commercial tank with 6 elements (can produce up to 185 gallons per hour at 60ºF rise) or 2 standard 50 gallon electric in parallel that can be wired for simultaneous element operation might work better. Just thinking out loud.
 
they are leaning towards 2-50 now, much cheaper than a 80. series was there idea and i have found out threw the net and you, that parallel would be better.. the simultanous element operation is something i am not aware of any place i can get more info on that?
 
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