# Generator Run Electric Hot Water Heater?



## velvetfoot (Oct 28, 2012)

I now have an electric hot fwater heater that I use but also have an indirect water heater (now drained) off the oil boiler.  I'm wondering if I should heat the hot water with the electric with the 7.5kW generator, or fill the indirect tank and run that.  I'm not sure how long it would take to heat the hot water with the generator, esp. after a couple of days when the water gets colder.  So, that could use more gasoline, but it'd be a little hassle to turn some valves and fill the indirect, which could be powered off a small genny.  Plus, I can't run the well pump at the same time as the water heater, so that'd have to be switched.

Ideas? Experiences?

Thanks.


----------



## Retired Guy (Oct 28, 2012)

My electric water heater has two 4500 W elements that do not come on simultaneously. My 65 gal tank takes about 45 minutes to reach max temperature.


----------



## velvetfoot (Oct 28, 2012)

Thanks.  I'll probably wind up filling up the indirect to save gas.


----------



## MasterMech (Nov 6, 2012)

Ran into this a bit last week velvetfoot. My opinion you were better off using the indirect. You'd need a 7KW genny to run the pump and the water heater, and still need some more surge capacity to get the well pump started. So unless you're packing 10KW (or more ) of heat, I'd say you did good.


----------



## woodgeek (Nov 6, 2012)

My well insulated DHW tank stayed warm for 4 days...The wife and I took a couple perfectly comfortable trickle showers during the 5 day outage. 

Insulate those tanks.

After that....the plan was heat a big pot of water on the propane camp stove and 'hobo bath' it. I guess I could get a bigger outdoor propane unit like for a crab boil or turkey fry, and heat enough water for a warm bathtub full.  Could clean the tykes every few days.


----------



## velvetfoot (Nov 6, 2012)

Luckily, I never had to use it, post-Sandy.
Our genny is 7500 watts with pretty good surge, but not for the pump and well at same time.  I count myself luck it starts the well pump.
I did figure that flipping the water heater breaker to run the well pump would've been a hassle.
Also, who'd a thunk that gasoline would've been in such short supply, (to power the big genny.) - so every bit saved is a good thing.
Turning a couple of valves and then draining the indirect out after it's all over is not a big deal.
Then, if we had any guests, they could take showers as well.


----------



## Mo Par (Nov 6, 2012)

My gen is 8000 watts.  I leave the water heater off while the 2 fridges and freezer are running.  If I need to heat up water I turn off the breakers for the fridges and freezers. 

John


----------



## trailrated (Nov 10, 2012)

I ran my elec. water heater on my 5500W (8250 surge) genny. It has 2 4500W elements and they don't operate at the same time. I would turn off all breakers I was using and and then hit the water heater breaker. I'd let it run for 30-45 minutes then shut the breaker. Then, hit the well pump breaker and shower. My wife and I could take separate showers and have plenty of hot water.


----------



## Highbeam (Nov 10, 2012)

Yes, you don't need to run both the well pump and the water heater. This is a great reason to have a tank type water heater, it heats up the 40-50 gallons and then you get a shower using about 2 gpm until the hot water runs out. Repeat as necessary. Most anks can go from ice cold to 120 in an hour. The two elements are indeed cycled. Cold tank starts with the top element to hurry up and heat the topmost part of the tank for fast recovery and then finishes off with the lower element to get the whole tank hot.

I have seen elements from 4500-5500 watts each. It's a big load for the genset but a resistance load so no surge on start up. Nice and steady 240 volt load that doesn't care how dirty your power may be or how pretty your sine wave is.


----------



## Dougsey (Nov 13, 2012)

Do all tank type water heaters use one element or the other... never both at the same time?


----------



## Retired Guy (Nov 13, 2012)

All the ones I looked at were that way.


----------



## MasterMech (Nov 13, 2012)

9KW is one helluva load to have running, even on a dedicated circuit.  37 Amps @ 240 volts.


----------



## velvetfoot (Nov 13, 2012)

I've never seen more than 4400 (or so-I know it's above 4kw) watts for my water heater as measured by "The Energy Detective, ver. 1".


----------



## maverick06 (Nov 14, 2012)

yep, the above is the same for my hot water heater, thats a lot of power. I thought about getting a heat pump hot water heater (hybrid hot water heater) as they are relatively light loads, nothing more than your fridge.  it would sure make life more comfy.... but not worth the cost for me when i was replacing my hot water heater.


----------



## Tramontana (Nov 14, 2012)

Sorry to be a jerk, but this is a pet peeve of mine...

...they are water heaters, not hot water heaters.

(there, I said it) 

Cheers!


----------



## fossil (Nov 14, 2012)

Tramontana said:


> "Sorry to be a jerk..."


 
Ah, well, hell, I guess ya just can't help it.


----------



## Tramontana (Nov 14, 2012)

Nope, can't always keep it in.


----------



## Corey (Nov 14, 2012)

Tramontana said:


> Sorry to be a jerk, but this is a pet peeve of mine...
> 
> ...they are water heaters, not hot water heaters.
> 
> ...


 
lol - I know several people with this same pet peeve.  My 'water heater' is operating in a cycle where the water falls to about 160ºF, the burner kicks on and heats up to ~170ºF.    So is 160ºF not hot water?  and going from 160º to 170º not heating that water?  Thus hot water heater?


----------



## firefighterjake (Nov 15, 2012)

Tramontana said:


> Sorry to be a jerk, but this is a pet peeve of mine...
> 
> ...they are water heaters, not hot water heaters.
> 
> ...


 
HehHeh . . . never thought about that before.


----------



## Retired Guy (Nov 15, 2012)

Maybe they are cold water heaters


----------



## Highbeam (Nov 15, 2012)

The only time it's not a hot water heater is when it is new and the tank is full of cold water. Even when some yahoo takes too long of a shower he will most likely be getting out before the water becomes straight 50 degree water.


----------



## nate379 (Nov 15, 2012)

Tramontana said:


> Sorry to be a jerk, but this is a pet peeve of mine...
> 
> ...they are water heaters, not hot water heaters.
> 
> ...



Thank You!  It bugs the heck out of me as well!


----------



## maverick06 (Nov 15, 2012)

wow, I sure started quite a conversation here! haha


----------



## sehome (Apr 30, 2017)

Tramontana said:


> Sorry to be a jerk, but this is a pet peeve of mine...
> ...they are water heaters, not hot water heaters.
> (there, I said it)
> Cheers!


Gosh, when I say things like this I am called a grammar nazi!


----------



## sehome (Apr 30, 2017)

velvetfoot said:


> I now have an electric hot fwater heater that I use but also have an indirect water heater (now drained) off the oil boiler.  I'm wondering if I should heat the hot water with the electric with the 7.5kW generator, or fill the indirect tank and run that.  I'm not sure how long it would take to heat the hot water with the generator, esp. after a couple of days when the water gets colder.  So, that could use more gasoline, but it'd be a little hassle to turn some valves and fill the indirect, which could be powered off a small genny.  Plus, I can't run the well pump at the same time as the water heater, so that'd have to be switched.
> 
> Ideas? Experiences?
> 
> Thanks.


   We face same issue: can I run my 3kw pump same time as 4.5kw hot water element?  Westinghouse 7kw gen.  Decided:  keep the hot water breaker turned OFF.   Pump and water uses are much more important.   Then, when water gets a bit coolish for washing  dishes,  turn off the pump, ON the hot water tank for the 15 mins. it takes., then  off.  
   This will irritate some, but maybe we all use too much hot water anyway,  I long ago disconnected the lower element in mine (to save power) so therefore am only heating about 15 gals of water not 40.
I heat only to 110-115.  It's worked for 30 years.  (I live in a Western county where it's common to have dirt on your hands and under your nails, and smell like sweat.)


----------



## peakbagger (May 1, 2017)

It would be interesting to rig up a hot water heat exchanger on the generator exhaust and use that to heat the hot water. A big portion of the fuel BTU content to generator is exhausted as heat. I work on combined heat and power systems for industry and institutions and we can recover about 50% of the heat input of the engine. We have two of these sitting in warehouse right now waiting to be installed  https://powergen.gepower.com/conten... 6/jenbacher-type-6-fs-en-non-metric-2016.pdf which will produce chilled water with a hot water absorption chiller and plenty of hot water. Unfortunately these systems  don't scale well but I have seen folks home build heat exchangers or use a water cooled exhaust from the small boat industry.


----------



## blades (May 1, 2017)

Number of years ago ( 70's) , designed exhust + eng coolant using exchangers to heat carpet cleaning solution set up as a package unit with a small diesel eng. - refined further dropped out small eng hooked up to transport power plant. Had to set up a thermal bypass to stay under 212 deg F, both of these designs are still in use- likely with some changes , Oh and the  pumps for solution injection/extraction  were also driven by same power plants.


----------



## Retired Guy (Jun 1, 2017)

blades said:


> Number of years ago ( 70's) , designed exhust + eng coolant using exchangers to heat carpet cleaning solution set up as a package unit with a small diesel eng. - refined further dropped out small eng hooked up to transport power plant. Had to set up a thermal bypass to stay under 212 deg F, both of these designs are still in use- likely with some changes , Oh and the  pumps for solution injection/extraction  were also driven by same power plants.


I remember about the same time Fiat was looking into residential co-generation systems (heat and electricity) from their engines installed in homes.


----------

