Heat dump - Elec Hot Water Tank

[veggie]

I am in the middle of a basement renovation and have a small window of time to add an additional hot water tank to my system.
The idea is to place an electric hot water tank just ahead of my regular (gas fired) water heater.
The electric unit would be wired to the ST5 generator circuit to act as a heat dump and also as a water heater in emergency situations.
With only 3kw available from the 6/1 engine, I cannot drive the two 240v/3000w elements in the water heater.
The plan would be to supply 120v power to each of the 240 elements with each element passing through a separate breaker allowing me to choose one element or two depending on the load dump requirements.
Has anyone else done this?
Any suggestions or concerns?

Thanks in advance,
veggie

[WGB]

Veggie check your water heater most if not all electrics run the top element till the upper tstat is satisfied, then switchs to the bottom element.
The two never run at the same time.

[veggie]

Thanks Jens,

The water tank has not yet been purchased, so let's assume for this discussion that the elements are 4500w.
Any problem running them at 120 volt with a breaker so that I can run each element separately ?

PS: Jens, how did calculate that a 240 volt / 4500 watt element makes 1125 watts at 120 volts?
Obviously it's not simply dividing by 2 as was done with the voltage.
It must be that you have 4500 watts TOTAL and 2250 watts per element.

veggie

[veggie]

Veggie check your water heater most if not all electrics run the top element till the upper tstat is satisfied, then switchs to the bottom element.
The two never run at the same time.

Hi Henry,
I need to control the elements. If they ever came on at the same time while I am powering other things, I would overload the ST5 - 6/1.
Therefore I suspect there will be many occasions when I want it limited to only one element just to keep the engine fully loaded.
Eg: If I'm charging the battery bank and not using full load, I may want to turn on an element and capture some energy.

Gary

[oliver90owner]

Power is I²R

Half the current, same resistance.

Or look at it how you are doing it.  You are halving the voltage, which will halve the current.

Now using Power = VI

Either way will do.

Regards, RAB

[potter]

Be sure to keep the thermostat in the circuit so that you don't overheat.

[oliver90owner]

WGB,

In UK ours are generally wired differently.  2 x 3kW, one short (top) and one long (to bottom) immersion heater.  Might be a dual (both into top of cylinder or two singles (one in top and one in the bottom).  

Top one is just that - top-up, for daytime use, as leccy is expensive (high grade energy).  

Bottom is for night time running when leccy rates can be cheaper due to production from base-load power stations running 'off-peak' demand.  One tariff, we call E-7, economy for 7 hours in the small hours.  Power at a much cheaper rate (approx 40%). So they operate on a timer change-over.

Otherwise it is much, much cheaper to heat water from primary energy sources.

Regards, RAB

[WGB]

Hi RAB,
 Thanks for the info.

I think Veggie is in Canada, not 100% sure, but the ones I saw up there are like ours in the US?


When I was working in the UK a couple years ago, I had a hard time having an instantaneous electric water heater in the shower stall with me LOL.
What the heck is the deal with that?

Bill

[AdeV]

When I was working in the UK a couple years ago, I had a hard time having an instantaneous electric water heater in the shower stall with me LOL.
What the heck is the deal with that?

It seems to be pretty much standard practice over here. They have a couple of advantages over a traditional tank-based hot water system: a) You have as long a shower as you like & it doesn't use up all the hot water; and b) if your boiler breaks down (a seemingly annual occurrence in the UK), you can still have a hot shower.

You lose one advantage if you have a combi boiler system - which can also generate endless amounts of hot water.... well, until it breaks down at least.

[WGB]

When I was working in the UK a couple years ago, I had a hard time having an instantaneous electric water heater in the shower stall with me LOL.
What the heck is the deal with that?

It seems to be pretty much standard practice over here. They have a couple of advantages over a traditional tank-based hot water system: a) You have as long a shower as you like & it doesn't use up all the hot water; and b) if your boiler breaks down (a seemingly annual occurrence in the UK), you can still have a hot shower.

You lose one advantage if you have a combi boiler system - which can also generate endless amounts of hot water.... well, until it breaks down at least.

LOL part I didn't like was having 440 getting wet with me!

[BruceM]

For folks in the US, Bradford White has rated it's commercial duty water heater thermostat for 9000 watts, so buying one of their units, and rewiring the bottom element in parallel, you can make a cheap 9000 watt boiler, or a very fast recovery water heater.

We've use them here on some highly insulated, all electric homes for in floor heat, where 4500 watts seemed marginal.  In most cases, the extra 4500 watts in just insurance, and has never been turned on.

When I checked on this many years ago, Bradford White was the only company offering this. 

You can also buy replacement water heater elements in a wide range of watts and for both 120 and 240V.