5500 watt elec hot water heater - 5000 watt generator

[nicksanspam]

Or use some of the 20 kW "waste heat" :-)

Nick

[hallerb]

First I have never tried this on such a large load but theres no reason it shouldnt work:) I have used this idea on small heaters in office equiptement over the years.

Put in a LARGE diode, and a switch.

On generator the heaters capacity will be cut by 1/2 the recovery rate will be twice as long.

makes thatr 5500 watt heater a 2750W heater ell within your generators capacity:)

[hallerb]

First I have never tried this on such a large load but theres no reason it shouldnt work:) I have used this idea on small heaters in office equiptement over the years.

Put in a LARGE diode, and a switch.

On generator the heaters capacity will be cut by 1/2 the recovery rate will be twice as long.

makes thatr 5500 watt heater a 2750W heater well within your generators capacity:)

[hallerb]

First I have never tried this on such a large load but theres no reason it shouldnt work:) I have used this idea on small heaters in office equiptement over the years.

Put in a LARGE diode, and a switch.

On generator the heaters capacity will be cut by 1/2 the recovery rate will be twice as long.

makes thatr 5500 watt heater a 2750W heater well within your generators capacity:)

[Mark Lloyd]

That may not work (there is essentially no change in peak demand). I'd like to hear from someone who knows more.

[Stormin Mormon]

It's definitely worth a try. Many generators have thier own circuit breaker, which should help protect the generator. Please expect th at 5,000 watts will burn probably two galons an hour of gasoline.

You might be better served to get two or three of these

pour about ten galons of water into the tub. We had a conversation about this on alt.survival, and aparently from what we can figure one immersion heater will warm 10 gals of water to bath temp in about four hours.

Please let us know how things go for you.

[hallerb]

copier heaters wattage are cut by 50% by installing a diode.

What happens is the heater only heats on 1/2 the cycle cutting power by

1/2

[Member, Takoma Park Volunteer]

The most cost effective, over the life of the unit, water heaters available are the high efficiency oil fire units. The initial cost is high but they will save you money over the life of the unit.

[sylvan butler]

That's for sure.

Nope. If the water is hot, no need to swap elements. :)

Maybe the simplest, but then you live with a performance impediment all the time.

I think the simplest would be to put in a switch or rewire the elements ONLY DURING AN OUTAGE such that both elements run in series. This way you get to heat your water, it takes an age, but when the power comes back on you get the full performance again just by undoing your change. No cost if you don't need a switch. And you don't have to deal with doing an element swap during an outage or living with weak elements during the other 99% of the time.

Given: Watts=Amps*Volts Volts=Ohms*Amps

If we use 240volt, 4800watt elements the math is nicer. :)

For a single element:

4800watts=Amps*240volt, Amps=20 240volts=Ohms*20amps, Ohms=12

Ohms are important, because they are the constant for a given heating element. Amps and so watts will change if we change the voltage. (That means your 5000w generator may be OK trying to run 5500w elements, because the voltage will drop and the power will drop and it might be fine.)

For two elements in series (2x the Ohms): Watts=240v*240v/24ohms, Watts=2400.

So you get 1/2 the wattage when you run the two elements in series. For your 5500watt elements, that means you get 2750watts. Nearly as good at heating as 3000watt elements, but you get 5500watts when all is well.

This is MUCH better than using 120v on one element because you are using both elements. With 120v and standard water heating wiring: Watts=120v*120v/12ohms, Watts=1200 (or 1/4 the wattage).

sdb

[CptDondo]

Yabutt.... I don't know that much about generators, but I would guess that such an off-balance load wouldn't make it happy....

Either wire them in series, or replace one with a 3KW element. Me, I'd replace both with 3KW elements. That way it's passive, no switches, no parts, no forgetting to change things over. OK, recovery is a bit longer, but with a high-efficiency 80 gal tank, you probably wouldn't notice unless you take long showers....

[mgkelson]

If you have a 20A, 240V outlet close to the water heater, then your wiring should be OK. You can see some pictures of various types of outlets at:

In poking around Google, it looks like this water heater is made by State Industries a subsidiary of A.O. Smith. So, you might want to give them a call and ask them how easy it is to switch back and forth between the two wattages. Or, you might be able to go to the sears store and if they have one in stock, you could ask to see the manual. My bet is that it would be relatively easy to switch back and forth.

State Water Heaters

500 Tennessee Waltz Pkwy Ashland City, TN 37015 phone: [phone]

A. O. Smith Water Products Company

500 Tennessee Waltz Parkway Ashland City , Tennessee, USA 37015 1-800-527-1953 FAX: [phone] [e-mail]

[spam disintegrator]

I thought I'd give an update on what I decided to do. (I already tried to post this once, but for whatever reason, my post never made it through).

First of all, a huge THANK YOU for all of your replies, ideas, and discussion.

I decided to go to Sears and buy the dual power unit. It has a .95 effeciency rating, which is a few points better than the ones Lowes and Homer Depot carry in my area.

I confirmed in the store what I was told by their reps on the phone- the bottom element can run at 3800 or 5500 watts. The top one is always 3800 watts.

Converting the bottom element back and forth between 3800 and 5500 simply involves adding or removing a metal "bridge plate" (i think they call it a buss) from the bottom element. It comes from the factory w/o the plate attached = 3800 watt. When you add the plate it bridges two connections on the bottom element = 5500 watt.

I don't know a lot about water heaters, but I think most elements only have two connections- this one has three, and when you bridge the two, you get 5500 watts.

So, during the 99.9% of the time when I am not running on generator power, I get better performance and during the .1% of the time when we might be out long enough to want some hot water, I can convert wattage w/o doing anything that 1) voids the factory warranty (ok, who knows if running on generator power might void the warranty too LOL) and 2) makes a big watery mess.

Anyhow, I don't have it in yet, as I'm waiting for a friend to help me on a weekend, but it's sitting in my basement ready to go.

Thanks again for all of your help!!!