run a 1200w water heater with 900w Generator

[sgtPluck]

Pardon me if this is a silly question, but I've never owned a portable generator until now.

If I run a 900w generator, then connect shore power cable and turn on my water heater (1200w element) will it just heat up more slowly or could it cause a problem?

[BillKny]

Originally Posted by sgtPluck

Pardon me if this is a silly question, but I've never owned a portable generator until now.

If I run a 900w generator, then connect shore power cable and turn on my water heater (1200w element) will it just heat up more slowly or could it cause a problem?

In all likely hood the generator will shut down from overload. In short, NO it will not work.

[coopec43]

Originally Posted by sgtPluck

Pardon me if this is a silly question, but I've never owned a portable generator until now.

If I run a 900w generator, then connect shore power cable and turn on my water heater (1200w element) will it just heat up more slowly or could it cause a problem?

Hope you don't electrocute the linesman doing maintenance on the marina power grid

[Captain Bill]

You will most likely fry the generator if it doesn't stall. It might not fry instantly but it probably will before you have hot water. I'm assuming 120v water heater, but if you replace the element with a 240v 1200 watt element it will only draw 600w at 120v. It will just take a while longer to get to the temp you want.

[BillKny]

Originally Posted by Captain Bill

You will most likely fry the generator if it doesn't stall. It might not fry instantly but it probably will before you have hot water. I'm assuming 120v water heater, but if you replace the element with a 240v 1200 watt element it will only draw 600w at 120v. It will just take a while longer to get to the temp you want.

For the person asking this question they have no business doing ANY wiring whatsoever....

[rslifkin]

Originally Posted by Captain Bill

You will most likely fry the generator if it doesn't stall. It might not fry instantly but it probably will before you have hot water. I'm assuming 120v water heater, but if you replace the element with a 240v 1200 watt element it will only draw 600w at 120v. It will just take a while longer to get to the temp you want.

A 240v 1200w element should be 300w at 120v. It'll go from drawing 5 amps to 2.5 (through the same resistance element) with half the voltage. And 2.5 amps at 120v is only 300 watts. Basically, for a resistive heating element, cutting voltage in half gives 1/4 of the power.

[Cadence]

I can't see the rational of doing it.

[ikanode]

Originally Posted by sgtPluck

If I run a 900w generator, then connect shore power cable and turn on my water heater (1200w element) will it just heat up more slowly or could it cause a problem?

You need to clarify what you mean by "then connect shore power cable". What are you connecting it to? Your generator or shore power?

[LoudMusic]

I agree you need to add more of your steps in here.

If you are running a 900W generator through a charger to charge your house battery bank, then an inverter from the house battery bank to the hot water heater (assuming this is an AC water heater?), you'll be drawing 300W from the battery (approximately - losses not calculated) and likely be fine.

[sgtPluck]

I meant connecting generator AC output to Shore Power AC input on the boat, then flipping on the heater 1200w element on AC circuit in the boat.

In my ignorance I thought it may be possible that the generator would happily put out its continuous rated load (750w) and that because the heating element is 1200w it would just not get as hot as designed. But it appears from responses that the generator itself will get overloaded/trip from the lack of resistance on the circuit.

[Cadence]

Originally Posted by sgtPluck

I meant connecting generator AC output to Shore Power AC input on the boat, then flipping on the heater 1200w element on AC circuit in the boat.

In my ignorance I thought it may be possible that the generator would happily put out its continuous rated load (750w) and that because the heating element is 1200w it would just not get as hot as designed. But it appears from responses that the generator itself will get overloaded/trip from the lack of resistance on the circuit.

I doubt the gen. will sync with the shore power. I hope the breaker trips on the gen. prior to it frying.

[CarlF]

I agree with the folks that believe it will draw 300watts (or 1/4th).

P=V^2/R - where P is watts, V is volts and R is resistance (which is fixed)

There's no "synching" with shore power as the generator is the only power source going into the inlet.

So it should work - if slowly.

[Stu Jackson]

Originally Posted by sgtPluck

... that the generator itself will get overloaded/trip from the lack of resistance on the circuit.

From the higher load on the generator than it is capable of producing.

[NorthCoastJoe]

I would be worried about back feeding into the grid. This idea is flat out dangerous.

Your 30 amp shore power should easily handle a 1200w water heater. If not you have bigger problems and a potential fire from an overheated electrical connection.

[Pete7]

Originally Posted by NorthCoastJoe

I would be worried about back feeding into the grid. This idea is flat out dangerous.

Your 30 amp shore power should easily handle a 1200w water heater. If not you have bigger problems and a potential fire from an overheated electrical connection.

I think and hope he means feed the generator power into the boats shore power connection as you might do when at anchor.

Sgt P, a 900w generator is a bit of a toy. You have a couple of other choices, ditch the generator and buy one twice the size. The Honda 22i would be nice and still a one arm lift. Alternatively swop out the heating element for a smaller size. A 750w size is available in the UK but we have 230v mains. A bit of investigation ought to find something better suited.