West Marine Cabin Heater recommended inverter

[Bustedknuckle84]

Here are the specs of the cabin heater:
Heat Source: AC Electric
Draw: 5A?13A
Btu: 5200Btu @ 1500W, 3120Btu @ 900W, 2080Btu @ 600W

Im trying to research what watt "size" inverter i need. The inverters have a continous and a peak wattage. I am trying to avoid upgrading my electrical setup(battteries, etc.) I plan to run the engine while the heater is running. I have 2 batteries(not deep cell) on a switch (1,2,all) What do you guys recommend to do or get?

 

[Don S]

Re: West Marine Cabin Heater recommended inverter

You DO NOT use inverters for heating. You can't carry enough batteries, or charge them after they are drained in short order.

 

[bruceb58]

Re: West Marine Cabin Heater recommended inverter

You would need over 125A to create 1500W. Not very feasable.

 

[Bondo]

Re: West Marine Cabin Heater recommended inverter

I plan to run the engine while the heater is running.

Ayuh,... Put a Bus heater in the cabin....

 

[Bustedknuckle84]

Re: West Marine Cabin Heater recommended inverter

how about if i just want to run the 900 watt or 600 watt option?

 

[Don S]

Re: West Marine Cabin Heater recommended inverter

NOT with an inverter.

 

[Outsider]

Re: West Marine Cabin Heater recommended inverter

Amps (required) = watts/volts. If I can do the math, anyone can ...

 

[Bustedknuckle84]

Re: West Marine Cabin Heater recommended inverter

how does volts play a factor? by your math theres a 13amp draw(required)= 1500/ ???? volts.... 1500/13amps=115 volts???

 

[bruceb58]

Re: West Marine Cabin Heater recommended inverter

1500w/12.6V = 119 Amps

Add in the fact that an inverter might be 95% efficient and you are up to 125 Amps off your 12V system.

 

[Bustedknuckle84]

Re: West Marine Cabin Heater recommended inverter

yikes! i think i got it, but how many amps does your stock system produce? @ 12.6volts that is....

 

[bruceb58]

Re: West Marine Cabin Heater recommended inverter

Most alternators that come stock on boats are 55 Amp but you can get larger ones. You never want to run them at their full rated outputs for very long and most don't reach that high of a current output until they are run at high RPMs.

Hopefully, that explains why this is a losing proposition.

 

[Don S]

Re: West Marine Cabin Heater recommended inverter

yikes! i think i got it, but how many amps does your stock system produce? @ 12.6volts that is....

If the boat is the one in your signature, the typical output for the Force 120 was 9 amps. (Nine, I didn't miss a number)
Like bruce said, that is only at high rpm.

 

[Silvertip]

Re: West Marine Cabin Heater recommended inverter

Here is the long and short of getting 120 volts AC out of an inverter with a 12.6 volt input. To get 1 amp of 120 Volts AC from that inverter you need to input 10 amps @ 12 volts and that ignores any losses in the conversion. That's a 10:1 conversion factor. To make this even more obvious, if you ran the heater at its 600 watt setting which is 5 amps @ 120 volts, you would need to input 50 amps at 12 volts. Here is a picture of an 800 watt inverter running off a garden tractor battery which is powering a 75 watt troublelight. The ammeter is in the positive lead of the battery (on the input side). Note that it is reading in excess of 6 amps. Therefore you have proof that at 750 Watts out (ten times more than the light), you would need to input 60 amps (10 times more than required to power the light). There is no free lunch when maiking electrical conversions like this.

 

[Bustedknuckle84]

Re: West Marine Cabin Heater recommended inverter

Thanks everyone for the info! I got it now, anyone want to buy a barely used west marine cabin heater???

 

[bruceb58]

Re: West Marine Cabin Heater recommended inverter

If the boat is the one in your signature, the typical output for the Force 120 was 9 amps. (Nine, I didn't miss a number)

I missed the boat in the signature. I was assuming a larger stern drive boat.