Running heaters off inverter vs. shore power

[it4llc]

I currently have 3 Xtreme heaters running in my boat, 1 in the bilge and 2 in the cabin. (The 2 in the cabin may be overkill as I winterize the freshwater system and the A/C.) I don't winterize the engine nor the generator. Right now I have the heaters set to run from shore power. The marina where we are supposedly doesn't usually lose power (there, I jinxed it) but in the rare case it did, is there a way to run the heaters from the inverter/batteries, while simultaneously charging the batteries from shore power, such that if the power did go out, the heaters would continue to run?

If I set the power panel to run from the inverter, then I can't turn on the battery charger on the power panel to recharge the batteries from shore power, so assuming I've got this correct, I guess my question really is whether there is a way to have the battery charger draw from shore power apart from the power panel? The Xtreme heater specs say the normal operating current is 4 amps, so even running all 3, I should get 8 hours of run time before hitting 50% discharge on a 200Ah bank, which would last at least a day or two since the heaters don't run non-stop. That would afford some additional peace of mind in the event of a power outage.

 

[watson1987]

That is 4A @ 120V AC, your 200Ah bank provides 12V DC.

If you run these off your inverter, you'll pull 40A each off your battery bank (assuming perfect inverter efficiency). In reality, it's closer to 50A with losses.

I'm not sure what inverter/charger you have, but I have mine set up to charge the batteries and act as a passthrough for shore power. If I lose shore power, my heaters/dehumidifiers will turn off, as they won't switch to inverter mode to run the 120V AC

My reasoning is that I would rather keep my battery bank alive to run my bilge pumps.

 

[it4llc]

Thanks for the explanation on the Ah - I was pretty impressed at how little they were drawing. Makes much more sense now. 😱 In my case, I'd rather sacrifice the batteries than the engine/generator if it were to get that cold.

We've got a Kisae inverter and an Abso charger. Neither of the manuals seem to detail how to set up as you describe, so I'm not sure if our Kisae can do that or not. I'm going to get the exact model though and do some more digging online to see what I can find....

 

[watson1987]

Kisae/Abso are the same company. Is it not an inverter/charger combo?

https://drive.google.com/file/d/17W01Cf ... share_link

You want In0 setting to match what I described as the inverter setting.
"Inverter is disabled, unit will not provide backup function when utility power is not available"

 

[SJI Sailor]

The difference in AC vs DC amp-hours means that the batteries would power the heaters for only a very short time (minutes, if at all). Agree with Watson1987 to use In0 setting so the AC goes off in case of shore power loss.

 

[SKing]

Another thing to consider is the extra heater needed vs the additional current draw on your shore power. At our marina we have had multiple boat fires over the last 20 years and our insurance rates for the marina have become a liability. The continuous current draw from heaters in the winter and loose connections at the boat create a risk. We now monitor the cords with an infrared heat gun, and ask boaters to reduce loads.

 

[Maggie Anne]

This question made me curious so I ran a test on my boat. I have two Caframo heaters, one in the galley and one in the master berth. I also have a an 800W Extreme engine compartment heater. All three were running, the Caframo units on low heat and low fan, the Extreme doesn't have a heat control. Anyway, the current draw was 110 amps, 1400 W, battery at 12.8V. So as others have mentioned, 440 Ah would not last long even at the low heat setting.