Acceptable voltage drops with heater?

I finished installing the heater in the boat yesterday and I was curious what you you guys thought were acceptable voltage drops.

The heater pulls 16 amps max. When I flip the heater on High, the voltage drops about 1.2 volts, as witnessed on perfect pass and the voltmeter. Is this an acceptable amount?

I have two 10 gauge wires that supply a fuse block that runs everything in the dash. I feel that I should have been been able to add the heater on to this circuit with out over taxing the wires, as it only runs the gauges and everything else with relatively low loads from the dash.

Thanks,
Eric

If it was a good connection there would be no noticeable voltage drop. With all the electronic stuff I had running, I wound up pulling another wire and running things like PP off a relay to lighten the load, and give the important electronics a full +- 14 volts.

So what is the voltage after turning the heater on, with the engine on and off?

The voltage was about 14 with the heater off and the engine running, and then drops to 12.8 or so with the engine running. I hadn't checked it with the engine off.

I pulled my heater off the ignition circuit and I get major voltage drop. At least 2 volts on high. If the boat is cold and the heater is on when we start up the PP cuts in and out until the revs come up a bit. I had not considered running a relay and a fresh line from the battery but that is a good idea.

Please check with a volt meter at the battery then report voltage drop. May be the power/ground is connected to the same as the PP?


How long are your wire runs? assuming run of less than 10ft then you should have 10-12 ga wire to the heater itself.

The voltage at 14 is alternator output and 12.8 is your battery without charge from the alternator. It sounds like you are measuring at idle and the load is kicking to hard for the alternator. If you get this at higher RPM (1500+) you must have voltage drop on the power lines.

I would pull another pair of mains for your accessories including your heater, go #8's or bigger on a 50A breaker. Don't forget the to pull a ground too.

Do as Mike suggests and pull a new wire for at least the heater. PP needs lots of juice to work properly, or it will beep at you and reboot.

Thanks guys for all your input...It's a sanger V215 and the runs are about 12 ft from the battery to the dash. I am gonna re do the mains, especially since I have some extra #2 laying around. I should probably run it through a relay as well so i don't have all that power running through the dash switch. The heater itself has #16. The voltage drop was consistent throughout all rpm ranges.

Remember to make the ground at least as good as the power line.

^ Agreed. At least someone remembered to mention it

A second accessory pannel is the way to go. I like these, http://bluesea.com/products/5026 , they are easy, positive, negitive buses with individual fuses. You still want a main fuse or breaker with in a foot of the battery though. Do the find your amp draw, do the math, make sure you run the right size wire.

If you want to skip the pannel just run the heater staight off the battery, no reason the screw with the dash wiring, you have a lot of sensitive gauges up their, and you never really know whats going to effect what.