Electric Heat

[iustasail]

Does anyone have any experience with electric heat for defrost etc.? Converting to a 6 and I expect to use headers(for cost and performance), no manifolds = no heat, no heat = fogy windows
even in Texas.

[BenI]

This isnt a big help ,but ill post it anyway. In florida I removed the heat exchangers on my VW bug. I added an auxilarary 12v socket (cig. lighter) under my dash, and hooked up a cheap 12v fan driven heater. It was small-hard to get a lot of current out of the stock alternator-and cheap but worked well enough. It also had a magnetic base so i attached it to the metal under the dash just during the winter.

I found the stock fan defrosted well, if you dont mind the cold air. Also, RainX makes a defogger that I applied to the windshield and thought it worked well.

Good Luck! You can always wear layers and pack a towel to 'defrost' the windows-itd be worth it if it meant driving a 6!

[Dave at Pelican Parts]

The numbers work out that you need a *lot* of power to make much in the way of heat. You'll never get enough heat to warm up the inside of the cockpit out of the 914's electrical system. You might get enough to clear off the windshield.

At least, that was the conclusion that some people who know their electricity (and that ain't me!) have come to.

--DD

[BenI]

Power = current * voltage

voltage is easy--12 for these cars
current can be approximated by the rating of your alternator. I dont know about the 914, but say its around 75amps.

Then the total power you can get out is 900watts. But then you have to account for other current drains, such as lights, engine, stereo, wipers...I once heard a good approximation is that these draw 40% of the available current. So 60% of 900 is 540watts.

Think about a hair dryer-theyre around 1600watts-can you imagine trying to heat the cabin with 1/3 of that?

The point is youre not going to warm up the cabin, but having warm air blown at you does make you less cold.

[iustasail]

Thanks for the input. It's been a long time since I was sleeping through thermodynamics class and the only insight I had on this topic was one of those "I knew this guy who had a friend who's neighbor had a dog that rode in the back of his 914 that had electric heat that was so hot it'd give you a tan"

[Germain]

I still dont buy the I cant heat my car unless I use heat exchangers. Now to heat the entire cabin on a 20 degree day is not what I mean, I mean heating on a 60 degree day. As for the 1600 watt hair dryer, well thats a 120V not 12V. Soo that makes\

1600 = X * 120
which makes X = 13.3 Amps. Accoring to your equation.
Even that sounds high.

That same hair dryer on a 12V would give

12V * 13.3Amps = 159.6 watts

Thats 1/4 of our available power, so yes now I can see heating the entire cabin on a 60 degree day.

Now as for how to heat the car with the power available I havn't figured out yet. but you can bet on me designing something. I live in Michigan, so days that are warm enough for no heat at all are only 2-3 months a year. I'll be posting my design up here when I get it done.

[BenI]

Why dont you run an aux oil cooler right into the cabin! You could even feed the lines through the seats and voila! heated seats just like a fancy car! Im just full of good ideas.

[BenI]

This goes with my serious post a few posts above-with the electric heater in my bug, the cabin would warm up, but it would take awhile--about 20 minutes to feel a difference. When i said you wont heat up the cabin, I should have said what i meant-you wont heat it up in the short time the heat exchangers will. My electric heater definatly worked, and im talking about in freezing temps.

[oredith]

i've thought about running the external oil cooler to the freshair intake.. so the fan can blew "sorta" warm air into the cabin, and cool the oil at the same time..

there's minor problems like needing the heat most when the car is coldest, etc though.. not to mention how messy it'd be if the cooler blew like the last one did...

Jeff

[Tim Polzin]

Volts times amps equal power, so..

1600 watts (hair dryer) at 120 volts equa; 13.3 amps

1600 watts at 12 volts equals 133.3 amps.

[Jim Osborn]

Get an air cooled VW magazine they have a lot of products and ideas on how to heat these retched things.

[John Rogers]

Tim, I thought the square root of 3 figured into power when you were talking three phase AC current? Or is the hair dryer single phase?

[This message has been edited by john rogers (edited 03-08-2000).]

[Tim Polzin]

You'll never let me live down the comments on the bugs, will you John :->. Anyway, those figures work on DC power. For AC, there is something about RMS values, but I must have slept through the rest of the high school physics course.

[This message has been edited by Tim Polzin (edited 03-08-2000).]

[Dave at Pelican Parts]

Germain, I think you've got the interpretation backwards. The wattage translates, more or less, into the amount of heat generated. So, to put out as much heat as a hair dryer, you'd have to run 133 amps (or maybe 133/root(2) or some such) to your heater. That assumes that you can't heat the air more efficiently than a hair dryer, which I'm pretty sure you can. Still, you'll need a heck of a lot of current to get even a modest amount of heat.

A friend of mine had an idea for his Six conversion (in progress). He thought maybe he could hook a small oil cooler up as a heater core in the engine bay, down by the inlet for the stock heater channel. A flapper valve could control if the air going through the cooler got dumped out, or pushed into the channel. You'd need to rig up some shrouding and some such, and have a separate fan switch. But it just might work!

Another friend with a Six conversion (also in progress) has already made a similar box that lives in the rear passenger fender, right by where the battery used to go.

--DD

[NOTRIGHT]

HAS ANYONE THOUGHT ABOUT A 12 VOLT POWER INVERTER AND RUNNING A HEATER OFF THAT

[JTB]

Tim was right - it does take 133.33 amps for a 1600 watt hair dryer to operate on 12 volts. To make a hair dryer work, you would need a power inverter, but the power inverter would still need 133.33 amps to give you 1600 watts at 120 volts. Actually a little more since it is not entirely efficent.

Power out (1600 watts) = Power in (1600 watts) - efficency losses (?)

BTW - 120 volt power in your house is 2 phase, not 3. Your welder might be wired to 3 phase, but nothing else.

Don't forget, the fan motor in a hair dryer takes a lot of power. The actual heating element is therefore less than 1600 watts. You would still need to move the air around the car somewhere, but if you were willing to move it slower than a hair dryer, you could get a fan that took less power.

[Germain]

*grumble*
Soon, very soon Ill have electic heat.
*grumble*

[Tim Polzin]

Another solution to heat. http://www.pelicanparts.com/ultimate/Forum12/HTML/000721.html

[Dave at Pelican Parts]

Pretty neat idea--IF you can figure out how to hook it up! I predict that you'd lose a good bit of trunk space at the very least...

--DD

[iustasail]

cool! I can add a gas leak to the front to go along with the fuel leak in the back; maybe the D-jet is just supposed to smell and it's not really a leak