Electric Heater And Inverter Sizing

[ronstang94]

I am going to install an electric heater in my 94 mustang. I have already deleted the heater tubes, hoses, and core. The car has a PA Performance alternator that makes more than 130 amps, and a red top Optima. The heater will only be used while the engine is running and the main purpose of the heater will be to quickly defrost the windshield on cold winter mornings. Other benefits include: being warm on my way to work, less items under the hood that get in the way and look bad, and finally keep my wife and two small girls warm if I ever manage to get my mustang car show worthy again.

I have a cheap "comfort zone" ceramic heater that I am going to harvest the heating element out of. It makes a ton of heat. Now I just need to figure out how large of an inverter I need. The problem is that I am not sure if the 1500 watt rating on the heater is peak power or constant power. See the links below for more information on the heater.

Ceramic Heater
CZ442 Ceramic Electric Portable Fan-Forced Heater, Black | Comfort zone
http://comfortzone-us.com/temp/CZ442_manual.pdf

I have been looking at the Cobra Inverters seen below. The 800 watt inverter is listed as 800 watts continuous and 1600 watts peak power. If the heater is 1500 watts peak and 800 watts or less continuous power then I think this would be a great set up. The 800 watt inverter is pretty cheap and I don't have any worries about it overworking my alternator or battery causing premature failure of any of the components.

However, if the heater is 1500 watts continuous power then I assume I would need the 1500 watt inverter listed as 1500 watts continuous power and 3000 watt peak power. The 1500 watt inverter is quite a bit more expensive. It is also quite a bit larger and might be harder to find a place to install it. I would also be worried that my alternator and battery could not support that large of an inverter.

Inverters
Cobra | Professional Grade Power inverters & Supplies

Any thoughts please. Thanks!

Ron

 

[jozsefsz]

Hey Ron,

Resistive type devices do not require surge watts. Devices and appliances with an electric motor in them require an additional requirement of watts to “start” them. So the concept of peak / continuous wattage doesn't apply as it would to a refrigerator or sump pump.

So, the 1500W rated heater is going to produce 1500W of heat continuously, and there is no 'surge' voltage (peak power) vs. continuous power to be concerned with. You'll want an inverter capable of putting out 1500W continuously, plus any fan wattage (and associated surge wattage). So the 1500W unit may actually not be enough. Note that the 1500W inverter is not going to suck up more amperage than the 800W unit by itself, how much it uses is dependent on the load you apply to it (your heater). It just won't trip constantly and overheat like the 800W inverter.

I'm not sure what the benefit of doing this is... you're removing a few pounds of heater core (and beneficial engine cooling) and replacing it with a very large and likely ineffective (and expensive) power drain. Keep in mind that 1500W coming from the alternator (where you'll substantially shorten its life) is going to require at least 2 hp parasitic loss (greater with inefficiencies). Then the inverter and heater assemblies themselves will probably weight more than the core and hoses.

I realize no one likes a heater core (or replacing it), but if you want heat even sporadically, it's the most effective and efficient way of doing things (using waste heat from the engine). Otherwise the manufacturers would have done things differently.

 

[ronstang94]

Well that sucks... Thank you though.. I didn't understand what kind of devices required additional power to start up and which ones required just a constant level of power.

This is not about weight reduction. There are several reasons why I thought this would be a good idea. First, I wanted to do this to get instant heat to defrost the windshield. It takes about 10 minutes for the engine to produce enough heat to defrost the windshield. An electric heater is almost instant. I don't have a garage to leave the car running inside of to warm up, and I would be very worried that my car would get stolen if I left it running in the driveway. I live in Phoenix, so it doesn't get very cold, but I need to be able to see out of the windshield... Second, I have already replaced the heater core before and it's a lot of work. I don't ever want to have to do it again... Third, I have done a lot of work to try to clean up the engine bay and remove any and all unnecessary clutter. Two reasons for this: it's easier to work on with less stuff in the way, and it looks good. I like everything to be clean and carshow worthy. Plus, the whole reason the core is broken again is because I had to remove the rubber heater core hoses to work on something and I had a really hard time trying to get the hoses off and out of the way, and I ended up snapping one of the tubes off the heater core... Lastly, the metal heater tubes that run across the intake manifold seem to have destroyed my engine wiring harness from the additional heat they put off. I know this sounds crazy, since the wiring harness already sits on top of a very hot engine. However, I think this because I had to replace almost all of the wires on the passenger side of my engine wiring harness, the ones that run to the fuel injectors, TPS, IAC, EGR, and temp sensor. The wires were bare in several places with the plastic coating crumbling off all over. The other half of the harness that runs to the fuel injectors on the drivers side of the engine were completely fine, so I removed the heater tubes.

Anyways, I think I am going to replace the heater core, but try to piggy back the electric heater on it. If I put power to only half the electric heater, I will only need 750 watts. It should still make pretty decent heat and the 800 watt inverter will do the trick. Then I can run rubber hoses around the side of the valve cover and just above the header to the heater core if I need more heat. I might even just run these hoses in the heart of winter and cap everything the rest of the year. Hopefully this will work well and look good.

Thoughts?

Thanks

 

[jozsefsz]

Sounds like a plan. Be sure to try out the heater inside the car on a nice cold morning (perhaps even before investing in the inverter just plugging it into an extension cord). I've not found that an electric heater in a cold room really puts out enough heat for quite a while. Luckily you're in Phoenix so hopefully your idea of cold isn't as ridiculous as mine in Cleveland.

I know there's nothing attractive about heater hoses and there's nothing good in replacing a heater core, I just consider them a necessary evil to stay warm around here. You're right you could just run the hoses seasonally if they mess up your engine-bay feng-shui. I'd just dress them up a bit with a braided hose kit myself. And install a nice remote-start for a toasty warm car before you even step outside without the fear of theft (it's how we roll around here).