Extension Cord

myredracer,

One has to factor the voltage in--most folks just don't bother, so they get lower or very occasionally higher wattages.

My 1500 watt oil filled is pretty much "spot on". My 1/2 size oil filled is 462 watts, instead of the rated 500.

pianotuna wrote:
So that 1500 watt heater puts out only 1,140 watts.

SoundGuy wrote:
Rarely does a so-called "1500 watt" electric heater actually draw 1500 watts, most often much less.

myredracer wrote:
I'd like to see a link from credible sources that can back that up.

I'd go remeasure each of the 1/2 dozen electric heaters I own but guess what - I don't have to "back up" anything and frankly don't care whether you believe it, or not. :p FACT is, only one of my heaters that are labeled as "1500 watt" draws anywhere near that much, ALL the rest pull much less.

The OP's original question was whether 100' of 12 gauge drawing from a 15 amp circuit would be suitable for his intended use and the answer is YES. Even assuming a maximum draw of 15 amps voltage drop over that 100' of 12 gauge would only be 4.76 volts. Heck, even if the unloaded source voltage was as low as 110 vac voltage drop over that length of 12 gauge, pulling 15 amps, would still only be a loss of 4.33% and well within a preferred maximum loss of 5%. Choosing 100' of 12 gauge is a no-brainer for the OP's intended purpose. It's also a much less costly solution than 100' of 10 gauge.

Our TT isn't that big. It is a 23' with no slide outs. Just a box. We camp in cooler weather all the time and the furnace does great to keep the temps up and comfortable in the TT. So we won't be using a supplemental heat source.

First, it looks like the TT is in the 28-30' range. If it is indeed a 1500 heater you want to run, it won't be enough in colder temps say around 40F and less. If you set the heater up in the living area, it'll be icy cold in the bedroom area and you may want an electric blanket or heavy quilt(s). We have 2KW of recessed heaters in a 29' TT and when it gets down to 40F, it starts to feel uncomfortable and at the least need to use heavy socks and blanket on legs. The heaters also run continuous in colder temps. But we have never had to use the furnace. We are never out more than a couple of days in cold weather so condensation not a big issue. We have a roof fan that runs continuous.

Recommendation:
1. Get a #10 ext. cord. What if you bought #12 and found it's not enough? Money wasted. Spend the extra $50 +/- and be done with it.
2. Get a cord that is UL rated otherwise the quality is unknown. I had the connector on two retail store extension cords melt in the driveway before I installed a 30 amp RV outlet where we park the TT. Ext. cords aren't required to be UL labeled so beware.
3. Voltage drop needs to consider the length of shore power cord, extension cord, receptacle you're plugged into to the upstream panel, and length from the panel to the main source panel. Even the length of poco wiring can be a factor. I guarantee voltage drop will be more than expected. I'd even measure it now at the recept. before buying a new cord. If it is low now, it'll only get worse.
4. Install a permanently mounted LED voltmeter inside to monitor voltage. If in an RV park, voltage can go up and down a lot over a 24 hour period.
5. If running a portable electric heater, it does have it's risks. Do not coil up it's cord or put it under a carpet. Install a dedicated receptacle from the RV's panel. Ensure that the safety clearances are maintained at all times. If it were me, I'd install a permanent fan-forced recessed heater. Portable 1500 watt heaters usually have just a #16 ga. cord. If you're on metered power, you could get a rather high electric bill one day (BTDT).
6. Consider using the furnace for heat.

In cold weather, you need to exhaust out moisture laden air to prevent condensation and the damage it can cause. At the least, you need to crack open windows/vents. This will of course mean you need more heat inside and further tax a 1500 watt heater. Or get a dehumidifier. But then will draw more power. A heater also won't circulate air, exacerbating condensation in cabinets/closets.

pianotuna wrote:
Hi,

Don't buy a premade cord. Go to an electrical wholesaler and purchase 100 feet of #10-3. Get the type rated for cold weather and UV resistant.

Tuna-man is right on the money. Most wholesalers sell to the public. Savings can be a LOT over retail. You can get quality commercial grade plugs and connectors that way too.

pianotuna wrote:
120 x 120 = 14,400

105 x 105 = 11,025

11,025 / 14,400 =~76% or a loss of 24% of wattage.

So that 1500 watt heater puts out only 1,140 watts.

On the money again. A 1500 watt heater in a TT will end up running pretty much non-stop in cold weather (BTDT) at or near 120 volts. It won't be comfortably warm inside at or near 120 volts, and if significant voltage drop, your feet will feel like ice and you will need to bundle up otherwise.

SoundGuy wrote:

pianotuna wrote:
So that 1500 watt heater puts out only 1,140 watts.

Rarely does a so-called "1500 watt" electric heater actually draw 1500 watts, most often much less. I've got a 1/2 dozen electric heaters of various types and only one comes anywhere near to drawing 1500 watts, one when running on HI draws a little over 900 watts despite the fact it's labeled as a "1500 watt" heater.

I'd like to see a link from credible sources that can back that up. I tested several heaters a few years ago and got the rated output on the labels. If they don't, they aren't complying with the applicable UL/CSA standard. I'd like to see where in the UL standard it's okay not to provide the rated output. If the output is a lot less than the label, at 105 volts, they will put out waaay less than 1500 watts and be next to useless.

Who understands voltage drop? Raise you hand.

rhagfo wrote:
Running a 1500 watt heater on a 100’ 12 gauge extension cord is asking for problems.

Nonsense, here in Ontario the campsite runs are quite long and countless times back when we owned a popup I'd often run 100' of 12 gauge and power an electric heater in the camper. Obviously the closer the source unloaded voltage is to a nominal 120 vac the better but because the heater is a resistance load it won't really care whether it's seeing 115 vac under load or 105 vac under load.

If no AC, portable heater, or microwave, then a good quality 12 ga. is suitable.
If you use the microwave, it might struggle with low voltage or amperage. You can definitely tell when that happens.
12 ga. is about $100
10 ga. is about $150. Both are extension cords with 15 Amp ends at Lowe’s.
Me, I’d go with 10 ga. because I could repurpose it later.

Seems like a bunch of confusion about heating and AC. We will only is the furnace not a 1500 watt heater. AC is not even a consideration as out highs are fairly hitting mit to upper 60's. We also have a gen set if we need any big loads we will hook that up and get the 30 ampswe need. Hope this clears some things up.

trailer_newbe wrote:
Go with 10 gauge not 12. The 12 will overheat at the plug when running the AC

If you mean air conditioner, he's not going to run it.

Go with 10 gauge not 12. The 12 will overheat at the plug when running the AC