RoyB wrote:
I like to use the oil filled radiator looking 1500 watt heaters here... They do not have the open flame or red hot flame core or make any noise except CLICK every now and then...
I use the low profile model which is perfect to sit one of those O2-COOL fans behind it if you want to move the air around some.
We also like to run a separate extension cord into our trailer forom the campground 20A Pedestal service to run our our portable 1500 Watt heater. This does not take away from the the 30A Pedestal service we are using...
Roy Ken
^^^^
I winter in Florida with 1 small dog and two cats. This kind seems to be the safest if tipped and it works like a champ.
It stores nicely under the dinette for travel.
travelnutz wrote:
myredracer,
The total voltage drop in the 6' long 16 gauge power cord (13 amp load rating) stranded copper wire with 1500 watts (12.5 amps) at 120 volts of AC going to the electric heater is only 6/10 of 1 volt. Meaning the heater is getting 119.4 volts of the 120 volts at the outlet. Negligible loss and means the 1500 watts would only drop to 1492.5 watts delivered to the heater's element due to voltage drop! The 16 gauge heater wire is not the issue at all for not getting a 1500 watts reading as claimed of the watts being consumed.
Further, even assuming there's 120 volts actually measured at the RV's entry circuit breaker box from shore power and then having a run of 25' of 14 gauge copper wire to the outlet the heater is plugged into, there still would only be a 1.6 volt drop at the outlet the actual heater wire is plugged into and with the heater turned on high selection. The 120 volts at the breaker would still measure 118.4 volts being delivered to the heater 16 gauge power cord. Check the voltage drop charts for yourself.
These 2 things are not the reason for the electric heater actually only drawing a measured 1300 or 1400 watts rather than the 1500 watts claimed by the manufacturer. Therefore, such heater will not deliver 5120 BTU's nor will it measure to be drawing 12.5 amps either.
Conversely, I can assure you that every 100 watt incandescent light bulb I've ever checked actually draws 100 watts just like is printed on the bulb but never had a claimed 1500 watt electric heater actually draw even as much as 1400 watts or even close to 12 amps of 120 volt AC.
Got my Mythbusters hat out and did a test on two 1500 watt ceramic cube heaters we have at home.
In the US, portable space heaters like these must comply with UL standard 1278 which requires a heater's rated output (as shown on it's label) to be at the voltage shown on the heater's label which for both heaters is 120 volts. Power input cannot be higher than 105 percent of it's rating (1575 watts for a 1500 watt heater). This standard has over 100 pages of very stringent requirements they must meet to become certified. In Canada, these heaters must comply with CSA standard 22.2 no. 46. I couldn't find a free copy of the Canadian standard online, but I would expect it to have the same stringent requirements as UL 1278, and wouldn't be surprised if the requirements are even higher. I am not using a high accuracy voltmeter or ammeter but they do correspond closely with two other voltmeters & ammeters I have.
The 1st heater is branded Comfort Zone and is labelled UL 1278. At 117.0 volts the heater draws 12.26 amps which is 1434 watts. To find the heater's wattage rating at 120 volts, it would be (120/117) x (120/117) x 1434 = 1508 watts. By UL 1278, power input is measured at the cord's plug. I did measure the voltage drop in the cord anyway and it was 0.8 volts.
The 2nd heater is branded Lancaster and it's label says it complies with CSA 22.2 no. 46. At 120.6 volts it draws 12.6 amps which is 1520 watts. At 120 volts, the power (using above formula) would be 1505 watts. The second test was on a different day hence the different voltage. (Our nextdoor neighbor has a manufacturing shop with 3-phase power and I suspect he is dragging the voltage down.)
As far as I can see, heaters should draw close to their listed rating at the listed voltage. There is also no benefit to a manufacturer reducing a heater's output since UL 1278 requires testing voltage to be adjusted until it produces the rating on it's label. It would be interesting to see someone try this on other heater types like say an oil-filled type. BTW, if you have a heater, it must be UL or CSA listed (on it's label) and if not, don't use it.
As a FWIW side note, Nichrome heating wire resistance goes up as it's temp. increases as the 2nd photo shows. I found that the initial current draw of the Comfort Zone heater was around a peak of 20 +/- amps during the first 4-5 seconds after being turned on. It took around 15 seconds or so before it reached a steady state of 12.26 amps. The second photo shows it's current at 19.89 amps (it changed too quickly to get a pic at the peak). This won't trip a circuit breaker because the duration is so short.
