With my last coach, we occasionally ran one or two 1500 watt electric space heaters, when connected to shore power in RV parks, to conserve use of propane. At one point I had a problem with my inverter and called an RV Electrical Systems specialist to help.
This is what he relayed to me:
This info is from the RV electrical specialist I spoke with:
"Portable electric heaters convert electricity into heat and in doing so cause a high amount of current to flow through your electric wiring in the RV. Your RV's electrical wiring system is designed to handle short duration use of high wattage appliances such as the microwave, hair dryers, and vacuums. The problem arises when a high wattage appliance is used for extended length of time (like an electric heater running overnight).
Your RV electrical system is protected by circuit breakers and GFI outlets to protect against electrical shorts, ground faults, and over current conditions.
The problem is that most circuits are protected by 15 amp circuit breakers. A 1500 watt electric heater normally pulls 12-13 amps, not enough to trip the breaker but just under its load rating. This amount of high current flowing through the wiring components for an extended length of time gets them very hot, hot enough to melt wiring insulation, electrical connectors, outlets, and destroy GFI outlets (if in the circuit). This could (and has) resulted in an electrical fire from the insulation or other electrical component overheating to the point of igniting. Your circuit breaker cannot sense the danger until it is too late and a short occurs from overheating wires touching.
If your coach is equipped with a hard wired inverter and an electric heater is operated for an extended period of time on one of the inverter supplied outlets, damage to the inverter or fire may very likely occur at some point. Last season alone, Sundance Custom RV was called due to 2 inverter fires and several more damaged from use of electric heaters.
The reason for the concern is that when shore power is supplied to the inverter, a set of relays (transfer switches) closes and the inverter becomes passive on the circuits it will supply power to, but the current still goes through the inverter relays. These relays are the "weakest link" in the circuit. Excessive, long-duration current on the circuit overheats the contacts on these relays until they either melt together (inverter damage) or overheat and ignite (inverter fire).
1) Utilize your RV's furnace for space heating
2) Check the manufacturer's label on the electric heater for the wattage of the unit. If it is rated at 1500 watts only - don't use it longer than a few minutes at a time. If it has a lower setting, 1000, or 750 watts, then use the lower settings, with caution.
3) Don't use an electric heater on a GFI protected circuit.
4) Never leave an electric heater unattended (this includes while sleeping)
5) Don't use an electric heater on an inverter supplied outlet.
6) Test your smoke detector regularly.
7) If you smell or see smoke when an electric heater is in operation, turn off the main circuit breaker (or park circuit breaker) and evacuate the coach immediately and call the fire department. Some fires occur inside walls and are not readily visible until too late."
This morning I did a test to try to find an outlet in my new coach which isn't fed through the inverter.
While connected to shore power, I shut off the 30A breaker coming from my inverter and then tested all the outlets in my coach to try to find one with power to it. It seems every outlet in my coach is fed through the 2800 watt Magnum Inverter.
I'm considering having an additional circuit installed in the coach, independent of the inverter, specifically for operating an electric space heater while connected to shore power.
What are your thoughts on this?
2011 HR Endeavor 43DFT with a 2012 Chevy Avalanche LTZ "toad".
RV manufacturers have some restrictions in their building of RVs. Sizes of circuit breakers and size of wire and types of outlets. If I plug in an appliance and it doesn't blow the circuit breaker I think I can assume that it is safe to use. Would I like the wiring to be more heavy duty? Probably, but I suspect it is OK to use the heater if it doesn't blow a breaker.
When there is an RV fire I'm just betting the fire marshal investigates the cause. If it were caused by sub standard wiring, or over fused circuit breakers I think the RV manufacturer would be in big trouble. I know they cut corners to save money but there is an electrical code to follow.
Find a different electrician. My Magnum Energy 2000w inverter has two 20a pass through circuit breakers.
Nothing wrong with the electrician that I spoke with when I had my last coach.
Fast forward to today... and my NEW coach. It has a Magnum MS Series Pure Sine Wave 2800 watt inverter/charger. But it appears that all of the many convenience outlets in my coach run passively through the inverter when I'm plugged into shore power. So using any of these outlets with an electric space heater at 1500 watts subjects the relays in the inverter to potentially high heat. Are they able to handle that for many hours on end or not? How can you know that for sure?
It sounds like the safest route is a 20amp circuit that does not run passively through the relays in the inverter.
Yes there is a "Risk" of electrical fire. If you saw how cheaply the wires are held into the receptacles, you would understand it. The wires are normally just pushed into the receptacle, and a tiny spring clip inside holds the connection tight. It works great in a lab, and never overheats in the first few months of use.
Yet 12 amps going through the connection weeks at a time can cause overheating. I only run my heater on 800 watts most of he time, so that is probably why I have not had a problem. Installing a new receptacle while using the screw connections, and perhaps upgrading to #12 wire, or even #10 wire is a good idea.
I would put one in the living area, one in the bedroom/bath area, and then you will be able to run electric heaters without worry about the wiring or receptacle overheating.
The screwed down connections very rarely overheat, while the push on connectors will and can be checked with a digital infrared point and shoot thermometer. You can also check circuit breakers too, an overheating one indicates large amount of amps going through it, or a loose wire connection. For the main breaker in your home panel, shutting off the main will stop the amperage going through it, but not shut off power to the main breaker, so extreme care must be used if you try to tighten those lugs, as they will still have power to them when the main breaker is off.
Also don't buy the "Cheapest" 68 cent receptacle, you can see the quality in the $4 one, it has more brass in the contacts, better clamp down terminals, ect. The ones installed in RV walls are built to not be installed in a electrical box. You will not find this kind in a typical hardware store, as they are not allowed in houses. You would install it much safer by using a home style box, with the receptacle inside it.
The cost difference between #12 and #10 wire is very minimal, especially because less than 30 feet of wire is involved. Yes you can use #10 wire on a 20 amp circuit breaker, even a 15 amp breaker, but not the other way around - IE #14 wire is about 1/2 the diameter and must be on a 15 amp breaker or less, while #12 must be on a 15 or 20 amp breaker. #10 max fuse size is limited to 30 amps in most cases, however exceptions allow it's use in higher amperage under certain situations. #10 will not get warm with 15 amps going through it for hours on end, that is your desire, so use it.
you guys are so fast to judge. I read about this too. it depends on the inverter and the circuity of that inverter, not in general all inverters are this way. and you ask who runs heaters with an inverter, depends on how the inverter is wired into the coach or TT.