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RVelectricity™ — Electric space heater power usage and warnings

Hi Mike,
RV newby here, with a (used) 2017 Pleasure-Way Sprinter. It gets icy cold inside at night, due to lack of insulation in walls and floors, and like many old folks, we “run cold.” The built-in propane heater is adequate, but its roaring noise and frequent cycling on and off wakes me up many times in the night.

I’d like to be able to plug in a very small, low-wattage space heater to maintain a steadier, quieter warmth. Keeping the rig at 60 inside would be just ducky! Even 55 would probably be good enough.

My question is two-pronged (ha ha), having to do with wiring.

1. On shore power, how can we tell if it’s OK to plug in a low-watt space heater without overloading or damaging the wiring in the rig? Or blowing a fuse, and having to try to track that down?  (Needless to say I’m very limited in my understanding of electrical systems.)

2. When boondocking or dry camping: We have 280 watts of solar on the roof, and a big battery, and there’s not much demand for that power. The refrigerator can run (quietly, ahhh) on propane.

I don’t have a heater picked out yet. I had purchased a little “desktop” heater that would run on 375 watts, but it was radiant, and I wanted a space heater that would warm the air, too—not just directly in its path. I’m hoping to be able to use an electric heater on 30-amp shore power OR off battery power when dry camped. We have 270 watts of solar on the roof. I understand it’s hard to find out much about wiring in Pleasure Way RV’s, and as I probably told you, my brain doesn’t have connections for power systems. Is there a way I can tell whether I’m going to blow a fuse, or damage the wiring, by plugging in a desktop-type space heater?

Thanks for considering my question! —Jody


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Dear Jody,
The first thing to consider is the ability of a 375-watt space heater to actually raise the temperature in your Sprinter RV. I doubt is will raise the internal temperature in your RV by more than a few degrees. But if you can localize the heat to just your sleeping area with curtains, it’s worth a try.

The problem with heating RVs of all types is they typically have very limited insulation with low R-values. That’s because every square inch inside of an RV is like gold, so adding in the 4 to 6 inches of insulation like you might have in your house is not practical. Plus, all the extra weight is another issue since RVs are always near their maximum weight limits.

So, heat them we must…

While 375 watts is a very small electric heater, if you’re running on battery power it will require around 32 amperes of current. To calculate this we simply need to divide the Watts (P) by the Volts (V) to calculate the Amps (I). So 375 watts / 12 volts = 31.25 amps, which I’ll round up to 32 amperes.

If you have a 100 amp-hr AGM battery, that you shouldn’t discharge below 50% State of Charge (SoC), that’s not even 2 hours of run time (100 amp-hrs / 32 amps = 1.56 hrs). So that’s 90 minutes of available running time before you run out of battery power with your stock AGM or FLA battery.

Lithium batteries to the rescue (maybe)…

However, lithium battery technology is helpful if you upgrade. A single 100 amp-hr lithium battery can be discharged down to 0% SoC, so that’s 3 hours of run time. To calculate we simply divide amp-hrs by amps to find time in hours. So 100 amp-hrs / 32 amps= 3 hrs.

If you put in 200 amp-hrs of lithium batteries, that will be 6 hours of run time for that little 375-watt heater, after which time your batteries will be flat at 0% SoC. But before you spend thousands of dollars to upgrade your batteries to lithium, the first thing you should do is test this 375-watt space heater on shore power on a cold night and see if the added temperature is acceptable. I’m guessing it won’t be, but there may be a solution.


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What about wiring damage?

If you do run a portable electric heater in your RV, I recommend you use the low power setting. So if it’s rated for 1,500/750-watts or 1,200/600-watts, set it to 750 or 600 watts. That’s because the stab-style outlets used in RVs can loosen up from road vibration and heating cycles. And every loose electrical connection has the potential for overheating under high current loads.

Note that a 1,500-watt setting on a space heater is 12.5 amps continuous (1,500 watts / 120 volts = 12.5 amps) while a 600 watt setting is only 6.25 amps (600 watts / 120 volts = 6.25 amps). Even though these stab-style outlets are rated for 15 amps, that’s only if they’re perfectly installed and properly maintained.

But no matter what kind and power space heaters you use, always inspect the power outlets for any signs of overheating which will show up as discoloration or melting. If you notice any issues at all, time to replace the outlet and inspect the power plug for any signs of damage as well.

Baby it’s cold outside…

If your existing RV furnace can’t keep up with the cold, and you don’t have enough electricity to power a portable electric heater, there is a supplemental heat source that’s advertised as safe and efficient. You can buy a propane catalytic heater anywhere, but are they safe, and just how much heat do they make?

Mr. Heater Buddy, with caveats….

While I’ve not actually tested one of these, I admit to being paranoid about any potential carbon monoxide source. But a lot of RVers think these are a great solution. And, indeed, they do provide a lot more heating than any portable electric heater can provide, especially from battery power.

For example,  a propane heater with a 9,000 BTU output is equivalent to a 2,600-watt electric heater. That’s because 1 BTU is equal to 0.293 watts, so simply calculate 9,000 x 0.293 = 2,630 watts. That’s 7 times the amount of heating that your little 375-watt heater can provide.

I’m not sure about these, just yet…

All the inside rated propane heaters I’ve looked at casually do have some sort of carbon monoxide and tip-over shutoff. However, there’s certainly a much higher fire potential if you’re not careful.

So while this may be your only option for supplemental heat in the dead of winter, I’m not recommending them just yet until I can do an in-depth safety study.

Let’s play safe out there….

Send your questions to me at my new RVelectricity forum here.

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.

For information on how to support RVelectricity and No~Shock~Zone articles, seminars and videos, please click the I Like Mike Campaign.

##RVT1035

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Tommy Molnar
3 days ago

I converted a 10×12 Bully Barn into a shop. It gets cold here in northern NV so I was looking for a way to heat it. I tried all kinds of heating methods and finally landed on small electric heater from Wally, set on the lowest setting. It keeps the shop easily livable. But, when I tried my two tank Heater Buddy, I quickly found it dangerous. I failed to crack a window (because I thought that would just keep the shop from warming). When I came back after an hour or two to see how it worked I got an immediate instant headache and felt nauseous. It had also turned off, but not before it filled my shop with CO2. So, I haven’t used it since. Maybe if I’d cracked a window things would have been different, but now I’m just too skeptical. We use the furnace in our trailer for all our heating needs. Period.

John Koenig
5 days ago

I picked up a Big Buddy heater a few years ago when I was going to be in a campground that had only 30A service with temps dropping to single digits overnight (I was in a 39′ Super-C diesel puller). The Big Buddy can use one OR two, one pound bottles of propane and, put out a LOT of heat from its’ big catalytic pad. On high setting, the one pound bottles would last less than six hours. In the weeks that I used it, my CO / propane detector never went off. In a small motorhome, I expect you’d be well served by the smallest Buddy catalytic heater (which is a small attachment to a standard one pound bottle). A set up like this is lightweight and compact and shouldn’t take up much space in your RV. Pick one up at a Walmart along with a bottle or two of propane. If you’re not happy, you should be able to return the Buddy Heater for a refund. The Big Buddy heater was MUCH quieter than the heater I had in my first RV (a 2010 17′ Casita Spirit Deluxe Travel Trailer). I hope this helps.

Michael Galvin, PhD
5 days ago

An electric Pelonis HT-1003 1200/1500W heater has been great heating our Class C for 5 years. Always on shore power on 1200W. Need to add the furnace when outside temps below about 40.

Suru
5 days ago

We have a small Mr. Buddy that we will use while dry camping. We always crack a window and never use it at night while sleeping. It will heat a small area on high for approximately 3 hours per bottle. It’s better than nothing. If we have electricity we use a small space heater that works much better than the Mr. Buddy.

LARRY M
5 days ago

Mike seems to me that the simplest saulation for this problem is to add the UL Listed RV Comfort Systems CheepHeat Hybrid Gas/Electric kit. Which give you the option to switch your furnace back and forth between gas or electric at the flip of a switch, just like the hot water heaters.

Mike Sokol
5 days ago
Reply to  LARRY M

That doesn’t work when you’re boondocking on battery power.

Last edited 5 days ago by Mike Sokol
Gene Bjerke
5 days ago

My experience with the Mr. Heater Buddy is that a one-pound propane tank will run it about five hours on the low setting. Not quite all night.

Thomas D
5 days ago

So glad you mentioned the stab type outlets found in rv’s JUNK. The wires kind of slide into a sharp grove. No way on earth does that make a good connection. Anyone using an electric heater should be aware of that and sleep with one eye and both ears open. BIG FIRE HAZARD.

Ron Seidl P.E.
5 days ago

I put in a separate receptacle near my power center wired to a new 15 amp breaker that I put in a spare slot. I made sure that I used the right wire and installed on the screw terminals not the push in connection. I recommend that if you intend to use any high wattage appliance in an RV, remove that receptacle and re-wire it to use the screw terminal connection.

Marc Stauffer
5 days ago

When plugged into shore power I have a small 120v cadet wall heater built into the storage area below the bench seat and hardwired into the electrical system on a 20 amp circuit. Works great! When boondocking it’s the propane furnace or my Dickenson marine woodstove.

Michael Roach
5 days ago

I have used the Big Buddy Heater in my 22′ TT and it will run me out. I’ve only used it on low most of the time, however you do need to be extra careful to not burn your house down ! That being said I could never trust it to leave it on while sleeping, plus the condensation problem gets pretty bad. I ended up removing my propane furnace and installing a diesel heater in that space which I can run on a low setting which is much quieter than the propane furnace was. As a bonus it’s a fuel miser too.

Last edited 5 days ago by Michael Roach
Richard
5 days ago

It’s ironic that the 2 Canadian builders of high-end small motorhomes, PleasureWay and Leisure Travel, make rigs that are generally ill-equipped for winter, yet the Florida-based competition, Coach House, makes their rigs 4-season (within limits). Southern California produces another 4-season capable rig from Lazy Daze. If cold-weather is her thing, she needs to sell this rig and move on to a better-insulated unit.

Dan
5 days ago

I used to use catalytic propane heaters in my service trucks and they work great, producing plenty of heat in a short time. The one drawback is that propane releases a lot of water when it burns and it will fog the windows in a short time. After a while that fog turns to frost. If you can live with frost on the inside of your windows, it works great. Just remember that it’s almost like having an open flame. I was not brave enough to drive my trucks with a heater burning, but that shouldn’t be a problem camping in one spot.

Bob
5 days ago

I agree that using any type of propane heater indoors will produce carbon monoxide.Using these without some sort of fresh air source is dangerous no matter what type, flame or catalytic, heater is used. An incoming air source and a vent to allow the CO to escape is necessary.
Having one running for 6-8 hours while sleeping could end up with a dangerous situation.

p z
5 days ago
Reply to  Bob

Don’t forget that the propane furnace is heating your underside storage wet bays in some rvs. without that heating in below freezing conditions could spell trouble if only heating inside rv using electric heater.

Tommy Molnar
3 days ago
Reply to  p z

Excellent point.