Full-time portable electric heater advice?

[70winnie]

Sent: 10/11/2004 9:15 PM

I'm thinking of buying a portable electric heater to keep in my Winnie over the winter.  We'll use it about one day a week as a temporary cabin, and I'd like it to be warm when we arrive and also warm enough to keep the pipes from freezing while we're away.

I'm a bit concerned about leaving a heater on while I'm away, and want to be certain to buy a model that's safe enough to leave running at about 50 degrees 24/7 (and of course warmer when I'm present).

I've heard that the electric radiator-style models (with a self-contained oil system) are the safest, but don't know if that's true.

Anyone have any real-world expertise or experience with leaving a portable heater on all the time (in your Winnie or anywhere else)?  If so, please share your thoughts.

[HeavyHaulTrucker]

Sent: 10/12/2004 12:56 AM

The oil-immersion heaters are your best bet for what you want to do.  They look like an old steam-type heat radiator, but operate on electricity by heating the oil & circulating it by convection throughout the radiator fins.  It is completely sealed, and they have a thermostat; best of all, if they fall over, they have a safety switch that turns them off automatically.

John

[Sea Hag]

Sent: 10/12/2004 9:03 AM

I Use an oil filled radiator type electric heater in mine , to suppliment the furnace , and use the electric alone while sleeping . The main reason I use this type is for the wattage setting . I use the 600 Watt - low setting after it has warmen the oil up . You don't want to draw the max amps , coach wireing will heat up .  I use mine in the winter once in a while but I winterize the water system and bring the water I need in portable containers . Sea Hag 

[mightybooboo]

Sent: 10/12/2004 6:46 PM

Those little cube heaters, 8x6x4 inches really throw out a lot of heat in a small size, 30-40 bucks.
BooBoo 

[Daved27c]

Sent: 10/13/2004 12:54 AM

Andrew;

We used an oil filled radiator to heat our basement playroom for a couple of years. While it was not as extreme as being the sole heat source for a Winne, it did a nice job. I did not have to worry about about overloading the circuit, as I wired the house, but I agree with Sea Hag about overloading the electrical circuits in the Winne. I think it is a good way to go, but knowing Northeast winters I think I would drain the tanks(and the lines) if possible.

Dave   

[70winnie]

Sent: 10/16/2004 2:49 PM

I've decided to buy an "in-wall" electric heater instead of a portable.  They're designed to be used like a regular heat source, on all the time.  The one I chose is pretty small, 1500W at 120V, claims to be for 150 square feet max (which is roughly what the inside of my Winnie is).  Cost about $70.  After I get it installed and use it this winter, I'll try to remember to report back on its performance.

[Sea Hag]

Sent: 10/19/2004 11:41 AM

1500 watts is just past the maximium safe rating of 1480 watts for a new 15amp circuit . I would run new #12  AC wireing  for it from the converter and maybe a seperate dedicated breaker . Sea Hag 

[Oz]

Sent: 10/19/2004 11:16 PM

I'm using new #10 for all of my 120V wiring just to be on the very-very-safe side.  I added a 70A breakerbox and ordered a 50A power cord (#6/3+g) for a supply line, even though I'll prolly never use anywhere close to that (even after I get an A/C).  I also plan to put every appliance (incl. the heater) on its own circuit, since there are 8 slots in the box.

But Sea Hag, I'm under the impression that 1500W / 120V = 12.5A , and that 1800W is the max that a 15A circuit could handle @ 120V.  Surprisingly, the heater doesn't list A in its specifications, only V and W.  I was going to protect the circuit with a 15A breaker.  I guess if the 15A keeps tripping, I'll have to upgrade to 20A.

Has my (limited) training taught me the wrong formula?  Hm?

[Sea Hag]

Sent: 10/22/2004 9:43 AM

No you are correct with that fromula 1800 watts is the Maximum that a 15 amp circuit can handle . but you should deduct 20% of the wattage to get what they call Safe Rateing .   The old wiring will not transfer heat back to the breaker as well as new wireing . the life expectancy is estimated at 30 years .  If I run my electric heater on high setting the recpticle gets quite warm .
   I wouln't suggest running # 10 between the pannel and the recpticles as the recpticle could burn before the breaker will trip due to the Over size  of the #10 wire I would use # 12 Max . Sea Hag 

[denisondc]

Sent: 10/22/2004 1:49 PM

Another reason to use #12 awg in place of #10 to the outlets, is that the terminals on the 15amp and 20amp duplex outlets arent sized to deal with the bending strength of #10 wire.   When you push the outlet back into the box, you definitely get bending loads.
  #12 wire is rated at 20 amperes continuous, #14 rated at 15 amps.  If you wanted to be thorough, use of UF housewire, while more of a chore when stripping insulation, will give you more resistance to the effects of being wet.  Thats why it is rated for Underground Feed.   
   Outlets age and weaken, just like anything else - me for instance-.  I should probably replace all three of the outlets in my winny, just to avoid trouble.   

[70winnie]

Sent: 10/23/2004 2:24 PM

Ack!  I just finished the wiring yesterday and used all #10.  Now I'm wondering if I should rip it out and replace it with #12 !?!?  Fortunately the wire is easy enough to access (it only runs through the wall in one place, and my wall panels are screwed on instead of glued).

I should mention that all of the recepticles are brand-new 20A GFI.  Isn't it correct that those would trip if there was an overload as well as if there was a short?  In other words, don't those eliminate the problem of the outlet burning up before the breaker in the box trips?

Re: bending loads, the hot and neutral wires are fed straight into slots in the back of the outlet and therefore not bent at all.  Only ground is bent, and that's a thinner wire (I think #12). Also, I've been careful not to put much excess wire in the boxes so there isn't any severe bending going on anywhere, really.  Definitely not as severe as a wire bent around a terminal screw.

Also, wouldn't the extra thickness of the #10 compensate for any load from the bend?  So wouldn't it therefore be able to carry at least as much current as the #12?


Oh I forgot to mention the electric heater is connected directly to the wiring with wire nuts, so there's no outlet to overheat there.

[denisondc]

Sent: 10/23/2004 4:23 PM

If you have the wires akready in place I would leave them there.
The bending load comes when you have the wires end inserted into the outlet, and you push the outlet back into the box and screw it into place. Its the physical force on the outlet asembly itself. If you didnt hear any cracking, you are probably okay.
The GFI outlets are good, IF.... you dont have nuisance tripping too often. This can be a problem in motorhomes, mostly with a GFI circuit breaker in the breaker box. But a GFI outlet probably wont save you from overload per se, unless it is also an -Overcurrent Circuit Protector outlet-. Which I havent heard of. Thats the function of the circuit breaker inside the breaker box. I dont know that any GFI outlets have that overcurrent protection, those in my house dont. The purpose of the ground fault interrupter is only to shut down the circuit when there is a difference between the current in the black wire, versus the current in the white wire. This would only happen if there was a fault in the circuitry. - such as a slight leakage to ground in an appliance, or if you got across an exposed wire yourself. I think they are made to trip if the current differential is over 5 milliamps. So if you were running an 1200 watt toaster oven, the GFI would shut the outlet off when there was 10.000 amps at one prong of the microwave plug, but 10.006 or 9.994 amps at the other prong. The extra .006 amps would be going through the grounding pring.
And my personal experience is that GFI outlets dont last as long as a regular outlet, before the GFI function doesnt work so well. Your probably okay for ten years though.

I hope the wires for the electric heater connection are inside a non-combustible enclosure - at least the NEC requires it be that way inside a house.


For useful info I found a really good explanatory site. I think he says what I said above.
http://repairfaq.ece.drexel.edu/REPAIR/whole/F_appfaq.html#APPFAQ_347
Read sections 15.21 and 15.22, and 16.4 and 16.4.

[70winnie]

Sent: 10/23/2004 6:42 PM

Thanks for the thoughts/clarifications/links, folks.

I didn't hear any noises when I installed the outlets but I will double-check them to be sure there's no excessive bending.  Better safe than sorry!

You're right that a GFCI is only for ground faults.  Fortunately I wasn't counting on it as a general-purpose circuit breaker, it's just a question that popped into my head.

I was already informed about excessive tripping of breaker-box GFCIs, which is why I went with GFCI-outlets instead.  Although I suspect that since I'm putting each device on its own circuit, cross-tripping probably wouldnt have been a problem in this case.  Although reading further on the subject of GFCI sensitivity, I'm wondering if I should use a non-GFCI outlet for the refrigerator (even though its on its own circuit).

I'm continuing to research all of these wiring issues. I'll report back with my findings.

[denisondc]

Sent: 10/23/2004 9:56 PM

I was hoping you would use the GFI outlets for all of your appliances, fridge included, and tell us if you have nuisance tripping, and why. 

[70winnie]

Sent: 10/23/2004 11:25 PM

Heh, OK Dave, I'll use GFCIs everywhere just for you. 

[Sea Hag]

Sent: 10/27/2004 10:47 AM

The only problem Ive had with GFI in my new addidtion is on my bathroom fan is connected to one . It trips sometimes when I shut the fan off . I believe the fan motor is sending a slight voltage back to the recepticle before it stops spinning , Kinda like a generator . They are not recomended for Space heaters , appliances or electric motors . However Local codes make Gfi recepticles or gfi breakers at the pannel maditory in the Bath ,garage,Basements ,Outside recepticles , couter tops by sinks, and for the close washing machine . Basicly anywhere water can be present on floor or ground . I used 20 amp Gfi's Recpts .in the garage and basement and haven't had any problems except with the 115amp hooked to the Fan .
   I'd keep an eye on the post pannel # 10 wireing I still feal it's over rateing the recepticles . It's used for 30 amp applications ,bigger wire isn't always better it should be matched to intended amps , breakers and  reecpticles .  Sea Hag