heating electrically a "back yard" report

[pianotuna]

Hi,

This is a test of a cold soaked RV, ambient temperature -31 C (-23.8 f) The test started at 2:00 but I had difficulty getting the cords "run". I'm plugged into one 30 amp and two 15 amp outlets. The inside of the RV started at -21 c (-5.8 f)--a testiment to solar gain--through the front window. I am running between 4500 and 5500 watts of electric heat, or 15354 to 18766 btu's.

The bedroom area is closed off by a sliding fabric door, with about 2300 watts of electric heat, or 7847 btu's. (This number is NOT in addition to the total above.)

The unit is a 2004 28'5" class C with many cold weather modifications.

The date is 2013 12 07 and the location is: 50.448487,-104.50848

inside rv; bed room; ambient temperature; time

-20. C (-4 f); -20 C (-4 f);;;;;; -31 C (-23.8 f); 15:00

5.70 C (42.3 f); no data;;;;;;;;;;-26 C (-14.8 f); 17:00

7.70 C (45.9 f); 14 C (57.2 f) ;-26 C (-14.8 f); 18:00

11.2 C (52.2 f); 16 C (60.8 f); -26 C (-14.8 f); 19:00 {door open from 18:00 to 19:00}

10.3 C (50.6 f); 23 C (73.4 f) ; -26 C (-14.8 f); 20:00 {door closed}

12.4 C (54.4 f); 24 C (75.2 f); -26.6 C (-15.8 f); 21:00

13.6 C (56.5 F); 25 c (77 f);;;; -26.8 C (-16.2 f); 22:00 {cracking door open}

15.1 C (59.2 F); 23 C (73.4 f); -26 C (-14.8 f);; 23:00 {door still open}

15.6 C (60.1 f); 22 C (71.6 f); -25.5 C (-13.9 f); 24:00 {door fully open}

time to sleep

[pianotuna]

Hi niner,

Thanks but you will give me a swelled head.

Mex--you are always so kind and patient. ¡Feliz Navidad

[MEXICOWANDERER]

It even chilled down here (Baja California Sur). Danged thermo-meter read 60 at dawn. Danged near froze me buns off. Gotta get a Thinsulate blanket. I'm tired of sleeping with ten pounds draped over me.

Good report PT. I dreamed of "vacuum panels" last night. The R- forty some odd factor. The place I rented has 2X6 frame and 1/2" plywood over top. Nothing on the inside. The only good point is when the sun rises the temperature inside goes up fast. But only 14C today.

[NinerBikes]

Pianotuna, I'm your not so secret admirer for going RV lifestyle in such a harsh climate. You are blessed with a good engineering head on your shoulders, makes me really appreciate living in So Cal and being able to visit areas you live in in the warmer months, heading north.

It is amazing how walls act like such a heat sink when first starting to warm up the "home", gotta get some heat into them too from the air space inside. We used to have to burn a cr*pload of hardwood, oak, when up at Mammoth Mtn Ski resort, when we first arrived in a pot belly stove to warm things up. Seems like it took at least 8 to 12 hours, depending on if the lows were in the teens or 0 to -10 F.

Your posts are always a good read, thanks for sharing and letting us learn from your extreme adventures.

[LennyH]

VintageRacer wrote:
'cause I was curious, I did some math. Basic rate for electricity is apparently 11.13 cents per KWH where you are, you used roughly 70 Kw in 9 hours, for about $8. The 24 hour equivalent would be about $21. If you did that for a month that would be $640. 5 heating months, $3200.

I was curious because I will be heating my shop with a 5500 watt electric heater this winter, this gives me a guideline to what I'll be spending each day that I turn the heat on. Sure hope it warms up where you are, or you don't need to live in your camper full time!

Brian

Your calculations for electric usage are right however the heaters will not run 24 hrs a day, after reaching the set temp. they turn off and restart as the temp drops, so I think you could allow 9 to 12 hour of the heater being on….so that said….
7.8KW X .1113 = around 87 Cents a Hour x 12H a day = 10.44 a day
x 30days = $ 313.20 a month NOT $ 640

Lenny H

[pianotuna]

Hi,

What you are talking about is the "cheap heat" system. It has some features that I don't like.

Advantages:

Nothing to trip over. (but my heaters are in otherwise wasted space)

Uses existing thermostat

is available in 3 "flavors"

can be set to run furnace fan at 1/2 speed (because other wise the smallest flavor blows pretty darned cool air, just like a heat strip)

Power is "brought to you" unlike propane which you must go and get.



Disadvantages:

Can not fail over to furnace

Can not replace all heating needs in the 30 amp flavor

Probably can not replace all heating needs in the "medium" flavor

Can not be used with 15 amp power

Can not be run to act as a helper to the furnace

takes 5 hours to install (and that is if you have done more than one).

Costs $500 smackers plus install (so in my opinion to call it cheap heat is an insult)

requires a good working knowledge of electricity to diy

voids the warranty on the furnace

the three flavors are identical--just wired differently to allow different output levels

the 30 amp flavor does only a few more watts than a heat strip in an air conditioner

the furnace fan gets a lot more hours on it

has the same noise level as the propane furnace.

Break even even for a full time RV'er is several years of use.

starlord wrote:
Saw a new item in the latest Trailer Life which might be of interest. Basically it's an add on for the furnace box and a switch on the wall like you have on some hot water heaters, has an electric heating coil that hooks in to the existing hot air ducts so you can run electric instead of propane to heat the trailer. No idea what the cost is for the unit but thought it was something to maybe check out.

[pianotuna]

Hi,

I am actually at a campground--a rarity for me. I got my last fancy cover, which blocks off the entire cab area--and I've had to turn down the wattage I'm using.

[mena661]

greenrvgreen wrote:
No bargain, cetainly, but compare that to the cost of ANY CG.

Some of us will never get the chance to use free electricity to run 5.5kW of heaters so we have to factor in CG costs.

[starlord]

Saw a new item in the latest Trailer Life which might be of interest. Basically it's an add on for the furnace box and a switch on the wall like you have on some hot water heaters, has an electric heating coil that hooks in to the existing hot air ducts so you can run electric instead of propane to heat the trailer. No idea what the cost is for the unit but thought it was something to maybe check out.

[mena661]

Thanks PT!

[pianotuna]

Hi mena,

A heat pump extracts heat from the air (or water, or ground). Essentially it is an air conditioner being run backwards.

The cost of running the compressor compared to the watts of heat extracted is about 100% more than running plain electric resistance heat at the lowest operating temperature for the "pump". The "catch" is that below freezing there is little heat that a unit can extract. They work well above about 4 C (40 f). There are some models that work below freezing.

In homes it is easy to dig down below the frost line--and use a heat pump to extract energy. There are also systems that work with water.

Unfortunately those water based and ground based systems are not available to rver's. I don't think that digging down 8 or 9 feet would be looked on favorably by a campground owner.

mena661 wrote:
What is the difference between a heat strip and a heat pump?

[greenrvgreen]

I had a second look at Brian/"Vintage Racer's" cost calculations, and the math seems a bit off to the high side.

If Tuna is running 5500 watts of heat, that's 5.5 kwh times the 11.13 rate, or 61 cents per hour at full blast. That's less than $15/day. No bargain, cetainly, but compare that to the cost of ANY CG.

Daytime use levelled off to 3-4 thousand watts. Can we call that 3500? 3.5 times 11.13 is a 39 cent hourly rate, or $4.68 for 12 hours. Add in $7.35 for the dark 12 hours, and you have an adjusted cost of $12.03 per day, or $375 per month--if you're plugged in. If you're running a gas gennie, the cost per kwh is likely 6 times as much, or $2,000 per month.

Again, I can't help thinking that bedroom is getting richly fed at 2300 watts of heat when nobody's in it.

[mena661]

What is the difference between a heat strip and a heat pump?

[ktmrfs]

pianotuna wrote:
Hi,

What KT said and add the air conditioner is noisy. The fan in it can eventually wear out, too. I do have a heat strip.

Usually, if there is a wall thermostat it is not possible to run the furnace and the heat strip at the same time. One of my many mods was to add a 2nd thermometer that is for the furnace only. That way I can run the heat strip--and if it can't keep up the furnace will "join the team".

I'm down to running 3 to 4 thousand watts now--but temp is supposed to drop to -31 C--so that may adjust itself upwards.

yup, absolutely correct.


yes, it is noisy, just like the AC on low, and unless you have the matching thermostat, yes only the heat strip runs. There is a thermostat that will switch between the heat strip and furnace when the temp drops enough.

But, it really is only a chill chaser and if you use it for that it's fine.

[MM49]

Thanks, That is exactly what it was like at the horse show. I though they were great on chilly fall day.
MM49

[pianotuna]

Hi,

What KT said and add the air conditioner is noisy. The fan in it can eventually wear out, too. I do have a heat strip.

Usually, if there is a wall thermostat it is not possible to run the furnace and the heat strip at the same time. One of my many mods was to add a 2nd thermometer that is for the furnace only. That way I can run the heat strip--and if it can't keep up the furnace will "join the team".

I'm down to running 3 to 4 thousand watts now--but temp is supposed to drop to -31 C--so that may adjust itself upwards.