What is using so much electricity? - HUGE electric bill!

[DaveVA78Chieftain]

Both the 110VAC and 12VDC heater elements are attached to the chimmney flue (side by side; 6"-8" long metal object the diameter of a ball point pen with wires attached).  The wire for 12VDC one goes back to the relay (pin 87).  If the relay is removable, then simply pull it out (pay attention to orientation for reinsertion).  If not removable then the drawing looks like there is a connector on the bottom of the relay for the heater (pin 87) that you can remove.  Object is, to remove power to the 12VDC element.  Once heater power is removed, the meter should slow down to a crawl in propane mode.  In 110VAC mode, meter will turn but hopefully not as fast.
110VAC element power is routed through control board (relay on control board) not the 12VDC relay at top of drawing.

Dave

[moonlitcoyote]

Total failure I pulled the covers off and had NO idea where that relay is or what it would look like. I thought I could figure it out by the picture, but alas I was WRONG... Being a woman, You'll never hear me say that again. I will try to post a picture of what everything looks like back there. Having camera problems at the moment but I'll have it shortly

[DaveVA78Chieftain]

Here is a link to some simplified information about how your AES style fridge works: http://www.rvmobile.com/tech/trouble/aes.htm
That is an overview page.  It has links to each mode of operation also.  Unfortunantly I have not found a site that has pictures in the repair document that show the internals a bit more clearly.

Ahh, ok, 2nd photo, the jumble of wires by the flue (above the propane ignitor) connect to the 12VDC relay (attached with a single phillips head screw).  testing info on pdf page 48 (A-6-41).  We are looking to lift the connector attached to pin 87

1st photo, I can see which wires are the 110VAC element (pins C & D on main board).  The sticker laying there that says RM 3800, the wires are between the letters .. "M" and "3" ...  They should disappear into the burner flue

Dave

Will be a little while later before I can respond any more tonight (the work day has come to an end so I am heading home)

[moonlitcoyote]

Thanks Dave for explaining everything so clearly. I got pin 87 disconnected and it made no change in the meter. But this time when I ran it off of propane it slowed the meter by at least 1/2. So at this point I do know that most of my draw is coming from the refrigerator. ... I had thought of buying a household fridge to set in the yard somewhere, but did I read correctly that they draw more electric than this one? At this rate I am really worried that I am going to have a $500 electric bill once I start running my A/C.

[ClydesdaleKevin]

MJ, even though the heating element draws a lot of power, it shouldn't stay on, and I think Dave has it right when he says its the relay...it should shut off when the propane is on, and it should also shut off when the fridge gets down to the preset temperature. 

That said, if the heating element is never shutting off, then a household fridge will draw LESS power than your nearly-broken RV fridge.

I think that until you get the fridge troubleshooted and fixed (and it might be other things besides the relay, like the circuit board, which tells the relay to shut the AC off when up to temperature, or when switched to propane) you might be better off setting a small household fridge up on your porch and not using the RV fridge until its working properly.  It would probably draw a lot less power, since the compressors shut off when down to temp, just like your heating element is supposed to shut off.

Good luck!

Kev

[moonlitcoyote]

I agree Kev, but even though I found the relay and saw that the meter slows way down on propane. I am still not positive that the heating element is staying on. I am thinking of just running it on propane for now, but the fridge is quite full and I am a bit worried it wont be cold enough.

[Froggy1936]

Hi MJ I think you are on the right track Disconnecting the 12 V heater (I discovered mine was on at all times so i just have it disconnected) I use propane wile traveling or no 110 available And found i have no need for 12V operation (wich will kill 2 batterys in a matter of hrs without alternator support). The other thing i noticed is The rust on the fridge plumbing This must be cleaned up (not agressivly) A small wire brush (toothbrush size)  and painted with a rust stop paint  any rust thru will make the fridge junk. Frank

[ibdilbert01]

BTW, by what I've been reading over in "Refrigerator Alternatives" (Yahoo Groups) a modern standard home fridge will use less electricity than most RV fridges.

In fact,  folks in that group have been zoning in on a fridge they are buying from one of the big box stores that is 16.8cf and on the average is only consuming 400wh a day (12kw a month).   

The fridge in my winnie consumes about 6amps on AC.   (I assume this varies on make / models / sizes)

(6a x 120v) = 720 watts

Assuming the heating element is only on 50% of the time, (720 x 24) *.5 = 8.64kwh (per day).

Thats 259.2kwh a month just to run the fridge if the heating element is cycling at 50%.

Sounds like yours (at least the 12v side) wasn't cycling at all which would explain your high bill. 

I am thinking of just running it on propane for now, but the fridge is quite full and I am a bit worried it wont be cold enough.

I'm sure all fridges are different, but mine actually runs a lot better on propane.

[DaveVA78Chieftain]

I lean towards Dilberts view.  12VDC heater was staying ON all the time however, without making voltage measurements I cannot confirm that.  I guess the first question to ask is, MJ, how familure are you with using a voltmeter to take measurements?  You have demonstrated much more prowness than many people so, I am just trying determine how far to dig into this.  Most anything I would recommend is going to be driven by whats in the repair manual.

My "apartment" size household fridge in my Chieftain draws 10-13 DC amps (70-90 startup) via an inverter.  While that sounds like a lot, convertering to AC usgae via the converter thats 13 x 12 =  156 watts.  156 / 120 x 1.1 (90% converter efficiency) = 1.43 AC amps.  The compressor lable plate says 1 amp running.  1.43 is basically the same.  I should also note that is not a pure sine wave inverter.

Now referring to page A-6-28 of the manual, your fridge pulls 2.7 amps in AC mode.
120 x 2.7 AC amps = 324 watts
(324 watts x 24hrs) x .5 = 3.888kwh/day in AC only mode  (multiply that # days in month; 30 days x 3.888 = 116.64kwh/month)

Now if the 12VDC element was never shutting OFF (key being never), then:
17.9 DC amps (from page A-6-28) x 12VDC = 215 watts
12VDC Converter translation = (215 watts / 120VDC) x 1.1 (90% converter efficiency) = 1.97 AC amps
1.97 AC amps times 120 volts = 236 watts (could have simply done 215 DC watts x 1.1 efficency = 236 also)
236 watts x 24hrs = 5.664kwh/day (remember, it is ON all the time)
Now if AC is cycling and DC is always ON then 3.888 + 5.664 = 9.552kwh/day
30 days x 9.552 =   286kwh/month

If both AC AND DC are always ON (24/7) then (324 + 236) x 24 =  13.44kwh/day (30 x 13.44 = 403kwh/month)

If on DC mode only and it was cycling properly then
236 watts x 24hrs) x .5 (50% duty cycle) =  2.832kwhr/day or 30 x 2.832 = 85kwh/month

To make that easier to grasp

DC only working properly: 2.832kwhr/day (85kwh/month)
AC only working properly: 3.888kwh/day (116.64kwh/month)
AC normal, DC always ON: 9.552kwh/day (286kwh/month)
AC and DC always ON: 13.44kwh/day (403kwh/month)

So, as you can see your usage can be drastically affected by the operation of the unit.  An improperly running unit can cost you 4 times as much to run.

Balls in your court regarding what direction you want to go from here.

Dave

[moonlitcoyote]

Thanks for that rundown Dave.

Since I have no need of 12v operation and I dont intend to hook up the ignition wire anytime soon. I will tape off the 12v heating element wire and leave it like that for now. Maybe I will see a difference in my electrical usuage next month having that done. I will also see about picking up a wire brush and some primer and cleaning up the back of the fridge. Is there any specific primer I will need for that or just any regular rust-o-leum?

[DaveVA78Chieftain]

Rust-o-leum should work fine on none piping parts.  Only thing you have to concern yourself with on piping is the heat generated in the flue section.  You may have to use a higher temperature auto engine paint on them.

If you decide to repair later, just remember that either the 12VDC relay is bad or the control board is messed up telling the relay to energize.

Dave

[moonlitcoyote]

Thank you, I just e-mailed this topic to myself so I have it for later reference should I decide to fix it. One problem down a few more to go.

[Oz]

See the New "Add Bookmark" tab above the top of this page of replies?  You can now bookmark all the topics you want to refer to later.

[ClydesdaleKevin]

Just make sure you check for recalls before running your fridge constantly on propane.  Our fridge is a rebuilt Dometic, not the same model as yours but I think its the same year.  When we bought it, it already had the recall modification done professionally by the rebuilders.  Basically, there was a very slight chance of fire if the wind came in just right through the exterior fridge door vent and blew the flame just right...so Dometic sent out a recall order, which required a sheet metal shield that covers all the wires and bottom of the flue where all the wires and heating elements go into the flue. 

Not saying yours will have this problem, but it would be a good idea to check with Dometic.

Kev