2004 Itasca 120V power loss to Kitchen outlet

Mongobird · 01-08-2025, 07:04 PM

I have not begun to really debug this problem, but I thought I would post it, in case there is a problem area on this family of RVs that I should be familiar with...

The winter has been exceptionally cold this year, and there are lots of chores to get accomplished in the rig. It is in a barn, so it is reasonably protected from the wind. But it still gets cold.

I am using a dual setting heater/fan combo for heat. It is on a SONOFF S31 switch, which is signaled by wifi in the barn. I can remotely turn on the heater, and do so prior to coming out for a work session. It is on low heat, which draws under 900 W. I have it plugged in to the left of the sink, at the appliance garage. Since the SONOFF S31 provides voltage, current and Watts, I have watched it throughout this season as well as last season when I used it for a similar purpose: to preheat a portion of the RV cabin. However, this season I am getting some readings which have me concerned.

As the ceramic heater heats up, the current draw increases. And the measured line voltage at the switch drops.

The 120 is the line voltage prior to turning the load on, Vline

The Watt number is a spot reading showing the Watts consumed by the appliance. W
The current for the load is calculated from Iload = W/Vline

The next figure is the line voltage present at the instant the power level is at the Wattage point. Vload

The final figure in each line is the calculated loss at the S31 switch, using the following:

load current = W / V and power loss= Vdrop * A , (Vline-Vdrop) * Iload which is the last figure:

120 / 250W / 118.3 (120-118.3) (250/120) = 3.54 watts loss of power

120 / 400W / 115.4 (120-115.4) (400/120) = 15.33 W
120 / 800W / 114.9 (120-114.9) (800/120) = 34W

So my concern is that too much power is being lost, and it is enough to cause a fire. So I have decided to stop running the heater, until I find the source of the problem.

I will probably start will voltage drop measurements made at the GFCI, which is in the bathroom.

If anyone has seen this issue, I am open to possible sources that I might check for brunt insulation or even warm temperatures, prior to exhaustively looking for the problem.

Thanks.

bigb · 01-08-2025, 07:30 PM

If I understand your details, voltage/power/current is decreasing at the load but total circuit current is increasing? So you are looking for where that missing current is being used?

If you know the circuit layout can't you just start moving the heater upstream to rule out an arcing fault at any of the receptacles/connections?

Mongobird · 01-08-2025, 07:35 PM

Yes, power is being consumed. Somewhere. Perhaps at an aging connection.

I have not started the diagnosis, mostly due to time, and the fact that it is very cold right now. I will probably go after things this weekend, and if I do, I will post my findings.

bigb · 01-08-2025, 07:57 PM

With the design of RV receptacles you could possibly have a glowing connection. Look at the 6th page of the pdf I am linking, 2nd paragraph where it states that a glowing connection on a 15 amp circuit can consume up to 35 watts which is right where you are at. Move that heater upstream till the mystery load disappears.

https://nvlpubs.nist.gov/nistpubs/Le...sir76-1011.pdf

bigb · 01-08-2025, 08:10 PM

Page 26 of the pdf article 6.1 describes voltage drop with a glowing connection from less than 1 volt up to 7 volts. Again consistent with your findings. Note where it says none of this would be noticeable to the consumer.

I remember pulling a receptacle out of the wall at a house that was having problems and the backstab started a small flame as I was pulling it out of the wall. Another time at my mother's house they ran a space heater all night and there were loose wires on an upstream receptacle, the receptacle and wall plate was charred and there was a smoke stain 3 feet up the wall.

BTW I only run our space heater on 600 watts on the kitchen 20 amp circuit. Space heaters are a great tool for exposing wiring deficiencies.

bigb · 01-08-2025, 08:25 PM

Looking at your details again it looks like you are measuring current with the Sonoff which is at the load? If this is true it points to the Sonoff itself, the heater, or the kitchen outlet. Earlier I thought you were measuring the entire circuit current from upstream but if you are measuring it at the load the problem has to be from that point down.

Since the power measurement decreases while current rises though I am inclined to think it's in the Sonoff. If the current consuming fault was downstream of the Sonoff it would also show in the total power (watts) which it isn't.

Even if the fan motor in the heater was drawing more current from the voltage drop the Sonoff would show that in the total power consumed.

This is all based on the fact that current rises at the load but total power drops at the load, if this is what is actually happening. If current were actually dropping with voltage the problem could be anywhere in the circuit.

Mongobird · 01-09-2025, 09:20 AM

bigb, thanks for your comments, photos, etc.

The first receptacle in the circuit is in the bathroom. I will move the SONOFF and heater to there, and take a measurement. I have to check, but I think all the internal outlets, except for the washer/dryer are on that circuit.

I will also look at any losses when running the preheater for the engine, which is 120V.

Right now, I am feeding the rig with 120V via the 14-50 connector, so I will check that out as well.

We agree that this amount of power loss could create a dangerous amount of heat, and until I resolve this issue the heater will not be run.

At 11F, I am not anxious to go out and try to fix this today. Also at these temperatures, anything one touches has the opportunity to break, especially 2004 vintage plastic.

When I find the root cause, I will post it.

Thanks bigb, for posting, and for others who considered this issue.

bigb · 01-09-2025, 10:08 AM

Yes keep us posted. I am still wondering how the Sonoff can show the current rising yet the total power decreasing, that just does not add up. Unless there are parameters in the Sonoff that the user can set as not variable causing it to adjust the variable ones to be mathematically correct, or unless you are measuring current upstream of the Sonoff.

Barring that, this could just be a simple high resistance connection causing VD which in turn should reduce both power and current on a resistive load which can be located by just moving upstream till you get normal readings again.

Pointyears · 01-09-2025, 10:19 AM

Are you an electrician, Brian? I'm finding your posts to be very educational.

bigb · 01-09-2025, 10:26 AM

Quote:

Originally Posted by Pointyears

Are you an electrician, Brian? I'm finding your posts to be very educational.

Retired electrical contractor, however there are some very smart folks on here and on iRV2 that humble me. Troubleshooting has always interested me and was my favorite part of the job however it can also make a fool of you pretty quick if you don't resist the temptation to jump in and make non-factual based assumptions and guesses, which admittedly sometimes gets done for lack of facts, or incorrect facts given.

Mongobird · 01-09-2025, 11:02 AM

The SONOFF device shows increasing power (and current) but a dropping voltage at the device, which implies a loss of power from the power source to the SONOFF.

I presume that loss of power, implied by the voltage drop, is caused by likely resistive heating.

Morich · 01-09-2025, 11:07 AM

Volts and Ohms have been very reliable for a very long time!
Would there be value in checking the very complex and very new readings you are getting?
Not all new ideas and equipment are reliable over the long run!
One of the things I have learned is that it pays to test the test equipment before assuming it to be correct.

Your readings don't seem to make sense, so is now a good time to question/verify those readings before trusting them?

Mongobird · 01-09-2025, 11:23 AM

Quote:

Originally Posted by Morich

Volts and Ohms have been very reliable for a very long time!
Would there be value in checking the very complex and very new readings you are getting?
Not all new ideas and equipment are reliable over the long run!
One of the things I have learned is that it pays to test the test equipment before assuming it to be correct.

Your readings don't seem to make sense, so is now a good time to question/verify those readings before trusting them?

I took preliminary measurements with the smartswitch already connected to the heater. I have used those devices for nearly 10 years, and have 25 or more in my barn to help control and monitor things. Are they accurate? No, they can easily vary 2%. Then again, accuracy is not essential for resolving what I perceive as a gross loss of power.

I have conventional meters (too many to count) and will likely use one when I go poking, as the weather warms up.

My post was a preliminary fishing expedition, and I was looking for something like, "the bathroom GFCI is suspect, and I have had one develop bad contacts through the backstab used" or something like that.

To me, the measurements I made, and the analysis of them do make sense, and suggest a loss of power due to a series resistive load. I have stopped using the heater, because I believe continued use of it poses a fire risk. I just have not had suitable conditions to find the offending point.

If you don't think they make sense, kindly point out to me at least one of the specifics. Thank you.

Morich · 01-09-2025, 12:57 PM

Not here to argue.
Just pointing out that you seem to have some concerns about the readings you are getting. One way to cut the mind clutter when there is a concern is to check things!

As far as asking if there are known problem areas in the RV electrical? YES! It's almost a given that there will be faults!

Mongobird · 01-09-2025, 02:42 PM

Morich, I am not concerned about the validity of the data. I am concerned that it is indicative of a problem in the wiring integrity in the rig. Specifically, the current carrying capacity, without appreciable power loss.

No argument intended, just trying to communicate.

Factory drawings attached for the benefit of the next person who might be hunting down this problem.

Jim_HiTek · 01-11-2025, 02:58 PM

I believe your outlets are the slim IDC (Insulation Displacement Connector) types. These take up less room in a thin wall than standard electrical boxes so they are used in RVs to save space. Those can and do become overheated and consume wattage like in the picture of the screw terminal type above. But note they have passed all the UL and CSA tests and can have a very long functional life.

Anyway, first try to localize which outlet is overheated as mentioned above. Then pull the suspect outlet, open it up, carefully pull the wires out of the IDCs, straighten and pinch the gator IDCs, than move the wire 1/8" to 1/4" beyond the original position and using a tool that spans the IDC squish them back into the IDCs. Of course if you see that an IDC is blackened from over heating, you need a new outlet. There might be room inside a kitchen cabinet to install a standard outlet with nice screw terminals if the problem is with that outlet. If the appliance garage outlet is in the wall rather than a cabinet, then you'd need a new RV type outlet (most likely).

Okay. Probably too much information, but I was bored with nothing to do today.

Mongobird · 01-11-2025, 06:22 PM

Jim, thanks for the info. I will look up the receptacle you mention and get more familiar with them,

Bobn1957 · 01-15-2025, 08:46 PM

Quote:

Originally Posted by Mongobird

Yes, power is being consumed. Somewhere. Perhaps at an aging connection.

I have not started the diagnosis, mostly due to time, and the fact that it is very cold right now. I will probably go after things this weekend, and if I do, I will post my findings.

I would start at the outlet where the heater is plugged in, appliance outlets take a beating!

Morich · 01-16-2025, 06:36 AM

I don't see a clear plan of where and how the testing is done but my first thought is that it is missing what might be an obvious problem.
If just looking at the total of what the RV is using and deducting the amount of the known item, it seems very easy to think there are other items using power and not being accounted for in the figures.
Jumping to an overheated item like an outlet seems a bit early until they find what else is powered to use some of that "missing" current.
Items left plugged in like chargers and rechargable items like vacs will also need to be deducted to get closer to the correct current for the heater alone.