Lights flicker when furnace is on

[ThomasE]

Was out camping last weekend and noticed my interior lights dim and brighten rapidly whenever the furnace was running. Has anyone else experienced this? Not sure if it's a bad connection issue, or if the furnace blower is causing the flicker.

[honda03842]

Does the same thing happen when you run the water pump?

Norm

[ThomasE]

Originally Posted by honda03842

Does the same thing happen when you run the water pump?

Norm

The lights dim substantially whenever the water pump is on and cycles, which I attribute to the higher current draw. But the furnace blower, an Atwood 8012, draws little current.

[Casita Greg]

How is your battery voltage reading, at rest, with nothing on or running? If your battery is old, it may not be carrying a full charge anymore. If the battery is ok, then I would suspect undersized wiring, or corroded/dirty terminals/connections. Worth checking anyway, as these are "no-cost" things. Let us know what you can find out.

[Darwin Maring]

Greg is right on.

Check all connections starting with the battery connections, then ground connections, then the rest of the connections.

Here's another thought: I had a Miata with an older battery in it and it would do the same sort of thing then one day it (Exploded). It appeared there was an intermittent problem inside the battery and when the gas built up inside the battery, it sparked and Boom, all over the trunk where the battery was connected.

I could have avoided this by doing a LOAD test on the battery. A load test might have reveled a problem. It may be possible to get the battery load tested by taking it to Advance Auto (For Free).

[ThomasE]

I suspect it's the connections more than the battery, which is relatively new. All the wiring connections are made with crimp connectors or scotch locks, which seem to corrode over time or vibrate loose. I'll probably go in and do some jiggling of the connections, and solder every connection I can get at. My brakes went out on a 7000 mile Alaska trip, which I temporarily repaired it by adding another scotch-lock. When I got home I cut off every crimp / scotch lock, and soldered every connection for the brakes.

[ThomasE]

Also what gauge wire runs from your batteries to the power supply? Mine looks to be 14GA.

[Darwin Maring]

On our Scamp, the battery had a wire to the frame as did the converter, brakes and other DC items.

Once in a house that we lived in, the deck lite would go off and I found that the AC wire in the Pannel had never been tightened down so when it got hot, it moved and the lite went off and after it cooled, it went back on.

[Byron Kinnaman]

Originally Posted by Darwin Maring

On our Scamp, the battery had a wire to the frame as did the converter, brakes and other DC items.

Once in a house that we lived in, the deck lite would go off and I found that the AC wire in the Pannel had never been tightened down so when it got hot, it moved and the lite went off and after it cooled, it went back on.

OK, Your Scamp was altered by somebody then. Mine only has one connection to the frame, it's where the 120V comes in and it's the green "safety ground" as required by the National Electric Code. That's it, nothing else is connected to the frame.

[Darwin Maring]

Unplug the shore power then take the ground lead from the battery and then do an ohm check from the ground lead to the frame, is there connectivity?

Mine was wired this way at the factory. It also used the frame as the return for the electric brakes.

[Casita Greg]

Neither AC nor DC wiring should be using the frame for a return path for any branch circuits. Yes, it will "work" after a fashion, in so much that it will conduct electricity, but it is a "lazy man's way" of doing things, can be potentially dangerous, and is totally wrong from a circuit design standpoint. It will only lead to electrical problems down the road, such as backfeed on other circuits, "ghost power vampires" that can drain your battery when you think everything is turned off, electolytic component corrosion, increased radio interference (static), etc. In short, a whole panoply of self-inflicted bugaboos can arise from this style of circuit design. All DC wiring circuits should be TWO wire, and ALL ground wires should come together (terminate) on ONE common ground bus bar or ground strip. This ground bus is then connected to the frame AT ONLY ONE POINT! This is also the same connection point used for any trailer bonding wire. Multiple circuit grounds made to the frame are a big no no, but it is more common than not. Many "home electricians" do not understand the relationship between a "grounding system" and a "bonding system". Although they both (ideally) terminate at ONE COMMON POINT on the chassis (frame), they are NOT INTERCHANGEABLE in their use or function. In summary, NEVER use the trailer frame as a return leg in any circuit.

Bonding systems are meant to provide a low-resistance path to ground for any heavy overcurrent loads, such as a lightning strike or a direct short in any bonded system component's casing or enclosure to prevent electrocution. Using the frame as a return path is not what a bonding system is designed to do.

Your AC wiring should be grounded to the frame at the same ground point as your DC wiring and your frame/electrical component bonding connection. Again, this should be the same point as your DC and bonding grounds (1 ground point only).

[Raz]

ThomasE, my guess is you are seeing battery loading, a reduction in battery voltage due to higher current demand. Any increase in circuit current will cause a drop in battery voltage. Put a voltmeter on the battery and take note of the voltage as various things are turned on and off. Loading effect is more pronounced with an aging battery. Bad connections tend to draw less current not more so I don't see how a bad connection anywhere other than the light circuit itself causing the lights to dim. Please let us know what you find, Raz

[Byron Kinnaman]

Originally Posted by P. Raz

ThomasE, my guess is you are seeing battery loading, a reduction in battery voltage due to higher current demand. Any increase in circuit current will cause a drop in battery voltage. Put a voltmeter on the battery and take note of the voltage as various things are turned on and off. Loading effect is more pronounced with an aging battery. Bad connections tend to draw less current not more so I don't see how a bad connection anywhere other than the light circuit itself causing the lights to dim. Please let us know what you find, Raz

Let me see if I can explain how this works. A bad connection reduces the amount of current that can flow. This creates a voltage drop across the bad connection. When the something like the fan in furnace comes on it draws what is called "in rush" current which is higher than running current. That higher current through a defective connection causes a voltage drop across the defective connection which reduces the voltage available to very thing beyond the connection.
If the fuse or other connection at or near the battery are defective the lights will dim every time the furnace comes on. If the connection is bad enough the light will dim and the furnace will not come on.


One of the concerns of a defective connection is that they can heat up. In extreme cases a defective connection can actually cause a fire.

[Raz]

Originally Posted by Byron Kinnaman

Let me see if I can explain how this works. A bad connection reduces the amount of current that can flow. This creates a voltage drop across the bad connection. When the something like the fan in furnace comes on it draws what is called "in rush" current which is higher than running current. That higher current through a defective connection causes a voltage drop across the defective connection which reduces the voltage available to very thing beyond the connection. If the fuse or other connection at or near the battery are defective the lights will dim every time the furnace comes on. If the connection is bad enough the light will dim and the furnace will not come on. One of the concerns of a defective connection is that they can heat up. In extreme cases a defective connection can actually cause a fire.

My assumption is that the lights and the furnace are separate independent circuits although I suppose they could share a common return wire. If they are independent parallel circuits then the only way the lights can be effected is if the supply voltage drops. While I agree a bad connection in the furnace circuit will could cause a voltage divider between the connection and the furnace motor (there's your Kirchhoff's voltage law), it's not going to cause loading of the source as it will reduce the current not increase it.

The place where a bad connection would be an issue is between the battery and the distribution panel as that is common to both circuits. I'd start with a voltmeter at the battery. Raz

[Casita Greg]

Originally Posted by P. Raz

ThomasE, my guess is you are seeing battery loading, a reduction in battery voltage due to higher current demand. Any increase in circuit current will cause a drop in battery voltage. Put a voltmeter on the battery and take note of the voltage as various things are turned on and off. Loading effect is more pronounced with an aging battery. Bad connections tend to draw less current not more so I don't see how a bad connection anywhere other than the light circuit itself causing the lights to dim. Please let us know what you find, Raz

Obviously, the more "demand" that is placed on a battery (or any power source for that matter), there will be a relationship between the demand of the total cumulative "load", and the power sources' ability to meet that demand. It makes no difference whether the load is on the same circuit or on another circuit, the demand for power from the source (in this case, the battery), will be cumulative for ALL the loads being supplied.

Comparative analogy to visualize how electricity functions (as compared to a water system):
Voltage = think of it as the water pressure.
Amperage = think of it as the flow (i.e. gallons per minute).
Resistance = think of it as rusty pipes or undersized pipes.

I agree that poor connections do demand less current (amperage), but they also do require a higher voltage (electromotive force, or "pressure" if you will,) to overcome the increased resistance. If your voltage (pressure) is already marginal to begin with, any cumulative load (opening more faucets, thus increasing the flow, or "gpm") placed on that weak battery will result in a diminished ability to supply sufficient voltage to meet the demand.

Resistance, or the restriction of the flow so to speak, will require more force (voltage) to provide the same level of flow (amperage) to meet the demand. Resistance is not just found in wiring, appliances or connections, but also internally inside the battery as well. If this internal resistance becomes too much for the flow demanded (such as in a bad or severely deteriorated battery), then it would require extra voltage (pressure) to overcome this resistance, a condition which it obviously cannot meet. When it can no longer keep up with this demand, the flow comes out as a dribble instead of a strong stream. This is why your lights dim. It's not how many hoses you have, it's how many you have turned on at one time, and how much of a flow they each put out.

I don't know if I can make it any simpler than this either... Hope it helps you to understand the relationship between all the "players" here.

[ThomasE]

OK I think I figured out where the bad connection is. The main +12v line from the battery connects to a fuse block, that fuse block is the old style glass fuse type. The clips that hold the fuse in place is riveted to another metal block that you can insert the wire into and tighten a screw to hold the wire in place. The connection between the fuse clip, and the block holding the wire was loose since the only way it was held on was with a small rivet, I think this is a bad design. I temporarily bypassed the fuse block with an inline fuse holder, and the flicker is gone when I turn on the furnace. Not only that, but when I turn on the water pump, the lights now barely dim.

But I'm not done yet, I really hated that glass fuse block because I already had another problem on a different circuit with that type of clips. I got some ATO fuse blocks from Kragens, I've taken out my power supply and ripped off that old glass fuse block, and installed the ATO fuse block. I need to pick up a few more connectors tonight to finish the job.

[ThomasE]

I replaced the old glass fuse block with a new ATO fuse block and all is well now. The culprit was a bad connection for the fuse clip of the +12v line coming from the battery. The lights and furnace are on different circuits, as is the water pump. But due to the bad +12 connection at the fuse block, having multiple things going at once likely dropped the voltage enough to get my LED lights flickering.

[Francesca Knowles]

Originally Posted by Casita Greg

Neither AC nor DC wiring should be using the frame for a return path for any branch circuits. Yes, it will "work" after a fashion, in so much that it will conduct electricity, but it is a "lazy man's way" of doing things, can be potentially dangerous, and is totally wrong from a circuit design standpoint. It will only lead to electrical problems down the road, such as backfeed on other circuits, "ghost power vampires" that can drain your battery when you think everything is turned off, electolytic component corrosion, increased radio interference (static), etc. In short, a whole panoply of self-inflicted bugaboos can arise from this style of circuit design. All DC wiring circuits should be TWO wire, and ALL ground wires should come together (terminate) on ONE common ground bus bar or ground strip. This ground bus is then connected to the frame AT ONLY ONE POINT! This is also the same connection point used for any trailer bonding wire. Multiple circuit grounds made to the frame are a big no no, but it is more common than not. Many "home electricians" do not understand the relationship between a "grounding system" and a "bonding system". Although they both (ideally) terminate at ONE COMMON POINT on the chassis (frame), they are NOT INTERCHANGEABLE in their use or function. In summary, NEVER use the trailer frame as a return leg in any circuit.

Bonding systems are meant to provide a low-resistance path to ground for any heavy overcurrent loads, such as a lightning strike or a direct short in any bonded system component's casing or enclosure to prevent electrocution. Using the frame as a return path is not what a bonding system is designed to do.

Your AC wiring should be grounded to the frame at the same ground point as your DC wiring and your frame/electrical component bonding connection. Again, this should be the same point as your DC and bonding grounds (1 ground point only).

Hello-

I've been following this thread as best I can and have some questions related to the above post.
The first picture shows my (factory installed) converter, with 110v line. Two green groundwires are attached at the point labeled "equip. ground". The smaller wire is groundwire for the (added) charging unit in the foreground. The heavier wire goes through a hole in the floor and (2nd picture) is affixed to the trailer frame outside. The 110v circuit breaker is at the other side of the trailer, and I don't see any groundwire affixed to the frame in that area.
The tongue-mounted battery is connected at the converter (blue line in picture) and is (wrongly?) grounded to the frame at the tongue.
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My Questions are:
1) Is the single ground you refer to the heavy green ground shown above?
2) If so, does it serve as ground for all electricals including 110v.?
and
3) If the battery is incorrectly grounded to the trailer tongue, should I run it all the way back to the connection point shown in 1st picture?
OR
.....b) The picture below is the factory installed pigtail-to-trailer wiring connection point at front of trailer. Should I attach the battery groundwire here? What the heck am I looking at here, anyway? There are two 15a fuses in that interconnected bundle. Is this the point at which both battery connections should have been made in the first place?

Trillium front wires 002.jpg Views: 9 Size: 277.0 KB ID: 35673" style="margin: 2px" />

Thanks, I hope.

Francesca

[Casita Greg]

Hi Francesca,
From what I was able to trace out from viewing your photos, it appears that your large green wire is your main ground to the frame. It appears that all your other grounds (converter, charger, and 120vac ground lines) seem to eventually terminate (as best I can tell from your pics) into the same heavy green wire connected to the frame (photo #2) where it comes through the floor. This does appear to be the point where all your ac and dc grounds come to one point, which is good. Of course, you would have to check your individual branch circuits to see if any "aftermarket" installations were "shortcut grounded" to the frame elsewhere in your trailer, as mods may well have been made over the years. This would require an actual "look-see" and visual wire trace to ascertain that they were properly grounded to your main ground bus.

I'm not entirely able to make out what the two 15 amp fused circuits go to from viewing the photos, but as far as your trailers' battery ground point goes, if you feel up to making the change, I would offer a suggestion to remove the presently attached battery ground from where it is now on the tongue, and run a new line from the negative terminal back to the ground point shown in your photo (where the big green wire hooks to the frame.)

Hope this helps.

[Francesca Knowles]

Originally Posted by Casita Greg

Hi Francesca,
From what I was able to trace out from your photos, it appears that your large green wire is your main ground. The grounds seem to terminate (as best I can tell from your pics) into one heavy green wire to the frame (photo #2) where it comes through the bulkhead.

Thanks for getting back!
Should I connect the battery ground at that point?
Or-
The battery install is ours- the trailer had never had its own before we got it, and my partner in crime (a double-"g" Gregg!) was more or less winging it with the install. He ran the wire all the way back to the converter, and it was a struggle to fit the heavy wire through the knockout with all the other wires. Now I'm wondering if both battery connections can be made at the harness shown in the third picture???
Sure would be simpler...

Thanks again,

Francesca