Converter Power Supply

System · October 2019

This discussion was created from comments split from: Shore power puzzle.

ScottG · October 2019

MuttonChops said:

...

...

@MuttonChops, FWIW, the 120V AC to 12V DC converter gets its power from the same breaker that control the GFI receptacle circuit.

At least that is how it is on mine. It's labelled that way, but since T@B circuit labeling is notoriously inaccurate, I've also tested it.

MuttonChops · October 2019

ScottG said:

@MuttonChops, FWIW, the 120V AC to 12V DC converter gets its power from the same breaker that control the GFI receptacle circuit.
At least that is how it is on mine. It's labelled that way, but since T@B circuit labeling is notoriously inaccurate, I've also tested it.

Thanks.
The circuit figure is a Cut & Paste from the Master 2017 320S Wiring Diagram created by one of our members.

Based on your comment I reviewed the WFCO Installation instructions and one figure does appear to support your information . . . it shows the Convertor Hot wire leading to second breaker position with a junction point and then the second wire (pigtail) is labeled "Available for A Branch". Will need to test it.
My unit is not labeled indicating how the Convertor gets VAC.

This wiring does raise a question/concern. My unit second breaker is 15A and labeled GFI. So it feeds all the VAC outlets PLUS it seems to feed the Convertor. Well Convertor draws 5+Amps. so that only leaves 9-10A for all the outlets - - - - - Maybe the second position breaker should be another 20A one - - -

Tundra57 · October 2019

Just a side comment. In general 12v converters are designed to charge a battery. Their output is not smooth DC, containing some ripple. Not all 12v equipment likes this ripple, it might make your tv or radio buzz. The converters usually expect the battery to be connected and switched on. Also with a battery connected the 12v rail can tolerate more startup loads like fans etc without the voltage dropping significantly. Maybe the converter will last longer with the battery connected?

Sharon_is_SAM · October 2019

Someone else here (maybe @DougH or @JEB) noted that the system works better with the battery included in the circuit. This is good to know. We tend to isolate our battery once fully charged when on full hook ups. Will avoid that in the future.

ScottG · October 2019

My tangential comment about the circuit that supplies power to the converter generated some interesting discussion, so I decided to kick it out here.

I was also prompted to check my own facts...

As @MuttonChops indicated, the GFI receptacle circuit is not labelled as the converter power source--at least not on the panel itself. The associated wiring diagram does indicate a hot wire running to the converter, but does not specifically indicate where it originates:

Image: https://us.v-cdn.net/5021717/uploads/editor/yb/ic41hhd3i4iu.jpg

However, another nearby sticker clearly states that the converter input is on a branch circuit:

Image: https://us.v-cdn.net/5021717/uploads/editor/qx/6htp6lhlz7n6.jpg

I'm sticking to my story that the 15A GFI circuit also powers the converter, but I can't verify where I read that (it isn't in the WFCO manual either) or if I just figured it out empirically by flipping breakers on and off. It was a while ago, so the next time I plug the T@B into shore power I will double-check my recollection.

ScottG · October 2019

MuttonChops said:

...
This wiring does raise a question/concern. My unit second breaker is 15A and labeled GFI. So it feeds all the VAC outlets PLUS it seems to feed the Convertor. Well Convertor draws 5+Amps. so that only leaves 9-10A for all the outlets - - - - - Maybe the second position breaker should be another 20A one - - -
...

Good point. However, before swapping out the breaker I would make sure all the wiring to the receptacles is 12g. Breakers are intended to keep wiring from overheating under excessive load; 14g wire is only rated for 15A and must therefore be protected by a 15A breaker.

Bayliss · October 2019

@ScottG and @MuttonChops.......interesting discussion. I went through this earlier this year. My WFCO panel for the 110 AC breakers was mislabeled by nüCamp. On my 2019 320S, the converter has SIX breakers, but nüCamp affixed the label for the previous configuration of the converter breakers. It took a while for me to get nüCamp to respond to my inquiry on what each circuit breaker protects, but I eventually received an answer from their tech department, plus a photo of how it should have been labeled:

"The 30amp is your main, and the first 15amp breaker is Dining Room GFI/Kitchen Rec. Second 15amp is Outside GFI/Rear inside Receptacle.

20amp – Alde

20amp – AC

20amp - Refrigerator"

[@Bayliss NOTE: as indicated on the the label in the photo below, the first 15A breaker also provides power to the converter. Additionally, the label identifies the first three breakers as "MAIN," with the last three breakers identified as Branch #3, Branch #4 and Branch #5.]

Image: https://us.v-cdn.net/5021717/uploads/editor/1z/e30rfdti9slp.jpg

NOTE: One thing that initially threw me for a loop when I was trying to confirm what each breaker controlled, is that when the first 15A breaker was off, in addition to the inside GFI and 110V outlets not having power, I also did not have power to the A/C Fan, FanTastic Fan, lights, propane-carbon monoxide detector, stereo, TV, holding tank monitoring panel, water pump and USB Outlets. HOWEVER, I soon realized that I was checking the WFCO breakers while the 12V battery was (intentionally, by me) disconnected. Once the battery was re-connected, all those systems worked........because they are 12V systems. As you know, the converter does its job and converts 110V/120V AC power to 12V DC to power those systems when you do not have a 12V battery connected.

I bring this up, because it is good to keep in mind that if you have disconnected/isolated your battery while hooked up at a campground, and you lose AC power, or the first 15A breaker trips, you will not have power to those 12V systems. @Sharon_is_SAM, this is another good reason (in addition to allowing your battery to continue to be charged by the converter) to leave the battery connected even if you have shore power.

ScottG · October 2019

Good info, @Bayless--and is also consistent with my recollection that the converter is powered by the 15A breaker that also powers the GFI receptacles. (I notice that the second line on the right side of your label actually says "converter" in addition to dining and kitchen receptacles.)

The main difference with your 2019 compared to my 2015 seems to be that the GFI receptacles have been split onto two circuits. I wonder if the overloading issue @MuttonChops raised drove this change.

Bayliss · October 2019

@ScottG, you are correct re the label indicating "converter" for the first 15A breaker. I was probably editing my post to add that info while you were writing your comments. I realized that John at nüCamp had not mentioned that in his E-mail response to me. I also clarified some other points in my post. I agree that nüCamp likely added a breaker to address overloading issues, plus as an extra safety feature since they control GFI outlets.

MuttonChops · October 2019

@Bayliss ; Great Information, thanks.

Believe My Unit has the extra 15A breaker and the older label. . . need to double check

ScottG · October 2019

Sounds like another receptacle was added somewhere along the line as well, I only have the dining, kitchen, and outdoor outlets.

Bayliss · October 2019

@ScottG, that receptacle on my 2019 320S is located under the rear cupboards at the rear passenger side of the trailer.

MuttonChops · October 2019

Bayliss said:

. . . my 2019 320S, the converter has SIX breakers, but nüCamp affixed the label for the previous configuration of the converter breakers.
"The 30amp is your main, and
the first 15amp breaker is Dining Room GFI/Kitchen Rec.
Second 15amp is Outside GFI/Rear inside Receptacle.
20amp – Alde
20amp – AC
20amp - Refrigerator"

{picture deleted)

Not sure why I never checked these before . . . but did so today and my
2018 320 S, built 02/2018 matches 100% with the information NuCamp provided @Bayliss
Without any correct labels (of course).
Have removed the NuCamp Four Breaker Label and installed a paper printed correct list.

Bayliss · October 2019

@MuttonChops, I need to do the same thing. Thanks to you, it will be a snap........copy/cut, paste and print.

dCliffhanger · October 2019

Me too!

DougH · August 2020

Borrowing a slightly older discussion for an additional observation on the WFCO converter / battery charger and the diagram at the top of this thread... this is all in boondocking mode / no external shore power..

I've got a few batteries in parallel. When that battery bank is powering an inverter that feeds the shore power circuit and all the outlets and lights in the camper, the WFCO wants to charge those same batteries (wasteful). So a fellow T@bber here said I can just pull the battery charger 12V fuse and stop that. That works, and works so well, I put in a switch to essentially pull that 30A fuse.

So if I have the air conditioner going, and a few lights and fans on, and the battery tub cutoff switch horizontal (battery on)... I'll see -53A on the battery monitor since the WFCO wants to charge the battery bank once the voltage drops enough below 13V. If I flip the new fuse switch I put in near the converter "Off", then BAM, it drops to -42A. Perfect. The WFCO had wanted to charge at 11A in that case, and we've dropped that pointless exercise, since the power to charge the batteries would need to come from the batteries with 2-3 layers of inefficiency along the way. I'm happy with that. Batteries will last much longer.

Going outside and turning off the tub cutoff switch has the same effect, but it might be raining or the campground might be filled with marauding grizzlies, so the internal switch is easier. The batteries are directly wired to the inverter, so even with the tub battery cutoff engaged, the inverter can still be going, but now rotating that tub switch to cutoff, the WFCO doesn't see any batteries to charge so battery monitor only shows -42A draw. As it should.

But wait, there is some confusion coming up, and a point to this post.

So now I leave the battery tub cutoff switch vertical (battery off) and turn off the inverter. No power, no 12V lights, as expected. Rotate the tub battery cutoff switch so the battery depiction is right side up (battery not cutoff) and the camper lights come on.

Now head inside and pull the battery charger fuse, or in my case flip off that new switch. Lights go back off.

Huh?

Does this mean 12V juice flows from the battery somehow through the battery charger circuit before reaching the 12V common bus? Or there's a relay in the battery charger circuit that must be powered on and active for the camper 12V bus to be connected to the battery? Seems so. Saves extra wiring? Just unexpected behavior.

But if I'm on the road and therefore running with the tub battery on for the emergency brakes and the 12V fridge, I have to have fuse #5 in or the new switch set to "On" for the battery charger.

And when I get to the boondocking campsite and need AC power I can turn on the inverter, but pull fuse #5 (or flip the new switch to "Off") so the battery charger is disabled.

Weird, but it's working for me. Just not sure I understand the innards of the WFCO box any more than I did before.

rh5555 · August 2020

I think your confusion arises from an incorrect diagram at the start of this thread.

There is no independent converter and battery charger - they are one and the same and feed all 6 fuses.

Image: https://us.v-cdn.net/5021717/uploads/editor/ek/xpksw81yu2jr.png

So when you hook up your inverter, not only does the WF-8735 try to charge the battery (stupid) but it also powers all the 12V appliances (not good). What you should do is figure out which breaker feeds the converter/battery charger and turn that one off. It is probably the 2nd breaker (15 Amps). Now all your 12V appliances are fed from the battery (backwards) via F6 and then out though F1, F2, F3 F4 or F5. Now your appliances are fed directly, rather than via the inverter and converter (inefficient).

But wait! The converter shares a breaker with your GFI outlets, so when you turn that breaker off, you lose power to those outlets too. The solution is to add a another breaker just for the converter (if you've got room), or route the power to the converter through an external 120V switch.

Denny16 · August 2020

Interesting discussion

The best solution is to wire in a transfer switch, that turns odd the WFCO power input from the breaker and switches in the Inverter, so it is one or the other, that way the inverter will not power the WFCO charger/converter. As you said, the Battery bank will connect via the 30amp F6 fuse and power the 12VDC distribution buss.

This will eliminate the power drain of the WFCO on the Inverter/battery bank.

Cheers

DougH · August 2020

@rh5555 Thanks! That first part makes much more sense. So F6 is the hot wire for battery charger out to charge tub battery when on shore power, and is also the line coming in from battery then connecting through F1-F5 to provide 12V power to everything when on battery power only. That fits the results of testing all combinations.

I only have a 12V top loader fridge now, so it sounds like I could move the battery charger over to the fridge relay. But I'd have to remember to move it back when I sell the T@B in case the next owner wants to put a stock 3-way back in. Your diagram shows the 12V converter charger coming off the 30A main breaker not the 15A GFCI, and I certainly can't flip off the main just to disable the charger. But Scott's diagram shows the hot line going to the GFCI breaker #2 as you stated. Moving the converter / charger over from the main or GFCI breaker to the last 20A fridge breaker could do the job. And that's about the right size breaker too. At present while at I'm not charging the battery on inverter power, I'm still wasting some battery time running the converter for any 12V lights or fans, instead of using the free cleaner DC power coming in on the F6 line.

@Denny16 I can try that. I'm obscenely plugging the inverter output into the unused Alde dual AC socket receptacle to power everything through that circuit. Easier than doing any responsible wiring. Flipping off the main on the WFCO might just work. As you say, 12V will come in on F6, and inverter is already powering outlets. Or do I then lose the safety of the breakers for the GFCI and air conditioner with the main breaker off? I should test short the air conditioner with a screwdriver while it's running off the inverter, and see what happens.

rh5555 · August 2020

my bad on the 120V line to the converter. Line should have ended in a question mark, as in I've no idea which breaker it goes to.

DougH · August 2020

rh5555 said:

my bad on the 120V line to the converter. Line should have ended in a question mark, as in I've no idea which breaker it goes to.

@rh5555 No matter, I can trace the line and just move it to the last breaker regardless where it comes off now, unless simply flipping off the main is good enough. Either way, I'd just always leave DC F6 in, and can take out the switch I added.

Denny16 · August 2020

@DougH, Plugging into the Alde outlet to power the AC plugs would bypass the breakers.
I think putting in an additional breaker for just the WFCO, that you can switch off to isolate the converter would be the easiest solution.

You can also buy a commercial inverter cutover switch, and possibly wire that into the WFCO?

cheers

MuttonChops · August 2020

rh5555 said:

I think your confusion arises from an incorrect diagram at the start of this thread.
There is no independent converter and battery charger - they are one and the same and feed all 6 fuses.

@rh5555; Can you provide documentation for your statement 'no independent converter and battery charger'. All of my research on RV Power Center Design/Operation indicate the Battery Charger is a functional separate part of the overall 120VAC to 12VDC Converter.

The following figure is representative of the operation (not actual circuit design).

Image: https://us.v-cdn.net/5021717/uploads/editor/zy/6msmg6jhs7cs.png

Denny16 · August 2020

According to the diagram above, the WFCO has a cut over relay, so just putting the WFCO on its own breaker or a cut off switch between the existing breaker and the converter, will keep the inverter from powering the WFCO, allowing its relay to engage the house 12VDC buss to the battery as originally designed.

Connect the inverter to the AC buss with another switch between the 30 amp shore power connection to the 30amp breaker (you could use a cutover dowuble pole single throw switch) or get a purpose made auto inverter cutover switch, that will switch between shore power and inverter based on having shore power connected or not.

cheers

rh5555 · August 2020

@MuttonChops, my assertion that "There is no independent converter and battery charger - they are one and the same and feed all 6 fuses." is, in truth, based upon opening up my WF-8955 converter in my TAB400 and observing that all the fuses have a common connection. I then read the WF-8735 manual, and it gave no pertinent information one way or the other. It seemed to pretty much duplicate the 8955's manual, so I assumed they were wired the same. Your circuit seems to be way more complicated than is necessary, and WFCO aims at the cheap end of the market, so I assumed...

Denny16 · August 2020

In order to get consistent current to the DC buss, and a three stage tapered charge current/voltage to the battery charging side, the house DC buss connection in the WFCO has to be after the AC/DC conversion and before the three stage charging circuit. They could be in the same chassis, but the wire connections would be at different points on the circuit boards. So MuttonChops diagram seems fairly accurate. The WFCO has to isolate the AC/DC selection relay) and the 12VDC Buss from the battery charging regulator.
cheers

rh5555 · August 2020

In theory, yes, but in practice no. The WF-8955 absolutely doesn't have a separate charger and house supply.

The most the converter can put out is 14.4V, which is within the acceptable voltage for all the "12V" appliances. In practice the WFCO chargers never go to the 14.4V "boost" mode, they are effectively fixed at 13.6V for the first 44 hours, and 13.2V thereafter. The 14.4V "boost" mode is basically a marketing gimmick. According to the manual, to enter boost mode the current must limit at 35 Amps when the converter is turned on. But hang on, there is a 30 Amp fuse on the line to the battery! The reason that no one reports this fuse blowing is because these converters never enter boost mode.

But to really resolve this, someone with a WF-8735 needs to go explore their wiring...

Denny16 · August 2020

Interesting, thanks for the update. I have not taken one apart, just working from theory, based on MuttonChops, and other inputs.
cheers

MuttonChops · August 2020

rh5555 said:

@MuttonChops, my assertion that "There is no independent converter and battery charger - they are one and the same and feed all 6 fuses." is, in truth, based upon opening up my WF-8955 converter in my TAB400 and observing that all the fuses have a common connection.
. . . WFCO aims at the cheap end of the market, so I assumed...

Your logic sounds good . . . cheap end of market . . .
I've found one diagram on web that supports your description.
There is no source reference with the diagram; don't know if it is from WFCO or article author.
I've not opened my 8735 to see if it follows the 8945 arrangement.

Image: https://us.v-cdn.net/5021717/uploads/editor/92/er40twohjkol.png

Denny16 · August 2020

Well, there goes my theory. Time to break out a VOM and see what gets power when.
cheers

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