-
Dock / Storage power getting 2 legs out of it
Okay, I have this thing stuffed over in the enclosed storage nearby … I’ve got it plugged into 120v via an adaptor that goes 15a->30a->50a basically one leg L1(A) of the AC is getting power. One of the trace inverters (A) is showing green/green so its got a full charge on that bank. The other inverter (B) is yellow only. Discharging. There’s no load on this leg according to the meter.
I’m concerned that some portion of the house batteries are slowly discharging with just the inverter load, even idle .. that the A side isn’t going to charge that, or there is some switch somewhere that I need to throw to combine the two legs for the purpose of storage. (having no conversion manual is really a PIA)
In the hopes that there’s a simple solution to this, I bought one of these: http://www.campingworld.com/shopping/item/50-amp-rv-box-adapter/25774 But without knowing before hand to look at the storage building, the city code requires these dock power systems on GFI, which the little box above will create a slight phase imbalance which (of course) will pop the GFIs on both legs. I can fix this by buying a pair of 120v-120v isolation transformers and a little clever wring, but I’m not sure thats thats the right answer. (removing the GFis isn’t an option though I considered some midnight rewiring when noone was looking to move the load around on them)
Thoughts?
-
8 Replies
-
Why not just wire it properly with the correct plug and breaker?
-
Why is only one leg getting power? A 15A or 30A adapter should be wired so the one 120V source is bridged across both legs of the 50A 120/240 RV plug.
You are correct that your 2 30A to one 50A adapter is going to great problems with GFCIs, if the the to 30A sources are out of phase. If they are in phase, the GFCI should be fine. For storage, a single 30A bridged acrossed both legs of your 50A plug should be more than enough power.
-
Its a rental facility, I’ve already asked and gotten an “oh we can’t do that” answer.
Why not just wire it properly with the correct plug and breaker?
-
Good question, I expected them to be bridged too, but its clearly not. (or something else is up) Thats how I went down the road to the the 2 > 1 box .. the el-cheapo bridge connector I bought at the RV store also pops the GFI .. (unless I use yet another adaptor to remove the ground) then I just get L1(A) again.
I’d really like to get 2 15a legs though (I have 2 isolated breakers @ 15 amps so it won’t overload them) which are theoretically in phase (according to my tester at least)
Why is only one leg getting power? A 15A or 30A
adapter should be wired so the one 120V source is bridged across both
legs of the 50A 120/240 RV plug.You are correct that your 2 30A to one 50A adapter is going to great
problems with GFCIs, if the the to 30A sources are out of phase. If
they are in phase, the GFCI should be fine. For storage, a single 30A
bridged acrossed both legs of your 50A plug should be more than enough
power. -
If the circuit you are using is a GFCI circuit you will trip the ground fault protection every time. A GFCI has nothing to do with the load, but has everything to do with tripping in the event of an open ground.
I know of only a few conversions that will work on a GFCI protected circuit and the reason they do is they establish a ground connection prior to the transfer switch recognizing and switching to shore power.
The voltage on both legs is a separate issue.
-
This is pretty much the conclusion I reached as well.. Hence the thought of using Isolation transformers to create a “new” leg beyond the GFI, so it wont trip.
If the circuit you are using is a GFCI circuit you
will trip the ground fault protection every time. A GFCI has nothing to
do with the load, but has everything to do with tripping in the event of
an open ground.I know of only a few conversions that will work on a GFCI protected
circuit and the reason they do is they establish a ground connection
prior to the transfer switch recognizing and switching to shore power.The voltage on both legs is a separate issue.
-
FWIW. the concern you will have is not related to ground. GFCI’s don’t trip because of a ground problem. They trip because current is leaking, presumably to ground. Here’s a good illustration: http://gfciplug.com/index.php/how-does-gfci-work
If you are taking two GFCI protected 110VAC sources through your 50A cord, it will not work. If you are really stuck with two circuits and you can’t get by with one (one should work) you have an option besides an isolation transformer, which may not work either.
You could wire your coach’s inverter/chargers so they can be plugged into an external source. This way each inverter/charger is plugged into it’s own GFCI protected shore outlet. This will work, but requires some thought on how to pull this off in your coach.
The isolation transformer will likely not work, unless you are planning to use two of them, one for each GFCI protected supply circuit. The critical obstacle is to make sure the load being returned on neutral is solely from the supply circuit. This can’t be done with the 50A input to the coach because the one neutral carries the load of both L1 and L2. BTW, the current carried by the 50A neutral will be less than the combined loads of L1 and L2 because L1 and L2 are not in phase with one another.
-
Updates:
I picked up another El-Cheapo 15a->30a->50a cable collection .. this one works insofar as L1 and L2 are indeed bridged. It does pop the GFI natively, but putting a ground-pole removing plug between them settles that down. (don’t tell the safety nazis) Right now both my house battery strings are getting charged .. and my fridge is running.
An isolation transformer here should in theory resolve this GFI popping …
Now .. to get more current out of this..
I have two Todd isolation transformers on order. http://www.toddsystems.com/Isob1.html that would be one for each leg. I did plan on wiring them up independently, but the neutral would be shared. I can measure the phase easy enough to make sure everything is in phase when its hooked up. Though I’m playing with some designs on a out-of-phase detection circuit that would only engage a relay allowing current to flow when both legs are in phase and not when they are out.
Ultimately the idea here (beyond keeping the house charged) is to bring in enough current to run one of the ACs or some kind of dehumidifier in-order to keep the humidity down inside the bus. Besides isolating the inverters .. I’ve also been thinking along the lines of just adding a transfer switch for one of the AC units and give it its own feed.
Log in to reply.