Having some difficulty with breaker/fuse placement.

[beckkl]

I purchased the 12V 1K MPP Solar unit for my camper, and am having trouble determining fuse/breaker sizing and placement. I will have 160W of panels and a 100AH AGM battery. My understanding is that I need about a 125A fuse on the positive of the battery, but the manual also mentions that the PV array should also be fused, as well as the incoming shore AC. The strange thing is that it mentions a 10A breaker on the incoming AC which seems very small. Not sure why. I definitely would like to be able to easily disconnect PV, so I was going to put a 40A breaker on the red wire. Is this correct?

 

[John Frum]

1000 watts ac = 8.333333333 ac amps
8.333333333 * 1.25 fuse factor = 10.416666667
10 amps ac fuse or breaker for shore power is good.

I'n not an expert on pv panels but a double poll breaker would not hurt.
A double poll breaker cuts both negative and positive.
The breaker should be 1.25 x the expect load or the max ampacity for the wire whichever is lower.

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PSA: don't buy cheap breakers! the cheap ones trip to low if you are lucky and weld shut if you are not.

 

[beckkl]

But in bypass mode I'm assuming I can pull more than 10A, correct? I'd like to run the Air conditioner when on shore power.

 

[John Frum]

But in bypass mode I'm assuming I can pull more than 10A, correct? I'd like to run the Air conditioner when on shore power.

If it specs a 10 amp over current protection on the shore power side I don't think so.

 

[beckkl]

Ugh, if this thing is limited to 1000W in line mode it completely defeats the purpose of why I chose this unit in the first place.

 

[John Frum]

Ugh, if this thing is limited to 1000W in line mode it completely defeats the purpose of why I chose this unit in the first place.

Bummer... devil last seen hiding in details.
Is it too late to cancel your order?

 

[beckkl]

Yeah. Maybe I can split the shore power and run one of the legs to a XANTRAX ats and the MPP unit. The MPP inverter output to the XANTRAX inverter input. Then the AC side in the RV would always be driven by shore power when it exists. The DC system would still correctly be maintained by the MPP unit.

 

[beckkl]

I should say a gopower ATS, since the XANTRAX is only rated to 15A

 

[KBWaldron]

Ugh, if this thing is limited to 1000W in line mode it completely defeats the purpose of why I chose this unit in the first place.

For the shore power breakers, consider an additional breaker just for the air conditioner if you are only going to run your A/C on shore power. it would only be live when shore power is available. Just don’t join that to the AC output of the all-in-one.
Put some kind of mark on the outlets that are only powered by shore power for your convenience.

 

[beckkl]

For the shore power breakers, consider an additional breaker just for the air conditioner if you are only going to run your A/C on shore power. it would only be live when shore power is available. Just don’t join that to the AC output of the all-in-one.
Put some kind of mark on the outlets that are only powered by shore power for your convenience.

Yeah, that could be a solution as well. Thanks.

 

[John Frum]

I should say a gopower ATS, since the XANTRAX is only rated to 15A

Cool that may help with the neutral gound bond switching issue that we never go to the bottom of.

 

[beckkl]

Any thoughts on how to connect the existing 12V WFCO fusebox? It has a 10AWG spliced into a 6AWG wire currently. That 6AWG wire runs to junction box in the front, where it is fed from the battery (also 6AWG). There are a few other 12V leads heading out to a few lights. I'd like to get the battery off the tongue, which means moving it close to the MPP unit in the back storage area. My first thought was to simply wire the 10AWG cable to the WFCO panel and the 6AWG headed to the junction box into a bus bar, then connect the battery to the bus bar with 6AWG cable. The WFCO box is fused at 30A. I don't know what fuses are downstream of the 6AWG cable, but since I'm replicating the same setup as before, I'm wondering if I am good to go.

 

[beckkl]

For the shore power breakers, consider an additional breaker just for the air conditioner if you are only going to run your A/C on shore power. it would only be live when shore power is available. Just don’t join that to the AC output of the all-in-one.
Put some kind of mark on the outlets that are only powered by shore power for your convenience.

The more I think about this, I think it is a better solution. The problem with the ATS is that if shore power cuts and the AC is running, I would overload the inverter. Not sure how bad this is, but certainly not good. If the circuit is completely isolated It might be better. Plus I think I can do it for quite a bit cheaper than the $80 transfer switch.

 

[John Frum]

The more I think about this, I think it is a better solution. The problem with the ATS is that if shore power cuts and the AC is running, I would overload the inverter. Not sure how bad this is, but certainly not good. If the circuit is completely isolated It might be better. Plus I think I can do it for quite a bit cheaper than the $80 transfer switch.

                              |->breaker->air_conditioner
shore_power->surge_protector->|
                              |->
                                 |->manual_transfer_switch->ac_panel_master_breaker
battery<->all_in_one------------>

 

[beckkl]

                              |->breaker->air_conditioner
shore_power->surge_protector->|
                              |->
                                 |->manual_transfer_switch->ac_panel_master_breaker
battery<->all_in_one------------>

What is the purpose of the manual transfer switch? Why not let the MPP handle this?

 

[John Frum]

What is the purpose of the manual transfer switch? Why not let the MPP handle this?

You are correct let me ammend my drawing.
Was borrowing from another thing I was doing.

 

[John Frum]

                              |->breaker->air_conditioner
shore_power->surge_protector->|->breaker->all_in_one->ac_panel_master_breaker

Just remember to disable the converter

 

[beckkl]

yep exactly what I was thinking. Going to grab some mini din breakers and wire them up in a panel. 10A for the MPP, 20A for the AC, and 15A for the microwave. Might even throw a double pole in there for the PV array, but I'm not sure if that should be in its own box. If I remember NEC classifies 50W and lower as LV.

 

[John Frum]

yep exactly what I was thinking. Going to grab some mini din breakers and wire them up in a panel. 10A for the MPP, 20A for the AC, and 15A for the microwave. Might even throw a double pole in there for the PV array, but I'm not sure if that should be in its own box. If I remember NEC classifies 50W and lower as LV.

The WFCO has AC and low voltage DC in the same box just separated by a bit of metal.

 

[John Frum]

@beckkl please acknowledge that you understand the significance of the neutral/ground bond and how its relates to mobile applications with shore power.