Can someone please take a peak at my basic wiring diagram and answer a few questions?

[Atl-atl]

Im rebuilding my 81 FWC Hawk and I need to put the wiring back together. I kept it all intact but removed it. Its very minimal but its old so I need to replace all the wires, the crappy tube fuse and re-route it all. I don't know much about wiring up systems like this so my questions are super basic. I have been researching which is what got me this far. I wrote into the diagram what I think are the correct answers to some of my questions. For now Im simply going to run a house battery that is not connected to the truck. My power needs are so small that I can trickle charge the battery out of the vehicle when not in use. I only camp once a month or so and when I do its usually only for one night and I don't really use any power. My only future power concerns will be how much I need to run the furnace overnight in cold weather if I decide to camp at a ski area or something like that.

Anyway here is my starting diagram. I plan to run a bluetop unless someone has a better suggestion.

My questions so far are:

- When running only a house battery what do I ground the battery negative terminal to?
- What size breaker do I use?
- What size wire do I run between the battery, breaker and fuse block?
- I plan to use a fuse block unless I should use something else. What size fuse do I need for my exterior light and my furnace?
- What size wire do I use from the fuse block to the light/furnace? 6mm?
- Can I ground the light to the camper frame? Thats the way it is currently.
- The furnace ground is currently back to the battery negative. Is that the correct way to do it?

 

[AndrewP]

While I disagree with not making your house battery part of your electrical system, I will take a stab at your questions. Just remember that adding the house battery into the rest of the system is no harder than the rest of your wiring and gains you significant flexibility. Even little stuff like arriving at your destination fully charged is helpful. In the end, it won't really matter because you can add the circuit to keep your trailer charged by the alternator later.

Also, If your wiring is 30+ years old, start completely over. You can upgrade to a better safer system and your wiring diagram is a good start.

Regarding fuse sizes-that's easy. Fuses protect wire. Use an ampacity chart like this:

https://www.bluesea.com/support/reference/529/Allowable_Amperage_in_Conductors_-_Wire_Sizing_Chart




- When running only a house battery what do I ground the battery negative terminal to?

The trailer frame. Or better, install a ground bus, and attach all your grounds there, and ground the whole thing to the trailer frame.

- What size breaker do I use?

This depends on the size of the wire to your fuse panel. Making MANY assumptions (like it isn't far from battery to fuse panel), I'd likely run 6 gauge to the fuse panel, and so I'd use about a 100 amp breaker as close to the battery as possible. This would also leave head room for future growth.

- What size wire do I run between the battery, breaker and fuse block?

See above. Your average fuse panel is usually 100 amp total, and you'll be far less because of your limited battery and charging capacity.

- I plan to use a fuse block unless I should use something else. What size fuse do I need for my exterior light and my furnace?

A fuse block is what you want. In fact, I use a fuse block that also contains a ground bus like this:

http://www.amazon.com/gp/product/B0... fuse block&qid=1445266953&ref_=sr_1_2&sr=8-2

- What size wire do I use from the fuse block to the light/furnace? 6mm?

What is the amperage draw of your furnace and how far is it from the fuse block? This is where I think your system will go wrong. The furnace likely draws significant power, and you are likely to have only 50 amp-hours of power available. Post up the amp draw of the furnace and we can give better advice.


- Can I ground the light to the camper frame? Thats the way it is currently.

Sure, but it's always better to run the ground back to the source. If you use the fuse block I show, you can attach the ground back to that.

- The furnace ground is currently back to the battery negative. Is that the correct way to do it?

It's a reasonable way. If the amp draw is under 30 amps, you can run the ground back to the ground side of the fuse block, but I would still ground the case of the furnace to the frame or battery. Again, what is the amp draw? I don't know what furnaces draw but it is likely a lot. You don't want to take your battery below 50% of capacity or you will kill your expensive AGM battery in short order.

 

[Atl-atl]

While I disagree with not making your house battery part of your electrical system, I will take a stab at your questions. Just remember that adding the house battery into the rest of the system is no harder than the rest of your wiring and gains you significant flexibility. Even little stuff like arriving at your destination fully charged is helpful. In the end, it won't really matter because you can add the circuit to keep your trailer charged by the alternator later.

Also, If your wiring is 30+ years old, start completely over. You can upgrade to a better safer system and your wiring diagram is a good start.

Regarding fuse sizes-that's easy. Fuses protect wire. Use an ampacity chart like this:

https://www.bluesea.com/support/reference/529/Allowable_Amperage_in_Conductors_-_Wire_Sizing_Chart




- When running only a house battery what do I ground the battery negative terminal to?

The trailer frame. Or better, install a ground bus, and attach all your grounds there, and ground the whole thing to the trailer frame.


- What size breaker do I use?

This depends on the size of the wire to your fuse panel. Making MANY assumptions (like it isn't far from battery to fuse panel), I'd likely run 6 gauge to the fuse panel, and so I'd use about a 100 amp breaker as close to the battery as possible. This would also leave head room for future growth.

- What size wire do I run between the battery, breaker and fuse block?

See above. Your average fuse panel is usually 100 amp total, and you'll be far less because of your limited battery and charging capacity.

- I plan to use a fuse block unless I should use something else. What size fuse do I need for my exterior light and my furnace?

A fuse block is what you want. In fact, I use a fuse block that also contains a ground bus like this:

http://www.amazon.com/gp/product/B0... fuse block&qid=1445266953&ref_=sr_1_2&sr=8-2

- What size wire do I use from the fuse block to the light/furnace? 6mm?

What is the amperage draw of your furnace and how far is it from the fuse block? This is where I think your system will go wrong. The furnace likely draws significant power, and you are likely to have only 50 amp-hours of power available. Post up the amp draw of the furnace and we can give better advice.


- Can I ground the light to the camper frame? Thats the way it is currently.

Sure, but it's always better to run the ground back to the source. If you use the fuse block I show, you can attach the ground back to that.

- The furnace ground is currently back to the battery negative. Is that the correct way to do it?

It's a reasonable way. If the amp draw is under 30 amps, you can run the ground back to the breaker, but I would still ground the case of the furnace to the frame or battery. Again, what is the amp draw? I don't know what furnaces draw but it is likely a lot. You don't want to take your battery below 50% of capacity or you will kill your expensive AGM battery in short order.

Thanks a ton for your help. I definitely understand some of the things you're saying but I think there is a little confusion. My camper is not a trailer, its a Four Wheel Campers "Hawk" truck bed slide-in pop-up camper. It is constructed entirely from aluminum. Is this still ok to ground to? I plan to put a battery in a box in the storage area under the seat of the camper. Thats where the power will be coming from and Ill remove it to re-charge when Im done with my trip. Can I use a ground bus for the furnace/light and ground the bus to the negative terminal? Do I then have to ground the negative terminal to something? The trucks frame? The whole point of not wiring the house battery to the trucks charging system was so I didn't have to wire the camper to the truck, so I can more easily remove the camper from the truck to use it for other truck stuff. This seems like relatively common practice among slide-in camper guys. My camper even came with a battery box already underneath the seat and the wiring was not grounded to anything other than the negative terminal of the house battery. In the grand scheme of things I guess it wouldn't be that much more difficult/time consuming to have a ground and power wire to remove when I take the camper out of the truck but for the sake of the post I started lets keep acting like I won't wire the house battery to the truck. I will be using all new wiring, fuses etc. I pulled the old stuff out but kept it intact so I can copy some of it when I re-wire.

- As for wire/fuse/breaker size I think I can figure it out based on what you've said and the chart you linked. Thank you for that.

- As for distances, I will be able to wire up the battery, breaker, fuse block/ground bus all right next to each other in the storage area under the seat. This is right across the floor from the furnace just a few feet away. The run of wire to the furnace will be 4-5 feet and to the light will be about 6-7 feet.

- As for amp draw, the light will be minimal but the furnace I do not know. I will have to contact Four Wheel Campers to get that info. Its not a huge furnace as the camper itself is small but I will get back to you.

Thanks again for your help!

 

[AndrewP]

I would treat the slide in like a trailer and everything else still applies. It will be even easier than a trailer because it will be closer to the charging source!

The amp draw of that furnace really matters, especially if the battery cannot be recharged. But yes, you can ground everything to the negative post of the battery. In the old wiring harness, how large are the wires that supplied the furnace previously? What amp fuse fed those wires? I'd start there as a minimum. But do your calculations, because you do not want to discharge your battery too much. The general rule for deep cycle batteries is no more than 50%.

For making a disconnect - an Anderson monolithic (SB series) power pole set up would be perfect for hooking up the camper and easy to disconnect when you slid the camper out of the bed.

 

[Atl-atl]

Ok, here is where you will either laugh or be scared hahaha.

In the pics below you'll see a rats nest of wiring that is the original(I think) wiring. The guy I bought it from claimed he was the 2nd owner and that everything worked it just needed a battery hooked up. I kind of believe him. The camper was actually in decent shape and looked to be mostly original when I took it home.

All of the wiring appears to be the same gauge, small. Keep in mind this is a 1981 model year camper. The furnace has ground/power and the T-stat has power(red) and control(I think, the blue wire) coming off the furnace. The original fuse block is a very old appearing glass-tube fuse piece. From the fuse block there was power and ground going to the house battery box. This is the wiring encased in white that you can see in the pic. Its still very small gauge wiring, the housing makes it look a little bit larger than it really is. The only other wiring that exists is for two interior lights(which I have eliminated) and one exterior light which has a switch in-line of its power wire and is grounded to the frame.

You can see a little better in this picture there are three wires coming through a hole in the plywood shelf. These are the three wires from the furnace.

Here is what the fuse block looks like.

I have no idea what amp fuses these might be heh. All of the wiring is the gauge you see in these pictures. Id be really surprised if the furnace was drawing much amperage and working correctly with wire this tiny.

 

[Atl-atl]

So today I called FWC and talked with Shaw in service. He said the only way to know for sure the amp draw of the furnace is to pull it out of the camper to see what the make/model is and contact the manufacturer. After that he added, FWC only ever uses 8, 10 or 12 gauge wire and that none of the furnaces they have ever used draw very much amperage. I guess this "proves" the existing wiring is likely the stock wiring. Now that I know this Im more confident to wire it up without worry about larger gauge wiring or battery drain.

How bad would it be to run a 30amp fuse for the furnace even if Im guessing it only draws 15 amps? As for the rear light I think I can go with a 15amp fuse and be in decent shape. This would give me 55 amps extra for future use if I ran a 100amp fuse block.

 

[AndrewP]

The fuse is only to protect the wire. So if you ran 8ga to the furnace and fused it with a 50 amp fuse, it would be ok. Similarly, if you used 10 gauge wire and fused at 30 amps, it will work fine. The problem is, you don't know what your heater draws. I'm guessing based on the pictures you posted, that 10 gauge wire and a 30 amp fuse would work.

 

[verdesardog]

That furnace probably draws 3 amps but can go as high as 10 for motor starting.