Fridge to battery?

[Rhythmtone]

I figured I'd start a new thread for this one - it's related (intertwined) with my "overhaul", but not exactly the same subject.

PO updated the refrigerator, it's really nice, but pulls 375 watts on DC! They used a professional shop, who upgraded the wire to 8AWG, but ignored the 20A max per circuit on the old DC board - there is now a 30A fuse there.

It seems to work fine, but I've never run it for long (yet) - I do like to use DC mode on long drives, and/or short stops, like at most an hour. The PO told me that they never used DC mode, and just drove with the propane on, or waited for shore power each night and used ice packs - but I do want to have the option of having it on when the alternator is running, because it's a feature after all.

The new PD4645 doesn't solve this unfortunately - I didn't realize I needed ONE 30A branch that wouldn't be there on the new board - my Roadtrek (2006) used a progressive dynamics 5000 panel (and totally separate charger / converter) that gave you up to four 30 amp branches, so I just didn't anticipate this, ugh.

I'm good with electrical, but I haven't been able to find a clear answer on this - what would it entail to skip the PD board (as many people do) and instead of using the OEM board go with something like this?

WFCO Arterra 89354555PC Fuse Panel https://a.co/d/dDRfqqu

If it's just larger wire to the battery or (drop-in) that would be nice, but I can't find a clear answer. Yes, my new converter has the pendant, so I don't *need* the board, but I would really like to avoid running the fridge all the way to the battery, when there really should just be one or two 30 amp branches on these upgrade kits. I'm not too worried about overall capacity, although I will check that tomorrow morning - I just want to run one 30 amp DC circuit for this really nice new fridge that they installed (albeit unsafely). But I'm not clear on what stepping up to a DC board with 40amp legs will affect, instead of 30 amp main legs. If the rating is the same for each branch and I'm not overcurrent then I don't see what difference it would make - unless I need to upgrade wiring to battery in case of future person does want to load it down?

Any advice is appreciated, thanks,
Dave
1999 Premier
Vacaville, California

[noluck]

that is crazy amp draw, i would never use 12 volt

[Rhythmtone]

I agree, it's ridiculous - my old one was 15 amps.

I'd still like to be able to use it when the motor is running though,

Thanks

[noluck]

have you confirmed with a amp meter? personally when driving i prefer to top up the batteries not just try to run the fridge with with the current available

[Rhythmtone]

Thanks for the reply,
I have not tried an amp meter as I don't believe that my multi meter has that setting, etc. - I was just going off the manufacturer's installation instructions that stated 275 watts (23 amps) and to connect to a 30A DC fuse leg.

I like to top off as well but I wasn't sure how much this would affect that - my limited understanding is that the alternator put out up to 130A and could do both - or I'd be happy to upgrade to a 180A/200A model, if necessary.

I'm in the process of changing out the converter / charger and would like to fix this at the same time - can I just purchase that higher rated board that I linked? Connection to batteries is 8AWG I believe, but could be changed to 6AWG if necessary.
Thanks
Dave

[Blue~Go]

Edited to add:

I see I didn't read your post all that well, so my post below probably won't really apply to you. I'm sorry; that was my fault. I answered again in my next post.

I'll leave this one here though in case it might be useful to a future person.

************

It sounds like you have an absorption refrigerator (i.e. it will run on propane). Makes sense, as that is what Chinooks were delivered with. Back in those days, they were "3-way" refrigerators. Meaning propane, 110v AC, or 12 volt DC.

The thing is, these things are absolute PIGS to run on electricity, AC or DC. But most people don't really care about that when on AC, as they are plugged in to a power pedestal. DC though.... yeah... HUGE load.

Newer versions of absorption refrigerators are only "2-way," meaning propane or 110 volt AC. My guess is they realized that running on DC was basically a liability, as they then had to (or SHOULD have) wired them to support this large load.

To make a comparison, the same size compressor refrigerator would have something like a BD50 12-volt compressor. It would take around 4 amps to run on DC (vs. like 30!). Or a slightly smaller one would have a BD35 and run on around 3 amps. Either way it's X duty cycle, of course.

If it were me I would do one of two things:

1) Keep the fridge, but only run it on AC (or propane). I believe you still do need to keep the DC wiring because it still needs a tiny amount of DC just to run the circuit board (but not the cold part of the fridge itself).

2) Remove and replace with a 12-volt compressor type refrigerator. You get more space (there is no "fireplace" in back) and less fire risk. But that said, it's a project and you then need to make sure you have enough battery bank and re-charging capablity to support it.

I did #2 myself. I have a 4.7 cubic foot Vitrifrigo refrigerator/freezer. This runs me around 50 amp hours per day in reasonable outdoor temps (bit more if it's over 90º out). By stepping down to this size, I was able to do two things:

1) Refrigerator no longer sticks out further than around 22" - so no more turning sideways to get to the entryway
2) Top of refrigerator is around 46" from the floor, which gives me nice sight lines and a "set down counter" by the door.

Vitrifrigo does make a larger version that fits quite well where the original Chinook unit was; I just wanted the smaller one for the wider aisle and the counter on top. The larger one also has the advantage of two doors on the outside (vs. mine has the thing where you open the main door and then the freezer is kind of a pull down plastic door). I would like the two doors but wouldn't give up my extra hall space and counter for it (but that's just me)

[Blue~Go]

Edited to add: Okay, dug out my original wiring notes (1999 Chinook Concourse as-built).

I think I see your problem. My original notes said this (straight from the Brown Box):

Circuit 5) 20 amp fuse -- 8 AWG red wire -- powers refrigerator only.

So there it is: Chinook used a 20 amp fuse and apparently that was fine for the original refrigerator.

So it sounds like whomever planned the new refrigerator install, didn't take this into account, and put in a higher draw unit (great, as if they weren't already piggy enough on DC!).

If I were you (and wanted to run this crazy thing on DC), I would remove that particular 8AWG wire from the brown box fuse panel altogether. The 8AWG wire is fine for 35+ amps. So I would use something like a 40a Maxi fuse or Midi fuse in it's own separate fuse block (ATC is really pushing it at 40a and most ATC fuse blocks are only rated to 30a anyway). Put the fuse as close to the beginning of the wire as you can (i.e the brown box).

********************************

Okay, I'll try again (tho the part I added above was after I found my original wiring notes, so is probably all you need to read of this post).

If the refrigerator takes 375 watts DC. Well, I like to use 11.5 volts for calculating. Yes, you shouldn't let your batteries get that low, but IIRC that's where the LVD cuts off, so..... (not to mention voltage drop).

So at 11.5 volts, 375 watts is 32.6 amps DC

On my 1999 the refrigerator had its own fuse in the DC fuse panel with a red 8AWG wire coming into it. This went ONLY to the refrigerator's DC power wire (nothing else on this fuse). Does yours not have this? I can't remember what size fuse was in it though..... but I will go look in my notes.

I also don't know if the original brown box had a 20-amp max for the fuses (I removed it early on and re-did my DC distribution system).

But ..... then you say 30 amp "branches" That sounds more like AC? But this refrigerator should run on something less than 4 amps of AC power. Just as reference (cuz who knows what PO's installers did) in my original Chinook wiring the refrigerator didn't even have its own AC breaker, but you simply plugged the AC cord of the refrigerator into a receptacle that was in the outer lower compartment (accessed from outside) and it was part of the "Outlets" AC circuit. So that circuit was ALL the outlets on one AC breaker. Still, fridge would only be drawing around 4 amps on AC, so unless you go crazy plugging things into the outlets, no problem.

So far I'm not very helpful, but I just want to be sure we're on the same page (I'm probably confused).

[Blue~Go]

Yep, posting again, LOL.

Okay so just a bit more data on the 8AWG and a 40 amp fuse. You can do that and stay within ampacity. I'll show my work.

1) ABYC ampacity chart.

Here you can see that with 105ºC rated wire (my Chinook had this), and not in an engine space, 8AWG has an ampacity of 80 amps. But we have to do more calculating.

2) A good rule of thumb to build in some safety factor, is to go down to the 90ºC rating. That's 70 amps.

3) Now there is a bundling factor (heat related). For 7-24 wires in a bundle, you have to multiply the ampacity rating by .71 The refrigerator wire goes across the Chinook in a gigantic tight bundle of wires so .71 X 70 = 49.7

Hence I would feel okay about a 40 amp fuse on that circuit. But just not an ATC fuse, and especially not in a 20-amp rated fuse block. Hence I would go with something like a Maxi fuse in a block (see Blue Sea 5006100 or 5068 and Blue Sea 5139) or a Midi fuse in a block (see Blue Sea 7720 and Blue Sea 5251).

[Rhythmtone]

Thanks for the reply!

Fridge runs 275 watts on DC (23 Amps) - sorry, my bad, the 325 watts is the AC rating.

Yes it has 8 AWG to the DC panel (circuit board), but as you can see, it's still undersized.

I really want to keep this thing, it costs $1350 to purchase and God knows what they paid to install it.

I guess the plan will be to divert the DC wire to the battery, with an inline fuse - but I can't just buy a higher rated board with the 30 amp DC circuits for slide outs?

Sorry about the wrong numbers, the above is correct,
Dave

[Blue~Go]

Fridge runs 275 watts on DC (23 Amps) - sorry, my bad, the 325 watts is the AC rating.

Well that's less bad.

Yes it has 8 AWG to the DC panel (circuit board), but as you can see, it's still undersized.

Yes, not the wire (you are sort of ok there) but the fuse panel rating itself is a bit low.

You could just run a 20 amp fuse in your existing fuse position and see how it goes. I say that as ... maybe the stock Chinook fridge also took 275 watts but managed to run without blowing 20 amp fuses. (I don't know what the original fridge used as I no longer have it.) If you only run it when driving, and you have your alternator combined with the house, then 275 watts ÷ 13.5 volts is only 20.3 amps. I suspect this is why it worked the way things are originally set up. Why not try it with a 20 amp fuse?

I really want to keep this thing, it costs $1350 to purchase and God knows what they paid to install it.

Fair enough. They can work well if you use propane or shorepower most of the time.

I guess the plan will be to divert the DC wire to the battery, with an inline fuse - but I can't just buy a higher rated board with the 30 amp DC circuits for slide outs?

Okay, I'm not sure I'm following but I'll make some comments and let me know if I've missed your intent.

That said, see above I would just try the original wiring with a 20 amp fuse, *when you are driving and combined*

1) No problem using the original 8AWG wire that goes to the brown box. Just remove the wire from the fuse position at the brown box and instead route it to one of the fuses I mentioned in the other post (they can easily take larger fuses).

2) Or if you WANT to run a new wire, then I see two choices Either run the new the wire around the overcab area and down to the batteries. This is what I did with my new fridge wire. For me, the voltage drop would have been around the same either way, but going around the front was easier as no need to deal with getting behind the shower. For you, presuming you are not changing out that meager, LONG 8AWG wire to the batteries from the Brown box, going around the rear would be much worse for voltage drop. OTOH, going around the front you would be taking a huge load off that aforementioned long/skinny/inadequate wire from the Brown box to the batteries. (I changed all that out so it was large/robust, and my batteries are under the couch, so that's why I say for me it was a horse apiece; for you going around the front with a new wire would be much better.)

If you do run new wire, and if you don't run a wire pair (i.e. you only run a positive wire), you might consider adding a jumper from the battery negative post to the frame, to supplement the Chinook negative frame jumper from the brown box (which is, you guessed it, small). (I ran an 8AWG pair, so no need.)

You will still have a LOT of voltage drop with 8AWG and that size load, but perhaps the absorption refrigerators don't care so much? With the compressor fridge the compressor controller doesn't want to see voltage drop. I just barely stayed under spec with my 8AWG pair and that's with only the ~40 watt draw of the DC compressor.