Big Blue's Transformation

[ArdWrknTrk]

I'm not worried about the caddy. I'm worried that someone will have something metal in their hand that will bridge from the positive stud of the inverter to the body of the inverter or the cab of the truck. Granted it is only 12v, but fused at maybe 150 amp that could do a lot of damage.

Speaking of fuses and fuse ratings, I'm thinking of going with the Bussman fuse holder shown below. It is supposed to be good up to 500A, which begs the question of what fuse I should use.

The compressor specs say 14A and 1.5 HP. As was noted, 1 HP = 746 watts, so doing the math it looks to me like the compressor will pull ~9A when running. If we assume 100% efficiency that means ~90A @ 12V, but we know it won't be 100% efficient. However, I know that the compressor ran fine with the inverter running on the piece of #2 wire that I'm going to use and the wire didn't get even the least bit warm. #2 is rated at 130A max, so I'm thinking of fusing it at 150A slo-blo.

Thoughts?

I have the HMEG's and I like them.

I won't say again I think you're crippling yourself by not setting up for the full 3k the inverter is capable of (or the 6,000W surge capacity)

You'd have more room and an easier time of you traded it away for a unit half its rating.

But I think the (slo-blow) fuse should be rated same as the #2 cable it is protecting.

 

[ArdWrknTrk]

Jim - Meant to say I checked out Surplus City and can't find any contactors with 12v coils. They don't even have a pick for that in the filter, although I did try other options.

I think I've found the one I want to use. It is Jameco Part no.: 552462 and is $34.95.

But, it is going to be a tight fit where I want to put it, which is right above the inverter. I'd originally thought I wanted to have one project box that filled that area, but at the top of the caddy the box can only be about 2 1/2" "thick" or the seatback will hit it. So maybe I want a box that isn't as "tall" and can hold the contactor, fuse, DC power ports, etc. Still need to work on that plan.

Last, as you probably know from the other thread, I got the nutserts installed today. And then one of them spun. It took me a long time to cut the head off that bolt, a little at a time to keep from melting the caddy. So I tack-welded all three nutserts in.

With that done I got the caddy bolted down. But to get the caddy to sit at the right angle I had to cut the carpet back, leaving it just on the bolt-on step. That leaned the caddy back against the rear wall just where I wanted it.

Then I cut slots in the trim panel and screwed it onto the rear wall. And now the caddy is SOLID!

Gary, I haven't found the contactor I "thought" I had seen.

I did find a few inexpensive relays on eBay that seem to fit the bill.

I will edit in the links, as I know how Nabble likes to dump me back to the forum home when I go to another (eBay) app.

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F273773850697

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F121927687709

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F293704944316

 

[Gary Lewis]

Gary, I haven't found the contactor I "thought" I had seen.

I did find a few inexpensive relays on eBay that seem to fit the bill.

I will edit in the links, as I know how Nabble likes to dump me back to the forum home when I go to another (eBay) app.

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F273773850697

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F121927687709

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F293704944316

I'll order a couple of the HMEG's as I also need to fuse the winch leads. But the winch can pull up to 330 amps, so it needs to be fused separately.

As for the inverter power, you are right that I'm limiting things by not providing the full power the inverter is capable of pulling. But the aux battery relay isn't capable of handling that much power. I've looked for my post that specifies what I put in, but I want to say it is only capable of 200 amps. And it is new so I'm reluctant to replace it.

Plus, the wiring that I already have installed for the positive and ground leads is #2, and that should be upgraded if I were to run larger wire from the aux battery relay to the inverter. And bending larger wire, like maybe 2/0, around the corners wouldn't be easy, if possible. In fact, getting that #2 in there was a challenge.

But let me tell you about my confusion regarding wire sizing. First, there's the question of how much current the inverter can actually pull. It is rated at 3000 watts, as you know, and 3000 divided by 12 v give 250 amps. But that assumes 100% efficiency if the 3000 watts is the rating for the output. But the inverter won't be 100% efficient. And it has a surge rating of twice that. So, how much input current might it actually draw?

I've guessed 300 amps, which assumes 80% efficiency. And I've guessed that the wiring would withstand the 100% overload for a brief period. But how big of wire is needed for a 300 amp load? I've found a whole BUNCH of web sites that purport to tell how large of wire I'd need for that, and they all have different answers. For the most part they say that for a 10' run I'd need larger than 2/0. And that's allowing for a 5% voltage drop, which is the max most of them allow for.

I say all of that to say that #2 wire is known to work for supplying enough power to the inverter to run the compressor that I have. And it fits in with the overall wiring scheme in the truck as well as it physically fits in the truck. So, I'm just going to have to be happy with that.

[Gary Lewis]

Gary, I haven't found the contactor I "thought" I had seen.

I did find a few inexpensive relays on eBay that seem to fit the bill.

I will edit in the links, as I know how Nabble likes to dump me back to the forum home when I go to another (eBay) app.

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F273773850697

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F121927687709

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F293704944316

Jim - I really thank you for looking! I appreciate you doing that!

However, looking at those relays, two of them have 20A contact ratings and one has a 25A rating. But the TE Connectivity contactor I found has a 30A & 1.5 HP rating, and my compressor is rated at 1.5 HP. So I don't think the 20A units will work, and the 25A unit's coil is rated at 12 AC.

Again, I appreciate your efforts. But I think I'm going with the TE Connectivity contactor - if I can figure out how to get it in a project box. Its size is shown as 3.3 x 2.5 x 2.5 (L" x W" x H"). That means that I need to find a project box that provides at least 2 1/2" inside. And my measurements say that a 3" tall x 3" wide box will fit down against the inverter and not hit the seatback. So if I can find a box that is maybe 3 x 3 x 6 - 11" long I'll have room for the contactor, AC outlet, DC fuse, and 2 or 3 DC power ports.

And from my scribbled parts list the contactor and project box are the last of the things I need to order. I got 10' of red and 10' of black #2, 4' of black shrink tube with adhesive, 10 MagnaLugs, and 25' of split loom on order this morning. Oh, I forgot the DC fuse, AC outlet, and DC power ports.

[kramttocs]

Jim - I really thank you for looking! I appreciate you doing that!

However, looking at those relays, two of them have 20A contact ratings and one has a 25A rating. But the TE Connectivity contactor I found has a 30A & 1.5 HP rating, and my compressor is rated at 1.5 HP. So I don't think the 20A units will work, and the 25A unit's coil is rated at 12 AC.

Again, I appreciate your efforts. But I think I'm going with the TE Connectivity contactor - if I can figure out how to get it in a project box. Its size is shown as 3.3 x 2.5 x 2.5 (L" x W" x H"). That means that I need to find a project box that provides at least 2 1/2" inside. And my measurements say that a 3" tall x 3" wide box will fit down against the inverter and not hit the seatback. So if I can find a box that is maybe 3 x 3 x 6 - 11" long I'll have room for the contactor, AC outlet, DC fuse, and 2 or 3 DC power ports.

And from my scribbled parts list the contactor and project box are the last of the things I need to order. I got 10' of red and 10' of black #2, 4' of black shrink tube with adhesive, 10 MagnaLugs, and 25' of split loom on order this morning. Oh, I forgot the DC fuse, AC outlet, and DC power ports.

Where are you buying the magnalugs from?

I've always ordered mine from zoro but haven't priced elsewhere in awhile.

[ArdWrknTrk]

Jim - I really thank you for looking! I appreciate you doing that!

However, looking at those relays, two of them have 20A contact ratings and one has a 25A rating. But the TE Connectivity contactor I found has a 30A & 1.5 HP rating, and my compressor is rated at 1.5 HP. So I don't think the 20A units will work, and the 25A unit's coil is rated at 12 AC.

Again, I appreciate your efforts. But I think I'm going with the TE Connectivity contactor - if I can figure out how to get it in a project box. Its size is shown as 3.3 x 2.5 x 2.5 (L" x W" x H"). That means that I need to find a project box that provides at least 2 1/2" inside. And my measurements say that a 3" tall x 3" wide box will fit down against the inverter and not hit the seatback. So if I can find a box that is maybe 3 x 3 x 6 - 11" long I'll have room for the contactor, AC outlet, DC fuse, and 2 or 3 DC power ports.

And from my scribbled parts list the contactor and project box are the last of the things I need to order. I got 10' of red and 10' of black #2, 4' of black shrink tube with adhesive, 10 MagnaLugs, and 25' of split loom on order this morning. Oh, I forgot the DC fuse, AC outlet, and DC power ports.

Look at the plug on that compressor.

It has two parallel blades (15A receptacle)

750W x 1.5 = 1,125. @ 120V = 9.375A... maybe I'm wrong???

Here you are talking about current going to the inverter but you're not accepting that 20A is 33% over current for the compressor's *cable* design.

There are actual Swiss made GE contactors available 12V DC coil, 20A @ 250V 50-60HZ from a surplus place in Austin.

New take-offs.

But I thought you were looking for the most compact solution.

[Gary Lewis]

Where are you buying the magnalugs from?

I've always ordered mine from zoro but haven't priced elsewhere in awhile.

Scott - Good question. This morning I determined that I needed 6401-005E so I searched for them and the top two hits were:

• Amazon: Oh look, cool! Amazon has them. For $59.95 for a pack of 5, meaning $11.99 each!!!!

• Century Tool: Oh yes! That's where I bought them before. LOOK! They are $11.66 for 5!

So, guess where I ordered from.

But they wanted big bucks for the wire, so I went back to Great Lakes Skipper. I got tinned #2 for $2.50/foot.

[Gary Lewis]

Look at the plug on that compressor.

It has two parallel blades (15A receptacle)

750W x 1.5 = 1,125. @ 120V = 9.375A... maybe I'm wrong???

Here you are talking about current going to the inverter but you're not accepting that 20A is 33% over current for the compressor's *cable* design.

There are actual Swiss made GE contactors available 12V DC coil, 20A @ 250V 50-60HZ from a surplus place in Austin.

New take-offs.

But I thought you were looking for the most compact solution.

Jim - I wish I'd taken a screenshot of the calculator on my phone. It had exactly the same calculation you showed. And if you go back several posts I think I said "~9 amp" for the running current. But I think the 14 amps is the starting current.

As for the current rating on the contactors, I believe they are for a purely resistance load. But a motor is an inductive load and it is much harder to break the arc of an inductive load than a resistance load. From what I've read the contacts have to go much farther apart, and rapidly, to do that effectively. Hence the "HP" rating, which is what I'm keying on.

And while I would like "compact", I've found a box that will accept the TE Connectivity contactor. It this LeMotech Waterproof Dustproof IP67 Junction Box that is 9.8 x 3.1 x 3.3" outside but 9.6" x 2.8" x 3.2" inside. That will allow the 3.3 x 2.5 x 2.5" contactor to sit in sideways. And, the box fits in the envelope of the caddy pretty well.

So now I'm laying out the contactor, AC outlet, fuse, and DC power ports to see if it'll all fit.

 

[ArdWrknTrk]

Jim - I wish I'd taken a screenshot of the calculator on my phone. It had exactly the same calculation you showed. And if you go back several posts I think I said "~9 amp" for the running current. But I think the 14 amps is the starting current.

As for the current rating on the contactors, I believe they are for a purely resistance load. But a motor is an inductive load and it is much harder to break the arc of an inductive load than a resistance load. From what I've read the contacts have to go much farther apart, and rapidly, to do that effectively. Hence the "HP" rating, which is what I'm keying on.

And while I would like "compact", I've found a box that will accept the TE Connectivity contactor. It this LeMotech Waterproof Dustproof IP67 Junction Box that is 9.8 x 3.1 x 3.3" outside but 9.6" x 2.8" x 3.2" inside. That will allow the 3.3 x 2.5 x 2.5" contactor to sit in sideways. And, the box fits in the envelope of the caddy pretty well.

So now I'm laying out the contactor, AC outlet, fuse, and DC power ports to see if it'll all fit.

Holy cow!

That's massive.

Yup, I understand about inrush and capacitor start motors.

A lot of relays come 'diode protected'

which I understand eliminates a most of the arcing.

But it seems you're all set for now, so full speed ahead!

[Gary Lewis]

Holy cow!

That's massive.

Yup, I understand about inrush and capacitor start motors.

A lot of relays come 'diode protected'

which I understand eliminates a most of the arcing.

But it seems you're all set for now, so full speed ahead!

Which, the contactor or the box? The contactor is big 'cause the contacts need to come way apart to break the arc. But the box neatly fits above the inverter and, hopefully, has room for all the bits and pieces.

Time for another, closely related, subject - how best to use the DPST contacts. Should I put the hot side of the AC through both contacts in series or parallel? In parallel it would cut the current each contact sees in half. But in series it might help break the arc.

Thoughts?