M1078A1 cab and chassis electrical upgrades including AC

MatthewWBailey said:

It's a red herring bc now the AHJ's only care about "how" I apply digital stamps, not the actual content of the drawing.

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In the construction industry, especially Public Works projects, engineers have become much more lawyerly over the years. No one really looks at the shop drawings until the pipe fitter points out why it won't work—

MatthewWBailey said:

I remember. I'll take this and draw it up in standard electrical fashion. You'll have to review/edit prior to permit submission .

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Looking at Post 19 the actual layout is more like this:



It is getting messy. It definitely needs to be redone, and I like your way best. You are welcome to do it, though I can import the schematics and edit them, too. I'd likely use GIMP or Inkscape. What software do you use?

hike said:

Looking at Post 19 the actual layout is more like this:

View attachment 929892

It is getting messy. It definitely needs to be redone, and I like your way best. You are welcome to do it, though I can import the schematics and edit them, too. I'd likely use GIMP or Inkscape. What software do you use?

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Autocad for drafting line diagrams, elevations, plan views. It's the standard thing since Moses

hike said:

Looking at Post 19 the actual layout is more like this:

View attachment 929892

It is getting messy. It definitely needs to be redone, and I like your way best. You are welcome to do it, though I can import the schematics and edit them, too. I'd likely use GIMP or Inkscape. What software do you use?

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We call that a point-to-point diagram which can get messy. We only use it for individual device in/out wiring details, so you can identify # of wires per device etc etc. the back of the TM has a bunch of point-to-point details on wiring terminals and cable assemblies. The Fmtv electrical schematics, 20 sheets, are drawn like "ladder diagrams" which are more organized into a system. These are better. Usually control schematics have 3 main types, p-to-p, ladder, and a topology. (Add a single line diagram for AC power, which is essentially a topology.). Your design needs a topology, which highlights the basic theory of operation and identifies major components for easy navigating/troubleshooting.

hike said:

In the construction industry, especially Public Works projects, engineers have become much more lawyerly over the years. No one really looks at the shop drawings until the pipe fitter points out why it won't work—

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Oh yea, wether it is right or not in the end is your buisness, but it won’t ever get to that stage if the Is are not dotted and the Ts crossed.

had an approved set of house plans in hand that I brought back to the engineer for “recommendations” because his end wall roof brace design wasn’t to code… Boy was he embarrassed At least I caught it before the inspector ever saw it…

MatthewWBailey said:

We call that a point-to-point diagram which can get messy. We only use it for individual device in/out wiring details, so you can identify # of wires per device etc etc. the back of the TM has a bunch of point-to-point details on wiring terminals and cable assemblies. The Fmtv electrical schematics, 20 sheets, are drawn like "ladder diagrams" which are more organized into a system. These are better. Usually control schematics have 3 main types, p-to-p, ladder, and a topology. (Add a single line diagram for AC power, which is essentially a topology.). Your design needs a topology, which highlights the basic theory of operation and identifies major components for easy navigating/troubleshooting.

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I appreciate the help—

hike said:

In the construction industry, especially Public Works projects, engineers have become much more lawyerly over the years. No one really looks at the shop drawings until the pipe fitter points out why it won't work—

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Yeah it's all about insurance and liability. I carry insurance so clients know they can sue me. The bureaucratic part has eclipsed the value/end-use-importance of the building/infrastructure. Lawyers have taken over this country with "statutory requirements" in every state. I used to just be an automation "design/build" guy in the private sector. Then on 1 public works job, a state agency said I was breaking the law by preforming "engineering" wo a license. So I got the license. Bureaucracy is just a way to mandate the funding for bureaucracy. I deal with it everyday.

Got the ceiling covered in Dynamat Xtreme, except one "test" spot. Though hot I can hold my hand on the Dynamat, the test spot is hotter. Difficult to keep my hand there long.



At 5:30pm CDT
Ambient outside 97°
Air in the closed up parked cab — 106°
Surface of the Dynamat Xtreme ceiling — 110°
Surface of interior bare ceiling — 129°

Not comfortable, but not bad for a closed up parked cab.

We have a box of Dynamat Core (fiber blanket) and another mega pack of Xtreme. Thinking of adding a second layer of Core on the ceiling and using the Xtreme on the door, side and rear panels/wall. Planning to install Xtreme directly to back wall, though the doors and rear panel areas are tough. What about mounting to the panels and covering with carpet? Has anyone tried that?

Also, @GeneralDisorder has me wondering if Lizard Skin would be a good addition to the exposed interior area to be painted? What kind of surface does Lizard Skin present? Could it be used in place of a primer layer and painted over with the finish?

hike said:

@GeneralDisorder has me wondering if Lizard Skin would be a good addition to the exposed interior area to be painted? What kind of surface does Lizard Skin present? Could it be used in place of a primer layer and painted over with the finish?

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Lizard Skin is AMAZING. It has a matt textured appearance. It can be painted. It dropped the inside skin temps in my M1079 box by 20+ degrees.

It's quite the engineered coating. It's used by the Navy, and by many integrators - used on the engine dog houses on fire trucks. Unlike Dynamat and other "consumer" solutions - "Lizard Skin" is just a consumer facing brand name that was spun off by Mascoat. It's made in the US:

GeneralDisorder said:

Lizard Skin is AMAZING. It has a matt textured appearance. It can be painted. It dropped the inside skin temps in my M1079 box by 20+ degrees.

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That looks really cool. Watched a couple videos and read the FAQ's.

Thinking about using the ceramic (thermal) coat on the exterior of our planned 'white' roof as an undercoat.

Thank you!

hike said:

Got the ceiling covered in Dynamat Xtreme, except one "test" spot. Though hot I can hold my hand on the Dynamat, the test spot is hotter. Difficult to keep my hand there long.

View attachment 929915

At 5:30pm CDT
Ambient outside 97°
Air in the closed up parked cab — 106°
Surface of the Dynamat Xtreme ceiling — 110°
Surface of interior bare ceiling — 129°

Not comfortable, but not bad for a closed up parked cab.

We have a box of Dynamat Core (fiber blanket) and another mega pack of Xtreme. Thinking of adding a second layer of Core on the ceiling and using the Xtreme on the door, side and rear panels/wall. Planning to install Xtreme directly to back wall, though the doors and rear panel areas are tough. What about mounting to the panels and covering with carpet? Has anyone tried that?

Also, @GeneralDisorder has me wondering if Lizard Skin would be a good addition to the exposed interior area to be painted? What kind of surface does Lizard Skin present? Could it be used in place of a primer layer and painted over with the finish?

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so how did that A/C perform under those conditions?

Ronmar said:

so how did that A/C perform under those conditions?

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All we have done with the AC so far is the bench test. Most of the insulation is in place now on the ceiling and rear wall. Need to finish the AC installation.

While the cab is stripped out we are going to paint some trim and all the bits we pulled out of the dash; build out and carpet the rear area floor storage and rear wall electrical (accessory) cabinet panels; build out and carpet the ceiling panels with map lights and such; install power windows and locks; insulate and carpet the door and rear side panels; build out the central console and storage.

If I can keep my paying work load light hoping to be putting everything back together by the end of the month? We'll see which month =)

I too am very anxious to see how this unit performs in the wild—

hike said:

Got the ceiling covered in Dynamat Xtreme, except one "test" spot. Though hot I can hold my hand on the Dynamat, the test spot is hotter. Difficult to keep my hand there long.

View attachment 929915

At 5:30pm CDT
Ambient outside 97°
Air in the closed up parked cab — 106°
Surface of the Dynamat Xtreme ceiling — 110°
Surface of interior bare ceiling — 129°

Not comfortable, but not bad for a closed up parked cab.

We have a box of Dynamat Core (fiber blanket) and another mega pack of Xtreme. Thinking of adding a second layer of Core on the ceiling and using the Xtreme on the door, side and rear panels/wall. Planning to install Xtreme directly to back wall, though the doors and rear panel areas are tough. What about mounting to the panels and covering with carpet? Has anyone tried that?

Also, @GeneralDisorder has me wondering if Lizard Skin would be a good addition to the exposed interior area to be painted? What kind of surface does Lizard Skin present? Could it be used in place of a primer layer and painted over with the finish?

Click to expand...

Regardless of the level of insulation, given enough time anything can get extremely hot. The more insulation the longer the process takes.
I have a 9kbtu mini split and it easily(less than 20% duty cycle) keeps the 20ft shipping container comfy during 90 degree temps in full sun.

aw113sgte said:

Regardless of the level of insulation, given enough time anything can get extremely hot. The more insulation the longer the process takes.
I have a 9kbtu mini split and it easily(less than 20% duty cycle) keeps the 20ft shipping container comfy during 90 degree temps in full sun.

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Right. Insulation adds resistance to conducive heat exchange. Your experience is encouraging.

As I recall your metal box is also painted a light color in a satin or gloss finish. Once we paint the roof bright white and perhaps improve the reflectivity with a satin or glossy finish less radiant energy should transfer to the metal, allowing less conductive energy to pass to the interior insulation.

We will be adding a light colored roof rack above as well mainly to catch sun before it reaches the roof, cast some shade and hopefully radiate most that heat away from the roof—

Slowly progressing. Painted the interior doors two tone: taupe and white.





Hoping to start going back together next week—

Man, this is a great build. Super informative

Update, and some real world testing.

We have the mockup for the cab overhead and rear wall console/storage built, still working on central console mockup.

The Nomadic rooftop AC worked satisfactorily through the summer, though not as well as I hoped. I think two one issue has affected its performance:
1— our electrical design provided separate truck and accessory circuits built off 4 group 31 batteries. One bank of 2 in series 12v 100ah batteries for each circuit backed up by the 24v 200a alternator. The banks/circuits were separated by a Victron Cyrix 230a combiner. With the 200a alternator backup I grossly underestimated the affect a 100ah AGM battery bank would have on the AC compressor designed for a 400ah system. In testing while driving about town and on the highway the combiner took way too long to connect the circuits/banks together allowing the draw to rapidly lower the 'voltage' near 18.5v in the accessory circuit before connecting. Then once connected the grossly under charged accessory circuit would pull the truck circuit down while the alternator was charging both circuits. The Victron unit sensed this and protected the truck batteries, which of course meant the accessory batteries never fully charged as the truck side drew down below the fail safe point too quickly. This cycle repeated every 20 to 30 minutes. Not a workable design, my fault. I expected the combiner to keep the circuits together much more time. Looking at the Victron spec sheet I should have known better;
2— the Nomadic 24v X3 unit in Max mode pulls about 58a. That's just under 1,400 watts. Which I believe produces just under 4,800 BTU/hour. When we first looked at these units Nomadic's spec sheet stated over 12,000 BTU for the unit. I am not a physics expert, nor an AC tech, but having a built a number of homes over the years I do know how to do the Manual J calcs. 12,000 BTU in the cab is sufficient for comfort even with all the glass. Not enough to make an ice box, but plenty for comfort. So, not being an expert, unless the conversion from watts to BTUs is much greater than 3.412 the Nomadic rooftop unit can't possibly put out 12,000 BTUs. Frankly I was reading the spec sheet and expecting, not inspecting as I should have been. My second mistake. Ronmar put us on the path to the correct BTU formula when looking for cooling air BTU's.

Where are we now? Here is the current electrical layout incorporated into our schematic sheet.


On schematic green wire is new (to be labeled); black is existing or rerouted with labels
1— removed LBCD;
2— removed remote battery disconnect;
3— placed TL 1 (alternator 24v), TL 37 (manual disconnect), and TL507 (inlet air heater) together in a gel sealed weather proof connector;
4— moved TL39 (alternator) to the battery side of the manual disconnect;
5— deleted the 12v path in battery box;
6— added a Victron Orion 24/12-70a dc/dc converter at the passenger footkick;
7— added 12v fuse block to driver foot kick;
8—added a Victron Orion 24/12-70a dc/dc converter at new back wall power center;
9— back wall power center has 1,000w dc/ac converter, 12v fuse block, 24v 60a fuse to AC;
10— added Nomadic 24v X3 rooftop AC to turret panel, we reconfigured the low voltage cutoff parameter to 24v to avoid truck battery draw down.

This configuration will allow the truck to assist the larger habitat system system using Victron Orion-TR Smart dc/dc chargers. Which I believe @Keith Knight suggested to me over a year ago.

How is it working now?
Over the past month running off 26.8 to 27.5 volts the AC has been much more effective and though I didn't anticipate it the truck seems happier, too. Now when first starting out we put the unit on Max mode, drawing 55 - 58 amps, for about half an hour and then switch to Eco (~33a) or Auto (~45a) modes depending on the outside temperature for the duration of our drive. That typically keeps the interior high 70's to low 80's. We haven't been in temps over 102 as yet, so we will see. The cab insulation isn't yet finished and none of the carpet is in, so this may work long term for our use case.

We are still looking for a complete RedDot Gen2 system and the DC systems are getting better each year. Nomadic has announced they are working to release new mini-split systems (heat and cool) that may have a good sizes for cab and habitat, respectively. We will see what we find as we continue on. (edit) We are getting at least 10,000 BTU's on 24v with <60 amps. (/edit) And I'll be doing my own math for BTU's these new Nomadic units may put out once released.

Also, I am thinking we need to add a fuse (¿225a?) between the batteries and X1 on the PDP.

Comments, suggestions, critiques all welcome. Still evolving the cab and chassis while planning the habitat—

I don't think you can get away from the physics of the vapor compression cycle. Motors are only so efficient even PWM DC motors. The engine driven compressor can suck down as much HP as it likes and the truck will not even blink. Even 5 HP is 3,728.14 Watts, or 133 amps at 28v. That's nothing for the CAT engine to donate - won't even be measurable in terms of performance or mileage. And the Red Dot system is somewhere in the range of 28,000 BTU's due to the need for operation in the 120 F desert with no insulation, no ceramic tint, and potentially running the gunner hatch wide open. 10,000 BTU's should suffice for normal civilian uses but that's still a LOT of amps for the 28v side. The HIMARS 300/300 could do it. Not much else though. Ridiculous amount of electricity required.

GeneralDisorder said:

I don't think you can get away from the physics of the vapor compression cycle. Motors are only so efficient even PWM DC motors. The engine driven compressor can suck down as much HP as it likes and the truck will not even blink. Even 5 HP is 3,728.14 Watts, or 133 amps at 28v. That's nothing for the CAT engine to donate - won't even be measurable in terms of performance or mileage. And the Red Dot system is somewhere in the range of 28,000 BTU's due to the need for operation in the 120 F desert with no insulation, no ceramic tint, and potentially running the gunner hatch wide open. 10,000 BTU's should suffice for normal civilian uses but that's still a LOT of amps for the 28v side. The HIMARS 300/300 could do it. Not much else though. Ridiculous amount of electricity required.

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Physics wins.

28,000 BTU is more than needed and the Gen1 and Gen2 units are a challenge to find. (edit) 3,700 watts = 10,000 BTU's. 10,000 - 12,000 is plenty. 5,000 Still the Nomadic makes it as comfortable as sitting in a shady breeze on a 102 day.

Ronmar put us on the path to the correct math for calculating BTU's when cooling air!
We then found a similar formula: CFM = BTU / ( dT x 1.08 ) or BTU = CFM x dT x 1.08

The Nomadic 24v X3 rooftop unit has a rated flow in Max mode at 2,423fpm, or 400cfm (12 x 2 vent to four 3" diameter vents, so let use 350 likely actual)
Observed dT is 28° between inlet and exit

350cfm x 28° x 1.08 = 10,584 BTU
400cfm x 28° x 1.08 = 12,096 BTU

Thank you @Ronmar You are mystic.
(/edit)

Time to start looking at compressor, condenser, expansion valve, dryer and evaporator specs to cobble one together. We are looking forward to watching @Ronmar build his creative AC unit—

I also must be missing some part of the physics (math) as Red Dot sells the E-6100-4-24P rated at 15,000BTU. I recall looking at these while looking at the Nomadic units that was rated at 12,480 BTU. At half the price, 40% of the weight and 70% the amp draw we tried the Nomadic.



I need another physics class and more knowledge about converting watts to BTU's—