Electric AC?

[spankybear]

I just found out about these right here... Has anybody installed these? Yes I know China,,, and Cheap but they are cheap... Anybody have any thoughts?

 

[MatthewWBailey]

I plan on installing an RV type roof AC. But there's no need to source a 12v or 24vdc unit. It's better performance to go with generic 115vac units and power it from an inverter that runs off 24vdc since that's a standard thing you'll need for a habitat, or just general utility. A 3000w inverter will do lots. You can run smaller wire and there'll be less strain on the alternator during compressor starts. Lots of options for 115vac RV units. Here's two..

RV Air Conditioner 13.5K Quiet AC Unit with Remote Control, Non-Ducted

Are you ready to upgrade your RV's air conditioner? Look no further than RecPro! With our sleek AC and its powerful cooling capabilities, this unit is the perfect addition to any RV.

www.recpro.com

https://www.etrailer.com/RV-Air-Conditioners/Advent-Air/ADV79FR.html

 

[GeneralDisorder]

First of all - don't believe the 12,000 BTU spec. It's probably lucky to achieve half that. Just like the Chinese diesel heaters that make wild claims and when tested end up being about 50% or less of the claimed performance.

Take note that the factory Red Dot AC is 30,000 BTU's. And that's a true rating.

Also note that not having the AC integrated into the HVAC leads to no drying of the air for defrost. So your defroster won't de-fog the windows which really sucks and leads to moisture buildup. Cab smells like mildew and you can't see out of any of the windows.

Yeah the factory system is expensive. It will also add significant value to the truck because it's been done right with factory parts. Some cobbled together Chinese mess is going to DEvalue the truck IMO.

It's also not going to work well without a LOT of insulation, ceramic window tint (more expensive than that AC unit), and probably painting the cab white to reflect as much heat as possible. Even then it's going to be weak sauce.

 

[Jake2670]

I'm not sure i agree with above statements on 115v over DC, there r other DC units out there if don't wanna order from china but FYI folks, most everything comes from china so goo luck not buying ch as for BTUs n insul , he's right, doing those 1st a good idea. let us know if you do it.

 

[MatthewWBailey]

I'm not sure i agree with above statements on 115v over DC, there r other DC units out there if don't wanna order from china but FYI folks, most everything comes from china so goo luck not buying ch as for BTUs n insul , he's right, doing those 1st a good idea. let us know if you do it.

What do you think

 

[Ronmar]

Well a 12,000 BTU window A/C pulls ~1000W when cooling, and 40A@24V is 960W, so it may be reasonably close to 12KBTU

A little anemic for a greenhouse of a cab like is found on the LMTV.

Can your alt handle the extra 40+A @24v load?

Have seen a few now who have gone the rooftop A/C-inverter route and they seem to think it performed OK, it probably is just really slow at getting to temp.

As mentioned, no defrost benefits...

Someone has to try it

 

[MatthewWBailey]

Someone has to try it

What are we? Guinea pigs?

 

[Ronmar]

of course... Aren't we all?

 

[spankybear]

The problem with using an inverter is the loss... A good inverter is what 85% effacement? You will not have that big of a loss with a 24 volt compressor. I have been looking and they seem to be brush less and this would be batter... I was thinking that maybe there is a way in install the evaporator in the stock heater box in the cab. I would install the compressor close to the battery so the loss would be less. I would install the condenser under the bed. Has me thinking at least.

As for China... I am sure the rooftop internals are made there... and so is the inverter... So

 

[hike]

Are you looking for a habitat or cab installation?

Characteristics you may wish to consider:
Decibels at max;
Air volume delivered;
Lowest temperature of output air flow;
BTU's.

Cost is likely a statement about quality of components and necessary labor to install a working system—

 

[MatthewWBailey]

The problem with using an inverter is the loss... A good inverter is what 85% effacement? You will not have that big of a loss with a 24 volt compressor. I have been looking and they seem to be brush less and this would be batter... I was thinking that maybe there is a way in install the evaporator in the stock heater box in the cab. I would install the compressor close to the battery so the loss would be less. I would install the condenser under the bed. Has me thinking at least.

As for China... I am sure the rooftop internals are made there... and so is the inverter... So

85? No those are 95 if they're cheapo. 97-98% for high quality. Victron is in that range. Modern inverters advanced far due to the solar industry.

 

[GeneralDisorder]

Yeah they are CRAZY efficient. My Victron 5000W inverter is 94-95% efficient and it's not the latest tech. And running higher voltage affords you savings in terms of wire sizing. You need HUGE wires (relatively speaking) to run 40A @ 12v or 24v compared to 120v.

Solar easily makes up the efficiency difference in terms of battery draw..... @ 40A you are talking an extra 2A from the batteries to the inverter to make up the 5% loss and you'll gain that back since the technology in mini-splits is first going into the 120v/240v units not the 24v units - which are an afterthought to that market.

 

[spankybear]

85? No those are 95 if they're cheapo. 97-98% for high quality. Victron is in that range. Modern inverters advanced far due to the solar industry.

Can you link to an inverter that is 98% efficient? I like to know... I would think it would take at least 2% just to run the electronics... then at working temps... I really find that hard to believe you are going to get 98% in real world applications. Heck I find it hard to believe a top tier one would be 95% in real world applications... maybe 90... maybe.

Anyway I look forward to read the specs on one that is 98% . And if it's affordable...

 

[spankybear]

Are you looking for a habitat or cab installation?

Characteristics you may wish to consider:
Decibels at max;
Air volume delivered;
Lowest temperature of output air flow;
BTU's.

Cost is likely a statement about quality of components and necessary labor to install a working system—

I am looking a cooling the cab... I haven't built a box yet... have other projects like maybe building out a HMMWV M997A2...

 

[MatthewWBailey]

Can you link to an inverter that is 98% efficient? I like to know... I would think it would take at least 2% just to run the electronics... then at working temps... I really find that hard to believe you are going to get 98% in real world applications. Heck I find it hard to believe a top tier one would be 95% in real world applications... maybe 90... maybe.

Anyway I look forward to read the specs on one that is 98% . And if it's affordable...

Efficiency %'s are arbitrary numbers so focusing on that alone is going to create disbelief. It's all about total watts vs total losses. 85-88% efficiencies are 1985 era inverters.

I'm not an expert at the RV market and I don't care what they're selling there bc it's typically crap. Efficiency to them is irrelevant to just providing some functionality. But For custom habitats, mobile or otherwise, the product choices are 96 on the low end, 99.5 on the high end.

SolarEdge.com, Sol-Ark.com are 2 possible choices imo for habitats with solar and battery. SE reports 99-99.5 on the SE7600 which is off grid capable. SolArk reports 97.5 production and 96 charging on both 24v and 48v input products. Victron Quattro reports 96% and those are 15+ yrs old now. Outback is only at 93.5 on the Radian but it goes up if you remove the charge controller.

Even Aimscorp.net (Aims power) reports 95 baseline, and Aims are old school inverters with poor transformers. The simple fact is that modern electronics are more advanced with lower losses than before.

The total loss is fixed aside from copper losses which are proportional. So achieving a high efficiency % is an easy numbers game. 100w loss on a 5000watt inverter is 98% efficient. 100w is a lot! BUT, the 100w is mostly a fixed loss so you have to pull 5000 to get the 98% efficiency. See how efficiency is a side show?

If you're deciding on something for a truck based on the difference between 98 and 95% efficiency, to me, you're looking at the wrong thing. Unless you're an investor in solar energy looking for max returns annually on a six figure+ outlay. Those guys scream at me if the commissioning is 1/2% lower than projected. And projected has to be 96-97+ just to make the numbers work up front.

I would not even spec an inverter less than 95 in todays world.

 

[hike]

The issues are properly insulating the cab, using materials to raise the albedo, creating shade above the cab, properly powering the HVAC system whether mechanically or electrically.

Looking at the products marketed to the RV market the small footprint typical DC/AC converters we see, even from Victron appear 88% efficient. Though those units won't support the loads HVAC require. Properly sized units are 94+% and require larger footprints. Still I doubt the existing dual voltage 100a alternator can support starting, charging and running the truck, and running HVAC in the cab with either converted AC or direct DC power. Without a mechanical compressor the electrical system requires upgrading.

From experience building homes I have learned over the years that huge HVAC systems do not overcome poor insulation, large south facing windows and low albedo exteriors. These cabs are very poorly insulated and also have significant glazing.

In our well insulated high albedo home of 2,600~ sqft in the Texas hill country with wide temperature swings (15° - 105°F) with moderate humidity is comfortable with 48,000~ BTU's, about 67% the size the HVAC contractors said was needed.

In an M107X cab insulating looks pretty straight forward using a mixture of common products and layering, interior (sides, floors, roof) and exterior (doghouse). The glazing is difficult to overcome reasonably. Still a well insulated M107X cab of less than 50 sqft shouldn't need 30,000 BTU's unless we are fighting in the desert in full battle gear and protection.

I wish we had found an M1078A1 or A1R with a Red Dot Gen2 unit, though a well insulated, high albedo cab with a Gen 1 should be very adequate. If true I would think a properly powered 12,000 BTU mechanical, AC or DC unit would be sufficient to cool a cab comfortably. Of course, my 'comfortably' and yours may be different temperatures!

I am no expert—

 

[MatthewWBailey]

The issues are properly insulating the cab, using materials to raise the albedo, creating shade above the cab, properly powering the HVAC system whether mechanically or electrically.

Looking at the products marketed to the RV market the small footprint typical DC/AC converters we see, even from Victron appear 88% efficient. Though those units won't support the loads HVAC require. Properly sized units are 94+% and require larger footprints. Still I doubt the existing dual voltage 100a alternator can support starting, charging and running the truck, and running HVAC in the cab with either converted AC or direct DC power. Without a mechanical compressor the electrical system requires upgrading.

From experience building homes I have learned over the years that huge HVAC systems do not overcome poor insulation, large south facing windows and low albedo exteriors. These cabs are very poorly insulated and also have significant glazing.

In our well insulated high albedo home of 2,600~ sqft in the Texas hill country with wide temperature swings (15° - 105°F) with moderate humidity is comfortable with 48,000~ BTU's, about 67% the size the HVAC contractors said was needed.

In an M107X cab insulating looks pretty straight forward using a mixture of common products and layering, interior (sides, floors, roof) and exterior (doghouse). The glazing is difficult to overcome reasonably. Still a well insulated M107X cab of less than 50 sqft shouldn't need 30,000 BTU's unless we are fighting in the desert in full battle gear and protection.

I wish we had found an M1078A1 or A1R with a Red Dot Gen2 unit, though a well insulated, high albedo cab with a Gen 1 should be very adequate. If true I would think a properly powered 12,000 BTU mechanical, AC or DC unit would be sufficient to cool a cab comfortably. Of course, my 'comfortably' and yours may be different temperatures!

I am no expert—

Yeah for sure. I'm not adding an ac until I deal with the cab insulation. It's just an aluminum junction box as is. The roof shade is a huge factor.

 

[GeneralDisorder]

Ceramic tint. And Lizard Skin coating for insulation. At least with the Red Dot Gen 2 it's powerful enough to make this comfortable in direct sun with 100 degree F ambient. My truck is three color NATO CARC and I have no cab shade because the HIMARS hatch precludes that option.

 

[hike]

Yeah for sure. I'm not adding an ac until I deal with the cab insulation. It's just an aluminum junction box as is. The roof shade is a huge factor.

We just stripped the cab out. Adding non truck accessory electrical off the second battery bank, second Victron 24/12v 70a, adding DynaMat and DynaCore sound and thermal insulation, painting the interior, building back wall and ceiling panels, 24v Nomadic x3 AC—

 

[hike]

Ceramic tint. And Lizard Skin coating for insulation. At least with the Red Dot Gen 2 it's powerful enough to make this comfortable in direct sun with 100 degree F ambient. My truck is three color NATO CARC and I have no cab shade because the HIMARS hatch precludes that option.

I need to look into the ceramic tint; we haven't addressed the glazing as yet.

We are painting the interior a light tan, and the three color exterior a lighter, yet to be agreed upon color. The roof will either have a light colored rack or fairing to add shade and thermal separation from the cab roof—