running rooftop a/c while underway

[LarryD]

I think we're all conflating a bunch of issues. 1. no one said not to "exercise" your gennie. Its your resource, expend it as you will. 2. Alternators provide capacity, the BIM determines rate. Your battery will recharge as the BIM allows. 3. I am not asking permission from anyone to do with my coach as I desire. Only seeking input from anyone who might have done similarly. We all know the old saw regarding opinions. I'll get to this mod soon hopefully and post my results. Anyone interested can follow and anyone not can ignore.

[lwmcguire]

Originally Posted by LarryD

I think I've confused folks. Running the a/c off the inverter while running main engine wont cost anything. Just have to move the a/c circuit onto the inverter.

the solar/batteries I mentioned is my desire to be able to boondock without shore power. Sorry about that.

You are wrong if you think loading up to large alternators won't cost anything

Fuel and heat will both increase significantly more than you think

Try it and report back

[lwmcguire]

Originally Posted by Beau388

Let's work on how the coach uses alternator electrical power. Starting with the rating of 175 amps @ 13.8 volts (2415 watts); it requires 1 hp to produce 650 watts in a perfect world or about 1.2 hp in a real world. So 2415/650=3.7x1.2=4.5 hp from the engine considering no hp loss due to belt drive. The 175 amps figure is derived at 2,800 rpm at 70 F degrees. As the copper windings heat-up, their resistance increases. Let's the cooling air is 130 F coming out of the radiator and the generator fan is able to keep the internal temperature to about 150 F. The loss is about 0.8% per degree or a 80 degree rise and a 55% decrease in available amperage. Something like 80 amps available. Your engine requires around 25 amps and the coach dash A/C requires 20 amps. So you are left with an access of 35 amps (483 watts). The smallest roof A/C I can find draws 1,100 watts, then there is inverter efficiency, starting load .....

Saved me from digging out my Excel spreadsheet

Ran dual alternators for years at a price for belts, alternators, and fuel

[LarryD]

Originally Posted by lwmcguire

Saved me from digging out my Excel spreadsheet

Ran dual alternators for years at a price for belts, alternators, and fuel

So, using the numbers above ( I get this is all approximations) on my SV34 with dual alternators I'll have 275amps available ~3300 watts for 25 min every hour. That will be sufficient to power and slightly charge (~1800 load, 2500w charge) but will over the 35 min where the BIM shuts down charging I'll net discharge (3085 watts drained over every hour used). I havent yet upgraded my batteries to lithium, so the plan is to build a big enough bank to provide 10 hrs of reserve.

[Wiley1]

Originally Posted by 16ACE27

Duck didn't say solar wouldn't charge; he said it has zero value when the batteries are being charged by a much larger power source. The much larger power source will likely output at a higher voltage which increases the backpressure against the solar controller so it will have to match that higher voltage which means it will output fewer amps.

In other words, the time reduction due to solar being connected to fully charge your house batteries when the larger power source is also connected is so small as to be insignificant.

Yes, but....

If I'm barreling down the road on a sunny day, running my A/C and fridge on inverter power, and my vehicle alternator can't keep up with the demand, the voltage across the battery bank is going to read something less than 12 volts. Adding a solar charger to the mix could bring it to a condition where the batteries are charging instead of discharging.

Do you disagree?

[16ACE27]

Originally Posted by Wiley1

Yes, but....

If I'm barreling down the road on a sunny day, running my A/C and fridge on inverter power, and my vehicle alternator can't keep up with the demand, the voltage across the battery bank is going to read something less than 12 volts. Adding a solar charger to the mix could bring it to a condition where the batteries are charging instead of discharging.

Do you disagree?

Well that would depend on the solar capacity. A 100 watt panel will give you at best 5 amps of charging (yeah I know that's only 60 watts but I'm not the one that calls it a 100 watt panel). How's that compare to what the alternators can provide?

[Wiley1]

Originally Posted by 16ACE27

Well that would depend on the solar capacity. A 100 watt panel will give you at best 5 amps of charging (yeah I know that's only 60 watts but I'm not the one that calls it a 100 watt panel). How's that compare to what the alternators can provide?

Let's not get bogged down with the math.
My point is, whatever charging current you get from solar, it is not Zero.

Someday I'll record the actual numbers from my Victron. But, just for illustration, let's assume the following:
> +10A charging current while driving down the road with fridge on
> - 10A discharging current after turning on the A/C
> + 5A charging current after bringing three solar panels online

I don't see these numbers as unrealistic.

[Pete'sMH]

Originally Posted by 16ACE27

Well that would depend on the solar capacity. A 100 watt panel will give you at best 5 amps of charging (yeah I know that's only 60 watts but I'm not the one that calls it a 100 watt panel). How's that compare to what the alternators can provide?

My 80W Renogy panel has been known to provide 5.9 A out of the controller. It is a useful current. Folks can do what they want, of course, but running the A/C on the road is about the only purpose for having a generator as far as I’m concerned. For sure we ran ours for a day and a half last February in Texas when there was no power at the park due to an ice storm and it was 20 degrees. It was, rather literally, a life saver. But really our only regular use for it is driving in hot weather. It would be difficult or impossible for us to wear it out in my lifetime.

[HappyWanderer]

We were having trouble with our 2019 Daybreak 22GO staying cool in the Texas Summer heat. We found this great improvement, quite by accident, someone stole our surge protector at a Colorado RV campground. We decided to upgrade to a Southwire surge protector with digital read out, surge and low pass filter, internal battery driven capacitor and real time current monitoring system. It costs around $300.00 for the new unit, but the air conditioner works Much more efficiently, our rig has one a/c unit. You can find the protector on sale below $250.00, if you look around. In the past, we would get so hot at night. We now have to turn the a/c on low at the lowest temperature to not shiver at night, while camping in Palo Duro canyon at 105f at night. What a great discovery, clean power allows the a/c unit to work so much more efficiently. Amazing.

[dkoldman]

Originally Posted by LarryD

I think we're all conflating a bunch of issues. 1. no one said not to "exercise" your gennie. Its your resource, expend it as you will. 2. Alternators provide capacity, the BIM determines rate. Your battery will recharge as the BIM allows. 3. I am not asking permission from anyone to do with my coach as I desire. Only seeking input from anyone who might have done similarly. We all know the old saw regarding opinions. I'll get to this mod soon hopefully and post my results. Anyone interested can follow and anyone not can ignore.

How can I follow or what is the status?

Your plight is perhaps the biggest misperception I had wrong about RVs and Generators before buying my own.

You see when we use to rent, I got annoyed with how much almost every RV owner restricted generator use to like 3 or 4 hours per day; and then a fee if you went over. I use to think they wear or tear very fast and the total hours affected it's worth.

But I have learned the opposite is true. I purposely try to run my genset for even the slightest of reason. We always run the generator when driving and over 90 degrees.

Despite all my efforts; on average I can only run about 8 hours a month.

[Beau388]

Originally Posted by dkoldman

How can I follow or what is the status?

Your plight is perhaps the biggest misperception I had wrong about RVs and Generators before buying my own.

You see when we use to rent, I got annoyed with how much almost every RV owner restricted generator use to like 3 or 4 hours per day; and then a fee if you went over. I use to think they wear or tear very fast and the total hours affected it's worth.

But I have learned the opposite is true. I purposely try to run my genset for even the slightest of reason. We always run the generator when driving and over 90 degrees.

Despite all my efforts; on average I can only run about 8 hours a month.

Totally agree. I still have the original KY 4000 Onan even though I converted the coach to 50 amps. I have no problems running both A/C at the same time if necessary. I ran the generator for 66+ hours continuously during the February "Big Freeze" when the Village was without power for 3.5 days. The generator just passed 450 hours on the last trip. When traveling in May through September season I usually start the generator when we unplug from the campsite and shut it down when we stop for the night. The hottest day of the year was Monday (81 low to 104 high) and we took the coach out for lunch in Hondo (El Restaurante Azteca) and to exercise everything since it had not moved for 30 days. Another 4.4 hours on the generator.

[Gmthrust]

Originally Posted by Beau388

Totally agree. I still have the original KY 4000 Onan even though I converted the coach to 50 amps. I have no problems running both A/C at the same time if necessary. I ran the generator for 66+ hours continuously during the February "Big Freeze" when the Village was without power for 3.5 days. The generator just passed 450 hours on the last trip. When traveling in May through September season I usually start the generator when we unplug from the campsite and shut it down when we stop for the night. The hottest day of the year was Monday (81 low to 104 high) and we took the coach out for lunch in Hondo (El Restaurante Azteca) and to exercise everything since it had not moved for 30 days. Another 4.4 hours on the generator.

Totally off-topic, but I did my initial flight screening for the AF in Hondo. Wasn't much there in the early 80s.

[Beau388]

Originally Posted by Gmthrust

Totally off-topic, but I did my initial flight screening for the AF in Hondo. Wasn't much there in the early 80s.

Hondo is now part on the Greater San Antonio metro statistical area. The city motto is "Hondo, This is God's Country". About 10,000 happy residents now there. Four lane divided highway from here to there (US-90). SouthWest Airlines serves KHDO with two flights per day.

[Wiley1]

Originally Posted by HappyWanderer

We decided to upgrade to a Southwire surge protector with digital read out, surge and low pass filter, internal battery driven capacitor and real time current monitoring system. It costs around $300.00 for the new unit, but the air conditioner works Much more efficiently, our rig has one a/c unit. You can find the protector on sale below $250.00, if you look around. In the past, we would get so hot at night. We now have to turn the a/c on low at the lowest temperature to not shiver at night, while camping in Palo Duro canyon at 105f at night. What a great discovery, clean power allows the a/c unit to work so much more efficiently. Amazing.

Amazing, yes. But, I don't understand how that is possible. A surge protector is just a device to shunt excess power to ground. It doesn't add any power. Even with a capacitor or two, I don't see how it could modify the incoming sine wave significantly. And why would you need to unless the power was dirty? The rooftop A/C unit is designed to run on a clean sine wave that alternates between +170v to -170v and back to +170v at the rate of 60 times per second. Reducing the peak-to-peak waveform would reduce the effective power delivered to the A/C unit, which would seem to hurt the efficiency of the A/C system, not help it. I don't get it.

Can somebody please explain?

[16ACE27]

Originally Posted by Wiley1

Amazing, yes. But, I don't understand how that is possible. A surge protector is just a device to shunt excess power to ground. It doesn't add any power. Even with a capacitor or two, I don't see how it could modify the incoming sine wave significantly. And why would you need to unless the power was dirty? The rooftop A/C unit is designed to run on a clean sine wave that alternates between +170v to -170v and back to +170v at the rate of 60 times per second. Reducing the peak-to-peak waveform would reduce the effective power delivered to the A/C unit, which would seem to hurt the efficiency of the A/C system, not help it. I don't get it.

Can somebody please explain?

I mostly agree with your questioning how a surge protector can make an A/C run better. The only thing I can come up with is the "internal battery driven capacitor" acting as reactive load reducer to bring the power factor closer to 1 as the A/C is such an inductive load.

[Wiley1]

Originally Posted by HappyWanderer

We decided to upgrade to a Southwire surge protector with digital read out, surge and low pass filter, internal battery driven capacitor and real time current monitoring system. It costs around $300.00 for the new unit

I find this intriguing so, to investigate further, I went directly to the source here:
https://rvpower.southwire.com/produc...ge-protection/

Southwire has 13 portable (plug-in) models and 3 hardwired models. I looked through the specs and brochures but I wasn't able to find any model with a "battery driven capacitor".

Can you tell me the model number of the unit you bought?

[16ACE27]

Originally Posted by Wiley1

I find this intriguing so, to investigate further, I went directly to the source here:
https://rvpower.southwire.com/produc...ge-protection/

Southwire has 13 portable (plug-in) models and 3 hardwired models. I looked through the specs and brochures but I wasn't able to find any model with a "battery driven capacitor".

Can you tell me the model number of the unit you bought?

Originally Posted by Google Search

No results found for Southwire "battery driven capacitor".

Don't hold your breath waiting for this Unicorn.

Southwire does make an autotransformer type product "30A and 50A Voltage Regulators" for RVs, but they have a disclaimer:

Originally Posted by Southwire

This device does not protect against faults or surges.

https://rvpower.southwire.com/produc...ge-regulators/

[chunker21]

Originally Posted by 16ACE27

Don't hold your breath waiting for this Unicorn.

Southwire does make an autotransformer type product "30A and 50A Voltage Regulators" for RVs, but they have a disclaimer:



https://rvpower.southwire.com/produc...ge-regulators/

You'd be surprised at what can help an air conditioner performance. Example the dealer installed a hinge on the step access to the battery area, (see post step caution) and my air conditioners are now keeping the coach cold, so cold I have to raise the thermostat. My thought is the hot air leakage around the missing step hinge letting hot air in from below caused the units to run more. Sealed off and secure the air conditioners are now more efficient. Either that or the OAT is 75 not 95.

[HappyWanderer]

Folks, sorry for my response being so slow. My wifr and i are both still working, and Family school activities absorb our free time.
Back to the A/C unit comments. Good responses, one and all. The A/c unit can run more efficiently because the capacitor can keep the a/c compressor working at a more constant speed, without the low power drop out. Pardon my comment about battery back up. The Southwire unit is 34930.
As i understand, the capacitor and surge protection helps keep input amperage at a specific limit, allowing the cylinder speed to stay (constant) and push out more cool air into the rig.

Ps. I am a mechanical guy and don't always use the right words.

Now, back to work. Been working from home for two years.
Happy Camping

[16ACE27]

Originally Posted by HappyWanderer

Folks, sorry for my response being so slow. My wifr and i are both still working, and Family school activities absorb our free time.
Back to the A/C unit comments. Good responses, one and all. The A/c unit can run more efficiently because the capacitor can keep the a/c compressor working at a more constant speed, without the low power drop out. Pardon my comment about battery back up. The Southwire unit is 34930.
As i understand, the capacitor and surge protection helps keep input amperage at a specific limit, allowing the cylinder speed to stay (constant) and push out more cool air into the rig.

Ps. I am a mechanical guy and don't always use the right words.

Now, back to work. Been working from home for two years.
Happy Camping

Capacitors don't store AC energy - they have no effect on AC surges.
Surge protectors don't keep current steady (minimize surges) - they protect downstream equipment from damaging surges.