Actual Ah demand for AirCon

[sailingharry]

Originally Posted by Putt-Putt

Perhaps it was just a typo, but Andre-Marie Ampere's name does indeed start with an A.

https://www.nist.gov/si-redefinition/ampere-history

It's funny how the mind reads what it expects to read. I read and re-read Jedi's post several times earlier, and then re-read it with purpose after you wrote this, and the typo would not compute. I just couldn't see that "E." I was expecting an "A" and that's all I ever saw.

[Putt-Putt]

It might be that Baronkrak was trying to make the same point in the "Hollywood" Post (#43) and you suffered from the same, can't see the forest for the trees condition there as well, as evidenced by your "in an odd fashion agreeing with us," Post (#44).

No harm done as I'm sure we all suffer this condition. I know for sure that on occasion, I do.

[s/v Jedi]

Originally Posted by Putt-Putt

Perhaps it was just a typo, but Andre-Marie Ampere's name does indeed start with an A.

https://www.nist.gov/si-redefinition/ampere-history

Yeah, I couldn’t edit it anymore…

[HKTim]

Originally Posted by witzgall

Chris from Balmar here. We are owned by Dometic, so I have run some numbers on our new Voyager variable speed AC units. The great thing about variable speed units is that when you slow a compressor down, the watts used drop at a greater percentage than the drop. For example, the running watts of a TX10 10k BTU unit, is 723 watts at 100%, but only 276 at 50% compressor speed.

So if you are running one at 100% compressor speed for 6 hours at 50% on time, the total battery power used would be 2385.9
wh, assuming a 90% efficient inverter. for a 12v system, that would be ~186ah, exclusive of a water pump.

Run the same system 100% of the time at 50% speed, and you consume 1821wh, 142ah.

Both examples give the same total BTUs of cooling over time, but you save about 23% in energy running at 50% compressor speed 100% of the time.

Chris

Chris. Have you come across any published reviews on the Dometic Voyagers? Would appreciate a bit of commentary, good and bad. I’ve asked elsewhere on this forum and so far can not find anyone willing to comment about them. I had Frigomar on my old boat and was quite happy. But am hoping the newer Voyager could be a further improvement on my new boat.

[Jerry Woodward]

and another related question:
I see the use of the term "inverter technology" associated with the Velair units. Is this just marketing BS for what is simply a variable speed compressor? I don't think they are using "inverter" in the same sense as we normally think of a DC to AC inverter?

The new Dometic Voyager units have a variable speed compressor. So am I correct in assuming that they "should" have similar advantages as the Velair units?

[Adelie]

Variable speed probably means the motor is being driven using a PWM (Pulse a width Modulation) controller. It’s a more efficient way to drive most motors when operating at anything other than max power.

[rslifkin]

Originally Posted by Jerry Woodward

and another related question:
I see the use of the term "inverter technology" associated with the Velair units. Is this just marketing BS for what is simply a variable speed compressor? I don't think they are using "inverter" in the same sense as we normally think of a DC to AC inverter?

The new Dometic Voyager units have a variable speed compressor. So am I correct in assuming that they "should" have similar advantages as the Velair units?

Yes, inverter units are generally variable speed compressors. At least some of them rectify the incoming AC power and then use an inverter to drive a compressor (sometimes 3 phase for higher efficiency) at variable speed.

[s/v Jedi]

Originally Posted by rslifkin

Yes, inverter units are generally variable speed compressors. At least some of them rectify the incoming AC power and then use an inverter to drive a compressor (sometimes 3 phase for higher efficiency) at variable speed.

Correct, you can fully assume they rectify incoming power, then invert it to 3-phase AC with variable frequency.

[Statistical]

Originally Posted by Jerry Woodward

The new Dometic Voyager units have a variable speed compressor. So am I correct in assuming that they "should" have similar advantages as the Velair units?

Yes. They are just be described/marketed differently.

The advantage of inverter units isn't the inverter. It is that using an inverter allows you to drive the compressor at lower output which is more efficient once it has brought the room temperature down. If a unit is described as variable speed it might be using an inverter or it might have a BLDC motor using a BLDC controller. It doesn't really matter the big advantage is being able to reduce the output of the compressor.

A "conventional" AC is overpowered once the room temp is near the target and as such it turns on and off but while on is full power. It is all or nothing.. It is full power for 10 minutes, turn off for 10 minutes back and forth. It is far more efficient to have an AC operating at 40% of peak output constantly than 100% of peak output with 50% duty cycle.