15k vs. 13.5k AC With Portable Gensets?

[regularguy]

That is an unusual generator design and not commonly found in RVs.  The most common inverter type generator is the Onan and it has no internal battery.

What Carl wrote about the starting battery is what I was referring to.

 

[GaryB]

Yamaha makes an EF2800i model that should handle the 15k a/c ok if Dometic's 1.74x start load factor is valid. The EF2800i is not as slick looking as the EF2400 but it weighs only  a little more and has the extra capacity you want.

Gary,

Have you ever heard the 2800 and 2400 run side by side (from a noise standpoint)?  I haven't and there's no Yamaha dealer closeby.  The 2800 is rated 60-67db, whereas the 2400 is rated 53-58db.  Since I really don't intend to do much CG boondocking (just occassional parking lot boondocking on the way to destination), will the extra 7-9db really make that much difference to us inside the RV, or to other parking lot boondockers a few hundred feet away?

Thanks!

 

[Gary RV_Wizard]

No I haven't and I have no idea why the EF2800i is so much louder than the IS models. And yes, 10 dB is a quite a bit louder.

I guess the EF3000is (or the fancier iSB with Boost system) would be a better choice than the EF2800.  However, the specs show the EF3000 models as being very heavy - 147 lbs. I can't figure that either - it uses the same engine as the 2800. Where does the extra 83 lbs come from? I can see it on the 3000iSB, which includes a heavy internal 12V battery, but not on the 3000iS with no battery.

Maybe an inquiry to Yamaha is in order to explain the differences.  Errors in web pages are not unusual either.

 

[Karl]

Regularguy,
For all practical purposes, a vapor and gas are the same. The difference is that a vapor is sometimes thought of as separate atoms or molecules of a substance diffused through a gas (normally air), but not combining (chemically) with it. The corresponding term would be a 'suspension', a diffusion of particles of material in a liquid. Liquids cannot be compressed, but gases (vapors) can. If that weren't the case, we wouldn't have the internal combustion engine, where gasoline vapor (gasoline and air) are compressed and then burned. Check out this link from NASA if you don't believe me. There are three states of matter - Solid, liquid, and gas. Vapor is merely a variation of a pure gas such as helium or hydrogen, and is not a separate state or entity. Air is a gas and contains a number of other gases, primarily nitrogen and oxygen, as well as other compound gases, liquids, and solids.

Can you provide a link to an a/c unit that doesn't have an expansion valve? I'd be very interested in seeing it.

 

[regularguy]

Regularguy,
For all practical purposes, a vapor and gas are the same. The difference is that a vapor is sometimes thought of as separate atoms or molecules of a substance diffused through a gas (normally air), but not combining (chemically) with it. The corresponding term would be a 'suspension', a diffusion of particles of material in a liquid. Liquids cannot be compressed, but gases (vapors) can. If that weren't the case, we wouldn't have the internal combustion engine, where gasoline vapor (gasoline and air) are compressed and then burned. Check out this link from NASA if you don't believe me. There are three states of matter - Solid, liquid, and gas. Vapor is merely a variation of a pure gas such as helium or hydrogen, and is not a separate state or entity. Air is a gas and contains a number of other gases, primarily nitrogen and oxygen, as well as other compound gases, liquids, and solids.

Can you provide a link to an a/c unit that doesn't have an expansion valve? I'd be very interested in seeing it.

Karl, First I apologize for spelling your name incorrectly before. Like I stated earlier, I am not here to debate or argue with you or anyone else. I also stated that I was using terminology familiar to the refrigeration / air-conditioning industry. My second post in response to you was only to clarify that fact. TO reiterate, we consider "gas" and "vapor" as separate entities because the liquid to vapor to gas .... then back to vapor, to liquid cycle is ALL important to the proper operation / efficiency of such units.  Yes in the real world gas and vapor are almost one in the same, but there is a reason for the two different words... especially in the HVAC industry. I also know about the internal combustion engine ( I am a certified Class-A automotive tech. I was certified in 1973) I am also a certified HVAC technician, (1984) Licensed Refrigeration Mechanic (1984) , and I hold a Masters in Mechanical engineering from the Wentworth Institute in MA (1979) I also hold a class 2 boiler license (1985) and a Building Operation / Operations Manager Certification (1998). I am currently the supervisor of Trades for The University of Massachusetts. So I do know (and agree with) what you have stated. Please understand the context of the terminology. We were not discussing internal combustion engines or the physical properties of matter in a liquid or gaseous state. We were merely adding to the discussion of electrical load, [for someones consideration in purchasing a generator] and in that regard the terminology sticks because it is and has been the industry standard "shop talk" since the first ammonia was boiled. This is how threads digress so much. We start by trying to answer a simple question of which generator to purchase and a few posts later we are linking to NASA. Should I tell students and apprentices that the liquid flashes out of the orifice into the evaporator into a vapor and then it absorbs heat and expands into a vapor then it absorbs more heat as it leaves the evaporator and it becomes a vapor! NO! We say it flashes to vapor, expands more and more to a gaseous state as it absorbs heat. If it didn't then how could we have vacuum at the point of flash and positive pressure thereafter.  We consider vapor as something that isn't compressible because it is much too dense. We could also consider the fact that the first law of thermodynamics states that energy can neither be created nor destroyed, and that holds true when discussing the properties of refrigeration,  but then someone would certainly come along and argue that the principals of nuclear energy dictate otherwise. Again, we are talking refrigeration terminology as an aside to and how it applies to electrical load.

 

[regularguy]

Regularguy,
For all practical purposes, a vapor and gas are the same. The difference is that a vapor is sometimes thought of as separate atoms or molecules of a substance diffused through a gas (normally air), but not combining (chemically) with it. The corresponding term would be a 'suspension', a diffusion of particles of material in a liquid. Liquids cannot be compressed, but gases (vapors) can. If that weren't the case, we wouldn't have the internal combustion engine, where gasoline vapor (gasoline and air) are compressed and then burned. Check out this link from NASA if you don't believe me. There are three states of matter - Solid, liquid, and gas. Vapor is merely a variation of a pure gas such as helium or hydrogen, and is not a separate state or entity. Air is a gas and contains a number of other gases, primarily nitrogen and oxygen, as well as other compound gases, liquids, and solids.

Can you provide a link to an a/c unit that doesn't have an expansion valve? I'd be very interested in seeing it.

Oh an BTW Vapors cannot truly be compressed. As you stated, "vapor is sometimes thought of as separate atoms or molecules of a substance diffused through a gas" and "The corresponding term would be a 'suspension'". When the atomized fuel "compressed" in an internal combustion engine, it isn't the liquid particles that are compressed it is the "gas" (air) that the atomized fuel is part of that gets compressed ( and yes I know that if gas did not have some degree of "moisture" it could not be compressed) but the moisture in the gas that is compressed in that case is as you stated, "combining (chemically)" or molecularly to be precise. Of course the NASA animation does not show the fact that as the "vapor" or "diffused" particles are  compressed the  molecular action creates heat and causes it to flash to a gas and the more efficiently it changes to a gas before ignition the more effective and efficient the subsequent combustion/ expansion is. We can go back and forth for eternity on this, but as the terms are incorporated into application, it is soon realized that textbook terminology has its place.... in textbooks.

 

[Karl]

Regularguy,
You're absolutely right - this has nothing to do with the original question, and further discussion here between the two of us would add nothing but confusion. I am absolutely awe inspired by all your degrees and certificates, and would like nothing more than to discuss this topic with you directly, but you have chosen to hide your email address. Should you wish to do so, please send me an email and we can go from there.

To all other RV Forum members: I apologize for getting so far of topic.