rogerw2
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Re: 3000W Chinese Gensets Info.
professor95 wrote: rogerw2 wrote: Professor, and All, I have purchased a Champion C46540 for RV use to power a Dometic 13.5BTU-hr A/C. I had previously borrowed a friends 7.5KW Generac and Man, was that noisy! Being a semi-retired EE, I did my calculations and came to the conclusion that 2KW ...... snip rogerw Wow, you ask some really complex questions. Actually, the questions bring to light some problems I really had not noticed. I need to do some of my own research into this before I respond. Meanwhile, perhaps Bob (TopRudder) and George (Mr Wizard) will also jump in. I do not mean to insinuate the two above are the only guys on this thread who can contribute - obviously there are many others who have similar expertise. One comment though, just about all of the newer 13.5 and 15K air conditioners using the scroll compressor also have what is commonly refered to as "soft start" technology. This is extremely effective and even allowed me to lock in the compressor on my previous Coleman 15K A/C with voltages as low as 85 VAC with a 1,700 watt mechanical inverter (dynamotor). If your A/C is of a similar design you really do not need to go further. BTW - welcome to the forum. If you are reading all of the pages, you are definately my new hero! Thanks for quick reply! And I really do wish to compliment you and others on this forum....very informative and collegial! I hope I did not imply to anyone that I had any trouble using my C46540 to run my 13.5K A/C..... It runs it very well; as others have said, "like a Champ!" I did have a little rocky road getting to that point because of a) my basic unfamiliarity with HVAC, which I have been lately trying to remediate, and, b) the mud dauber nests that were built onto the fan blade and rotor cage blower during inactivity and before purchasing the genny! (whump! whump! whump!) The "unfamiliarity" led to an early finding that mysteriously I could cut the air successfully on at the genny switch each time, but not at the thermostat.....turns out I was cutting the air OFF and THEN back ON at the thermostat, not giving the PTCR time to cool for a recycle, hence I would get the full locked rotor current and bog the genny down without re-starting. (When I would go out of the TT and do this at the genny, I was giving the PTCR more time to cool.) Once I studied up a bit and realized that I was causing the issue, no problems at all that I can detect. Of course, cleaning out the mud-dauber's nests gave me oppty to familiarize myself with my A/C unit (bonding...!) and to insulate various cold tubes with foam insulation and the external surfaces of the cold plenum with insulating sheathing such that it is more efficient now. But it did get me to thinking that maybe I could improve the "soft start" characteristics with a EPR instead of a PTCR operated start capacitor. Also, I like the timeout feature of the E-Series Supco products since, if a PTVR were to fail "closed" it would tend to burn out the start windings in the compressor motor. I suppose the Supco could also "fail closed" too, but it is presumably much more reliable than the common thermo-mechanical switch. My unit is only 3yrs old, and my guess is that you are correct that I do not really have to do anything to it for pure startup reasons. (I don't have a Clamp-style Ammeter to prove what the peak startup is....so I am guessing this is so.) However, my curiosity has been aroused as to what voltage a SPP6E and a SPP4E actuates the relay cut-out...and whether folks may be inadvertently really depending on the time-out instead of the potential feature of the product, and the reply from Supco left me still skeptical. BTW, I am trying to convince myself why I should not go out and buy a second C46540 as a backup, just in case..... Kudos and thanks! YHS, rogerw336Views0likes0CommentsRe: 3000W Chinese Gensets Info.
Professor, and All, I have purchased a Champion C46540 for RV use to power a Dometic 13.5BTU-hr A/C. I had previously borrowed a friends 7.5KW Generac and Man, was that noisy! Being a semi-retired EE, I did my calculations and came to the conclusion that 2KW would run the A/C excepting for start/rush current. However, all my professional work was with micro-Watts at the semiconductor chip level, and I had not acqainted myself with Rotating AC Machinery since schooldays in the early 1970s. I have spent long hours on the internet brushing up on inductiton motors, generators, etc, etc, leading up to this purchase... Long story short- the Champion met every expectation I had for it, and is much quieter of course than the Generac. This is a well-made machine! THEN I found this thread.....an amazing compendium of information and distilled experience on the very subject I had been wrestling with! Thank you Prof and All! When I started, I was a little apprehensive that maybe an ELM3000 would have been a better choice....when I got to about page 200 when the C46540 becomes the primo recomendation, I was beaming! I am currently on page 422 and am quite interested in the noise abatement discussion. I did some freefield noise measurements at 23ft on each side and got 68dbA(front) 67dbA(right) 72dBA(back) 72dBa(left) sides. I took a course in college on industrial noise abatement (sound fields are mathematically similar in important ways to electromagnetic fields, btw) and I find that most ideas I have had turns out to be anticipated and even prototyped in this thread as I read it. Excellent! I do have a practical question. I would like to improve the starting characteristic of my Dometic 13.5K so that as it ages it does not become a problem for a genny, also so restarts can occur quickly. After study, I am clear on why I want a Electronic Potential Rely product instead of a PTC Relay product to accomplish this. I researched online to find that nearly every RV reference to this situation uses a Supco SPP6E. A product brochure here http://www.supco.com/images/pdfproductsheets/E%20Class%20Prod%20Sheet.pdf specifies 170Volt to 277Volt operation for the SPP6E on the first page and then 90Volt to 277Volt on the second page. I emailed Supco and the reply informed me that the SPP6E is for 240Volt operation, not 120Volt operation, and the brochure has a type problem on this spec. They also disavowed any testing of their product with the Dometic A/C. This leads me to question whether users of the SPP6E in 120V applications are getting a true EPR functionality or whether the backup timeout feature of this same product is not actually the functionality they are depending on....? To make matter worse, the Supco catalog http://www.supco.com/images/pdfs/2006%20HVAC%20Catalog%20HVAC%20Section%202-51.pdf gives 90Volt to 277Volt for ALL of the E-series products.... Since it matters what voltage the EPR senses and opens at, and the SPP4E is uniformly specified at 90V minimum, has any one used this one? CAn anyone shed light on my confusion? YHS, rogerw336Views0likes0Comments
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