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RE: videos of honda 2k unit attempting to run an air conditioner
Well it turns out that reduced voltage starting is starting to be used with single phase air conditioners. This device: The first Single Phase, 208/240 VAC Soft Start is required to be used in the Maui area to limit inrush current to 100 amps. The approval letter from Rheem (available from the web page) says that testing with a Copeland compressor showed no damage to the compressor or the motor. The Rheem approval is for units in the 1.5 to 5 ton range. This is getting pretty close to RV air conditioners which are generally over one ton, and makes me even more skeptical that a low voltage start harms an air conditioner motor in any way whatsoever.
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Wayne Dohnal
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04/11/12 04:48pm |
Tech Issues
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RE: videos of honda 2k unit attempting to run an air conditioner
I think there's pretty wide agreement that low voltage operation damages motors, but that statement in itself is not addressing the issue in this thread, which is low starting voltage that lasts a second or two, with the motor successfully starting. If somebody finds a document or can give expert testimony that the low starting voltage for a short duration causes damage, that's what I want to hear. Since this exact situation is intentionally created in lots of motor situations, it would help me to also know why it hurts an RV air conditioner motor while being neutral or beneficial with other motors. I know that the reduced starting voltage technology is used almost exclusively with larger motors, but as I noted earlier the technology is working its way downward, an example being consumer central vac motors that are spun up over an approximate 5 second interval using an itty-bitty triac.
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Wayne Dohnal
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04/11/12 02:41pm |
Tech Issues
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RE: Im having problems reading my multimeter
The readings are often in k-ohms, so it could mean 549 ohms. Does it change when you heat up and cool the thermistor?
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Wayne Dohnal
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04/10/12 11:07pm |
Tech Issues
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RE: The Official unofficial CPE 2000i Generator Thread
Concerning the discussion about the new Xantrex inverter with generator support, 3 posts up, there is now one seemingly knowledgeable claim that generator support is accomplished by throwing the transfer relay. The post is at http://www.technomadia.com/2012/04/boosted-electrons-better-views/, and is currently about 2/3 down on the web page. It starts with "Sean says:". A partial snip says:
"The way the new Freedom units implement “generator support” is by disconnecting the loads entirely from the incoming power and switching them to the inverter. At the same time, the battery charger is brought back on line and connected to the input power."
My only agenda in posting this is to give a heads up that there are multiple reports that this device may not be what the Xantrex Marketing department wants you to assume it is. I won't believe it for sure until I see it independently confirmed, but at this point it's sure sounding like this feature was invented by the Marketing department.
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Wayne Dohnal
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04/10/12 07:46pm |
Tech Issues
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RE: videos of honda 2k unit attempting to run an air conditioner
I appreciate this being a civil discussion. Responding to a few points:
1. I graduated with an MSEE 40 years ago. Don't recall any motor discussion in EE classes, but at the same time I know I've forgotten very much of what I never used after school. Motors were covered some in 2nd year Physics. Power transmission was covered in EE.
2. For what I'm trying to accomplish, it's not an issue if an air conditioner is a good candidate for soft start or not. The only thing I'm challenging is the claim that a voltage dip at startup is abusing the motor, and pointing out that this very thing is routinely and widely done intentionally.
3. Without knowing the A-D algorithm of the meter and if it's frontended with a sample/hold, I couldn't begin to guess the direction and magnitude of an error from a changing input. Maybe the current is the issue and maybe it's not, but the abuse discussion is focused 100% on the voltage reading.
4. I finally recalled that every freezer I've ever owned will have the motor stall if power is removed and quickly restored while it's running. Window air conditioners, too. Just about everybody has heard it: Motor stalls for a few seconds, breaker trips, breaker resets, motor stalls for a few seconds, repeat for a few minutes. Is this motor abuse? It's certainly more stressful than a low voltage start, and is a normal occurrence.
Edit: Thinking more about the meter reading, my comment above was too simplistic. In addition to the A-D algorithm there's the issue of how the meter resolves an AC waveform to a voltage reading. Does it read peaks and assume a sine wave? Does it use some algorithm to attempt an RMS reading? When the voltage waveform has a discontinuity due to a current spike, does this trick the algorithm? With the significant voltage dip and non-sinusoidal waveform that changes every half-cycle, I think it's a safe bet that if you gave a scope trace to 10 different engineers and asked "what's the voltage", you'd get 10 different answers. (Same principle as 10 CPAs doing the same tax return). When I ran the same test using an analog meter I recorded that the voltage dipped to around 90 (and recovered more slowly), but this is subject to the same pitfalls I just ranted about.
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Wayne Dohnal
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04/10/12 07:29pm |
Tech Issues
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RE: videos of honda 2k unit attempting to run an air conditioner
No push-back intended from me. My statement is based on my own experiences. Example, my Xantrex ProwattSW 2000 inverter will run my I only say this in reference to (your statement) an air cond being an easier start load than a 1000w microwave. Your statement seems to disregard the Air cond's surge...Please explain...
I was specifically responding to "I seriously doubt that a 1000w M/W draws more than an RV air cond...", and not addressing startup current, which I don't have a measurement for. I can say that the eu2000i struggled longer starting the microwave but that's hardly scientific. In one case the generator is getting hit with a stopped motor, and in the other case with a discharged capacitor. It's pretty difficult to measure the startup power and I don't have either of the devices any more anyway. The eu2000i does start my current 15,000 btuh air conditioner without a whole lot of fanfare on a moderate temp day but after a few minutes of running the watts creep up past 1,600 so that's an infeasible combination. I didn't want to muddy the waters with another issue: Unless demonstrated otherwise, I don't trust a DVM to correctly read a fast-moving value. So I'm not convinced the voltage actually went to 59, and I'm honestly surprised that it recovered to 120 so quickly. For measurements like that I drag out the scope or analog meter. All of this I believe is irrelevant to the motor abuse issue.
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Wayne Dohnal
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04/10/12 03:13pm |
Tech Issues
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RE: videos of honda 2k unit attempting to run an air conditioner
Since, by your own admission, you are not an engineer, it is going to be very difficult to offer an explanation that would satisfy you from an electrical engineering standpoint. I AM an electrical engineer with no specialty whatsoever in motors. As an engineer I know that what seems like a perfectly logical premise often turns out to be the opposite of reality when the facts are known. The electrical engineering explanation is not enough. Things like the heat rise of the affected masses and mechanical issues are also in play.
I seriously doubt that a 1000w M/W draws more than an RV air cond...That is UNLESS the Microwave is experiencing a 'locked rotor' condition. Having measured it, I seriously know for a fact that the 1000 watt Dometic branded microwave in my previous RV drew 12-1/2 amps at 120 volts, or 1,500 watts, while the 13,500 btuh Dometic standard efficiency air conditioner pulled 11-1/2 amps and about 1320 watts sitting in full sun on a 90+ day. Several others have reported similar measurements on the numerous "will an eu2000i run an air conditioner" threads over many years.
If the Wikipedia Motor Soft Starter Article is to be believed, "A motor soft starter is a device used with AC electric motors to temporarily reduce the load and torque in the powertrain of the motor during startup. This reduces the mechanical stress on the motor and shaft, as well as the electrodynamic stresses on the attached power cables and electrical distribution network, extending the lifespan of the system." and "Electrical soft starters can be any control system that reduces the torque by temporarily reducing the voltage or current input, or a device that temporarily alters how the motor is connected in the electric circuit." This is not talking about a hard start cap, a totally different device. Soft start and hard start terminology is often incorrectly used on the forum.
Why all the pushback for wanting the assertions of abuse to be backed up by real data, or wanting confirmation from somebody who has expert status with motors?
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Wayne Dohnal
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04/10/12 12:58pm |
Tech Issues
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RE: videos of honda 2k unit attempting to run an air conditioner
Is it an issue when your blood pressure should drop to say 80 / 40 for just one second?I can't image what blood pressure has to do with motors, but is it an issue when a Reduced Voltage Motor Starter is used? These devices are widely used with larger motors, and do exactly what is being claimed as "abuse" in this thread. Are thousands and thousands of very expensive motors being routinely and knowingly abused by devices from large companies with engineers who actually know about motors? The main application is industrial motors but they're also used in newer home central vacs, which have about the same power requirement as an RV air conditioner. It keeps the lights from dimming when the vac is turned on.
Cummins - Reduced Voltage Motor Starting
There are numerous documents on the Internet about the harm caused by steady-state low voltage motor operation. Can anybody find any real data for startup-only voltage dips? I'm not claiming any expertise because I'm not a motor engineer, but before I embrace them, I'd like the abuse claims backed up by more than seemingly logical conclusions.
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Wayne Dohnal
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04/10/12 10:39am |
Tech Issues
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RE: videos of honda 2k unit attempting to run an air conditioner
If you want to see scope traces of an eu2000i starting a circular saw, check out this post: eu2000i post in Champion thread. A 13,500 btuh air conditioner is of course a heavier load. What relevant in this post is (1) That the eu2000i holds its waveform pretty well during the startup sequence, and (2) The eu2000i can supply about 30 amps (rms) for the first few half cycles, after which the maximum current ramps downward.
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Wayne Dohnal
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04/09/12 09:38pm |
Tech Issues
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RE: videos of honda 2k unit attempting to run an air conditioner
And why doesn't anybody ever seem to think that running a 1,000 microwave, which draws more than many 13,500 btuh air conditioners, abuses the microwave or generator?
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Wayne Dohnal
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04/09/12 09:42am |
Tech Issues
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RE: Low voltage - how low is low
All of my electrical appliances say plus or minus 10% from 120 volt AC. Gives a safe range of 107 to 132 volts.I'm curious what a few examples are. All of the RV equipment specs I've seen are based off of 115. I have seen a few consumer products from China that base off of 120.
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Wayne Dohnal
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04/04/12 02:00pm |
Tech Issues
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RE: Low voltage - how low is low
The standard device operating voltage is 115 +/-10%. If you have a high-current device like the air conditioner running you have to allow for a couple volt drop in the wiring unless you're measuring right at the high current device, so 105 is probably a good benchmark. I agree with the need to calibrate the plug-in meter against one known to be pretty close.
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Wayne Dohnal
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04/04/12 10:08am |
Tech Issues
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RE: 30 amp circuit in garage for RV - does it require a GFI?
I assume everybody answering this question has researched the local codes for the OP. Stealing from another post: "Whether your installation of a dedicated 30A receptacle outlet intended strictly for this RV classifies as an exception can ONLY be answered by your local authority (inspector, town office, etc)....they have the final say on these types of scenario's."
http://en.allexperts.com/q/Electrical-Wiring-Home-1734/110V-30A-RV-outlet.htm
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Wayne Dohnal
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04/02/12 09:50am |
Tech Issues
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RE: Ground cable replacment
A few people (myself included) have reported significant RFI problems with PD converters that affect AM radio and VHF television channels. My PD9160A injects the RFI into the AC power connection, making all of the AC wiring its antenna. I've also used Magnetek and WFCO converters, with no RFI issues.
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Wayne Dohnal
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04/01/12 10:10pm |
Tech Issues
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RE: 12 volt ground
12v Ground wires on RV's are by code white in color. Well most of the time....If that's true, Fleetwood sure doesn't follow it. Every DC circuit Fleetwood-installed ground wire in my rig is black with a color stripe. Several circuits use white wires to carry +12. The German chassis follows the convention of all ground wires being brown, and the RVP thermostat's ground wire is blue.
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Wayne Dohnal
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03/31/12 09:22am |
Tech Issues
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RE: Champion 2000w inverter in Canada question.
I read that due to Canadian electrical code, selling generators with the parallel port ability is prohibited.The Canadian eu1000i is parallel capable. Take a look at the last feature listed for the EU1000iKC2.
http://powerequipment.honda.ca/powerevent/generators
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Wayne Dohnal
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03/30/12 09:43am |
Tech Issues
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RE: local garage and bearing nut adjustment
Most people adjust them too loosely. After adjustment there should be no bearing play at all. If there is then they are going to wear prematurely.With no claim to being an expert, I started with wheel bearings when cars were rear wheel drive and the front wheels all had tapered roller bearings. The accepted adjustment procedure handed down from mechanics and car enthusiasts was to tighten the nut as much as possible while still having a small amount of play when the bearing is cold. If there's no slight clink-clink when rocking the wheel (when cold), the bearing is too tight and will wear prematurely. I have fortunately never had a failure of this type of bearing in cars or trailers.
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Wayne Dohnal
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03/29/12 03:40pm |
Tech Issues
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RE: What is an easy to use Photo Re-Sizing Program?
This one integrates into windows Explorer Image Resizer
x2 on this one. Easy to use, handy options, and the smallest jpg files for the resolution that I've seen out of any photo program.
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Wayne Dohnal
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03/27/12 11:23am |
Technology Corner
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RE: Quick and easy CD disposal
Just because you can fry one or a thousand CD's doesn't mean you're not stressing the Klystron. They don't like being driven into an open load... It's a transmitter...
Just break them and be done.Why on earth shouldn't I have the right to stress my klystron if I choose to, and just for my own convenience, no less? The original question was: Any easy way to make a CD unreadable? The microwave is a valid solution. OK, there are some negative side effects with the microwave, as well as side effects with cutting and breaking. Now everybody should be able to balance convenience vs. risks and make their own choice.
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Wayne Dohnal
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03/26/12 07:13pm |
Technology Corner
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RE: Quick and easy CD disposal
I've fried hundreds of CDs in the microwave over many years and never had a microwave failure. It takes about 2 seconds. The only negative side effect is the fried CDs smell pretty bad.
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Wayne Dohnal
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03/25/12 11:52pm |
Technology Corner
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