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RE: What's the difference in a Heat Pump and an A/C?
"..but the ones I have are actually electric furnaces that completely heat the house when the temperature gets cold enough"
That's exactly the way my 30 year old Carrier HP works and why I want to replace it with a new one with a very high efficiency heat pump section -> so that an expensive electric heat boost section of the new heat pump doesn't have to run anywhere near as much at any given cold temperature.
Air conditioner/heat pump combination units for RVs could be built the same way: Very high efficiency compressor machinery supplemented with a 1500 watt boost heat coil. As an added benefit, a high efficiency compressor section in 13.5K combination RV models would make it possible to run them with the Honda 2000 inverter generator in far more situations - of course with the 1500 watt boost heat coil locked out when using the Honda so as to run just the heat pump part of the unit for heating in moderate cold temperatures.
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pnichols
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11/07/09 09:13am |
Tech Issues
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RE: Personal safety while boondocking
Browning four-round semiauto BAR in 300 Winchester Magnum (30-06 on steroids) ... but don't carry it in the MH ... would put us over the rig's CCC limit. ;)
(Instead, we have an extended range cell phone system and an axe in our rig.)
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pnichols
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11/06/09 11:48am |
Public Lands, Boondocking and Dry Camping
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RE: The true costs of running a generator?
This entire discussion thread has been very interesting and educational.
Here's an excellent article on some RV electrical power options and when/how to use them. It's a little off-topic, but is related and very infomative for the curious. Even though it's from a specific Class B manufactuer the principles and methods talked about apply to all RV types:
http://www.sportsmobile.com/1_heating_ac.html
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pnichols
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11/05/09 11:27pm |
Tech Issues
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RE: What's the difference in a Heat Pump and an A/C?
"The efficiency of the heat-pump in these "new-systems" still have a limit at around 40 degrees."
Well, not necessarily so any longer. As I said in other posts above, the 40 degree outside temperature heat pump efficiency limitation is becoming an old rule of thumb.
Here's what's possible in modern state-of-the-art air heat pumps:
http://www.energysavers.gov/your_home/space_heating_cooling/index.cfm/mytopic=12620
Especially notice the advanced technologies sections near the end of this article.
Also note that old or new technology air heat pumps do not suddenly drop off as outside temperatures get below 40 degrees - their efficiency declines in a smooth fashion. This means the electric or gas heat booster units built into air heat pumps merely have to come on more and more as the heat pump section operates at less and less efficiency.
The new advanced techonology heat pumps in cold climates may still require supplemental boost gas or electric heating sections for low outside temperature extremes, but their boost sections will not be needed as much at any given low temperature as the boost sections in older air pump systems .... hence the new heat pumps with their sophisticated decision-making controls can miminmize the cost of heating at any given time and outside temperature. In moderate outside temperatures, of course the new air heat pumps will use less electricity than earlier ones.
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pnichols
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11/05/09 10:18pm |
Tech Issues
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RE: How long will it take to charge my battery?
"These would be my suggestions for a complete test."
Sal,
I did several tests similar to what you list a couple of years ago and the data is in the rig and unavailable right now. Our Class C rig is in the shop getting the overhead forward facing bunk window replaced after being shattered by a rock this summer. :(
All my testing at this time indicated "pretty good" current replacement by the 7345 (~8 feet of 8 AWG cabling and frame ground) into my 200 AH AGM coach battery set. The batteries reached 90%-95% SOC, if my memory serves me right, in around 3 hours from around 55% SOC (30 amps discharge rate for 3 hours). Alternatively, this time was shortened a bit as indicated by comparison data I took using the V10's alternator (~8 feet of 6 AWG cabling and frame ground). I estimated reaching 90%-95% SOC by watching the ammeter sink to under 5 amps charge acceptance rate and then cross-checking terminal voltage after 24 hours of settling - however I can't recall if my batteries's performance curves showed under 5 amps as being above 90% SOC, but the curves in my last link below definitely show 90%-95% as being about right in this amount of time.
My batteries may be the reason for my thinking the 7345 was doing well, as they are somewhat unusual for use in an RV. They're a couple of Interstate labeled but C&D Technologies manufactured "motive power" 100 AH-each 12V AGM batteries intended for use in wheelchairs, residential solar systems, etc.
Note from this .pdf spec, that since they are to be floated at 13.5V to 13.8V, the 7345 does not damage them. However, since they are AGM ("VRLA") batteries, the 7345 applied voltages also happen to charge them quite fast. As for needing to "sock" them with 14+V periodically, the V10's engine alternator serves this purpose:
http://www.cdstandbypower.com/product/battery/vrla/pdf/dcs_100it.pdf
Notice below in this C&D Technologies technical paper on their VRLA ("AGM") batteries in Figure 1 & Figure 10 that charging voltages right in the range of what the 7345 is capable of (2.25 V/cell = 13.5V and 2.30 V/cell = 13.8V) for outputs of 20 to 30 amps gives times of 2 to 4 hours for recharging from around 50%-55% SOC to around 95% SOC. Note also the "0.1C" shown in the curves. This is 20 amps for my 200 AH battery set:
http://www.cdtechno.com/custserv/pdf/2130.pdf
The subtle learning for me after studying these curves was that the terminal voltage versus energy replacement time for charging of AGM/VRLA batteries is VERY CRITICAL ... especially so in my situation of achieving terminal voltage in the high end of the 7345's 13.5V to 13.8V heavy loading range. Hence my constant emphasis that charge cable size is VERY CRITICAL and that one should strive for every tenth of a volt improvement they can make in applying the highest voltage possible on the terminals of the battery being charged - depending of course on how fast you want to charge plus maximum currents recommended by the battery manufacturer.
As I talked about above, my batteries may be OK with the single stage 7345 assuming I'm OK with around 3 hours charge time. However this degree of terminal voltage sensitivity may not be present with wet cell lead acid battereis, so maybe the use of brute force 14.X higher charge voltages is what's required with them for anywhere near reasonable charging times.
My thinking at this point is that it's not all battery and cable resistance issues, but also may depend upon the chemistry, materials, and construction of the battery as to how well the 73XX single stage converter family does with RV deep cycle batteries.
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pnichols
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11/05/09 09:03pm |
Tech Issues
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RE: How long will it take to charge my battery?
What Sal did could be a great - but tricky - feature addition to any high end multi-stage charger to remove cable size effects. However so far I've seen none with remote voltage sensing.
This may be because remote voltage sensing has potentially serious downsides:
First the charger must be internally protected from over-voltage and over-current damage which is not difficult to include, and is often included, in designs - some of which Sal's modification takes into account with regards to his 7345 converter. The second danger could be much greater and a possible product liability issue for a charger manufacturer. Remote voltage sensing improperly installed could easily "fool" many users into thinking their high power charger could now be used with long runs of 10 or 12 or even 14 awg charge cabling (not talking about the separate sensing wire) because they might try it and initially see that -"Gee, look at that ... 14.6 volts on the battery terminals 25 feet from the charger and the charger is pumping 60 amps into the battery".
This is because the charger would now be maintaining the 14.6 volts on the battery terminals no matter what and normal battery acceptance rates would allow the battery to draw the 60 amps. In a few minutes or seconds the too-small charge cabling would begin to get really hot - maybe in some hidden place or at some connector along it's length - and start a fire in their rig. The charge cabling awg size would have to be chosen carefully/properly so as to be able to carry the charger's maximum current without the cabling or it's connectors heating past safe limits. Charge cabling would also now have to definitely be fused properly based on it's awg size, it's length, any corroded connectors along it's length, and the charger's maximum current.
Without remote voltage sensing, manufacturers and us users can now pay little attention to the above heating hazards since voltage drop in too-small charge cabling is keeping us safe because battery acceptance is getting "automatically" depressed enough such that charger current maximums are not getting pumped through too-small cabling due to the physics. We are OK on safety - but not OK on getting all the current from our chargers and into our batteries that we paid for.
My vote is for chargers to be as close to batteries as possible (just like with large inverters) and to use very large cabling/connector sizes so as to both maximize charger current delivery plus therefore wind up with cabling/connector sizes so beefy that heating is not an issue with most converters or chargers that are commonly used in RVs.
i.e. Many, many Parallax 7345 converters are in the field. Other than the problem of their fixed voltage float boiling some lead acid batteries, how many of us are using 2 awg cabling on their 7345 outputs? Their output terminal lugs are sized for this and they would do much better charging batteries starting at low SOC values.
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pnichols
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11/04/09 05:38pm |
Tech Issues
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RE: How long will it take to charge my battery?
"Why not invest in a nice 100A panel meter? Here's one for $20."
Sal,
I've installed these quite some time ago to monitor my coach batteries:
http://www.ecovantageenergy.com/catalog/items/item204.htm
http://store.solar-electric.com/mka-100-100.html
http://www.bestconverter.com/Voltminder_p_178.html
The meters are mounted right on the dash so I can also keep an eye on things while driving. The ammeter shows me when the alternator has the batteries topped up. The voltmeter tells me that A) I didn't forget to switch ON the coach battery switch so the refrig is operating, and B) that the boost relay that connects the coach and chassis batteries together is operating reliably. I recently had to change this to a silver alloy contact relay because Winnebago's stock relay was getting intermittent (probably corrosion on the contacts).
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pnichols
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11/03/09 11:42pm |
Tech Issues
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RE: What's the difference in a Heat Pump and an A/C?
There are also new state of the art air-to-air heat pumps for home installations that are effective under 30 degrees. Some of these can have electric heat strip boost or propane boost. At low outside temperatures their computerized controls choose pure heat pump mode, or pure propane mode, or pure electric heat strip mode, or a combination of two of the three - depending upon which mode is the most energy efficient.
They're probably using variable speed rotary compressors with perhaps two stages in series to accomplish this and their efficiency rating numbers are way superior to my 30 year old Carrier's. There's no reason other than "money" that RV air-to-air roof top heat pumps couldn't be offered in scaled down versions of these very efficient home units - with either heat strip or propane boost to deal with outside temperatures below 30 degrees.
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pnichols
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11/03/09 05:48pm |
Tech Issues
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RE: How long will it take to charge my battery?
"I have about 23 feet of 8 awg cable going from converter to the battery."
Sal,
As you probably know, the Parallax 7345 output lugs are specified to fit up to and including 2 awg cable. I'm really curious as to what current my 7345 would pump into my 200 AH AGM coach battery bank with the batteries down to 50% SOC and 8 feet of 2 awg cable between the 7345 and the batteries. I think I have it written down somewhere what cable drop I measured with the Winnebago stock 8 awg cable in place (about 8 feet) in parallel with a large battery jumper cable strand I ran in parallel to the stock 8 awg. I'll have to look it up. I'd prefer to have real data along with the equation's prediction.
I'm on somewhat of a mission to force/show/prove my 7345 to be "just fine" with my 200 AH AGM batteries. I'm reluctant to modify it's output feedback so as to rule out cable resistance cuz I prefer not to mess with the 7345 internals. Currently, with about 30 minutes of V10 idling alternator charging time through 7 feet of 6 awg cabling plus 2 hours of converter charging through 8 feet of 8 awg cabling I think I'm getting up to 90% SOC from around 50% SOC with the fast AGMs.
I can of course pick up another expensive 3-stage charger it I ever need it - but I want proof it's cost effective to do so. I have a sophisticated and pricey solid state switching 3-stage trolling motor charger but it's only 15 amps, but I can't really see any way of using it along with the 7345 to emulate a 60 amp 3-stage charger.
P.S. Don't be so hard on your 7345. After all, don't they set one back $150 to $180 new? I think it's notorious "charging problem" is merely one of speed (charge time) with dinosaur-technology wet cell LA batteries and too-small cable sizes. I'll bet the 7345 would have a different reputation if manufacturers had been installing them with 2 awg cabling all along. ;)
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pnichols
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11/03/09 05:37pm |
Tech Issues
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RE: What's the difference in a Heat Pump and an A/C?
".. there is NO REASON to have a Heat Strip on a Heat Pump since they all have either Hydronic or Furnace system on board for sub freezing temps."
If you have hookups or have a dry camp generator running .... why use either your own propane or excessive generator fuel? If temperatures are 40 degrees on up, an RV heat pump is the least expensive electrical way to heat since you are not making new heat. If for some unfortunate/emergency reason when dry camping in 40 degrees on up temperatures you are forced to get some heat into your RV for awhile using a generator, it will use less fuel powering a heat pump then it would by creating new heat from only a standard electric heater to get the same BTU's.
For marginally lower temperatures - say 35 to 40 degrees - getting some heat out of an RV's heat pump plus installed heat strips in it will STILL take less hookup or generator power than through only use of standard electrical heaters.
"The reason for a Electric heat coil on Home heat Pump systems is for Heat when it stays below freezing and the Heat Pump cannot get the BTU's of heat out of the air."
As I said, my home system has two heat strip stages. On the first stage the home is getting heated some by the heat pump and some by the first stage electrical heating elements. This is less expensive than no heat pump at all.
This reasoning also applies to an RV heat pump being supplemented/helped in the 35 to 40 degree range by 5000+ BTU's coming from it's heat strip.
"The Heat Pump mode puts out more heat."
Not in the 35 to 40 degree range - in heat pump mode you would get SOME BTU"s but not enough. Heat strips would provide 5000+ BTU's additional.
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pnichols
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11/03/09 02:38pm |
Tech Issues
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RE: What's the difference in a Heat Pump and an A/C?
"Heat pumps units will not accomodate a heat strip."
This MAY be true for some or all RV air conditioner/heat pump combinations - I'm not sure. We've had an air conditioner/heat pump unit (AKA an "air conditioner that can run in reverse") in our residence - as our ONLY source of cooling and heating - for over 30 years and it has two stages of heat strips thermostatically controlled to kick in one or both stages for BTU boost depending upon how low outside temperatures get such that it's air-to-air heat pump mode no longer can work well.
I see no reason why an RV air conditioner/heat pump unit couldn't also include heat strips - other than it would require two separate 15 amp circuits feeding the unit so as to run both the compressor (for heat pump processing) and 1500W heat strip (for boost) at the same time.
By the way using a 110V, 15 amp, powered air conditioner/heat pump in an RV invalidates the axiom many quote to the affect that "1500 watts provides about 5000 BTU's of heat and there is no way around it". This statement is only true when using electrical power to create new heat. A heat pump can provide well beyond 5000 BTU's of heat to an RV's inderior from it's ~1500 watt 110V input .... because it merely transfers existing heat from the outside into the interior .... it does not create new heat. For situations where it's not super cold outside (below about ~35-40 degrees), it's a far more efficient use of (the Earth's) resources to heat your rig with a heat pump (and it's heat strips not on) instead of with a standard electric heater.
That's assuming you can get the warm air from the heat pump circulated down low in your rig - which is difficult with a ceiling mounted and ducted air conditioner/heat pump. If this problem is dealt with adequately, then it seems to me that an RV with an air conditioner/heat pump with heat strips - plus a conventional propane furnace - would indeed be a rig with a very versatile and flexible setup for interior temperature (and humidity) control.
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pnichols
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11/03/09 11:55am |
Tech Issues
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RE: 2008 E450 front hitch
Bill,
Thanks for those excellent links!
I've been looking for a front hitch to use for carrying a small scooter on our Itasca 24 foot Class C.
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pnichols
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11/03/09 11:22am |
Class C Motorhomes
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RE: How long will it take to charge my battery?
"Of couse can go much longer without running the 3.4A/40 watt/12v furnace fan."
I'm curious as to what kind of furnace you have. I thought most RV propane furnace blowers use more than 3.4A ... more like 6-7 amps. Or did you mean an average of 3.4A per hour because it's only ON an average of one half the time when heating your rig?
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pnichols
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11/02/09 08:02pm |
Tech Issues
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RE: Generator Question
"And I wish the Honda 650 was still on the market."
Floyd, they still are and here's an example:
http://phoenix.craigslist.org/evl/for/1446876930.html
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pnichols
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11/01/09 11:34pm |
Tech Issues
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RE: Time For New Batteries --> 12 volt vs 6 Volt ???
Paul,
RV batteries aren't rocket science if you keep the most important thing in mind:
Always buy a battery, whether it be 6V or 12V, that is labeled and advertised to be for only DEEP CYCLE use.
After this, pay as much as you can afford to get quality and then take care of it properly.
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pnichols
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11/01/09 04:31pm |
Tech Issues
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RE: onan sine wave?
"....but after the generator starts the UPS doesn't recognize the generator."
Now that is strange. I wonder if this is a grounding anamoly in a UPS with respect to where the ground pronge in a motorhome's 110V receptacle winds up with shore power versus generator power?
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pnichols
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11/01/09 04:24pm |
Tech Issues
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RE: dead outlets
Note that with some GFI outlets if they every trip from a fault they will never reset again so you have to replace them.
The Leviton GFI in my rig is this type. It will reset of course whenever you are "testing" it but if you, say, somehow get it wet so it trips .... you're out of luck and have to buy a new one. Leviton calls this a "new feature" of their GFI's. Very frustrating until you figure this out about your "supposedly good" GFI - I know from experience. (Can be expensive too at maybe $15 each - plus your time to install another one.)
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pnichols
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11/01/09 04:16pm |
Class C Motorhomes
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RE: Generator Question
"I would love to know what kind of special spark plug you have that quiets down the generator. What makes it special and where can I get one!"
Here's the special plug I switched to in both my portable Honda camping generator and my motorhome's 4KW built-in Onan generator:
http://www.e3sparkplugs.com/
Ater reading all about the research, engineering, and personal user testimonials concerning this plug, I decided to give them a try in our camping generators. Both generators seem to run smoother, quieter, and less burdened sounding. I have not made any precise gas consumption measurements yet, if ever ... but I figure that gas consumption just about has to be reduced a bit if the generators sound less burdened and smoother.
I just wrote down the numbers off the stock plugs that were in the two generators and took them into a automotive parts store that sold E3 spark plugs and then purchased the correct E3 plug as indicated on the E3 cross-reference chart.
Although these plugs are available for most automotive engine applications, they seem to be most popular for small engines such as ATV, motorcycle, snowmobile, etc..
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pnichols
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11/01/09 03:54pm |
Tech Issues
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RE: Voltage reading at charger/convertor and at battery
Sal, a few posts above you stated this: "I used that method to determine that my battery disconnect solenoid had very high resistance. I didn't activate the solenoid for over a year and the contacts corroded a little bit. After flipping the solenoid on/off a few times the contacts got a lot better. But still, I didn't like the voltage drop and removed the solenoid."
A bit off topic, but you might want to replace your battery disconnect solenoid with this rugged silver alloy contact solenoid:
http://shopping.murcal.com/Catalog/Bear-DC-Contactor-Family/114-1211-020;jsessionid=0a010c471f43e3c1a11ecc744d4b88c1f3921dcee21e.e3eSch4MaN4Re34Pa38Ta38Naxf0
I've put many hours of use on the solenoid above in the coach/chassis battery-combining "boost" application in my rig and it has performed very well ... reliable and ~no voltage drop because of the silver. I see no reason that this silver alloy contact solenoid couldn't also be used as the coach battery disconnect solenoid.
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pnichols
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10/31/09 11:56pm |
Tech Issues
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RE: Generator Question
"The 49db, on Eco-Throttle..."
That is the lowest dB noise spec I've seen on any portable generator, anywhere, at any time.
I think I've walked past/heard non-portable generators even quieter, but no portables quieter than the EU3000is.
Hats off to Honda on this one ... fantastic design/engineering job!
P.S. I own another model portable Honda (non-inverting) generator that runs at a constant 3600 RPM and has the quietest full speed noise spec that I've seen on any portable generator, anywhere, at any time. My Honda EX650 runs at a constant 3600 RPM at 54dB.
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pnichols
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10/31/09 02:10pm |
Tech Issues
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