Generator/AC Shootout 2015 v1.4

Copyright (C) 2015 by padgett, all rights reserved

Note This is a limited experience. The trailer and generators are all single examples purchased at retail. It is possible that one or more may not be a representative example. Its purpose is to sove a personal problem

Electrical and Mechanical concepts expressed are from observation and experience & would be glad to discuss. Can contact me at app1 at 6007 dot us.

Table of contents

The Tests
The Videos
Appendix A: Fan Delay
Appendix B: Soft Start Device
Appendix C:The Generators
Appendix D:Thoughts on future designs.
Appenix E: Other Devices Considered but not Tested.

Background and Motivation

Am a Floridian and about 40% of my travel trailering time I dry camp at events such as Sun'n'Fun in Lakeland where I have been flagging aircraft for years. This year it was at the end of April and we are having a warmer year than usual. After several hours on a hot runway in the sun, I needed to cool off. Unfortunately the generator I had purchased specifically for the task of running the AC kept stalling. This went on for five days. I took a lot of showers even though I had to haul the water. Once home I resolved that would never happen again.

Having had both a small (21') Class A Diesel Pusher (Vixen) and a 24' (unfolded) hard sided trailer (TrailManor) this century (and many various popups previously) have found two standards for smaller units (and some large) in 2015:
1) Honda EU2000i inverter/generator
2) 13,500 btu rooftop AC

Also waded through an enormous number of postings on different forums related to trying to run a camper AC on a EU2000i or similar. These seemed to fall into three categories:
1) Won't work. No Way, No How, Uh Uh. Must have at least a 3,000W generator.
2) Tried it and it didn't always work.
3) Works great for me. (considerable numbers of these had a specific product to sell, sometimes magnetic.)

The problem has always been starting the AC which can require a momentary (350-700 milliseconds) surge of up to 50A for typical units.

So my basic criteria was based to a certain extent on the systems I had which fortunately matched the industry standards: an '06 TrailManor 2720SL with a Coleman Mach III 13,500btu roof AC. This has a vented rear storage compartment currently for the batteries and solar controller which also has 23x14.5x24" remaining where a generator could be stored.that is easily accessable from the outside. Since the generator must be lifted into this compartment I also imposed a weight limit of 70 lbs (inc gas and oil). I cannot comfortably lift 90 or 100 lbs when bent over.

2006 TrailManor 2720SL unfolded. || Electrical closet (battery cover not fitted)

The Bottom Line

In consideration of those with short attention spans, the conclusion first: You get what you pay for (prices are retail for parts only in mid-2015). With a soft start device you do not need two generators:

For $12 you can get a "hard start" capacitor that really does not do much if your OEM starting capacitor was there (some ACs may not have a starting capacitor) and good. Small generators will grunt and strain and start the AC "usually" but cannot be counted on to cycle properly. Peak load is about 40A

For $40 you can add a time delay relay to seperate the compressor motor start load from the blower motor. Generators that started about 50% of the time before will start the AC reliably now. Generators that were not starting at all before probably still will not start every time. Peak load is about 34A.
Note: to have AC while sleeping it must be able to cycle reliably. 50% stall or even 2% stall is too much, it must have 100% reliability or must not cycle once started.

For $320 you can add a "soft start" device. For me this is the real answer. After installing the Easy Start, every generator I tested will start the AC reliably, even those that would stall every time before. Both the generator and the air conditioner are stressed less, voltage drops are not as great, and recovery is very fast. Peak starting load is now about 21A.

Altitude considerations: At 10,000 feet a generator's output is reduced by about 30%. Only the Predator has sufficent power to be expected to reliably run the Air Con at this altitude with the nominally 2200W continuous reduced to 1550W. The AirCon will still require about 1450W to run.

Using this criteria, the Westpro will probably reach its maximum at 6,000ft and the Honda at 3,000ft. For anything above about 2500 ft, different jetting is advised.

Modifications made to the AC

The roof AC on the Trailmanor is a Coleman Model 9203C876 and is labeled as having a compressor with LRA of 58.4A and a RLA of 8.9A Certain modifications were made from stock for testing. These are in order of difficulty,effectiveness, and price:

First) 88-108uf Coleman starting capacitor had failed and was replaced with a 146uf (measured) Supco SPP-6 (not "E" per Supco recommendation) - $12.00

Second) A time delay relay was added to the AC fan motor circuit that could be switched in or out - $40.00
Note: this is the only mod that goes in the air handler, others must be made to the roof unit.

Third) Time delay disabled and compressor starting capacitor replaced with a Micro-Air "Easy Start" starting module - $318.00

Note: All generators have had an appropriate breakin period and oil changed to Mobil 1 full synthetic: 10W-30 for the Honda and Predator, 15w-40 for the Westpro per specification.

The Tests


All tests were conducted in my back yard and with my '06 TrailManor. Before noon the roof is in shade and modifications to the roof unit could be done. After noon the trailer was in direct Florida sun.

The first two weeks of July this year have been warmer than usual with my backyard tenperarures exceeding 100F by 2 pm (two different thermometers, I like redundancy when using OTC equipment) on many days. The 9th and 11th of July were two of these. On the 13th it was 101F at 2pm and 76F at 6 pm. Interesting weather.

Test Equipment

Since I wanted to capture as clear and repeatable test as possible yet needed to use the equipment I already had, the parameters to be captured needed to be carefully thought out. The current display was actually recorded on two different inexpensive ammeters which confirmed each other but only one is shown.

The inside rig consts of AC voltmeters both digital and analog, frequency display, a waveform display, a timer to capture increments all recorded using a webcam and Acer Switch 12 convertible with identification of the test. to capture for later review.

The analog voltmeter and the waveform capture device (a pocket oscilloscope) respond the fastest (critical in the videos) while the digital frequency (nominally 60hz) and voltmeter show the extent of the swings.

Note: these instruments are all personal and consumer grade but have proven reasonably accurate and repeatable

For validation and providing a starting point for the tests, first a setup of the test equipment and web cam were made, ammeters clamped to the AC power line. and several startups made on shore power.

The Links for the videos capturing the test runs can be found at the end of this page.


All of the generators have been run sufficiently for breakin and refilled with Mobil 1 full synthetic oil, 10w-30 for the Honda and Predator and 15w-40 for the Westpro (per instructions). For testing an afternoon outside temperature of at least 95F and a sunny day was required.

Sound Test

For the sound test a db meter was set up at a distance of 20 feet from the generators which were oriented tangental to the meter. Readings were corrected to 40 db (quiet, suburban) and tested with both no load and an 800W loading: At no load both the Honda and the Westpro recorded 58 db and the Predator 61 db. With an 800W load the Predator increased to 63 db and the others both 60 db. This is not very loud and with a sound deadening enclosure could be reduced further. Practical experience is that few find a Honda 2000 objectionable and the WestPro is the same with the Predator slightly louder probably due to its larger engine.

HS capacitor and Fan Delay Tests 9 July

Each started easily @ 101F indicated with choke only needed for a few seconds. For this sequence testing was with the SPP6 hard starting capacitor but fan start delay disabled. Second a sequence was run with the fan delay enabled

Both the Honda and the Westpro started the AC successfully on all trials with the Westpro recovering faster than the Honda each time which was a surprise since it has the smallest motor but re-enforces the conjection that a short stroke can usually accellerate faster than a longer one. This may have hindered the Predator as it has the longest stroke and is the only undersquare engine. 40mm vs 58mm strokes

The Predator had more trouble, not starting at all with just the hard start capacitor and succeeding only once in three trys with the fan delay. The time it did start, it did recover very quickly.

Note: At various other times both the Honda and the Westpro have stalled with the SPP6 alone.

Soft Start Device Tests 11 July, 2015

Since this sequence was to test the soft start device a certain anount of setup was required as the rootop AC had to be opened, the SPP6 starting capacitor removed , and the soft start device installed with two additional connections to be added.

There is insufficient room in the capacitor compartment for the device, it had to be located along side but still under the main cover.


Following the refit of the soft start device I immediately saw significanly lower peak amps and the Honda and Westpro (in ECON mode) and the Predator were reliably starting every time. This is the answer I was searching for.

The fan starts first and the 6-7A momentary load is enough to take the generator out of economy mode. Then a few seconds later when the soft start device ramps up the peak is low enough to more than offset the running current of the fan. e.g. the actual current required to run the fan (2.7A typ) and start the compressor (18.3A typ) is now about 21A. Both the Honda and the Westpro are able to start reliably from ECON

Go to Conclusions

Video Links

Peak current for each series did not vary noticably and is shown at the bottom of each test series. Video (.mp4) is a single representative of multiple repeat runs that were trimmed and compressed from the original 20 MB files to show the start sequence and stabilization. Each is 12-15 seconds long. An .mp4 player is required to view.

Important things to watch for are primarily the relation the values for one generator to another.
1) Depth of voltage drop when compressor starts. With EasyStart there are two events, a smaller one for the fan and a few seconds later a larger one for the compressor.
2) Duration of the dips
3) Change in voltage before and after an event
4) Stability of frequency during an event
5) Distortion of the waveform during an event.

Tests with SPP6

Shore Power***

Predator did not start with SPP6

Tests with SPP6 and Fan Delay

Shore Power***
Predator start*
Predator no start*

Tests with Soft Start

Shore Power***
Westpro on ECON**

*The two Predator videos under fan delay were to show the difference between a stall without recovery and a good start. No starts were seen on all three at various tmes just more often on the Predator (see ECON note)
**The two videos for the WestPro under EasyStart show almost no difference between ECON on and off.
***The reason you see a drop on shore power is probably because there are about 150 feet of AWG 10 wire between the load center and the AC plug. Use of AWG 12 or less would be worse.

Bottom Line:

The devices selected were ones I thought would work for my personal use and they are. The surprise was the failure of the Predator to work reliably even with the fan delay. I suspect the major contributers were the inability to turn ECON off and the long stroke engine affecting its ability to rev up quickly and far enough. The latter could bear additional study but to do that I'd have to remove the Easy-Start.

ps I'd like to thank Bill for proofing the draft and making some very valuable suggestions.

Note on the author

Padgett has recently retired after 35 years with elements of a major defense contractor. He has a dual degree, Electrical and Mechanical (ME6), in engineering from what is now the Kettiering Institute; a Master of Science degree from the Florida Institute of Technology; and is a registered Professional Engineer (Florida). He has a longstanding desire to travel around the US slowly.

Manufacturer's or Vendor's Links

Honda (purchased in Lakeland)
Westpro (purchased from Amazon)
Predator (purchased in Orlando)
EasyStart (purchased from Micro-Air)
Time Delay Relay (purchased in Orlando
SPP6 (not E) hard start capacitor (purchased from Amazon)

If interested in details, see the appendicies below.

Appendix A: Fan Delay

Before the TrailManor I had a Vixen 21ft class A RV with a similar issue. It has a split 13,500 btu AC under the dinette table normally running on shore power only. It started the blower but waited for about 2 minutes to start the compressor motor. A friend deveoped a kit that changed out the capacitors and added a relay to allow a Honda EU200i specifically to run the AC. For me the results were mixed but the 1986 vintage AC was a few generations older than the '06 Coleman in the TM.

So for the tests I decided to try delaying the fan start for a few seconds. While browsing at a local surplus house (I get some of my my best ideas from wandering in surplus houses, junk yards, and flea markets.) I found a 0-5 second time delay relay for 120vac and with a 7A rating.

With some wire, an octal socket, a bypass switch, and some insulated blade connectors, adding the fan delay to the air handler was a simple plug and play operation.

A second function was to change the fan from continuous operation to only when the compressor is running. This minimises load and fuel use when the AC is not cooling. This does not affect operation when fan only is selected.

Appendix B: Soft Start Devices

Small electric motors are allowed to draw high currents on startup primarily because it is the simplest way to make them: apply power sufficient to start the motor regardless of the phase position. It just did not matter. A starting capacitor (typically around 100uf) may reduce this somewhat say from a 60A LRA to a 40A surge. but must be removed from the circuit once the motor starts.

OTOH when starting very large motors, such excess currents could not be supported so the "soft starter" device was developed. Since for very large devices the multi-thousand dollar price of a device that could handle the necessary current was justified and found to have a side benefit: the motors lasted much longer. There are several ways to create such devices from simple magnetic amplifiers (big 1:1 autotransformers) to microprocesser based SCR (silcon controlled rectfier) devices.

With the drop in the prices of simple microprocessors, such a device is possible for a single phase motor under 30 running amps (e.g. a typical roof 13,500 AC is a single phase motor and pulls about 12-13A once running). These provide a ramped and staged application of power learned from the characteristics of the AC. While much less expensive than their big cousins, a preassembled soft start device will run about $320 (2015). The end result is that the peak starting current is reduced significantly. A 65% drop from LRA (Locked Rotor Amps) is claimed and appears to be justified. (a 64% reduction from the 58A LRA spec of the Coleman was observed).

Once I found about these smaller units (today primarily used for marine applications) I contacted Micro-Air in New Jersey about their Easy-Start.

They graciously sent me one for testing. In the end, I was so impressed by the device seeing 50% reduction in the peak amps and much faster response times with all of the generators now starting the AC that it was purchased for permanent instalation in my trailer.

While using the fan delay with the Soft Start device would be counterproductive, I do plan to rewire the circuit in the air handler so that the cfan only operates when the compressor is running. This will allow the generator to return to ECON mode when not running the AC.

Appendix C: Generators

In the course of this test I looked at the specs of A Lot of different devices, at one point had nearly 30 candidate portable generator/inverters. In the end I just had to make some arbritrary rules:

a) must be under 70lb fully loaded
b) must fit in a space 23" Long x14.5" Wide x 24" High (size of my storage compartment)
c) between 2200 and 2800 surge watts (had to include the baseline EU2000i though)

Note: since my TM now has two GC2 batteries, 200W of solar panels, and a 1KW inverter (none of which is standard equipment) the trials could be made with no loads other than the AC. In practise this may require an isolation or transfer switch.

Generator-inverters selected:

Honda EU2000i. Most expensive, considered most reliable but lowest overall power. Could run the AC but only has about 150W reserve. 3 year warrenty

Westpro (Westinghouse) WH2000iXLT. Cost with warrenty is a wash with Predator, smallest engine, lightest, about 350W reserve. 2 year mixed warrenty

Predator 2500: Lowest cost but shortest warrenty (can purchase service contract). Biggest, heaviest, largest reserve: 750W. 90 day warreny

All claimed to have very little distortion (less than 3%) and produced "modified sine waves". All are between 2000 and 2500W.

None is really "the best", all have limitations but if you can live with the 350W reserve (emough for Infotainment), my choice is the Westinghouse with the most sound deadener of any since I have solar/GC2s/inverter for larger loads. If what is needed is brute force, then the Predator. If you have other power sources (i.e. solar to make coffee so can dedicate to AC) and need the highest maintainability & availability of parts then the Honda. But all can serve well if you understand their limitations (and have a service manual).

I had the EU2000i from my Vixen and when I purchased the TrailManor in April '14 I also purchased a Predator thinking that the specs looked more capable than the Honda. I was not entirely correct. Vascillated for over a week on the Westpro. One the one hand I already had two generators (three if you count the 4kW to run essential services in my house when the mains power goes away (Floridians will understand, Californians probably won't.)).

On the other hand I had seen several rave comments about the Westpro. Despite having the smallest engine, it had a 200W higher run current rating than the Honda and was said to be both light and quiet. Also the 1.3 gallon tank and small engine implied a longer run time on a tank than the others. Free shipping and the lowest price from Amazon was the decider. It just felt like the right thing to do.

Though I would have liked to include an American made generator, one wasn't found that qualified.

Emissions plates provide clues to motor manufacturers.

Control panels: while laid out differently they are functionally the same: two 20A 120vac sockets, a circuit breaker. Three lights: Low Oil, Overload, & Output, a 12v output (cigarette lighter socket on the Westpro). Note that each of the 120VAC sockets has one slot with a sideways slit (like an F with the top bar removed). This indicates a 20A socket rather than 15 even though few have seen a 20A plug.

All have CDI ignitions which means there is no need to pull the cord very hard, if going to start then all start with a rather gentle pull. At 100F ambient the choke is only needed momentarily. I did notice that all react well to turning the gas on, then waiting for a few seconds for it to trickle to the carb before trying. Also if it doesn't start immediately wait a few more seconds. I suspect many of the "hard to start" comments resulted from impatience.

Engine size: Are mixed with the Westpro the smallest but also the newest design at 79cc, the Honda (which I suspect may be underrated) at 98.5cc and the Predator at 125cc.

Power Output: The Honda is the lowest rated at 2000W (surge) and 1600W (continuous). It was very reliable in starting the AC but also was slightly slower recovering than the Westpro. The Westpro is in the middle with a 2200W (surge) and 1800W (continuous). The Predator is the largest in every way with 2500W (surge) and 2200W (continuous). This would appear to have the largest reserve and when it did start, appeared to have the lowest voltage drop..

Honda: 50 lbs Westpro: 48 lbs Predator: 70 lbs All weighed with full gas tank and proper amount of oil..

Pricing and cost:
The Predator is the lowest priced but also has the shortest guarentee (90 days) I would strongly suggest a one or two year additional service contract. With the contract the total price is greater than the Westpro unless one is found at the $399 price.

The Honda had the lowest rated output and had the highest pricetag.($999 on sale occasionally for $899): It is also the oldest of the three and has the most hours but the longest warranty: 3 years. Nothing has been needed and is a standard in the RV industry.

In the middle is the Westpro with the smallest engine but a significantly higher power rating than the Honda and a price in the middle also ($564 from Amazon). One year parts and labor, second year parts only.

No Load Voltage Test:

Voltages seen from generators with very little to no load

I did exchange several emails with the Predator vendor asking if this voltage was normal and if it could be adjusted but never received a meaningful reply.

Reserve: One crude test of the reserve capacity is how much the voltage dropped between no load and the 12A load of a running AC. The less the drop the more reserve.
Honda 124.7-121.5= 3.2v drop
WestPro 120.3-117.9= 2.4v drop
Predator 118.6-117.9=.7v drop
This is not surprising considering that with the AC running the Honda was at 90% of advertised running capacity, Westpro: 80% and Predator: 65%

Distortion & Waveforms: I found several references that the Honda is safe for electroncs. "Quality power. Frequency does not change with varying loads." Given that, when heavily loaded I saw considerable distortion in the Honda and the freqency scale jumped around a lot which I did not see in the others. The Honda was one I had had for several years while the others were 2014 or 2015 vintage. This can be seen in these still belowfrom the runs with just the SPP6.

Sample Waveforms and frequency.

Parallel: Both the Honda and the Westpro can be paralleled for double the capacity with purchase of a second generator and a seperate parallel cable (comes with the Honda EU2000i companion) though this test is of a single example of each.

Reliability Experienced: Probably the Honda. It has needed nothing since I bought it other than regular maintenance and one cleaning of old gas. Reliability is a major selling point and you pay for it. OTOH both the WestPro and the Predator have been replaced under warranty though in fairness i doubt that the Westpro needed any more than the carb cleaned.

I do not know what happened to the Predator but at about a year and a month it suddenly became very hard to pull the rope. Called the 800 number and gave my informataion. Was given an RMA. Just took to the local HF and they gave me a new one.

The WestPro was different & developed a fuel leak 8 days after receipt. With permission I removed the side cover to check for a hose that had fallen off but it was clear that the leak was from the upper part of the carburetor and consistant with a stuck float. Normally this is something I would just fix, nothing unusual about the carb however after an e-mail exchange Westpro decided to just send me a new unit. Problem discovered on Monday, new unit arrived on Thursday from Wisconsin and included a stcker to ship the failed one back. Hardest part was draning all of the gas.

In both cases I was just a retail customer but replacement was quick and easy.

Run Time on a Tank: This is the most misleading and empherical yet I felt at least a SWAG should be made. From published data the WestPro has the longest at 13 hours and Honda the shortest at 3.4 hours but when you look at the loads a different story appears:
Honda: 3.4 hours at rated load (1600W)
Westpro: 13 hours at 50% (900W)
Predator: 5 1/2 hours at 50% (1100W)

Normalizing for a 1440W load looks something like this:
Honda: 3.7 hours
Westpro: 8.1 hours
Predator: 4.2 hours

Note this has not been tested in any way and I would expect an AC to cycle during the night but is good for a starting point. Best case is for the generator to be able to support AC during the sleeping hours. Key here would be use of the EasyStart to allow ECON mode and a minor rewire of the air handler to turn the fan off when the compressor is not cooling (this was already done with the fan delay) could be beneficial..

Appendix D: Thoughts on Generator Design

I have to wonder if the bore and particularly the stroke is a factor in being able to ramp up for a sudden load. Both the Honda and the Westpro were oversquare (Honda: 56x40mm, Westpro 48.6x43mm) while the Predator was undersquare (52.4x57.8mm). The Predator was also the only one not to have a switchable "ECON" setting which makes me wonder if it is naturally on "ECON". In the case of the Honda and the Westpro, turning on the "ECON" resulted in unreliable AC starts even with the fan delay. Tests had "ECON" turned off where there was a choice. With the soft start devce, "ECON" was left on.

I suspect the Predator may have had a triple wammy in responding to a sudden load: lowest starting voltage, longest stroke, and no way to turn off "ECON". This could explain why the largest generator had the hardest time starting the AC without the soft starter but showed the least strain running when it did start.

Since the devices operate by generating AC, rectifying to DC and then using a stable inverter to create the 120vac this allows a stable frequency and very low distortion even under heavy load. This also raises the possibility of connecting a battery such as a jump box to the DC and using the very high capacitance of the battery to limit the effects of a starting surge.

When I developed the fan delay concept it was a low cost (under $50) solution but it was limited. The Predator would not reliably start the AC and ECON had to be turned off for the Honda and the Westpro to do so.

On reflection this was because we had a horse race going whether the generator could ramp up quickly enough to support the momentary load. The torquey Predator simply could not ramp up fast enough even though it had significantly higher running capacity than the other two. ECON seemed to slow the idle rpm enough to make them unreliable so SPP6 and Fan Delay test were performed with ECON turned off. It is posible that the Predator is normally in ECON mode which would also have contributed to non-starting. Once it did start it indicated the highest reserve power

There are a number of other means that could be used to allow a 2200W (continuous) generator to support a 4,000W momentary load at 10,000 feet (like a small turbosupercharger good for about 5 psi boost) but this paper was designed to look at available devices and simple modifications. Anyhing else would take considerably more effort. Besides this was enough to solve my problem.

Appendix E: Others - devices considered but not selected.

I had to eliminate some very popular ones such as the Yamaha EF2400iSHC (16.5" wide, 75 lbs), the Champion 75531i (24.4" long, 95 lbs), and the Briggs & Stratton P3000 (28.5" long, 15" wide, 90 lbs) since had to be something that I could lift and fit in the storage compartment..

Soft Start Devices:
The vendors that I knew of for the Test were, the Micro-Air Easy Start and the Dometic Smart-Start. In selection I contacted Micro-Air first and they were receptive to the test.

Since then a reader suggested a third and potentially lower cost soft start device, the
Gen-Pro Sure Start. The reader has since provided a video of the Sure-Start on a Coleman Mach III like mine and with a Predator generator/inverter. At 39 seconds you can hear the generator ramp up and at 41 seconds the compressor start so the delay is sufficient for the Predator to stabilize. This was repeatable and using the cycling switch as well so sounds like a good alternative.

This seems to be aka SureStart 6 from Hyper Engineering

Copyright (C) 2015 by padgett, all rights reserved
This page was written using Windows 7 Notepad. Some habits die hard.
All photos taken locally. I have never been very good at graphcs.