Soft start capacitors

[MNRon]

Should every ac have a soft star cap installed? If so, why don’t they come that way? Is there any downside?
Thanks

[bacollins]

My Harbor Freight generator (2500W) (2200 run) would not start the Coleman 13,500 A/C on my Jaco TT. I bought a Supco hard start capacitor from Amazon, $6.95, wired it in according to the instructions to the run cap, turned on the A/C, nada, wouldn't start. So, I wired it into the start cap, turned on the A/C, voila, started right up without a whimper from the gen. Ran it for 30 minutes with no problems so I guess I'm good to go.

[2edgesword]

ktmrfs wrote:

2edgesword wrote:

Home Skillet wrote:
Over the years, I have tried all those hard start capacitors mentioned.

Nothing compares to the Micro-Air soft start.
No more generator surging when the a/c cycles, etc.

LINK

I would think if you're doing a lot of camping off the electric grid then the extra cost between a hard start capacitor ($10) and the Micro-Air Soft Start ($300) isn't an issue. For me the few times I anticipated and have had to run the A/C on a generator didn't justify the additional cost. It requires some human power management on my part (primarily no microwave while the A/C is running) but doable.

we do lot's of off grid camping and my experience with the soft start kits and a honda 2000 was it would reliably start the AC under these conditions.

1) sea level to 500ft, temps below 85F
2) generator warmed up turned off eco mode

and or course everything else turned off.

Once above 1000Ft especially with temps near 90F, it would not reliably start the AC even with the soft start kit. By 2000ft it was a 100% no go.

Now different brands and models of AC units vary, along with what generator you have.

As a comparison my second smaller trailer has a coleman "polar cub" a 9500BTU AC with a very good soft start circuit, optimized for low LRA and that AC unit I can start with the honda 2000 at 6000+ ft and any temps and run it all day long with no problems.

With the microair easy start with my Coleman MachIII I can leave the honda 2000 in eco mode and reliably and smoothly start the AC to at least 4500FT 95F, 6500Ft density altitude. generator ramps up smoothly.

Now at 6500FT density altitude the honda 2000 does run out of poop and will overload after about 20 minutes, so it did mean paralled honda 2000 at that altitude. But then I could get the batteries charged as well.

Son now has one of the honda 2000's, I have the honda 2200 so we shall see if the extra 200VA and 25% larger engine solves the altitude problem.

If a soft start kit solves the AC problem under the temp and altitude conditions you experience, go for it. If not, the micro air will solve the starting problem, but it doesn't lower running current so high altitudes may still be an issue with one generator.

If I were doing a lot of off grid camping the microair would be the way to go. I think the frequency of use versus cost factor is a major factor in making the decision which way to go.

[CJW8]

I just installed 2 Micro Air Soft Starts. See my recent post (cooling improvements). Before, my 3400 watt Champion inverter generator would start one 15K AC at my home at 4600 feet elevation. At 7000 feet, forget it. I am anxious now to try it at elevation.

[j-d]

Our Class C came from factory with a 4KW Onan RV GenSet, and a Coleman Mach 15000 A/C with a model number that says it has OEM Hard Start. Inspection confirms that.

[GordonThree]

Chum lee wrote:
IME whenever a manufacturer designs/builds a situation/component that isn't as fool proof as possible, Murphy's law eventually takes effect.

In life, Murphy's Law states "Whatever can go wrong eventually will."

IMO, with regard to RV gennys and AC units, this is a manufacturers way of telling its customers, "Look guys and gals, just buy the correct size generator." (if you want your system to work reliably most of the time) The manufacturer has NO IDEA OR CONTROL OVER what foolish things their customers might try so they opt for the most fail safe mode possible. If you decide to alter their design, it now becomes your design and the manufacturer is quick to point that out to you when/if things go wrong.

Chum lee

x2 for that. The vast majority of aircon units on RVs never see any boondocking service let alone users wanting to run the unit with a small inverter generator on eco mode. Those are extreme edge-case scenarios.

[Chum_lee]

IME whenever a manufacturer designs/builds a situation/component that isn't as fool proof as possible, Murphy's law eventually takes effect.

In life, Murphy's Law states "Whatever can go wrong eventually will."

IMO, with regard to RV gennys and AC units, this is a manufacturers way of telling its customers, "Look guys and gals, just buy the correct size generator." (if you want your system to work reliably most of the time) The manufacturer has NO IDEA OR CONTROL OVER what foolish things their customers might try so they opt for the most fail safe mode possible. If you decide to alter their design, it now becomes your design and the manufacturer is quick to point that out to you when/if things go wrong.

Chum lee

[myredracer]

Adding a "hard" start capacitor that reduces the starting current would be a good thing for starting under low voltage conditions and where wire runs to a pedestal are long because the motor windings wouldn't get stressed as much at startup and could potentially reduce the chances of premature failure of an AC unit. How many RV-ers monitor voltage or know what good or bad voltage levels are tho?

I think all AC units should have them but just think of the increased purchase cost of a new RV... :R And just guessing, I would expect that the AC unit manufacturers would rather sell you a replacement AC unit than a capacitor.

[ktmrfs]

2edgesword wrote:

Home Skillet wrote:
Over the years, I have tried all those hard start capacitors mentioned.

Nothing compares to the Micro-Air soft start.
No more generator surging when the a/c cycles, etc.

LINK

I would think if you're doing a lot of camping off the electric grid then the extra cost between a hard start capacitor ($10) and the Micro-Air Soft Start ($300) isn't an issue. For me the few times I anticipated and have had to run the A/C on a generator didn't justify the additional cost. It requires some human power management on my part (primarily no microwave while the A/C is running) but doable.

we do lot's of off grid camping and my experience with the soft start kits and a honda 2000 was it would reliably start the AC under these conditions.

1) sea level to 500ft, temps below 85F
2) generator warmed up turned off eco mode

and or course everything else turned off.

Once above 1000Ft especially with temps near 90F, it would not reliably start the AC even with the soft start kit. By 2000ft it was a 100% no go.

Now different brands and models of AC units vary, along with what generator you have.

As a comparison my second smaller trailer has a coleman "polar cub" a 9500BTU AC with a very good soft start circuit, optimized for low LRA and that AC unit I can start with the honda 2000 at 6000+ ft and any temps and run it all day long with no problems.

With the microair easy start with my Coleman MachIII I can leave the honda 2000 in eco mode and reliably and smoothly start the AC to at least 4500FT 95F, 6500Ft density altitude. generator ramps up smoothly.

Now at 6500FT density altitude the honda 2000 does run out of poop and will overload after about 20 minutes, so it did mean paralled honda 2000 at that altitude. But then I could get the batteries charged as well.

Son now has one of the honda 2000's, I have the honda 2200 so we shall see if the extra 200VA and 25% larger engine solves the altitude problem.

If a soft start kit solves the AC problem under the temp and altitude conditions you experience, go for it. If not, the micro air will solve the starting problem, but it doesn't lower running current so high altitudes may still be an issue with one generator.

[2edgesword]

Home Skillet wrote:
Over the years, I have tried all those hard start capacitors mentioned.

Nothing compares to the Micro-Air soft start.
No more generator surging when the a/c cycles, etc.

LINK

I would think if you're doing a lot of camping off the electric grid then the extra cost between a hard start capacitor ($10) and the Micro-Air Soft Start ($300) isn't an issue. For me the few times I anticipated and have had to run the A/C on a generator didn't justify the additional cost. It requires some human power management on my part (primarily no microwave while the A/C is running) but doable.

[Home_Skillet]

Over the years, I have tried all those hard start capacitors mentioned.

Nothing compares to the Micro-Air soft start.
No more generator surging when the a/c cycles, etc.

LINK

[ktmrfs]

mntnflyr4fun wrote:
I recently installed a "hard start" capacitor and an AC fan delay circuit to my Coleman Mach III 13,500 AC unit.

As I was investigating the AC starting load requirements, I realized that to get the most performance (ie: max reduction in load to my generator) I needed to not only have more power available, but I could also reduce the total load at startup by delaying the fan for a couple seconds which is another motor being started at the same time as the compressor motor.

Amazing difference in performance. Prior to the install (which took about 20 min.) my Honda EU2000i would choke out trying to start the AC unit due to the very high load required at startup. In fact last summer on a trip to Louisiana, I tried to start the AC with my gen. and blew both Capacitors in the AC due to low current during startup.

Not only is the generator trying to start the AC motor, it is also trying to start the fan at the same time along with any added loads like maybe your converter trying to charge a battery etc. and 2000 watts was nowhere close to enough.

By installing the hard start capacitor to increase the available starting current AND by delaying the start up of the fan by a couple seconds, as if by magic the AC starts and runs with no trouble and my EU2000i doesn't seem to be struggling to run it after it has started. I am sure I don't have alot of extra power to do much else with from my 2000watts, but on a hot day, a little AC can be just what the Dr. ordered.

Amazing what a little booster and a smart delay circuit can do for about $100 bucks and 20 min. on top of the RV with a couple hand tools. Both parts installed in the AC unit on top of the RV with minimal effort or technical proficiency needed.

I bought the RV Coleman Dometic Duo-Therm A/C Compressor Hard Start Kit + tips +instructions and the RV-AC Starter prevents Generator Stalls, Overload trips at Air Conditioner Start on Ebay.

Cheap upgrade, simple to install and I immediately called my brother and told him he should purchase as well. Living in Oregon, we don't get much call for the AC when dry campingbu so we both run undersized suitcase generators and this little mod. was a game changer.

Now I can sell one of my EU2000i generators and use the money for a solar kit....seems like a great value to me.

Yes, delaying the start of the fan motor can make a noticeable difference in starting the AC from a generator. your phasing in the inrush currents, and reducing the load. I had a 30 second delay between the compressor and fan. It helped and along with the supco kit let me start the AC at lower altitude and moderate temps. However at over about 1500ft and 90F I still ended up with a not start condition.

BTW the micro air does this time delay trick as well. However they swap the sequence, start the fan FIRST then the AC. starting the fan first gets the generator to start off the eco mode low rpm and start ramping up the RPM before they hit it with the compressor load.

[GordonThree]

The start or run capacitor in an air conditioner is not "storing" a charge to provide the motor with an extra kick. Yes, that's what capacitors do in a DC circuit, but in an AC circuit, they do something else.

In an AC circuit, a capacitor is used to alter the relationship between voltage and current.

The math is sort of explained here:
AC Capacitor Circuits

[dougrainer]

Atlee wrote:
Why not offer the soft start Micro air as an option. Knowing what I know now, I would spring for an additional $350-$500 for that option.

The SUPCO spp6 is available for near peanuts now. Why don't all A/C's come from the factory with those installed?

GordonThree wrote:


soft start means some form of software is controlling the current limiting. microair for example, is a soft start controller

hard start means plain old physics is controlling the current limiting. SUPCO spp6 for example

why don't all ac units have one installed? cost and need. Most RVs that spend their entire life sitting at a seasonal or full time site, wired into the grid, don't need any help starting and restarting the motor. so the hard start cap would be one more thing that can wear out and need service, and it's not providing much benefit.

for soft starters, they're very expensive and again, mostly redundant.

why trailer manuf haven't switched over to inverter type split unit AC, with a digital compressor motor and separate fan motors, who knows ... these mini split roll off assembly lines by the millions and have decades of industry experience behind them now.

the old fashioned Coleman (assorted brands) rooftop units really seem dated, but maybe Elkhart has an enormous warehouse full of the Coleman, so they keep using them and keep building more?

COST. RVP offers a Hard Start kit on certain models, but it adds cost. A few dollars here and a few dollars there and you get hundreds of thousands of dollars saved. Hard Start kits are not really needed for Motorized with Gensets. They(RVP) offer the optional Hard Start kit if Towable makers want to option that for portable Gensets. Hard Starts are needed when towable owners use NON RV Gensets and go with portable gensets. If you dig into the Options when buying a new RVP AC you can special order the AC with the Hard Start kit. Very few retailers have the Hard Start AC's in stock. They have to order them. Not sure, but Dometic "may" have the option also. BTW, Elkhart is NOT the warehouse for RVP. Wichita, Kansas is. That is where they are built and shipped out of. Doug

[Atlee]

Why not offer the soft start Micro air as an option. Knowing what I know now, I would spring for an additional $350-$500 for that option.

The SUPCO spp6 is available for near peanuts now. Why don't all A/C's come from the factory with those installed?

GordonThree wrote:


soft start means some form of software is controlling the current limiting. microair for example, is a soft start controller

hard start means plain old physics is controlling the current limiting. SUPCO spp6 for example

why don't all ac units have one installed? cost and need. Most RVs that spend their entire life sitting at a seasonal or full time site, wired into the grid, don't need any help starting and restarting the motor. so the hard start cap would be one more thing that can wear out and need service, and it's not providing much benefit.

for soft starters, they're very expensive and again, mostly redundant.

why trailer manuf haven't switched over to inverter type split unit AC, with a digital compressor motor and separate fan motors, who knows ... these mini split roll off assembly lines by the millions and have decades of industry experience behind them now.

the old fashioned Coleman (assorted brands) rooftop units really seem dated, but maybe Elkhart has an enormous warehouse full of the Coleman, so they keep using them and keep building more?