AC Hard Start Capacitor

[BuddyRay]

Figuring that I'm getting a little old to climb around on my 5th wheel RV roof, I asked my dealer to put a Hard Start Capacitor in my AC unit.

It's not that I'm having a problem, but I plan to buy a generator and since the unit is in the shop for some other upgrades I thought I'd have one done.

The Service manager (who I trust) called Coleman to verify the part and Coleman told him that all their AC units are now shipped from the factory with hard start capacitors and that my serial number already had one factory installed.

I'm skeptical. I may just have to get up on the roof myself anyway to verify.

Anybody else heard this?

[Camper_bob]

I think they come with a capacitor, but it's not very big? I know the vernacular there is not right, but I'm not an electrician.

I was a bit concerned about my generator having enough umph to get my AC going as well, but when I tested it, the genny had no problem getting things going. I may install one anyway (assuming I don't have one of the newer fancy units that already includes one) as they are cheap, and it would be even easier on the genny, and the AC compressor.

For reference, I'm running a Champion Power Equipment 100216 3650W RV Ready Portable Generator. I think that's the one I have in the garage. Anyway, it's not an inverter generator, but it's quiet enough for my purposes (limited use on the road or in "dispersed" camping situation (the beach)).

I'm interested to know what you find out here.

[John7349]

Originally Posted by BuddyRay

Figuring that I'm getting a little old to climb around on my 5th wheel RV roof, I asked my dealer to put a Hard Start Capacitor in my AC unit.

It's not that I'm having a problem, but I plan to buy a generator and since the unit is in the shop for some other upgrades I thought I'd have one done.

The Service manager (who I trust) called Coleman to verify the part and Coleman told him that all their AC units are now shipped from the factory with hard start capacitors and that my serial number already had one factory installed.

I'm skeptical. I may just have to get up on the roof myself anyway to verify.

Anybody else heard this?

BuddyRay
Have not heard that, but I suspect it could be. I replaced one in my old 2008 Outback and it worked great.

With my 2017 Jayco, there seems to be no strain at all when it starts up. I'll know when I try my Honda 2000i.

Like you, I don't belong on roofs anymore.

[pconroy]

Can I ask - what's a hard-start cap? I think I've heard of soft-start caps, where the idea is that the cap is charged to lower in the inrush current needs. Is a hard-start capacitor the same thing?
thanks

[BuddyRay]

Yes pconroy. There is usually a capacitor on any large motor, including both fans and compressors in AC units.
A hard start capacitor adds a second cap to the compressor to increase capacity and keep the compressor from putting a short term load on a generator.


Buddy Ray - Atlanta
---------------
Jayco Eagle HT 26.5RLS
Ford F150 Lariat, 3.5L V6 Ecoboost
Max Tow Pkg, 36gal tank
Reese Sidewinder and Reese Titan 16k hitch

[BullDozerBob]

Spent forty years in the HVACR business.
All fan (except shaded pole) motors and compressors use run capacitors. Soft start(PCT) and start capacitors do keep the initial current inrush time to a minimum. The compressors used in RV A/C are for the most part scroll compressors which don't need start assist as they start with equalized pressures on the scroll plate. Only large(4 hp and up) scrolls use start assist capacitors.
Hard start kits use a start capacitor and a relay to switch the start capacitor out of the circuit once the compressor starts.
Gone are reciprocating (piston) compressors which have used start gear consistently.
Soft start won't hurt - just another expense that might not be needed.

BullDozerBob

[oldmanAZ]

Originally Posted by BullDozerBob

Spent forty years in the HVACR business.
All fan (except shaded pole) motors and compressors use run capacitors. Soft start(PCT) and start capacitors do keep the initial current inrush time to a minimum. The compressors used in RV A/C are for the most part scroll compressors which don't need start assist as they start with equalized pressures on the scroll plate. Only large(4 hp and up) scrolls use start assist capacitors.
Hard start kits use a start capacitor and a relay to switch the start capacitor out of the circuit once the compressor starts.
Gone are reciprocating (piston) compressors which have used start gear consistently.
Soft start won't hurt - just another expense that might not be needed.

BullDozerBob

Thanks for the info. It's always good to hear from those with actual experience.

Your last sentence, however, left me wondering... If soft start won't hurt, and it might not be needed, will it help (assuming most of us have small scroll compressors)?

Many (most?) of us have 30amp circuits plugged to RV campground outlets or generators. Unlike the power sources we have in our homes etc., frequently those sources are marginal (low voltage in campgrounds is common in hot weather). Under those situations, would having a soft start capacitor be helpful?

[BuddyRay]

BullDozerBob,

I also appreciate your expertise.
But there are several posts elsewhere on this forum (search "Hard Start Capacitor") where users have posted experience with running AC units off generators that are very close to the Amps required for the AC. They say their AC would blow the generator breaker until they added a hard start capacitor - then it starts and runs fine on the generator.
Also, both Dometic and Coleman sell hard start capacitors on their parts site. I know because my dealer ordered one from Coleman.
But it's also interesting, because when the service manager called Coleman support to find out where/how to install it, they told him my model "already had a hard start capacitor installed from the factory."
I've never tried running mine off a generator but was planning to buy one next year - that's why I asked my dealer to install the capacitor.

So despite your clear and knowledgeable explanation - not everything adds up.

I'm wondering if older RV's used different type compressors?
Or running on a generator brings special issues?
Or not all RV AC use Scroll compressors?

[BullDozerBob]

I'm in the process of trading in a 2004 25DS Greyhawk with a 4kw Onan. Never have had a problem running the A/C on generator. Issues can arise if the coach has two rooftop a/c's and the microwave running.
Common sense always prevails.
We used to joke in the A/C business that " most thermostat problems were TWO LEGGED"
Best to set the stat at a comfort setting and just leave it alone.
Short cycling a unit can trip breakers-overload a generator.
Good discussion

Thanks

BullDozerBob

[RAurand]

Has anyone used this? If so, what were the results?
I am thinking this would be GREAT for boon docking.


Micro-Air - Products

[M&A]

Originally Posted by RAurand

Has anyone used this? If so, what were the results?
I am thinking this would be GREAT for boon docking.


Micro-Air - Products

I've been looking at that and my thinking is this: my 3K inverter generator doesn't have an issue starting my 13.5K air when not in "eco" mode, and once the air is running, if I switch to eco, it will idle down considerably. So I wonder if this box will allow for an eco start, maybe giving enough time for the RPMs to increase without a voltage dip.

[RAurand]

Originally Posted by M&A

I've been looking at that and my thinking is this: my 3K inverter generator doesn't have an issue starting my 13.5K air when not in "eco" mode, and once the air is running, if I switch to eco, it will idle down considerably. So I wonder if this box will allow for an eco start, maybe giving enough time for the RPMs to increase without a voltage dip.

Well, According to the videos I have been watching, It causes a 15 second delay thus allowing for the Generator to spool up from ECO mode to full power BEFORE the air Conditioner tries to start. Watch the full Video. Pay attention to the before and after PEAK Amps. As they stated, the Micro Air learns your compressor and as it does, the Peak amps comes down. He is starting that AC with a 2000 watt generator.
I am seriously thinking of getting this for boon docking.
Here are 2 links:

https://www.youtube.com/watch?v=p2K0ptvYb6Q

https://www.youtube.com/watch?v=soP0uZFd0nQ

[JPBeck]

With mine it depends on the altitude. If I'm at sea level I can get it going with just one but at home (3000 feet) I have to run both of my Hondas.

It's a Coleman 5000btu eco(something).

[M&A]

Originally Posted by RAurand

Well, According to the videos I have been watching, It causes a 15 second delay thus allowing for the Generator to spool up from ECO mode to full power BEFORE the air Conditioner tries to start. Watch the full Video. Pay attention to the before and after PEAK Amps. As they stated, the Micro Air learns your compressor and as it does, the Peak amps comes down. He is starting that AC with a 2000 watt generator.
I am seriously thinking of getting this for boon docking.
Here are 2 links:

Well, mine will arrive in three or so days -

[RAurand]

Originally Posted by M&A

Well, mine will arrive in three or so days -

PLEASE, Let us know how it goes.

[M&A]

Originally Posted by RAurand

PLEASE, Let us know how it goes.

Will do. I'm very curious about this device. My work involves, among other things, several thousand 480V soft starts and VFDs. Should be interesting; I do have some really good test gear. We have a ten day trip in four weeks, so I need to hustle with this and a couple other things.

[M&A]

Originally Posted by RAurand

PLEASE, Let us know how it goes.

Wow! Went from 44.4 starting amps to 16.9. Really too hot on my Orlando roof today to play with better measurement gear, and I'm sure my current probe wasn't catching peaks too well but I am really impressed.

The big test was with my generator - echo mode is amazing. It revs just a little when the compressor kicks in and settles just above idle.

I've also noted that now I can't tell when the compressor comes on from inside. Before it was announced by a brief drop in the fan speed and now that doesn't occur. It was annoying at night since I'm a very light sleeper.

[10canyon53]

That's an impressive improvement.

To try to answer a question that went unanswered earlier in this thread, yes, older A/C units used a different type of compressor. Scroll compressors were just starting to become common in the residential market when I entered the HVACR industry 25 years ago. While I have never played with RV A/C units, they do seem to lag behind in the technology department. I am a former commercial refrigeration technician and am currently employed as a technical service advisor and technical trainer for the worlds largest and most technologically advanced HVAC manufacturer. The industry is moving towards frequency drive compressors (known in the HVAC industry as Inverter compressors) and I wonder how long it will be before the RV A/C manufacturers follow the trend. I have seen 4 ton Inverter compressors start up at 0.8 amps.

[Grumpy]

Originally Posted by 10canyon53

The industry is moving towards frequency drive compressors (known in the HVAC industry as Inverter compressors) and I wonder how long it will be before the RV A/C manufacturers follow the trend. I have seen 4 ton Inverter compressors start up at 0.8 amps.

That's what I love about the Samsung Residential fridge (inverter compressor)in our PINNACLE. Max current draw is 3.9 amps so the inverter is barely working.

[RAurand]

Originally Posted by Grumpy

That's what I love about the Samsung Residential fridge (inverter compressor)in our PINNACLE. Max current draw is 3.9 amps so the inverter is barely working.

Yes, BUT, we are talking about RV Air Conditioners here and using 2000 watt generators running in ecno mode starting them by using the Micro-AIR Soft Start.