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A/C Compressor Soft Starter

C

Check Break

Member
I just figured out there are 1Ph soft starters for small motors (1.5hp to 7hp). Now that RV-s and residences on backup generators are the norm, it appears I'm the only one not starting my A/C compressor with a soft starter.

One starter I've been looking at is the Hyper Engineering Sure Start. They've been around at least ten years and appear to have at least one copycat, so maybe they're doing something right.

http://hypereng.com/single_phase.html

http://hypereng.com/literature/SC5600HM-SureStart-Specification-Catalog.pdf

My compressor draws 137.8 LRA and 19.2 RLA, so their Model SS1B16-32SN for 16-32 RLA should work. I've haven't been able to get any info out of Hyper, but have spoken to a few folks selling these units online. Most don't know anything about them and one guy told me that the only thing he knows is they won't work with a scroll compressor. I've come to believe he's way off base, as all the residential A/C units I seen the past 30 years use scroll compressors.

Forgot to mention I'm doing this to ease up on my gasoline powered generator. 12kw (15kw surge) that is tripping its 46A breaker on startup. The 14kw diesel powered generator doesn't even know there's a load on it. Gas and NG has its benefits during short power outages until I get the diesel permanently installed, and I'm told the compressor will last longer with a soft starter.

If anyone has any advice, I'd appreciate it.
 

A scroll compressor responds better
To a soft start kit vs a reciprocating Compressor .
That said , I have had the best success by adding the largest hard start kit available to compressors .
A six ton scroll compressor here uses to draw 166peak amps when starting and would dim the lights .
Not it draws a peak of 99 amps , starts and runs up to speed faster and barely dims the lights .
Also installed a hard start kit on the son s trailer AC . The ancient , smoking 4000W Generac was sometimes unable to start the AC compressor on the first attempt . Now the AC starts in a few seconds and without noticeably bogging down the generator rpm s . The Governor does have the throttle wide open for several seconds .
 
I have no experience with the Hyper Engineering product. They talk a lot about what their product supposedly does, but are pretty light on details as far as how it actually works. It sounds like a good product, and I'm sure it has a price to match.

The Supco SPP6 uses a positive temperature coefficient relay and a large capacitor to improve starting torque. These popular units are widely available for around ten bucks and work on just about any AC. I put one on my RV air conditioner to deal with dodgy campground power and it hasn't given any trouble. Our RV generator never had any problem starting the 15K Btu/hr air conditioner before I installed it, so I can't actually say I noticed any difference.

Supco sells a wide variety of hard start capacitors. If you go to the link below and click on the 'Downloads' tab, then pick the link under 'Application Sheets', you'll find a brochure that describes how their various devices work.
Supco SPP6
 
Is this what you are calling a soft start kit?

TOMORAL SPP6 Hard Start Kit for Air Conditioner PTC Relay Start
Capacitor with 500% Increase Starting Torque Suitable for RV
Vent Booster Fan HVAC Compressor Motor etc.
cvphoto136467.jpg


My compressor draws 137.8 LRA and 19.2 RLA

That's a lot of amps to start with a generator..

I have an electric chainsaw, 70 LRA makes my 4000w generator to
grunt and moan. Chainsaw has brushes and is easier to start.

My generator won't start a 1.5 hp air compressor.

They used to make different size hard start kits. bigger
capacitor. You can piggyback them, add 2.

I would be afraid of burning up the generator and AC.
Electric motors and generators don't play well together..
What does the owner's manual of the generator say about motors?
 
Their use is gaining popularity in RV circles as they can allow a smaller portable genset (maybe 2 or 2.2
KW) to start the rooftop AC unit where such isn't possible without a Soft Start. My genset is capable of
starting and running my AC without one so I have no need.

John T
 
Another option would be to put a valve on the tubing going from the pump to the tank. If you opened the valve until the compressor was running it would start a
lot easier. The air pressure is what makes a compressor start hard.
 
Thanks for the info. I have a hard start kit that I haven't installed. Didn't know they can be doubled. Put one on my folks' A/C and it lowered the surge demand a little, but it's only a 4 ton unit and the generator never had issues starting it. I bought a new breaker for the generator to help figure out if the old one is weak and am going to order a soft start. I can see a lot of possibilities for these things beyond the A/C unit.
 

A soft start is a variable frequency drive of sorts .
It limits the amount of current the electrical load can draw . Drawback can be a slow start
or a no start with high torque demand loads .
 
''one guy told me that the only thing he knows is they won't work with a scroll compressor''

There may be some basis for that, with a scroll compressor you want a QUICK, dependable start in the correct direction, as they don't work if they start with reverse motor rotation, current draw is WAY up and after a minute or two they trip the overload protector.
Click to expand...
 
Check Break,

I don't know when the terminology
changed, we use to call them hard
start kit.

Very simple and easy to install and
they were readly available for
residential A/C systems.

Usually was a low voltage issue
from the mains. Sometime a tight
compressor.

I still have this one left.
Probably have the instructions?
Been many years,

Guido.
<img
src=https://www.yesterdaystractors.com/cvphotos/cvphoto136651.jpg>
 
(quoted from post at 12:19:08 09/25/22) Check Break,

I don't know when the terminology
changed, we use to call them hard
start kit.

Very simple and easy to install and
they were readly available for
residential A/C systems.

Usually was a low voltage issue
from the mains. Sometime a tight
compressor.

I still have this one left.
Probably have the instructions?
Been many years,

Guido.
&lt;img
src=https://www.yesterdaystractors.com/cvphotos/cvphoto136651.jpg&gt;
Click to expand...

Up until last week, all I was aware of was a hard start kit. The same type you're familiar with and still very popular. A second start capacitor and nothing complicated. The soft starter is chip and board design that starts the motor slowly and builds up torque. A little slower than a hard starter. Really no need for one unless you're trying to start a motor without grid power and are using limited input. I intended to order one last week but was looking for the best price until I got sidetracked. Story of my life. If this works, I'm going to install them on my well pump and pressure pump to reduce the size of the generator needed. I think this also solves a problem with our irrigation pumps. They need a 100KW genset to start them now, but I've been looking around and think I can save some money with a soft starter and a 60KW generator. One thing at a time and it takes me a long time to do anything now.
 
(quoted from post at 18:55:04 09/23/22)
''one guy told me that the only thing he knows is they won't work with a scroll compressor''

There may be some basis for that, with a scroll compressor you want a QUICK, dependable start in the correct direction, as they don't work if they start with reverse motor rotation, current draw is WAY up and after a minute or two they trip the overload protector.
Click to expand...

If this happens, I'll use it on my pressure pump. It won't go to waste. Sometimes the only way to figure something out is to take a gamble. I've lost more than a few but far more have paid off.
Click to expand...
 
(quoted from post at 15:14:59 09/23/22)
A soft start is a variable frequency drive of sorts .
It limits the amount of current the electrical load can draw . Drawback can be a slow start
or a no start with high torque demand loads .
Click to expand...

The new A/C units have a solenoid actuated bypass valve of sorts to reduce load against the compressor. My compressor is at least 25 years old so I know it doesn't have a bypass. If she chokes, the starter will get repurposed.
 
checkbreak,

it's been 30 plus years since I serviced central air units. Anyhow like I said the one I posted was very
effective for low voltage and tight compressor. I am not much of a fan when another piece of equipment
modifies OEM design,

Guido.
 
Check Break,

Sounds as if the compressor motors have been drastically downsized. Newer refrigerants also carry much
higher pressures. Anyhow, even the old motors, would have a hard time short starting, if they were short
cycled and the pressures were not equalized on both sides of the system.

R22 was the last set of gauges a bough for house A/C units. So it has been awhile.......


Guido.
 
(quoted from post at 15:31:24 09/25/22) checkbreak,

it's been 30 plus years since I serviced central air units. Anyhow like I said the one I posted was very
effective for low voltage and tight compressor. I am not much of a fan when another piece of equipment
modifies OEM design,

Guido.
Click to expand...

Thanks for the help. I'm leery of OEM re-engineering as well.
 

Bypass or not . The hard start kit reduced the peak current demand . It also shortened the length of time for the compressor to achieve full operational rpm .
 
(quoted from post at 02:40:11 09/26/22)
Bypass or not . The hard start kit reduced the peak current demand . It also shortened the length of time for the compressor to achieve full operational rpm .
Click to expand...

I've read that this reduction in time to achieve rated rpm reduces motor life. Not sure if this is true or just a marketing ploy to sell soft starters.
 
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