Soft Start Kit ?

Richard D._2

I have been retired 7 years so been out of the loop awhile lol
A buddy was asking me about a Micro Air Soft Start Kit !
I think his AC Guy told him about it !
He is in Tx. so his AC runs a lot lol ,
Told me his lights dim when AC starts ,
His AC system is maybe 2 y/o
He does have a 200A service and New Square D Panel, Ditched the old Federal

So what do you all think about the control ?
What about the brand ?
Best brand ?
Do they really work ?
FYI I do not believe adds 100% saying they are perfect lol
Any opinions would be great
Thank You

Hope my e mail notification works lol

leonz

Have your friend request that the utility come and do a meter
test to verify the existing transformers windings have not
begun to fail.

Brown outs are a symptom of a possible bad transformer especially
when 3 or more services that feed from it.

They will come by and install a temporary round gauge graph to
monitor and document the meters/transformers performance.

Richard D._2

Leonz
Thank You I;ll pass it on,
He is rural so should not be a big load area but maybe being out there may be a issue ! I'll pass your info on,
He is Retired ARMY and LEO so I try to help when I can,,
Again THANK YOU

ChrisJ

Lights in a house ALWAYS dim when a compressor starts to some extent.
It depends on how much they dim whether or not it's an issue.


That said, I've considered a soft start for my compressor as well. Also I believe they help a lot if you're running on a backup generator.

@njtommy

JUGHNE

Light dimming is common with AC start up.

If rural in the country, the voltage regulator that has to adjust for that additional load could be several miles from the customer.

I have a fair sized transformer 150' from my house, it serves only one other house.
My service lateral is oversized for the load.

I still get just a slight bump in the lights when a 2 ton AC kicks in.
If I couldn't hear it start I would never notice the lights.

Richard D._2

First THANK YOU all for the info..
I'll pass it on
As for transformers he told me there is one at each house on his road ! so I assume a long road with few houses !
I was thinking lights dim a little from the load of a compressor is not all bad !
Glad to see it is not uncommon !

ChrisJ said:

Lights in a house ALWAYS dim when a compressor starts to some extent.
It depends on how much they dim whether or not it's an issue.


That said, I've considered a soft start for my compressor as well. Also I believe they help a lot if you're running on a backup generator.

@njtommy

He does have a Back Up generator Thanks for that info as well,
Ill pass it on

WMno57

Another rural point of data.
My hood also has a transformer for each home, and I have a whole house Generic 16 KW genset. The 16 KW rating is overly optimistic, and for running watts, not starting watts.
My AC dims the lights on grid power. The AC will start on genset power, but I don't recommend it. I had a power outage, and during the outage the thermostat called for cooling. Both the AC and the genset struggled. There should have been a sub panel for genset power loads, but that was installed before my ownership.
If your friend wants AC on backup power, the smallest 240 volt window shaker would be less stress on the generator and AC. 240, so it pulls from both legs.

ChrisJ

WMno57 said:

Another rural point of data.
My hood also has a transformer for each home, and I have a whole house Generic 16 KW genset. The 16 KW rating is overly optimistic, and for running watts, not starting watts.
My AC dims the lights on grid power. The AC will start on genset power, but I don't recommend it. I had a power outage, and during the outage the thermostat called for cooling. Both the AC and the genset struggled. There should have been a sub panel for genset power loads, but that was installed before my ownership. If your friend wants AC on backup power, the smallest 240 volt window shaker would be less stress on the generator and AC. 240, so it pulls from both legs.

A droop in voltage (dimming lights) doesn't necessarily indicate an issue. It depends on how much of a droop and for how long.

When I was testing out my home built 8KW natural gas generator I tried starting my 3 ton 2 stage A/C on it.

The generator certainly didn't like it, but the compressor didn't seem to care much. It started fine.
If it was 90F+ out and our power goes out for any length of time I can guarantee I'll be running the A/C on that generator. Although I may manually control it so I can keep the load to a minimum during starting.


In my specific case, mine is a B&S 570cc vtwin with a 12KWH alternator. So, when it comes to running a 3 ton AC it's definitely a baby. And even though the alternator can do 50A @ 120V *2, the engine can't. It makes life easier if the load is imbalanced, but the total output is still limited to 8-9kw.

The 16KW Generac my dad has uses the same engine as their much larger 20kw model, I think 1000cc. His has absolutely no problem starting the 3 ton single stage A/C. In fact, I think he did a test where the well pump was running and several other large loads and it still started the A/C just fine.


A soft start can very well make it easier on things especially if the dimming lights bothers people, or even causes issues with equipment etc but it's probably usually not necessary.

In regards to stress on a generator, in my opinion, the generator doesn't care and isn't effected in the least by the short 80A draw from an AC compressor. It causes an abrupt blip of the throttle and a sudden slow down of frequency and drop in voltage, but I don't think the actual equipment is effected by it. It's not long enough to create any heat in the alternator.

Other things being powered may not tolerate the drop in voltage and frequency, but I don't think the generator cares at all.

ratio

Interesting. I have a Honda 5k portable, rated 5k5 starting (but I heard that a cheaper brand would be rated 7k starting) that will run the central air on two houses, along with some lights, four fridges, & two deep freezers. I don't believe that both ACs ever started at the same time, though. Didn't run the electric dryers either, but I had a gas one for just that case!

Also, that was brand new, we haven't seen an extended outage that effected both houses since then. The distribution breaks between our houses, so minor disturbances rarely takes us both down.

ChrisJ

ratio said:

Interesting. I have a Honda 5k portable, rated 5k5 starting (but I heard that a cheaper brand would be rated 7k starting) that will run the central air on two houses, along with some lights, four fridges, & two deep freezers. I don't believe that both ACs ever started at the same time, though. Didn't run the electric dryers either, but I had a gas one for just that case!

Also, that was brand new, we haven't seen an extended outage that effected both houses since then. The distribution breaks between our houses, so minor disturbances rarely takes us both down.

I'd think another thing to consider in this is the size unit, as well as what kind of metering device does it have. Mine is using a non-bleed txv.

ratio

My house: 2½ ton, R-22, piston; other house: 2 ton (IIRC), R-22, TXV, probably non-bleed.

HVACNUT

Have you checked starting amps on the compressor? Connections are tight? Grounds? Is there a hard start cap/relay? 
The lights dimming can be normal but if the compressor is approaching locked rotor amps on start, there's obviously a problem. 

ChrisJ

HVACNUT said:

Have you checked starting amps on the compressor? Connections are tight? Grounds? Is there a hard start cap/relay? 
The lights dimming can be normal but if the compressor is approaching locked rotor amps on start, there's obviously a problem. 

Shouldn't it draw close to LRA on startup?
It's technically starting stalled so there's no back EMF at that point.

I wouldn't expect grounds to matter at all.

ratio

Measure the winding resistance & you'll get an idea of start current. You'll need a meter that will latch inrush current to measure it, as it shouldn't take much more than a few revolutions before counter EMF becomes noticable.

mattmia2

ratio said:

Measure the winding resistance & you'll get an idea of start current. You'll need a meter that will latch inrush current to measure it, as it shouldn't take much more than a few revolutions before counter EMF becomes noticable.

You would need lab type equipment to log the inrush, typical field service type multi meters only read a few times a second and would only capture something close to the peak current by sheer luck.

ratio

My Fluke has an inrush setting, as does my UEI. At least the Fluke capture a not unreasonable value, i.e. 42A on a ¾ HP single phase motor tapped for 120 volts. (Haven't tried the UEI.)

You've got me wondering now, I'm going to have to check them out & see just how accurate they are.

mattmia2

ratio said:

My Fluke has an inrush setting, as does my UEI. At least the Fluke capture a not unreasonable value, i.e. 42A on a ¾ HP single phase motor tapped for 120 volts. (Haven't tried the UEI.)

You've got me wondering now, I'm going to have to check them out & see just how accurate they are.

If it has a setting for it and is designed for motor servicing, it might have some special circuitry to capture the peak. Even then it is so brief that parasitic impedance of things get in the way of measurement. It is like the way that the edge of a real world square wave is never square.