Generator inlet question

[dmaxfireman]

Situation:
I have a generator inlet and an EU7000is generator (5500 running 7500 surge) that replaced a slightly larger albeit much louder Generac. Generator is for emergency backup only. This past summer we used it during a very hot week and it had trouble kicking on the central air. Installed an OEM hard start kit and dropped LRA from 78 to 63. Running amps around 15-18. Both numbers (even before the hard start kit) are within spec for the A/C unit.

Generator now kicks on the central air without too much trouble (not as easily as with street power) but once fired up has no problem maintaining.

My generator inlet is run with 60ft of 10/3 to the panel and the A/C is also run with 10/3 55ft from the panel. So the 10/3 run from the generator through the panel would be 115ft.


Question:
Would changing the inlet circuit to 8/3 or even the A/C circuit as well lessen the "golfball through a garden hose" effect on the inrush with the generator? Thought process being this is a very expensive generator and a couple hundred dollars in wire is cheap insurance to make life easier on the generator.

 

[nadogail]

IMHO, I don't think you will see an appreciable difference.

Any advice you take from me is guaranteed to be worth exactly what you pay me for it.

 

[theoldwizard1]

Large gauge wire would help, but it is hard to say how much. NM-B (indoor Romex) is about $1/ft for 8/2 and $1.50/ft for 8/3. If you are running in conduit, you can use THHN/THWN which is about $0.40/ft.

What kind of "hard start" kit did you install ?

This is one of the best Micro-Air EasyStart

 

[wyliesdiesels]

Doubt it will make much difference but you could calculate the resistance difference between the gauges, using the values in table 9 in chapter 9

 

[dmaxfireman]

Large gauge wire would help, but it is hard to say how much. NM-B (indoor Romex) is about $1/ft for 8/2 and $1.50/ft for 8/3. If you are running in conduit, you can use THHN/THWN which is about $0.40/ft.

What kind of "hard start" kit did you install ?

This is one of the best Micro-Air EasyStart

OEM Recommended

BAYKSKT260

 

[rlitman]

Large gauge wire would help, but it is hard to say how much...

I'm going to go out on a limb and say that large gauge wire can make the problem worse.

The resistance of the wire already does a little to limit the inrush current, and that rush of current is the limiting factor when it comes to an inverter generator.

 

[theoldwizard1]

OEM Recommended

BAYKSKT260

That is a "classic" 5-2-1 hard start kit. IMHO, that is not a "soft" starter like the Micro-Air EasyStart. A 5-2-1 is basically a second starting capacitor.

The Micro-Air works on the principles described in this video How to make a Soft starter and why it is sometimes mandatory to use!

 

[larry4406]

That is a "classic" 5-2-1 hard start kit. IMHO, that is not a "soft" starter like the Micro-Air EasyStart. A 5-2-1 is basically a second starting capacitor.

The Micro-Air works on the principles described in this video How to make a Soft starter and why it is sometimes mandatory to use!

You seem to recommend this device at every opportunity. Is it truly the best thing since sliced bread? Own one?

 

[theoldwizard1]

You seem to recommend this device at every opportunity. Is it truly the best thing since sliced bread? Own one?

No, but I am (well, was) an engineer and understand the basic principals (i.e. Ohm's Law) presented in the video. Only an inline resistor can inexpensively limit current.

Is the device worth the cost ? No, when you realize it can probably be built for <$100.

 

[dmaxfireman]

That is a "classic" 5-2-1 hard start kit. IMHO, that is not a "soft" starter like the Micro-Air EasyStart. A 5-2-1 is basically a second starting capacitor.

The Micro-Air works on the principles described in this video How to make a Soft starter and why it is sometimes mandatory to use!

What is the difference between what I installed and what you are recommending? I'm not an engineer, would just like to understand the difference in how it is functioning.

 

[wyliesdiesels]

What is the difference between what I installed and what you are recommending? I'm not an engineer, would just like to understand the difference in how it is functioning.

the BAYKSKT260 is just a start cap with a relay

while the Micro-Air EasyStart© has some kind of circuitry that does a 4-part startup

Per the link here

It employs a 4-part start ramp sequence that is self-optimizing, resulting in the lowest possible start-up current. EasyStart can deliver 65-75% start current reduction as compared to a compressor's LRA (locked-rotor amperage).

I do not know what components the Micro-Air EasyStart© has but it's way better than a start cap...

A start cap cannot reduce the in-rush current by that much so...

 

[rlitman]

...I do not know what components the Micro-Air EasyStart© has but it's way better than a start cap...

A start cap cannot reduce the in-rush current by that much so...

Caps are the CAUSE of in-rush currents.

The EasyStart (just watched a video on their site), looks to do two things. It has an on-delay relay on the compressor, so the fan inrush and compressor inrush currents are separated by a few seconds (that's genius really). And then it has whatever magic it does to reduce those separated inrush currents themselves.

First thing that comes to mind for me would be to have an NTC thermistor in series with each cap (an AC actually has two caps; though both are usually contained within the same housing). NTC thermistors are a common component used to limit inrush currents, and with one on each cap, you could claim a 4-stage startup, where both the fan and compressor have a slow start followed by full power. Of course, I'm not claiming that is their magic sauce, nor am I providing a schematic to get around their IP. Rather, I'm saying all this, so as to say I do believe their claims, and don't think it's electrical hogwash (unlike many similar looking components, such as the power factor correction quackery sold to put on peoples electric meters to save money).

It could be all that, plus the 5-2-1 secondary cap and potential relay too. Who knows, but I agree with TOW, that it probably works.

 

[theoldwizard1]

I do not know what components the Micro-Air EasyStart© has but it's way better than a start cap...

A start cap cannot reduce the in-rush current by that much so...

Caps are the CAUSE of in-rush currents.

rlitman hit the nail on the head ! I guess no one want to watch the video done by the guy with German accent !

A completely DISCHARGED capacitor "looks" like a short circuit, so it tries to take as much current as possible to bring it up to "full". (Think of filling a bucket with a hose. Except, the hose is directly connected to the bucket with no air gap and bucket has a huge vacuum on it. That vacuum can be so high that it will collapse the hose !)

In an electric circuit, the way you "limit current" is by placing a resistor in series (in line) with the load. (Ohm's Law I=E/R; current equals voltage divided by resistance. Increase resistance, decrease current.) Of course in this case you want to do it for a short time, just long enough to "charge" the capacitor at a slower rate. Then it must be "removed" from the circuit or the motor will not get enough current to "run".

Your start up time might go from 1-2 seconds to 4-5 seconds.

 

[Noltz]

Touching on your comment of swapping to 8-3, do yourself a favor and pull 6 awg THHN. I'm regretting going with 8-3 because now I want to take advantage of having a larger generator and installing a 50A inlet, but I cannot because I used NM-b instead of THHN and it isn't rated for 50A. 6 gauge THHN can handle your current inlet and if you choose to, 50A later. Only downside is you must make sure 6ga will fit your inlet, or count on making a 6 to 8 connection somewhere easy to access later.

 

[dmaxfireman]

I spoke with the folks at Micro Air this morning. They spent 30min on the phone explaining the how and why to me. Their attention to detail on the phone was exceptional and have no doubt if I need anything they will be sure to help out. I placed my order but unfortunately won't get a chance to test it out until temps warm up again in spring.

The product is 100% designed, made, and tested in America. The unit is also UL listed.

Will update this thread when I can test it out.

 

[AP514]

Also look at HYPER SURESTART Same type of Soft Start idea.
I just installed one -- thread below.

https://www.garagejournal.com/forum/showthread.php?t=467347

 

[dmaxfireman]

Also look at HYPER SURESTART Same type of Soft Start idea.
I just installed one -- thread below.

https://www.garagejournal.com/forum/showthread.php?t=467347

I did check them out. The deterrent was no phone number to call to answer questions. The Micro Air folks, answered the phone, answered my questions beyond any reasonable expectation. Then went on to ask about my setup, made suggestions, etc.

Today it is so rare to find customer support folks who don't read a computer generated script, speak clear English and are not only willing to look past their nose to help but are genuinely happy to do it. I will gladly spend the extra money to buy from a company that prioritizes these values.