# softstart?

Discussion in 'The Projects Forum' started by Mr. Alex, Jan 7, 2015.

1. ### Mr. Alex Thread Starter New Member

Oct 13, 2014
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has anybody ever seen a diffrence in there electric bill by installing a SoftStart ? we have a 100hp Sullair Vacuum and when the shop doesnt use it our bill is \$500-\$900 a month , and when we use do use it our bill is from \$3500-\$4500 a month and thats like 14hrs-25hrs a month ... i want to know if softstart is going to save our shop money

2. ### wayneh Expert

Sep 9, 2010
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By what mechanism would it save money?

Savings would come from making it as convenient as possible to turn it off whenever possible and on again only as needed. Don't let it run when it's not needed.

3. ### GopherT AAC Fanatic!

Nov 23, 2012
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4,039
100 hp = 74600 watts

Each hour of operation is 74.6kwH consumption
25 hours per month is 25*74.6 kwH = 1865 kWh

\$2400 per month extra for running vs. not running would indicate a electric rate of:\$1.24/kWh.

I suggest that you find a new electric utility. You are paying about 10x what we pay (unless my math is wrong).

4. ### jpanhalt AAC Fanatic!

Jan 18, 2008
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Have you had your power factor checked? The supplier may charge more if you are below 90 to 95%.

John

5. ### wayneh Expert

Sep 9, 2010
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Nice analysis. Makes me wonder if the vacuum is only running when other operations are also going on. Operations that use a lot more electricity than the vacuum.

6. ### Mr. Alex Thread Starter New Member

Oct 13, 2014
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i work in a paper converting company and we have 3 panels coming into our biulding and our 100hp motor is the biggest motor hooked up to it , the rest are 7hp ,10, and 20 hp envelope machines

7. ### strantor AAC Fanatic!

Oct 3, 2010
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\$500-\$900 no compressor, \$3500-\$4500 with compressor, gives difference extremes of \$2600-\$4000.

\$2600-\$4000 for 1865kWh works out to \$1.39/kWh-\$2.14/kWh. I'll call it \$1.77/kWh (avg).

I pay \$0.11/kWh for my house, which has crappy insulation. In Texas summers with my wife keeping it 68 degrees in the house all day, my bill maxes out @\$500. That's 4,545kWh/mo for my house. My 4,545kWh/mo would cost OP \$8,045/mo at his rate of \$1.77/kWh.

I want to know what is going on in OP's shop during the months he isn't using the compressor. If he's paying \$1.77/kWh and his bill is only \$700 (avg) that means he's only using 395kWh/mo, about 9% of what I use at the house. Assuming 12 hour shifts, 20 days/mo, that's about enough for an incandescent light bulb and a bench grinder.

8. ### strantor AAC Fanatic!

Oct 3, 2010
4,302
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OP:
IF what you report is not an error (in the utility billing statement, in the meter or the meter reader's log, or in your employees reports to you about what is running and when) or a gross exaggeration, then it would appear the utility service provider is charging you a penalty of 15X the national average of 12c/kwh when you run the compressor. IF this penalty is solely for power factor, then it's absolutely ludicrous; a typical power factor penaly is 1.4X, not 15X. Anyway, IF all the above is true, and IF by "softstart" you mean a Variable Frequency AC Drive, then yes, a VFD will fix your power factor issue.

You should be able to run the compressor 24hrs/day, 20days/month for that extra \$4k you're spending. And that's assuming the compressor has a massive air leak and runs continuously, never building the pressure to trip the cutoff switch.

9. ### tcmtech Well-Known Member

Nov 4, 2013
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This all sounds a bit suspicious to me being that every single item or penalty you are paying for is shown on your electric bill of which most anyone who works for the company should be able to request from your utility company without problems.

The thing that I see is that either the utility company is playing some unethical games or you have someone in charge of your company's finances that really needs to be drop kicked out the door for gross incompetence for not having questioned any of the high bills or you have some shady politics going on in your company and the work force is being fed some BS about high operating costs to keep the operating costs low or to hide some other problem in the company.

Either way no matter which one pf the three someone needs to be called out on all of this.

If the bills are real every penalty charge should be documented as to when why and for how much. If not a quick review of the past and present electric bills by most any lawyer should bring about some attention your utility company won't want.

10. ### BillB3857 Senior Member

Feb 28, 2009
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Are you a paying a Peak Demand penalty? If so, soft start would help but many compressors need to get up to run speed quickly. The volume of the line between the compressor and the unloader valve makes that difference.

11. ### Glenn Holland Member

Dec 26, 2014
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My interpretation is that "SoftStart" refers to an electronic starter instead of an "Across the line" or an alternative "WYE/Delta" contactor. If the vacuum is running steady for long periods, changing the starter won't provide much savings.

Jul 18, 2013
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Depending what the application is, if the Vacuum pump runs for long duration's and only used some of the time it might pay to unload it by closing off most or part of the air input.
also depends on what pump technology is used to produce the Vacuum.
Max.

13. ### GopherT AAC Fanatic!

Nov 23, 2012
6,315
4,039
If the OP is using the vacuum pump directly without a tank (or with an undersized tank) he could be experiencing too many on/off cycles and cause a problem. Insufficient hysteresis could also cause too many on/off cycles.