# blower addition



## circuitman1 (Mar 14, 2013)

first of all where are you going to get the 480/277 voltage? i don't even believe even a transformer exists, may be wrong. know of a 480 to 120/240 or 480 to 120 /208 the later is three phase. you only have a 120/208 service. why not get motors for this voltage?so this is a no go to start with i believe.there may be away of back feeding a three phase unit but would not recommend it.:whistling2::whistling2::whistling2:


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## micromind (Aug 11, 2007)

The pole-mount pots are good for 208 amps. The existing load is 100 amps, that leaves about 110. 

Each 10HP motor will need about 25 amps. Each 15 will need about 35 amps. 25 X 3 = 75. 35 X 3 = 105. 105 + 75 = 190. Add a bit for the losses of the dry-type transformer and the VFD. 

Since pole-mount pots are oil filled, they'll take this kind of an overload for a short time, like 10 minutes every hour or so. 

If the main is less than 300 amps (I suspect it's 200 amps), it'll likely trip.

It'd very likely work if the blowers are running for only a short time and the main is big enough. 

I'd highly recommend connecting the motors for low voltage and using a 240 volt VFD. 

The VFD will have very little effect on the power going to the house. If it ends up being a problem, a line reactor will solve it. 

Assuming it's a 200 amp main, the 3 - 10HP motors will be ok. The 3 - 15s will probably be ok if they don't run a long time. All 6 motors will be trouble. 

One solution is if possible run the VFD at around 45 or 50HZ max. This will cut back on the current.


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## garfield (Jul 30, 2009)

Micromind it does have a 400 amp main breaker ........350 mcm aluminum on the utility side of the meter. The blowers can run for a max of 90 seconds every 5 minutes because that's how long a Carwash is. I have a used dry type transformer and I was thinking I would have faster acceleration because of more torque at 480 versus 208. The vfd is half price for 105 amps @480 volts versus more than double the amps @208 as well.


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## micromind (Aug 11, 2007)

The pole-mount pots will very likely be ok with a 90 second overload every 5 minutes. 

If the dry-type transformer is 208∆ - 277/480Y you'll be fine. If it's 480∆ - 120/208Y, you'll need to do 3 things;

1) Make sure that X0 is not connected to anything. You might need to remove the factory ground strap, but when reverse-feeding a 4 wire Y, nothing can be connected to X0.

2) You'll most likely need to disable the MOVs in the VFD. Hopefully the manual will tell you how, but if they're left in the circuit with anything other than a solidly grounded Y, eventually they'll blow up. 

3) Ground one of the 480 phases, usually H2. If it's left floating, it'll eventually wreck the VFD. 

Given the new info, it sounds like this installation will be ok.

Rob


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## garfield (Jul 30, 2009)

Okay now that we've gone down to the end of that road you have me thinking the transformers will be okay for the vfd. Is it likely they would be okay for the inrush with across the line starts? The normal way to do that uses just across the line starters with a six second delay or whatever between starts. Maybe I should just start one 10 hp and one 15 hp together for a total of three starts and then in 18 seconds everything will be started. This would be 208 forgetting about the transformer and the VFD. Another concern I have is when you drop out all of those motors at once does it create a surge or flicker? Is it worth staggering the stops as well?


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## micromind (Aug 11, 2007)

If the motors are all across-the-lines, when all of them drop out at the same time, there's no voltage surge to speak of, it'll stay stable. 

If possible, I'd start the 15s first (one at a time), then the 10s (again, one at a time). However, if a 10 and 15 were started together across-the-lines, then the other 2 sets were brought on in sequence, you'd very likely be ok. Especially if the motors are 230/460 and not 200 volt. The starting current of a 230 volt motor on 208 is considerably less than a 200 volt one. 

The starting current of a 10HP 230 volt motor on 208 is roughly 130 amps, a 15 would be nearly 180. I realize this sounds like a lot, but the transformers can handle it. You might notice a bit of voltage dip though.


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## varmit (Apr 19, 2009)

Run the motors on 208. By installing a step up transformer, you would increase the service load for no benefit. A 200/230 volt VFD is capable of excellerating a motor at the same rate as a 480 volt VFD.

If you start motors of this size repeatedly at five minute intervals, the motors will have a very short life. There needs to be some timer logic to maintain the motor running for some period of time after a start - say 15 minutes. If no car has entered the car wash at the end of this time delay, the fans will shut down. If the VFDs have a "Flying Start" parameter option, be sure that this is enabled. This will help prevent drive faults from restarting the motors during a coast to stop.

A delay interval, between each motor starting is a good plan. 

Logic that will work well for this application is to lessen the speed command, of the motors, to a slower speed (Just fast enough for motor cooling) between drying cycles. When the dryers are needed, the VFD/motors are ramped up. If you can run the motors in this "idle" mode at 25% to 30% nameplate RPM, you will be below the fan curve far enough that the motors will have very little load, as the fans will be moving almost no air.


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## Peewee0413 (Oct 18, 2012)

Carwash do "stagger start" their motors. Most likely with timers And nobody would idle the fans. Waste of power. I'd think they'd use SS's..


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## Vintage Sounds (Oct 23, 2009)

circuitman1 said:


> first of all where are you going to get the 480/277 voltage? i don't even believe even a transformer exists, may be wrong. know of a 480 to 120/240 or 480 to 120 /208 the later is three phase. you only have a 120/208 service. why not get motors for this voltage?so this is a no go to start with i believe.there may be away of back feeding a three phase unit but would not recommend it.:whistling2::whistling2::whistling2:


 there is this thing out there called a step-up transformer, you may have heard of it?


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## don_resqcapt19 (Jul 18, 2010)

What other loads are there? You have a 75 kVA transformer bank, and are adding 75 kVA of motor load (rule of thumb 1 hp = 1 kVA)


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## JRaef (Mar 23, 2009)

don_resqcapt19 said:


> What other loads are there? You have a 75 kVA transformer bank, and are adding 75 kVA of motor load (rule of thumb 1 hp = 1 kVA)


This is the salient point here, there is no free lunch. 

What you do or don't do with transformers or no transformers, drives or no drives, makes no difference to this bottom line. Your service can, right now, barely handle the given new load WITHOUT the rest of the car wash being run already. The ONLY possible way to make this work would be for the car wash owner to program the car wash so that you CANNOT have anything else running when those blowers are running. That means limiting the throughput of the car wash, i.e. you cannot have car #2 enter at the other end while car #1 is getting a blow dry. From my experience with car washes, that will be unacceptable. On a hot day after a rain storm, they want to maximize their profit by running cars through as fast and furious as possible.

As to whether or not the utility pots can or cannot handle the repeated overload is, technically, not your call. Or put another way, if you ask, and THEY decide to let them be overloaded (which is entirely likely), and one fries, then the onus is on them. If you do NOT tell them of the increased load and one of the transformers fries, they will want to be paid not only for the transformer, but for the cost for their crew to replace it, THEN they will charge the car wash owner for the higher service, and possibly BACK charge him for what he got away with anyway.

And just for the record, stepping up to 480V buys you nothing; watts = watts = watts. But it WILL lose power heating up that transformer.


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## circuitman1 (Mar 14, 2013)

Vintage Sounds said:


> there is this thing out there called a step-up transformer, you may have heard of it?


yeap! know all about them. but don't believe there widely used for these applications. may be wrong too, just never seen that many. just the down type. there also transformers that are called auto transformers that are step up.


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## Peewee0413 (Oct 18, 2012)

circuitman1 said:


> yeap! know all about them. but don't believe there widely used for these applications. may be wrong too, just never seen that many. just the down type. there also transformers that are called auto transformers that are step up.



Looking down shaking my head....


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## circuitman1 (Mar 14, 2013)

Peewee0413 said:


> Looking down shaking my head....


:001_huh::001_huh::001_huh: always saw that you had the proper voltage or right motors. don't dispute they exist. also like jraef said you gain nothing, but it is what it is.:thumbup::thumbup:


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