variable frequency drives for dryers

[carnut2]

Variable Frequency Drives...should we have put them in when we built our wash? Maybe

Should we be considering adding them now?

Hypothetical wash runs 75000 cars a year and their electric bill is about $2500-3000 a month running nine 15 amp dryers.

The cost of the VFD's will be about 20K. Anyone have any figures on recouping this cost? There is a tax saving of about 8-10k with our power company over 3 years.

 

[Washmee]

I installed a VFD on my 7.5hp well pump this fall. It has caused all kinds of other problems at my wash with other electronic devices. In particular my POS system and my photo eyes. I was told that the Dahms(Mikes) are removing them from many locations due to these type of issues. Be sure to get someone who really understands the issues these devices can cause at a carwash.

 

[mjwalsh]

I installed a VFD on my 7.5hp well pump this fall. It has caused all kinds of other problems at my wash with other electronic devices. In particular my POS system and my photo eyes. I was told that the Dahms(Mikes) are removing them from many locations due to these type of issues. Be sure to get someone who really understands the issues these devices can cause at a carwash.

Carnut2, Jon & others,

Was everyone in on the install fussy enough with a specific isolated earth ground for it? Without trying to be a smart*ss I would think that a pump or a fan application would have the fewest issues compared to some VFD applications. Shielded wires properly grounded also become more important.

I do agree that VFDs can be less forgiving from what I have gathered. I only have about 9 months experience with a few 3-5 HP VFDs so I too am still potentially learning.

MikeW

 

[carnut2]

MikeW -

We didn't have the money to install from the get go and so I am sure the contractor did not take the addition of VFD's in to consideration.

I know of one wash here in our major mertropolitan area that added them to a 10 year old wash, but the owner is a little reluctant to share info, understandably. However, I am hoping someone in a different part of the country can share whether it is just another gimmick or if it is a real savings.

I could see at a wash that is running 100k a year, they probably never have their dryers slow down or shut off, but we have spurts on most days with a lot of wasted amping up.

 

[mjwalsh]

MikeW -

We didn't have the money to install from the get go and so I am sure the contractor did not take the addition of VFD's in to consideration.

I know of one wash here in our major mertropolitan area that added them to a 10 year old wash, but the owner is a little reluctant to share info, understandably. However, I am hoping someone in a different part of the country can share whether it is just another gimmick or if it is a real savings.

I could see at a wash that is running 100k a year, they probably never have their dryers slow down or shut off, but we have spurts on most days with a lot of wasted amping up.

carnut2,

Based on putting a clamp on ammeter on the wires of the VFD driven motors that I have worked with --- I personally think you are absolutely right about potential significant electrical savings. Especially if your motors are already 3 phase & even more so if they are are already "inverter duty" rated --- making the transition less costly &/or risky for you to do.

I would think there is a graph from a google search that you can share with us that could show hi speed blower with VFDs vs the same blower without a VFD comparisons!

MikeW

 

[MEP001]

Running motors on a VFD plays a much bigger role in energy savings if your electric bill is based on a demand charge. If you want to maximize energy savings, find someone who can help you with a program to let the motors soft-start with minimum amp draw, idle down between cars and shut off when not needed. If you don't have a demand charge and you don't set things up properly, you probably won't save any money with the changeover.

 

[sparkey]

Many of the good VFD's run at a power factor of 1 so you are not paying for lost energy.

If line reactors are not installed before the drive it can put harmonics back on the power lines which can cause problems with other equiptment.

 

[carnut2]

We definitely have a demand charge. In our area, our electric bill doubles for three months of the year due to peak demand.

 

[mjwalsh]

Many of the good VFD's run at a power factor of 1 so you are not paying for lost energy.

If line reactors are not installed before the drive it can put harmonics back on the power lines which can cause problems with other equiptment.

Sparkey,

Good point. Our 3-5 HP VFDs inputs were single phase so a line reactor was not an option for us. So far no problems back into our very electronic facility. So the shielded wires & the isolated ground must be helping.

It seems like some more expensive VFDs may have less chance of causing a harmonics problem --- I am not sure.

MikeW

 

[my2cents]

Line reactors and/or load reactors along with shielded cable are a must when using VFD's. If your dryer manufacturer offers a air gate type of system that bolts on your intake, that may be a better option and provide the same electrical savings as a VFd without added expense of new cable and reactors. In addition, a VFD when it goes bad has more cost to replace than a across line starter.
From a new install stand point, I would not suggest a VFD when using an intake gate system - its unnecessary. The gates eliminate the spike when they start up, are better for open bed pick -ups and are a less expensive option than VFD's. I know they are available on Proto-Vest, PECO, MacNeil and Sonny's products,so if you have one of those dryers I suggest calling the mfg.

 

[carnut2]

We do use Peco dryers so I will call my manufacturer about the gates. Thanks...big help!

 

[Emerald in NJ]

We do use Peco dryers so I will call my manufacturer about the gates. Thanks...big help!

I also have PECO dryers. I am curious if you decided to install these. I just sent my distributor an email asking about them but kind of want to hear from someone who actually has them.
thanks

 

[JimmyJaffa]

There is one more solution other than a VFD, and that is a soft start. If you are only going to use the maximum rated rpm of the motor, and not reversing it, than a soft start is best. We use VFD's on our electric friction equipment where the rpm needed to be controlled. For dryers and pumps, the ramp up provided by a soft start is comparable with a VFD at about 1/2 the cost and keeps your electric demand in check.