Restaurant POS...

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steve66

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Re: Restaurant POS...

If indeed there is a neutral-ground bond at the service disconnect, then should the neutral be separate, "floating", from the equipment ground in the panel?
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Yes, the general rule is "One and only one" neutral to ground bond.

Check out www.powervar.com. It looks like they are basically isolation transformers. (I'll be Square D wishes they could sell 360VA worth of transformer for $1700!!)

The voltages the tech measured were probably "high frequency noise" voltages. You can't measure that with a DMM.

Steve
 
dereckbc

dereckbc

Moderator
Staff member
Location
Plano, TX
Re: Restaurant POS...

Originally posted by 1793:
If indeed there is a neutral-ground bond at the service disconnect, then should the neutral be separate, "floating", from the equipment ground in the panel?
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Yes as already stated. I was under the impression the POS were on shared circuits with other equipment, meanuing some load which would develop higher voltage drop. That is why I questioned the voltages. The only thing I can think of is to use an isolation transformer, or re-route the circuits away from any equipment which might induce noise on the circuit. However IMO if the equipment is that sensitive, the real culprit is the design of the equipment rather than the electrical supply. .2 volts N-G at the load indicates a low loss circuit for the load, far better than the maximum 2 volts by IEEE and all other PQ organazations.
 
physis

physis

Senior Member
Re: Restaurant POS...

Some things you can protect from the outside world all you want. What happens if you spend thousands of dollars and it turns out that the thing generates noise of it's own (like from the printer) that locks it up.
 
physis

physis

Senior Member
Re: Restaurant POS...

I read the letter.

Oscilloscope readings from location (outlet) to location were the same,
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No kidding.

leading us to believe some of the kitchen equipment is on the same circuit as your POS system.
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I had no idea that there is a method to determine whether or not a receptacle is on a shared circuit using an oscilloscope. If you could ask Hershel for me I'm interested in knowing how to do that.


The cordless telephone may create communications problems with your POS system.
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It wont work next to a telephone? Oh, a wireless telephone.

The voltage measurements reported in the letter would be an obvious concern. However your measurements look very good. I think it's very unlikely that both sets of measurements are accurate. It's remotely possible that the two different conditions existed at two different times, but that different? I doubt it.

I would be very surprised if the recommended actions remedied the problem. I think you can hope for reduce at best.

Edit: I left a letter out.

[ March 10, 2005, 05:06 PM: Message edited by: physis ]
 
steve66

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Re: Restaurant POS...

It wont work next to a telephone? Oh, a wireless telephone.
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But apparently it will work next to a wireless telephone plugged into a different circuit!!!
 
1793

1793

Senior Member
Location
Louisville, Kentucky
Occupation
Inspector
Re: Restaurant POS...

Just got off the phone with Hershel, the computer guy. He told me that when he tested the line he loaded it to 15 amps and then record the results as indicated in the "Letter". My readings were actual use readings. In my, humble, opinion you should test what you have. Please correct me if I'm wrong.

His response to the Isolated Ground is to have a DEDICATED PANEL connected to NOTHING else in the building. This new panel would be for the POS ONLY. This includes a new driven ground to this new Isolated Panel.

Before I called Hershel, I spoke with my customer and there has been some discussion about changing from "PC Charge" & "Chow"(?) to maybe "Focus"(?) for his POS.

I welcome and expect some comments.

Norb
 
physis

physis

Senior Member
Re: Restaurant POS...

So now he's intentionally putting a voltage drop on the circuit and pointing out that it's not within the required specs?

It's own panel? It's own ground?

Does he want his own power company too?

Why is your customer putting himself and his business through this?

Edit: And if he's going to load down your circuits why doesn't he ask for 8 AWG conductors too, if that's enough.

[ March 10, 2005, 05:45 PM: Message edited by: physis ]
 
dereckbc

dereckbc

Moderator
Staff member
Location
Plano, TX
Re: Restaurant POS...

Originally posted by 1793:
His response to the Isolated Ground is to have a DEDICATED PANEL connected to NOTHING else in the building. This new panel would be for the POS ONLY. This includes a new driven ground to this new Isolated Panel. Norb
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Well sometimes I have to be cynical in order to get a point across. He is an idiot, and knows nothing of the code. This would be in direct violation of 250.4(5). Furthermore it would only make the noise problem worse, not to mention be extremely dangerous to personnel and equipment in question.

My personal opinion is the POS people are fishing and the electrical is the scapegoat. The full load voltages would be a valid measurement if they jived as I stated earlier. If you have a 10-volt drop from line-to-neutral, you can expect 5-volts N-G. There is no practical way to be at 10-volt L-N drop, and only have .2-volts N-G, unless the neutral conductor happened to be a 2/0 on a 20-amp circuit :roll: .

The tightest spec I have ever seen or specified that can be achieved is for a 4-volt L-N drop, with 2-volt N-G, or in other words a 3.3% voltage drop at full load. Five percent is the standard in PQ circles which equates to 6-volts L-N drop, and 3-volts N-G at full load.

[ March 10, 2005, 07:16 PM: Message edited by: dereckbc ]
 
C

caj1962

Senior Member
Re: Restaurant POS...

Be a hero tomorrow and sell your customer a 50 dollar or so ups and call it good. tell the sales guy to hush and fix or replace his equipment because you have given him what he wants. all the isolation he needs
 
dereckbc

dereckbc

Moderator
Staff member
Location
Plano, TX
Re: Restaurant POS...

Jeff, inexpensive UPS do not provide any isolation or wave form correction. They are referred to as "Stand-By" types which the output is connected directly to the input via a relay. It would require a "Line Interactive", or "Dual Conversion" type UPS to provide any isolation or wave form correction. They start at around $500 for small units.
 
C

caj1962

Senior Member
Re: Restaurant POS...

My point with UPS is that this guy has no clue. So throw a bone and make him fix the equipment. I just did a big POS replacement and the manufacture recomended exactly what I posted. They to had the isolated panel and all points originating out of said panel. Well this is a hospital and I would have had to run run circuits 3 floors and 200-300 feet. We installed the UPS as recomended and they were happy. Now when they fail in about a here because the battery dies I probably won't replace them.
 
physis

physis

Senior Member
Re: Restaurant POS...

What? I can't believe it! You don't kn.....

Just kidding. :D

Uninterruptable Power Supply.

Edit: And I thought it would be POS that people wouldn't know.

[ March 11, 2005, 02:37 PM: Message edited by: physis ]
 
1793

1793

Senior Member
Location
Louisville, Kentucky
Occupation
Inspector
Re: Restaurant POS...

Physis:

Thanks I hate to admit when I don't know something but sometimes it's the best course of action to ask and get out in the open.

Norb
 
physis

physis

Senior Member
Re: Restaurant POS...

My experience with this sort of thing is that as a retailer you represent the manufacturer and they put the retailer in a position where they need to defend the product. From all appearances, that's what's going on here.
 
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