230 V electrical problems 1

[jimmylovesni]

We have 3to 4 different pieces of equipment running on 230V lines in our building that have got damaged in the last month (all are -80C freezers. Some of the freezers are brand new.

What is the best way to analyze the power? I have a 1000X voltage probe and a few Oscopes and was thinking of taking some FFTs and looking at 60Hz signal (time domain) as well. Does this seem logical?

thanks
Jim

 

[Skogsgurra]

You *could* find something.

But far better to use a power analyzer and set trig limits to standard values. That way, you will see when you get transients, brown outs, swells, distortion and all other things that may kill your equipment.

Just looking at the supply when everything is fine usually doesn't help.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[jimmylovesni]

ok.

are there surge suppressors similar to the 120V equipvalents that are sold for 230V 20A?

 

[rbulsara]

Power analyzing can be expensive too. Are you sure that the power quality is the culprit? You provided no details. It may be worthwhile analyzing the issue with help of a good electrical engineer.

Rafiq Bulsara

http://www.srengineersct.com

 

[jraef]

If you are in the US and it's 230V 3 phase, read my response in this thread, the same may apply to you.

thread237-290178



"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[jimmylovesni]

thank you.
jraef - It is single phase though.

rbulsara - I really dont know its power, but its alot of equipment that has failed as well as hang ups, new equipment. The maintaince people running the building are trying to stay its that the equipment is not maintained, but two of the $40k freezers are from different models and less than a month old. I dunno. Could be probability.

Ill scope it tomorrow. I waited today to talk with the maintaince/engineeering people before I did anything. Not sure what ill find.

 

[PHovnanian]

Rafiq is correct about the analyzers being expensive. But if you contact a good engineering consultant, they'll either have that equipment to conduct a survey or they can rent it. Either way, an engineer will have to interpret the data as well as possibly examining the failed equipment to determine likely causes. At $40K a piece, it might be a low price to pay.

 

[rbulsara]

What I meant was that before you decide to monitor power, ascertain within reason that it is the probable cause. The cause can be just a misapplication or something that can be found out by simpler checks. Unfocused data gathering only creates information overload, that may or may not be relevant and creates confusion.



Rafiq Bulsara

http://www.srengineersct.com

 

[racobb]

Unless you have already done so, you may want to take a look at the "brand new freezers" nameplate and see what the voltage rating really is. You can do that for free. Did they come from a US manufacturer or off shore, assuming you are in the US?

Measure the voltage at the units.

Is your system actually 230 or 208 volts?

As others have pointed out, the best approach is to keep it simple and check the most obvious to start with.

Alan

 

[waross]

How has the weather been there lately? Condensors in a cold ambient location may not be returning all the oil. Probably not, but the point is that refrigeration burnouts may not always have an electrical cause.
Does the utility use an old type electromechanical Watt-Hour Meter or one of the newer electronic meters. Some electronic meters may be set to log voltage, current and other parameters every 15 minutes. Some utilities are kind enough to download the logs and e-mail them in Excell format. I have used that information to solve a couple of problems.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ccjersey]

Are the freezers free-standing units with everything in the unit, or built-in with field installed lines and external condensers. Were these freezers replacements for other units or is this a new installation?

Hard to imagine month old units having cleaning or maintenance problems, but I guess it's possible to have a bad dust problem or maybe more likely a poor choice of location for air flow, ambient temperatures etc.

Refrigeration units are usually very well protected against electrical supply problems. I think it's more likely the usage they are seeing (cooling load etc) might be too much. Pulling a -40 degree freezer down to shutoff temperature takes a lot of compressor work, and frequent door opening, poor gaskets on the doors etc make a huge difference in the workload for the compressors.

 

[jimmylovesni]

they were professionally installed refrigrators.
they are 208V

one of hte maintaince people had a monitor attached in the building that logs data. They did record what they call a small fluctiation the day we had the last problem. They also attached another closer to the freezers. i guess we are manually checking it for now.

 

[davidbeach]

So, what is the 230V in reference to?

 

[racobb]

UH....so are you saying that you are operating 208 volt freezers on a 230 volt system that may actually be 240 volts nominal and rise to 250 volts or more?

Alan

 

[waross]

are there surge suppressors similar to the 120V equipvalents that are sold for 230V 20A?

Use the 120 volt suppressors and connect them from line to neutral.
If you are using 208 volt rated compressors on a 230 Volt system get ready for a lot of burnouts.
208 Volts is a very common commercial voltage, and there are a lot of 208 Volt rated compressors out there. If a supplier has been sloppy and supplied 208 volt equipment for a 230 (nominal 240 Volt) system you may have a claim. If the mistake was in your organization be discrete.
LPS to racobb for the heads up on this issue.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[racobb]

OK folks, I thought I was pretty good at the slang thing but for the last few months I have been unable to figure out what LPS means. I know this is off subject ( probably OS) but wasn't worth (WW) starting a new thread (NT). Will someone please humor me and help me out. (WSPHMAHMO)

Tounge in cheek! (TIC)
Thanks

Alan

 

[davidbeach]

Little Purple Star.

 

[racobb]

Thanks David!

Alan

 

[itsmoked]

I'd say probably the number one refer compressor killer is a supply voltage problem. Generally too low. So you should definitely check the name plate on the machine and then check the name plates on the actual compressors.

The next would be bad cooling of the returned gas. A minus 80C freezer is absolutely going to be a cascade system. It will likely have three compressor stages with different refrigerants in each loop. Everything has to be dead nuts on or failure is assured by some stage not getting the cooling it needs from the next stage above.

You/they need to have a crack refrigeration guy who understands the vulgarities of a cascade system check everything.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

I worked with some to-notch refrigeration engineers on some cascaded low temperature setups. The experts considered about minus 73 C to be the safe limit. Below that fractionation of the air may start to occur with possible dangerously oxygen rich concentrations. At minus 80 C you are probably still safe but working with a reduced safety margin.
Our setup was two stage but I agree with itsmoked about needing experienced help on-site.
I am surprised that the compressors are not belt driven.
A malfunction in one stage may cause an overload and eventual burnout in another stage.

Bill
--------------------
"Why not the best?"
Jimmy Carter