Low voltage at Waste Water Plant UV

[kris davis]

We got a call to check out a Waste Water Plant we renovated 4 years ago. The U.V. system is burning bulbs and ballast up faster than normal. The U.V. tech said they need at least 270 volts at thier ballast but they our only getting 268-270 volts. When you shut the power off the the U.V. unit the voltage goes up to 271-273 volts. Each unit has a 480v4w 100 amp feed to them.
Also I started and stopped a 100hp pump and the voltage only dropped .5 volts

 

[mcclary's electrical]

Check voltage at service panel, if you're within 3% at the furthest point from service, he's blowing smoke.If you exceed 3%,,you should read 210.19 a 1 FPN 4 directly expresses a warning about improper voltage due to VD. Undervoltage conditions reduce the capability and reliability of lighting circuits. Table 9, chapter 9 should be used to calculate VD in relation to wire size and length.

 

[kris davis]

Where the service comes in there is a med voltage transformer stepping down to 480v. We tool a reading there and got 280-278 volts. From the Main Switchboard they have two Med voltage feeds going to two transformers in the main building. At those two transformers we are reading 272-270 volts.

 

[brian john]

If the voltage is constantly low, verified by power monitor trending data, you could install a 480 delta to 480Y/277 VAC transformer and boost voltage with the taps.


What is the low to high acceptable voltage.

 

[jeremysterling]

We got a call to check out a Waste Water Plant we renovated 4 years ago. The U.V. system is burning bulbs and ballast up faster than normal. The U.V. tech said they need at least 270 volts at thier ballast but they our only getting 268-270 volts. When you shut the power off the the U.V. unit the voltage goes up to 271-273 volts. Each unit has a 480v4w 100 amp feed to them.
Also I started and stopped a 100hp pump and the voltage only dropped .5 volts

Interesting system...

 

[USMC1302]

This one sounds eerily familiar. I had a plant eating bulbs and ballasts(seemingly). First I would ask after four years(?), how often before that were lamps and ballasts being changed? Who was doing that work? I found an improperly wired ballast in one situation, and the original installation/terminations incorrect in another. Check the schematic carefully, especially if someone else has been in there. Good luck, those lamps and ballasts are pricey.

 

[kris davis]

Brian, the Trojan U.V. tech said anything below 270 volts on their ballast they start having trouble with them. What I don't understand is how the voltage drops 3-4 volts on each phase after you fore the system up.

This one sounds eerily familiar. I had a plant eating bulbs and ballasts(seemingly). First I would ask after four years(?), how often before that were lamps and ballasts being changed? Who was doing that work? I found an improperly wired ballast in one situation, and the original installation/terminations incorrect in another. Check the schematic carefully, especially if someone else has been in there. Good luck, those lamps and ballasts are pricey.

My boss wants to stay away from service calls he stays busy enough with our other work. I am interested in helping these guys because they act like they can't find anyone else that knows what is going on there.

 

[brian john]

Has to be VD in the system, you can measure the VD from point to point to isolate the cause.

Start at the main and measure along the feeder at all accessible points with the system up and running.

You can also measure FOP )Fall of Potential) from point to point and determine the VD.

The key would be what is the maximum voltage the system can stand.

I have worked on several of the systems and in some areas the utilization voltage is 465y/265 and there were no issues.

What is your location.

 

[kris davis]

Morehead KY

 

[USMC1302]

What is the voltage reading at the ballast with the output disconnected? I have (2) Trojan systems in operation and have also had trouble with the lamp holders and quartz sleeves.

 

[kris davis]

I didn't check it inside the unit.

 

[JFletcher]

Other causes of premature failure in UV lights is improper/infrequent cleaning of the quartz covers and mishandling of the bulbs. If the water quality coming from secondary treatment has dropped, or too much FeCl2/FeCl3 is added in secondary treatment, that will also decrease lamp life due to scaling/staining of the covers and the subsequent overheating as a result.

If the lamp and ballast life was acceptable or within normal specs when first installed, I would look more toward operational/maintenance issues.

 

[brian john]

=
If the lamp and ballast life was acceptable or within normal specs when first installed, I would look more toward operational/maintenance issues.

It is a common practice when things are unknown to blame it on the mysteries of electricity.

1. I would get the specs from the manufacture for the complete system voltage ranges should be published there.

After this or in conjunction with this.

2. I would do voltage trending.

3. I would try to determine where the VD is in the system or if it is inherent due to conductor sizing.

 

[augie47]

Where the service comes in there is a med voltage transformer stepping down to 480v. We tool a reading there and got 280-278 volts. From the Main Switchboard they have two Med voltage feeds going to two transformers in the main building. At those two transformers we are reading 272-270 volts.

Check the line-to-line voltage at the two transformers. You might need to adjust the taps since that neutral voltage is lower than at the service transformer.