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Blinking Lights 2

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markstg

markstg

Industrial
Aug 22, 2006
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At my house I have a 5 ton, 2 stage scroll compressor condensing unit, and my house lights blink on the unit starting.
Specs are 118 LRA, 230V, 23 FLA.

Lamps are incandescent 130 V.
Service size is 200A, 120/240V, single phase
Measurements at the unit disconnect switch are:
Normal Voltage 246 V
Starting Voltage: 231 V
Starting Amps: 121 A
Running Amps: 10 A (Low Stage)
Starting time: 1 second.
Start is on Low stage.

This is on a 1 year old house and has done this since installed.
There is no issue when the compressor goes from low stage to high stage.

Neutrals have all been checked, Meter, Panelboard, and are all tight.

Power compnay service is: 50KVA transformer, 7 Houses on overhead lateral, my service drop from lateral tap to service is 80ft., lateral distance tap to transformer is 120ft. POCO conductors are aluminum don't know size. POCO not interested in my blinking lights with such small voltage drop.

Attached is the Power company recording of Voltage and Current at my service.

I was thinking placing a capacitor at my service may mitigate the dimming lights. Any thoughts.


 
 http://files.engineering.com/getfile.aspx?folder=54b0a051-cbde-49a3-9fbf-63c08ad6514c&file=Smith_Power_Quality_Recording.pdf
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I'm somewhat surprised this thread has generated so much interest and commentary. This is a 200 A residential service (single-phase) and the motor is pulling 120 A locked rotor. There will be flicker. It would be shocking if there were not. The OP needs to accept that, replace the single-phase motor with a three-phase and start from an AFD, or pay for separate service.

 
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@ LionelHutz

Are you sure - or just pretty sure?

I wasn't aware that it could be a single phase motor. Sounds awfully impractical. Why does one do that?

OK, I have visited the US many times and everytime I've seen poles bending over from transformers with 4160 V in and single phase out. But very often there are three "buckets" - so three-phase seems to be available.


Gunnar Englund
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
 
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Just because it is a 200A service with a 120A motor start current Does Not mean there must be flicker.

Thanks to all who have parcipated in this post, I have learned alot.
 
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@Skogsgurra

This is a single phase motor. This is a residential area and single phase is all that is available on the pole.
 
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Just because it is a 200A service with a 120A motor start current Does Not mean there must be flicker.
Click to expand...

Based on what?

Increased current creates additional voltage drop in the transformer and conductors. If the voltage drop is great enough there will be perceptible flicker. In theory, the voltage drop could be reduced to levels that are not noticeable by installing much larger conductors and a larger service transformer. In practice, a "200 A" utility service means you have a 200 A main breaker. It does not tell you the size of the utility's transformer, the transformer loading, or the impedance of the system up to your service panel. For virtually any standard residential service, an impact load of 120 A is going to create some flicker.

 
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Quote

Increased current creates additional voltage drop in the transformer and conductors. If the voltage drop is great enough there will be perceptible flicker. In theory, the voltage drop could be reduced to levels that are not noticeable by installing much larger conductors and a larger service transformer.


Agreed


Quote

In practice, a "200 A" utility service means you have a 200 A main breaker. It does not tell you the size of the utility's transformer, the transformer loading, or the impedance of the system up to your service panel.


Agreed



Quote
For virtually any standard residential service, an impact load of 120 A is going to create some flicker.

Key words, "any standard residential service". I specifically submitted my load study to the Power Co. at the time of my service request showing my itemized loads steady state ( 167A )and the largest STARTING currrent load (AC #1 5 Ton, 120A.) Further the Power Company standards state Momentary start up loads up to 150A are acceptable. It appears the Power Company installed a "standard service".

But what this thread is really about was why capacitors added could or could not solve the transient voltage dip causing the blinking lights, and if they couldn't that the only solution is changes on the Power Company Side, as you describe.
 
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I'm sorry you are unhappy with the situation, but "acceptable" to the Power Company just means that your inrush won't be bothering other customers, not that you will never experience flicker. If you can get your neighbors to start complaining, you might get somewhere.

Flicker is a problem because it bothers people, not because it represents a safety issue or causes any damage to equipment.

I'm not sure that the Power company is going to do much if you are only one complaining, since you are the one creating the flicker. Not unless you are willing to pay for the solution. I actually think the adjustable frequency drive and a three-phase motor is going to be the most cost-effective solution.

Also, FWIW, when a homeowner or contractor provides a load estimate to the utility, they will typically assume that the actual peak load will be about 50% of the calculated total, based on long experience. Utilties do not follow the NEC when sizing transformer or feeders.

Best of luck.

Dave
 
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I contacted my neighbors and they are not experiencing flicker. So I'm a lone wolf here. Don't see how I could change my motor in the carrier system condensing unit.
 
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As I said, Smoked - sounds awfully impractical.

I have a three-phase 400 V 25 A incoming line. 230 V line-neutral. Quite happy with that.

Gunnar Englund
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
 
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marksta; Sorry you have this issue. I know things like this can be grating.

The solutions i see are varied:

1) Reserve yourself to ignore it.

2) Install modern lighting instead of archaic flicker prone incandescents.

3) If a particular appliance is bothered by it get a UPS to run just it. (I once had a computer in a tannery that would reboot every time a leather scissor table's hydraulic motor pack started. Ultimately the solution was a small UPS for the computer. Every time the button was pushed on the table the UPS beeped and kept the comp happily running.)

4) As Skogs is checking, work up an inrush limiter KUSA that provides just barely enough resistance to the starting compressor as to minimize the flicker.

5) Put in an equal size unloaded motor to the compressor's motor that you start first. It will store kinetic energy locally (on the condenser unit's end of the supply line.) Then when the compressor starts the already spinning motor will 'generate' to supply energy into the voltage drop.

6) Switch the compressor out for a three phase unit. Use an oversized VFD to convert your single phase power into 3 phase power. This can eliminate ALL flicker.

Personally I'd probably go with #2. A buddy just dropped his power bill $20/month by switching all his incandescent bulbs out for LEDs.

Keith Cress
kcress -
 
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Sorry - I misread your first post - I thought you had some type of air compressor. You're right - a retrofit would not be easy. You might check with Carrier to see if they have a unit with a soft-start or AFD. If these neighbors are on the same transformer secondary, that indicates a lot of the voltage drop is in your service cables. Increasing the size of those should not be outrageously expensive.

If you're interested, there is quite a bit of information on line regarding flicker. Unfortunately even small levels of voltage fluctuation can cause noticeable flicker. Maybe the link below will be of use if you haven't done more reading than you want on flicker:

 
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Installed a room with LED lamps, and They Do Not Flicker.

If I ever get the wave forms from the Power Company I will post for general interest.

thanks.
 
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That's what itsmoked suggested. If he or others helped you, consider pressing the like button to vote them a little purple star

=====================================
(2B)+(2B)' ?
 
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Look on the bright side. If you are in Africa and the lights flicker, it means the electricity is still on!
Thanks I have learnt a lot. For me, cables and connections. There is a high impendance somewhere.
 
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Hi folks,

It is a very long thread. I have just read some part of it.

For those who have followed the discussion I wonder if there is something in the thread about reducing flicker by just applying series capacitors.
The capacitive reactance of the series capacitor nullifies the inductive reactace of the feeder reducing the voltage drop due to the compressor operation at the point on which the lamp is connected. So the flicker will be reduced.


Best Regards,

Herivelto S. Bronzeado
Brasília, Brazil
 
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