Lights dimming?? - Page 2 - Electrician Talk - Professional Electrical Contractors Forum

switchleg · 10-22-2009, 12:32 PM

[quote=waco;133296]Isn't clear if the problem is new, but if it is, then something has changed with regards to the unit or the service or both. Bad L1 and L2 service connections seem most probable.

Yes, the problem started after the lightning strike. The A/C company is going to come take a look at the unit and if its fine then the problem most likely will be with the service or POCO transformer.
I also suggested to the customer about having a TVSS unit installed at the main to keep this from happening again.
Question: I have installed TVSS units at the main in the past. The other day at a different house I did see one of these units installed at the main but also at the A/C unit. Does this provide extra protection or is it a waste of money? Seems like a waste if there is one at the main because everything else is downstream and should be protected. Right?

ElectricBill · 10-22-2009, 10:46 PM

When checking the voltage drop be sure to add as much load as possible. I ran into a problem when the copper overhead laterals were replaced with AL. About 500 feet from transformer feeding 5 households. The POCO may have made similar improvements

after the lightning damage . I made sure the Dryer, oven/stove and water heater were running then did the voltage reading in my house. If you can reproduce the problem they shouldn't give you a hard time.

waco · 10-23-2009, 09:42 AM

Quote:

Originally Posted by ElectricBill

When checking the voltage drop be sure to add as much load as possible. I ran into a problem when the copper overhead laterals were replaced with AL. About 500 feet from transformer feeding 5 households. The POCO may have made similar improvements

after the lightning damage . I made sure the Dryer, oven/stove and water heater were running then did the voltage reading in my house. If you can reproduce the problem they shouldn't give you a hard time.

Absolutely!

brian john · 10-23-2009, 04:00 PM

[quote=switchleg;133335]

Quote:

Originally Posted by waco

Isn't clear if the problem is new, but if it is, then something has changed with regards to the unit or the service or both. Bad L1 and L2 service connections seem most probable.

Yes, the problem started after the lightning strike. The A/C company is going to come take a look at the unit and if its fine then the problem most likely will be with the service or POCO transformer.
I also suggested to the customer about having a TVSS unit installed at the main to keep this from happening again.
Question: I have installed TVSS units at the main in the past. The other day at a different house I did see one of these units installed at the main but also at the A/C unit. Does this provide extra protection or is it a waste of money? Seems like a waste if there is one at the main because everything else is downstream and should be protected. Right?

Multi level TVSS is the best design if you are going to install TVSS, at the main service, subpanels and loads.

robelectric · 10-23-2009, 08:45 PM

I have come across this several times.
Most times it was the power companies issue. These are the issues I came across:
The power companies transformer was under sized for all of the houses it was powering.
The wire from their transformer to the service is undersized.
Sometimes people replace their ac units to high efficiency units. These have a very high inrush current on startup.
Find out if anyone that is fed from the same transformer has replaced any ac units lately. If so it may be enough to put it close to the transformers limit and therefore cause issues for every house feeding from it.

AussieApprentice · 10-23-2009, 09:18 PM

Quote:

Originally Posted by waco

Riveter has a good point, but if the problem is recent, either the condenser is failing or the service legs are dropping too much voltage. I'd use a regular voltmeter to see if the service voltage is dipping on condenser start up. I bet it is.

I'll second that.

switchleg · 10-24-2009, 12:02 PM

"A regular voltage meter." Is this a reference to a DMM or something like a Wiggy? Also, when taking the measurement, the test leads need to be on the lugs while the inrush current is happening. Correct? My understanding is that VD only happens when there is load present. Conduct test at the main then move downstream? Thanks again dudes.

switchleg · 11-07-2009, 11:00 AM

UPDATE: Poco came out and changed out their lightning arrester, tightened some loose connections, and is upgrading the trans from a 25kva to a 50kva. I don't think any of this has helped, but still needed to be done anyway. The problem is with the compressor motor. I have isolated it down to that. Somehow the lightning strike did something to the motor to cause a large inrush current on start up. Customer is pleased. I also installed a CHSMAX SPD to help prevent future problems. Thanks.