Blinking Lights

[markstg]

Experiment Results

Experiment Results

I obtained 2 - 100 ufd run capacitors and connected them in parallel to my service.

The blinking lights are not noticeable with the capacitors in the circuit when the compressor starts.
I did 10 test and unless you are looking directly at the lights the blinking is not perceivable.

 

[Little Bill]

I obtained 2 - 100 ufd run capacitors and connected them in parallel to my service.

The blinking lights are not noticeable with the capacitors in the circuit when the compressor starts.
I did 10 test and unless you are looking directly at the lights the blinking is not perceivable.

When you say parallel, did you just put one on each leg of the 240V and to the neutral?
Or did you connect both caps to both legs and not to the neutral?

 

[markstg]

When you say parallel, did you just put one on each leg of the 240V and to the neutral?
Or did you connect both caps to both legs and not to the neutral?

i connected the caps in parallel than then to a 2 pole breaker in my service, no neutral involved.

 

[kwired]

I am not up to speed on doing calculations involving capacitors, but one must also take into consideration what kind of current these will draw, both reactive and resistive current. There is some resistive component though it probably is pretty low. Because you have current flow you will have resistance in conductors as well - this will be real power that is lost to resistance. When there is an inductive load running you get the advantages of countering the effects of the inductive reactance, and the closer the capacitor and inductor are to each other the less line losses there will be, but when there is no inductive load running you are wasting any real power consumed in the capacitor circuit.

 

[markstg]

I am not up to speed on doing calculations involving capacitors, but one must also take into consideration what kind of current these will draw, both reactive and resistive current. There is some resistive component though it probably is pretty low. Because you have current flow you will have resistance in conductors as well - this will be real power that is lost to resistance. When there is an inductive load running you get the advantages of countering the effects of the inductive reactance, and the closer the capacitor and inductor are to each other the less line losses there will be, but when there is no inductive load running you are wasting any real power consumed in the capacitor circuit.

The resistive component of the current due to the capacitors in the circuit is miniscule, and I don't think worth talking about. For that you can go to the post discussing the scam about adding capacitors to save money.

The problem, discussed earlier, with leaving the capacitors in the circuit without my motor load, is that my capacitors will provide KVARS for the other houses on my lateral. If KVARS are not required, my voltage will rise and long term that would probably be bad.

 

[kwired]

The resistive component of the current due to the capacitors in the circuit is miniscule, and I don't think worth talking about. For that you can go to the post discussing the scam about adding capacitors to save money.

The problem, discussed earlier, with leaving the capacitors in the circuit without my motor load, is that my capacitors will provide KVARS for the other houses on my lateral. If KVARS are not required, my voltage will rise and long term that would probably be bad.

I agree the resistive component (of the capacitor) is probably minuscule. But whether current is true power or apparent power it still is real current to the conductors and will still be resistive component in the conductors. Now if you have capacitor close to motor load you will get maximum effect of reducing the resistive losses - provided you are correcting to near unity power factor.

May not seem like the loss is that great, but if you have a long service conductor every amp gets more critical for voltage drop issues.

 

[markstg]

I obtained 2 - 100 ufd run capacitors and connected them in parallel to my service.

The blinking lights are not noticeable with the capacitors in the circuit when the compressor starts.
I did 10 test and unless you are looking directly at the lights the blinking is not perceivable.

My test was flawed, and the lights do still blink with the capacitor in the circuit, for what appears to be a lesser duration.

Back to the drawing board.

 

[kwired]

My test was flawed, and the lights do still blink with the capacitor in the circuit, for what appears to be a lesser duration.

Back to the drawing board.

That initial surge of real power is what is getting you more then power factor is a problem. Like I have said before you need to use reduced voltage starting methods to lessen the real power power instantaneous demand upon energization, and this will eliminate the worst part of the voltage fluctuation to other loads on a common supply.

 

[mbrooke]

Imo, a capacitor will do nothing significant. I say order a large enough STATCOM :thumbsup: If you really want to eliminate dimming I would either upsize the service drop or the transformer, if not both. Since you have a 200amp service, if you were to tell the poco "i am installing a tankless water heater" they would be forced to upsize something. I have noticed that in all electric resistive heat homes where a 50kva serves 2 homes dimming is far, far less than with gas homes where a single 25kv serves 7 homes.

 

[GoldDigger]

If the voltage drop is high enough, the capacitor can allow for higher starting voltage to be seen by the motor, resulting in higher torque and hence faster starting. That means a shorter dip. Did Mark also notice any chance in the motor sound?
If the capacitors also reduce the running voltage drop that could show up subjectively as a change in the dip itself. A recording voltmeter at the light would tell the true story.
Also a recording ammeter on the motor.

 

[GoldDigger]

Imo, a capacitor will do nothing significant. I say order a large enough STATCOM :thumbsup: If you really want to eliminate dimming I would either upsize the service drop or the transformer, if not both. Since you have a 200amp service, if you were to tell the poco "i am installing a tankless water heater" they would be forced to upsize something. I have noticed that in all electric resistive heat homes where a 50kva serves 2 homes dimming is far, far less than with gas homes where a single 25kv serves 7 homes.

They would be forced to upsize something all right, but they may also (try to) charge you for it since you have changed your calculated and real load.
Even though it is still within the nominal capacity of the service

 

[kwired]

Imo, a capacitor will do nothing significant. I say order a large enough STATCOM :thumbsup: If you really want to eliminate dimming I would either upsize the service drop or the transformer, if not both. Since you have a 200amp service, if you were to tell the poco "i am installing a tankless water heater" they would be forced to upsize something. I have noticed that in all electric resistive heat homes where a 50kva serves 2 homes dimming is far, far less than with gas homes where a single 25kv serves 7 homes.

They would be forced to upsize something all right, but they may also (try to) charge you for it since you have changed your calculated and real load.
Even though it is still within the nominal capacity of the service

Beat me to it, most will not upgrade such equipment unless they will get some return on their investment, if energy sold is not going to have much of a change they are not interested in doing it for no charge.

 

[mbrooke]

They would be forced to upsize something all right, but they may also (try to) charge you for it since you have changed your calculated and real load.
Even though it is still within the nominal capacity of the service

Beat me to it, most will not upgrade such equipment unless they will get some return on their investment, if energy sold is not going to have much of a change they are not interested in doing it for no charge.

Id agree there could be a charge. But its worth the try. If the equipment is old anyway they might do it for free.


Out of curiosity, how big of a capacitor would you need to raise the voltage to the unit to the point some dimming is eliminated?

 

[GoldDigger]

There would be no point in going beyond the capacitance needed to correct the STARTING power factor to 1.
And probably not much benefit to going beyond correcting the running PF to unity.

 

[Little Bill]

Imo, a capacitor will do nothing significant. I say order a large enough STATCOM :thumbsup: If you really want to eliminate dimming I would either upsize the service drop or the transformer, if not both. Since you have a 200amp service, if you were to tell the poco "i am installing a tankless water heater" they would be forced to upsize something. I have noticed that in all electric resistive heat homes where a 50kva serves 2 homes dimming is far, far less than with gas homes where a single 25kv serves 7 homes.

My thinking is if you just upsize the service cables and the problem is the transformer is too small (or too many services on it) you may actually make the problem worse. You would be decreasing the resistance of the wires/conductors and with the transformer too small, it would show an even more noticeable symptom such as the dimming lights.

 

[gar]

140727-2230 EDT

markstg:

In posts 28, and 31 I suggested you try a GE dimmable CFL. This may not meet some other criteria, but I believe you will see much less flicker.

In post 34 I provided an approximation of the RC time constant at startup. This is really a relationship of available power and the capacitor contributes little in comparison to the required startup load.

It may br possible to build a fairly simple circuit that would provide both dimming and voltage regulation. I don't think it is worth the effort. Just live with the flickering, or try the GE bulb.

Little Bill:

Other customers' steady state loads on the transformer have little effect on the change in voltage from the motor transient load. Those other loads will have their own effect. Heavier wire from the transformer will not increase the transient voltage drop from motor starting.

 

[markstg]

The experiment shows that adding capacitance did not solve the light dimming as ya'll predicted.

Thanks for hanging with me.

 

[gadfly56]

The experiment shows that adding capacitance did not solve the light dimming as ya'll predicted.

Thanks for hanging with me.

Negative results are not the same as negative information. When interviewed regarding his attempts to perfect a practical electric lamp, Thomas Edison made some remark to the effect that none of the experiments failed, but he now knew over 1,000 ways NOT to make a suitable lamp filament.

 

[markstg]

Negative results are not the same as negative information. When interviewed regarding his attempts to perfect a practical electric lamp, Thomas Edison made some remark to the effect that none of the experiments failed, but he now knew over 1,000 ways NOT to make a suitable lamp filament.

Well I do have some new information. The scroll compressor starts unloaded, and does not need a Start Capacitor to get it running, nor is one installed on my system. So I've ordered the Hard Start Kit. Can't hurt.

thanks again.

 

[kwired]

Well I do have some new information. The scroll compressor starts unloaded, and does not need a Start Capacitor to get it running, nor is one installed on my system. So I've ordered the Hard Start Kit. Can't hurt.

thanks again.

I've mentioned this before but not sure if I did in this thread.

All a hard start kit is is a capacitor an potential relay to switch it out of the circuit when the motor has reached a certain speed and the voltage across the potential relay finally rises enough to cut the capacitor from the circuit. The capacitor is wired in as a start capacitor, most compressors only have a run capacitor and do not need the extra phase shift to get them started as long as head pressure of refrigerant is down. By adding the hard start you are going to give the start winding a boost in phase shift to help raise acceleration ability. This will take more power but in a shorter duration to make that happen. That will mean higher amps which will result in higher voltage drop, which is exactly what you are trying to avoid. The compromise here will be it will happen for shorter duration though, but it still will happen.