Flickering lights caused by heat pump starting.

[MatBirch]

If you didn’t already know, I’m in the middle of a whole house rewire, removing all of the old knob and tube. Since we bought the place, the chandelier in the dining room flickers when the heat pump starts. The chandelier has led bulbs in it. The heat pump has a new circuit and wire from panel to pump, and was serviced just about a month ago.
I had thought that the problem was that the light was connected to an overly loaded circuit on the knob and tube. This weekend, that light was on my list, and got it all newly run. New wire, new circuit.
Still flickers... actually worse. It is now more of a full blink, not a faint flicker.
New symptom added to the list- wife bought a new lamp over the weekend. LED bulb in it. It is plugged into an outlet on another of my brand new circuits.
Two LED fixtures, two brand new circuits, both blink.
FWIW the service panel was replaced in 2014 with a new 200 amp SquareD QO panel.

Larger wire on the heat pump?

 

[Jim greengo]

Have you checked for loose wires in panel?

 

[ducatithunder]

When they upgraded the service did they add any additional load? Could be the transformer is undersized feeding your main panel. Could check it with a meter on the mains and start the HP up or other large items. I had the same issue prior to putting in an additional 100 amp sub for the garage out back. I talked to BGE and found out the transformer was undersized. They came out and replaced it with a larger one, no more issues.

LED lights will telegraph voltage drops more then normal bulbs. Fun fact, we have been replacing all the 32W florescent lights onboard the ship I work on with new LEDs. Saves a ton of power, no more grounds due to ballasts or extra wiring or vibrations. The catch is anytime a large consumer is started, ie a large pump or deck winches the lights dim or blink for that second or two until the generator recovers. Kinda of nerve wrecking until you get used to it. In the old days if the fluorescents blinked like that chances were you were about to black out.

 

[Captain Spaulding]

It’s pretty common for heat pumps to do that. Check to be sure your neutral is well connected and not showing signs of heat, but it’s probably normal.

 

[Higgins]

If you didn’t already know, I’m in the middle of a whole house rewire, removing all of the old knob and tube. Since we bought the place, the chandelier in the dining room flickers when the heat pump starts. The chandelier has led bulbs in it. The heat pump has a new circuit and wire from panel to pump, and was serviced just about a month ago.
I had thought that the problem was that the light was connected to an overly loaded circuit on the knob and tube. This weekend, that light was on my list, and got it all newly run. New wire, new circuit.
Still flickers... actually worse. It is now more of a full blink, not a faint flicker.
New symptom added to the list- wife bought a new lamp over the weekend. LED bulb in it. It is plugged into an outlet on another of my brand new circuits.
Two LED fixtures, two brand new circuits, both blink.
FWIW the service panel was replaced in 2014 with a new 200 amp SquareD QO panel.

Larger wire on the heat pump?

If they are on dimmer switches, most likely the dimmer does not support dimming LED lights....
Guess how I know! Took several months to figure out !!

 

[larry4406]

I had a new townhouse under construction two years ago. Bath vanity LED light would flicker/blink on start up of that bathroom's fart fan. Replaced LED with another of same brand and same thing. Then went to a different brand LED and problem went away.

Electrician had chased his tail checking everything and all connections on that circuit and found nothing.

 

[MatBirch]

If they are on dimmer switches, most likely the dimmer does not support dimming LED lights....
Guess how I know! Took several months to figure out !!

The dining room chandelier is on an old fashioned dimmer. I thought I had the issue isolated to that, but when we added the little lamp this weekend and it started blinking too, I dismissed it. I still plan on changing out the dimmer, as I want a slide instead of the old spinning dial. Plus they only dim so far before acting up.

 

[MatBirch]

Have you checked for loose wires in panel?

It’s pretty common for heat pumps to do that. Check to be sure your neutral is well connected and not showing signs of heat, but it’s probably normal.

I haven't specifically checked that circuit, but I will. I've been in and out of the panel with every new circuit and it looks great, but I will double check it.

Thanks!

 

[American Locomotive]

LED bulbs tend to be very sensitive to minor voltage changes. I would say it is "normal". You could get a multi-meter with a bar graph display and see the voltage dip in real time.

 

[toplessHO]

other option is to go with a soft start kit for the heat pump.
then its win win

 

[cybrdyke]

Regardless of anything else, your dimmer for the chandelier has to go. It's hard to troubleshoot anything else with a known problem in the circuit.
Are the LED bulbs in the chandelier dimmable?
How many are there?
Are you sharing neutrals as you re-wire?
CD

 

[theoldwizard1]

Flicker as in on-off-on-off-on-off-on or blink on-off-on ? You need to check as many circuits as is possible throughout the house.

If it is a blink (on-off-on), then it is possible that the power coming into your house is dropping low when the heat pump starts. This is difficult to prove. Ultimately you have to annoy the power company long enough that they will temporarily install a special meter that records the voltage over time. Don't bother buying a meter. They will not believe anything except their own equipment.

(Happened to my Dad. The transformer was under rated. Once it was upgraded, the problem went away.)

 

[yeldogt]

How much of a flicker ? I have the same thing at our beach house when the dryer goes on ... you can see it as you are looking right at the bulb. It's a momentary slight change ...

Not old wiring

 

[MatBirch]

How much of a flicker ? I have the same thing at our beach house when the dryer goes on ... you can see it as you are looking right at the bulb. It's a momentary slight change ...

Not old wiring

Well, during dinner, it's usually the only light on in the room. Before I removed it from that OLD, overloaded K&T circuit, it would just sort of dim. Now it goes enough off enough to darken the room, and leave everyone looking at each other! LOL. Not on every start-up, but sometimes. Especially that first start of the evening.

I figured that a new circuit and wiring would be better, but it made it worse. I think it's sort of like a skipping CD... The new wiring gave it a more "crisp" power supply, instead of the old fuzzy analog stuff...

 

[nadogail]

I have found that LED lamps are very sensitive to minor voltage fluctuations that were unoticed when incandesants were used.

I attribute this to the hysteresys of the filament in the incandesant lamps.

 

[wyliesdiesels]

could be many things.

the way to track it down is by putting a meter with min max avg option onto the main hot lugs then kicking on the HP.

Then go back and see how low the voltage sags.

record the voltage, then do the process again but this time connecting between one hot leg and neutral. record voltage

Do it again for the other hot leg.

This will tell you if its both legs that are sagging (most likely transformer) or just one leg (same leg lights are on) indicative of bad connection somewhere.

does your service drop have any splices in it? reason i ask is i used to live in a house that was fed by a pony pole with splices on the drop wire. every time we ran the 3/4hp GD the lights would flicker

troubleshooter called out and he put his hand on the splices and one of them was very hot to the point it hurt his hand. he fixed the splice and the problem went away...

 

[yeldogt]

Well, during dinner, it's usually the only light on in the room. Before I removed it from that OLD, overloaded K&T circuit, it would just sort of dim. Now it goes enough off enough to darken the room, and leave everyone looking at each other! LOL. Not on every start-up, but sometimes. Especially that first start of the evening.

I figured that a new circuit and wiring would be better, but it made it worse. I think it's sort of like a skipping CD... The new wiring gave it a more "crisp" power supply, instead of the old fuzzy analog stuff...

That's something else

 

[MatBirch]

So funny thing happened- long story, but insurance jerks threatened to cancel us if we didn’t trim our trees. Can’t let that happen until my rewire is done ...
Even though the tree guys had the poco shut us down, they still damaged the line.
The power guy came back to fix it, and discovered that the cable was really old, and actually abraded to the point of the conductors being exposed in places.
New service feeds and HEY! light flicker is dramatically reduced!

Now I just have about 4 cords of work to do...

 

[ducatithunder]

Good to here. Poco really need to be brow beat to get things fixed on there end. Squeaky wheel will eventually get the grease.

 

[theoldwizard1]

Even though the tree guys had the poco shut us down, they still damaged the line.
The power guy came back to fix it, and discovered that the cable was really old, and actually abraded to the point of the conductors being exposed in places.

Years ago, the neighbor had a power issue. POCO sent a guy out and determined that the insulation had abraded where is was rubbing as it passed through a large notch in a tree.

Sparky decided it wasn't that bad, so he dropped the line, wrapped tape around the abrasion and then put some kind of hard cover over it. The fun part was watching him try to re-hang the wire !

 

[Two Sheds]

We recently installed a whole-house heat pump, and we often notice a brief dimming for a few milliseconds when it starts up. It's a pretty long run from our house to the transformer.

 

[theoldwizard1]

We recently installed a whole-house heat pump, and we often notice a brief dimming for a few milliseconds when it starts up. It's a pretty long run from our house to the transformer.

You need to complain to the POCO. Once they have proved it to themselves, they will install a larger transformer.

 

[wrenchguy]

So funny thing happened- long story, but insurance jerks threatened to cancel us if we didn’t trim our trees. Can’t let that happen until my rewire is done ...
Even though the tree guys had the poco shut us down, they still damaged the line.
The power guy came back to fix it, and discovered that the cable was really old, and actually abraded to the point of the conductors being exposed in places.
New service feeds and HEY! light flicker is dramatically reduced!

Now I just have about 4 cords of work to do...

This?
Mine have been noticeable flickering last 2months or so (no electrical work going on at all) . Then yesterday AM half my breakers went bad at the same time. WTF! Took meter to the b-box and determined 1 hot conductor only 50 volts. WTF.
Called power company and told them situation AND mentioned that there was a forced pole relocate across from me and they changed my pole then.
This was last summer and now its figured theres a failed conductor splice below grade right near my new pole. I now have a small temporary transformer at the meter box till they get it fixed. Oh yea my lights aren't flickering tonight.
Good luck with your project.

 

[wyliesdiesels]

This?
Mine have been noticeable flickering last 2months or so (no electrical work going on at all) . Then yesterday AM half my breakers went bad at the same time. WTF! Took meter to the b-box and determined 1 hot conductor only 50 volts. WTF.
Called power company and told them situation AND mentioned that there was a forced pole relocate across from me and they changed my pole then.
This was last summer and now its figured theres a failed conductor splice below grade right near my new pole. I now have a small temporary transformer at the meter box till they get it fixed. Oh yea my lights aren't flickering tonight.
Good luck with your project.

Did they run high voltage lines on the ground?

 

[wrenchguy]

Did they run high voltage lines on the ground?

I'm not sure what ur asking?
The small temporary transformer is something called a "service saver" with short leads and a meter looking thing plugged in place of my meter. From what they told me its using the good conductor voltage to make up voltage for the bad conductor then into the b-box. The whole thing reminds me of a big battery charger on wheels. Its leads are not touching the patio slab.
They won't dig at the pole by hand because my n-gas line is nearby (3'). They scheduled a vac truck and we'll go on from there.

 

[wyliesdiesels]

I'm not sure what ur asking?
The small temporary transformer is something called a "service saver" with short leads and a meter looking thing plugged in place of my meter. From what they told me its using the good conductor voltage to make up voltage for the bad conductor then into the b-box. The whole thing reminds me of a big battery charger on wheels. Its leads are not touching the patio slab.
They won't dig at the pole by hand because my n-gas line is nearby (3'). They scheduled a vac truck and we'll go on from there.

I thought they ran high voltage primary lines on the ground to feed this transformer. Doesn't sound like it since they're using secondary wire which would not be rated for voltage over 600v.

 

[Dagny]

How big is your heatpump? 5 ton would be about 5 hp. Not many residential services will start a 5 without some dimming.

 

[wrenchguy]

This?
Mine have been noticeable flickering last 2months or so (no electrical work going on at all) . Then yesterday AM half my breakers went bad at the same time. WTF! Took meter to the b-box and determined 1 hot conductor only 50 volts. WTF.
Called power company and told them situation AND mentioned that there was a forced pole relocate across from me and they changed my pole then.
This was last summer and now its figured theres a failed conductor splice below grade right near my new pole. I now have a small temporary transformer at the meter box till they get it fixed. Oh yea my lights aren't flickering tonight.
Good luck with your project.

Not sure how this post will show up?
So 8pm last night the 9th i lost power to 1/2 my breakers again. No horsing around with flickering lights this time.... straight out dead.
This time i was heads up with the issue!

The other conductor/leg that was ok 1-22-21 went bad at the splice.
Called PC and repaired at 10:30pm no service saver used.
They sent 2 guys and just dug it up, cut out the bad and spliced it. WTF

I wonder how many more times this is going to happen using splice kits???
Problem is i don't know when 1/2 goes down.... plus my 220 well is trying to start, dead fridge or trying to start on low voltage. WTF

 

[wyliesdiesels]

so the PoCo wont replace the service lateral?

 

[Milton Shaw]

Some of those underground service cables use insulation that is like candy to termites. It's soy based and they now use pieces of that insulation in the bait traps for termites so they can treat them it they show up. That means all those cables will have problems until they are replaced. I would go with conduit and replace it all so that it would not require being dug up again if they fail again.

 

[wrenchguy]

Its about 150' from box to pole. For 32 years It was 1 piece coming across the street overhead, down PoCo's pole and under ground to the box. I'm assuming it the P C's responsibly. I don't understand why they didn't make the splices under the shield/guard on the pole last summer- rather than underground. It's only buried 6"-8" deep in the area of these splices.

 

[ludakris04]

LED lights will telegraph voltage drops more then normal bulbs. Fun fact, we have been replacing all the 32W florescent lights onboard the ship I work on with new LEDs. Saves a ton of power, no more grounds due to ballasts or extra wiring or vibrations. The catch is anytime a large consumer is started, ie a large pump or deck winches the lights dim or blink for that second or two until the generator recovers. Kinda of nerve wrecking until you get used to it. In the old days if the fluorescents blinked like that chances were you were about to black out.

This... the heat pump is going to cause a surge when it starts..
the effect of a small surge on a bulb pulling 60 watts vs a bulb pulling 6 watts...
the % drop will be much more on the LED.