HVAC voltage spikes

[KnightFire]

Disclosure, this isn't happening in my garage, but my house.

We've just had a home built and have noticed an odd problem. Every time the thermostat kicks the heat pump(s) on (A/C right now), the lights flicker, not dim, but actually flicker, it effects anything plugged into an outlet and it's actually shut my TV off twice (all my AV equip is now on surge protectors).

I have 2 HVAC units, one for each floor of the house (the basement is run off the 1st floor HVAC). I have (2) 200 amp panels the house pulls it's power from, with plenty of open spaces so pulling too much through the panel should NOT be the problem.

I tried to replicate the issue by manually adjusting the thermostat while the electrician that wired the house was there, but I couldn't. It's most notable at night, however when I was trying to replicate the issue with the electrician I turned on the same lights I use at night, no joy...figures right?

Another odd possible symptom, the thermostat clicks LOUDLY (both of them) when they reach their preset temp to turn on the HVAC units, I've never had happen with a house before either.

Due to the house being new, it is of course under warranty, I'm calling the company again to let them have another look, whether I can duplicate the problem or not, I will insist they check the wiring/load. When I couldn't duplicate it the first time, they just said, "give us a call if it persists..."

I've seen this happen when your pulling too much of a load on a single circuit, but this 'flicker' affects the entire house, not just a single circuit. I'm lost...

What could the problem be? I'd like to have a clue the next time the electricians show up.

Sorry for the long post, just trying to be detailed and specific...

TIA!

 

[bmwpower]

Check to see what else is on that circuit. There should be a 240v line for the compressor and a 120v line the fan and other circuitry. See if they somehow tied your AV equipment into that same 120v line.

Check all the wiring for the heat pump. Are the wires connected tightly at the panel and the pump?

Maybe try swapping the AV circuit to another leg on the panel.

I was going to suggest that it's pulling too much compared to what your supply is, but 2 - 200A panels is plenty of juice.

 

[KnightFire]

Check to see what else is on that circuit. There should be a 240v line for the compressor and a 120v line the fan and other circuitry. See if they somehow tied your AV equipment into that same 120v line.

Check all the wiring for the heat pump. Are the wires connected tightly at the panel and the pump?

Maybe try swapping the AV circuit to another leg on the panel.

I was going to suggest that it's pulling too much compared to what your supply is, but 2 - 200A panels is plenty of juice.

I'm a bit confused, what is your definition for AV? When I used it, I was simply meaning my Audio/Visual and voltage sensitive gear was on surge protectors (just a small preventive measure)...

When you say circuit, are you referring to the HVAC circuit? As the issue effects all the circuits of the house. I was under the impression that each HVAC had it's own circuit (by code), so there should be nothing else on it, correct?

All wires seemed to be tightly connected...thank you for your response! I'm good with low voltage stuff, but admit I'm a bit out of my depth when it comes to 110+V

 

[bmwpower]

I'm a bit confused, what is your definition for AV? When I used it, I was simply meaning my Audio/Visual and voltage sensitive gear was on surge protectors (just a small preventive measure)...

When you say circuit, are you referring to the HVAC circuit? As the issue effects all the circuits of the house. I was under the impression that each HVAC had it's own circuit (by code), so there should be nothing else on it, correct?

All wires seemed to be tightly connected...

Yea, I thought it was affecting the audio video circuit your stuff was connected to. If it's affecting the entire house, that's different.

Yea, HVAC circuit. There should be nothing else on the 120v HVAC circuit, but you never know. But since I now realize it affects the whole house, I would say it's not isolated to one circuit.

Are the main lugs nice and tight? It sound like you don't have enough juice. Maybe have the power company check your panel feed. Could be something as silly as the connector on the telephone pole is loose, if your power is routed that way. Mine had actually popped off the pole once.

It's a flicker, right? Not a surge, right?

 

[KnightFire]

Yea, I thought it was affecting the audio video circuit your stuff was connected to. If it's affecting the entire house, that's different.

Yea, HVAC circuit. There should be nothing else on the 120v HVAC circuit, but you never know. But since I now realize it affects the whole house, I would say it's not isolated to one circuit.

Are the main lugs nice and tight? It's a flicker, right? Not a surge, right?

Correct, it's a 'flicker' at least that's how I would define it, but I would imagine anytime there is a loss of power and re-establishment of power quickly, there is a surge, thats a 100% assumption on my part. I've not had any electrical surge damage to any of my components or electrical gear.

The "main lugs", are those behind/before the panels? If so, is it safe to check them without having the utility company? Or are they in the panel, where I can access them safely by using the master on/off? Obviously I've not checked those as I have no idea where they are, LOL.

 

[bmwpower]

Correct, it's a 'flicker' at least that's how I would define it, but I would imagine anytime there is a loss of power and re-establishment of power quickly, there is a surge, thats a 100% assumption on my part. I've not had any electrical surge damage to any of my components or electrical gear.

The "main lugs", are those behind/before the panels? If so, is it safe to check them without having the utility company? Or are they in the panel, where I can access them safely by using the master on/off? Obviously I've not checked those as I have no idea where they are, LOL.

You can check them, but be EXTREMELY careful. Not to scare you, but you can die from the power in the main cables. They're located behind the panel's front panel.

You can tighten the lugs with a screwdriver, just be sure not to touch the screwdriver to anything else.

It's probably best to leave this procedure to a professional if you've not done it before.

Are you main cables copper or aluminum?

BTW, you can't turn off the power with the main switch...the feed is always powered. The switch only turns off power to your circuits.

 

[stimpy]

had the same problem at my house and found out it wasn't my wiring it was the power companys line as the grid I was on was taxed out because of a new subdivision I had a device installed on the line by one of my buddies who is a electrician and there was a noticable power drop at night (100-105 volt from all the draw eventually resulting in a transformer exploding from the overload !! ) the solution was the power company ran new lines and divided the grid since then no more flickering or dimming and my compressor runs better ( doesn't struggle to start up )

 

[KnightFire]

You can check them, but be EXTREMELY careful. Not to scare you, but you can die from the power in the main cables. They're located behind the panel's front panel.

You can tighten the lugs with a screwdriver, just be sure not to touch the screwdriver to anything else.

It's probably best to leave this procedure to a professional if you've not done it before.

Are you main cables copper or aluminum?

BTW, you can't turn off the power with the main switch...the feed is always powered. The switch only turns off power to your circuits.

Yah, that's why I was asking exactly where these lugs are, I'm not touching ANYTHING that's coming straight from the grid, that I can't turn off first.

I believe the mains are copper, again another assumption on my part, I'll have to ask the builder. I know copper is more effecient, would aluminum cables contribute to the problem?

I do know that there are a few other houses built in my immediate neighborhood (it's a brand new development with only 4 homes finished, one being the model), no one else has reported these issues and I've been in the model several times, never once saw the lights flicker or heard the thermostat turn on (with a loud CLACK)...so it seems to be just my house, so I know it's not a grid problem, but local to just me...which pointed me in the direction of the panel...or some type of poor wiring.

Stimpy:
What was the device called? That's exactly what I want the company to do, attach some type of load measuring device to my lines/outlets so they know I'm not crazy, LOL.

 

[RPH]

Power Quality meter, very expensive. Have builder check and force HVAC to come on with full load on in the house. Make the worst case you can demostrate. It could very well be power company problem but you have to prove it. The power company may install quality meter to monitor for problem.

 

[KnightFire]

SWEET, thanks for the info everyone!

I've called the builder and expect them to show up tomorrow. At least now I have a little bit of knowledge on the subject and know what to ask about.

I LOVE this place! 8)

 

[timgr]

I believe the mains are copper, again another assumption on my part, I'll have to ask the builder. I know copper is more effecient, would aluminum cables contribute to the problem?

Technically, yes, but the size of the wire matters too, and should compensate for the choice of conductor metal. And big aluminum wires are common today for feed-in, because of the cost, so you shouldn't be in any unusual situation if the feed-in is aluminum. Aluminum house wiring got a bad rep because small-sized aluminum wires weren't treated for corrosion at each end, and the connections would go bad. The code today says that every aluminum wire connection has to be coated with a corrosion-preventing goo to prevent high-resistance connections.

If the wire is big enough to handle the demand, and the connections are made properly, you should see no drop in voltage when your motor starts.

 

[stimpy]

if the cables coming in to the house from the pole( source) was aluminum it can cause problems as electricity vibrates when under a heavy load ( hense the 60 hz buzz ) and also the heating of a load being on a aluminum cable can cause connections to loosen also from the cable expanding from the generated heat , then cooling and shrinking , thats why many states outlawed it in homes as it created fire hazards when it loosened up and caused resistance and the amperage would raise heating the wire up with the load draw . the quality meter my buddie had had a little disc that recorded all the info on it so the electric comp. had something to see , they also looked at my 100amp box with a thermal gun to see if there was any hot spots form excessive resistance ( there where a couple of loose connections on some heavy drawers the washer and dryer and the kitchen ) good luck with the survey hope they find the problem .

 

[Franz©]

Go to the Dranetz BMI website, and study up on power quality analizers. There is more than enough info there to keep you from sounding like an idiot, and you should learn enough to know when the "electrician" is bullshotting.

Insist that somebody, be it the PoCo or the builder run a Dranetz on your system for at least 24 hours.

Since you say the system is in AC mode now, the problem is related to compressor starting. Possibilitys include the AC contractor not installing a soft start kit on the compressor to put $$$ in his pocket, poor connections at the machine and breaker, and the cheap homeowner line loadcenter most builders use. Homeowner load centers and breakers are low quality. I've seen quite a few HO line breakers with insufficient clamping force on the buss to properly maintain connection. Eventually, this leads to arcing, and erosion of bothe the buss and breaker to failure. You could already have arcing, so insist on breakers being pulled so you can inspect the buss.

Also be aware compressor starting currents vary tremendously as the machine cycles. A compressor can easily reach locked rotor amps if it restarts before the system has equalized. Some systems have refuse to restart controls to prevent this. Builder spec systems rarely include this.

 

[Charles (in GA)]

The A/C is one of the largest draws in the house and the most "sudden" when it starts up. Do BOTH of the A/C units do this?

It sounds like you have a loose cable somewhere, in the meter socket outside, even out at the transformer, or possibly in one of the panels. If the two A/C units are on different panels, and they both cause the same problem, you can rule out the panels, but it could be the disconnect outside or the meter sockets. It probably isn't the neutral, the A/C doesn't use the neutral, its 240V and just shares the two hots.

Are you sure that EVERYTHING in the house flickers, or do you have some lights that don't? This would indicate that its one of the hots.

As already noted, it could easily be a power company problem.

Charles

 

[bmwpower]

Correct me if I'm wrong, but the power company only owns the cable feed, meter, and connections in the meter, correct? ie, if it's a problem with the connection of the cable to the panel, that's the homeowner's problem.

 

[stimpy]

depends on the franchise contract the power company has with the state /municpality . here in illinois it depends on who you have as a provider and what its going into ( business/residential ) most residential you are correct but some times the pow co. won't let contractors hook the line to the box from the meter on new builds .

 

[larry4406]

I built houses in Northern VA for the past six years, and experienced flicker in a couple of the houses when the 5 ton a/c unit kicked on. In some cases, the flicker was reduced/eliminated by tightening the main lugs, grounds, breaker lugs, etc. In other cases, could not eliminated at all. I had the HVAC company add "hard start kits" (a capacitor?) to no avail.

The Load Letter (request for electrical service) that the power company (Dominion) has you sign has a disclosure at the bottom of the form acknowledging that voltage flicker may occur when starting large loads. I had the power company come out to some of the houses and basically told me I was SOL because the house was at the end of the feeder line and was suffering from voltage drop on startup.

I have the same problem in my current house, 400 Amp service and I am second to the end of the line.

 

[KnightFire]

I built houses in Northern VA for the past six years, and experienced flicker in a couple of the houses when the 5 ton a/c unit kicked on. In some cases, the flicker was reduced/eliminated by tightening the main lugs, grounds, breaker lugs, etc. In other cases, could not eliminated at all. I had the HVAC company add "hard start kits" (a capacitor?) to no avail.

The Load Letter (request for electrical service) that the power company (Dominion) has you sign has a disclosure at the bottom of the form acknowledging that voltage flicker may occur when starting large loads. I had the power company come out to some of the houses and basically told me I was SOL because the house was at the end of the feeder line and was suffering from voltage drop on startup.

I have the same problem in my current house, 400 Amp service and I am second to the end of the line.

I'm actually the 2nd house inside the community (only the model is closer the road/main feeder line than I am).

 

[KnightFire]

The A/C is one of the largest draws in the house and the most "sudden" when it starts up. Do BOTH of the A/C units do this?

It sounds like you have a loose cable somewhere, in the meter socket outside, even out at the transformer, or possibly in one of the panels. If the two A/C units are on different panels, and they both cause the same problem, you can rule out the panels, but it could be the disconnect outside or the meter sockets. It probably isn't the neutral, the A/C doesn't use the neutral, its 240V and just shares the two hots.

Are you sure that EVERYTHING in the house flickers, or do you have some lights that don't? This would indicate that its one of the hots.

As already noted, it could easily be a power company problem.

Charles

Charles:
Both units cause the whole house to flicker, I'm quite certain it's the entire house, I can hear and see the effects of it on items, other than lights, when it happens.

 

[KnightFire]

Go to the Dranetz BMI website, and study up on power quality analizers. There is more than enough info there to keep you from sounding like an idiot, and you should learn enough to know when the "electrician" is bullshotting.

Insist that somebody, be it the PoCo or the builder run a Dranetz on your system for at least 24 hours.

Since you say the system is in AC mode now, the problem is related to compressor starting. Possibilitys include the AC contractor not installing a soft start kit on the compressor to put $$$ in his pocket, poor connections at the machine and breaker, and the cheap homeowner line loadcenter most builders use. Homeowner load centers and breakers are low quality. I've seen quite a few HO line breakers with insufficient clamping force on the buss to properly maintain connection. Eventually, this leads to arcing, and erosion of bothe the buss and breaker to failure. You could already have arcing, so insist on breakers being pulled so you can inspect the buss.

Also be aware compressor starting currents vary tremendously as the machine cycles. A compressor can easily reach locked rotor amps if it restarts before the system has equalized. Some systems have refuse to restart controls to prevent this. Builder spec systems rarely include this.

Awesome info! Thank you.

Thank you to all of you who gave me a piece of info, or a clue on this. I will at least have some knowledge when the electrician comes.

I'll keep everyone apprised of how it turns out.

Thanks!!!!

 

[KnightFire]

Just a quick update:
The electrician never showed up, I'm shocked (sarcasm). I'll be calling yet again. However, last night the entire neighborhood (4 houses) had a power outage last night, for about 6 hrs. I wonder if a transformer blew due to the new communities (all 4 houses LOL) draw on the grid, as some of you had happen.

 

[RPH]

Where I work we build high frequency converters to the megawatt size. We had a problem with line voltage on the incomming power. We could actually here the frequency shift on the unit when the line dropped. Power company comes out checks and declares no problem found. This went on for about a year. It got to the point back in test it creating real problems for us. Out comes the power company, argues with the power engineers, looks at our data and now procedes to look "into" the matter. Within the week problem disappears, it was reported back that when they built the new Sams Club down the street they forgot to hook up the compensation capacitors on the line. Just stay on task and the solution will be found.