# Flickering lights with Point of Use Heater



## scorogers (Jul 24, 2012)

Recently did a 200 amp residential upgrade on a house. Part of the reason for the upgrade was the customer wanted a 19kw  point of use heater for under the kitchen sink. This unit requires 2 independent double pole 40amp breakers. The unit works fine except when it is on, some (not all) of the lights tend to "pulsate". They do not completely turn off and on and the dimming is very minimal. But it is quite apparent in some (not all) of the fixtures. I did some research and read about voltage drop from the transformer (the house is located in the City of Santa Cruz so it is not rural) and decided to call my local utility (pG&E). The hooked up a machine and connected it to the main lugs. The voltage was 119v on one leg and 118v on another leg. The machine they ran (called the beast) generates about 5kw and took the voltage on one leg down to 112v and the other leg jumped to 121v. PG & E allows 5% threshold of voltage in either direction (114v-126v). Since one leg dropped to 112v he decided to look into it. Long story short, ther was a "capacitor bank?" just down the street. When he flipped it on the voltage drop only went down to 114v on one leg and 121v on the other leg. Since it was within their threshold, they considered it fixed. The pulsating seemed to be a "little" better but is still apparent. Is there anything else I should be looking at?


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## scorogers (Jul 24, 2012)

Oh yeah. It is worth mentioning that the house was built in 1906 and the lights that are pulsating are a mixture of Romex and knob/tube wiring but it no way overloaded. I always knock down the knob/tube wiring down to 15amp breakers to be safe. The majority of lights that tend to pulsate are on the Lutron "Maestro" dimmer. I think I will try to bypass these dimmers tomorrow.


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## scorogers (Jul 24, 2012)

So no feedback?


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## Wirenuting (Sep 12, 2010)

scorogers said:


> So no feedback?


What did your EC say about it?


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## scorogers (Jul 24, 2012)

Wirenuting said:


> What did your EC say about it?


I am the EC


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## Wirenuting (Sep 12, 2010)

scorogers said:


> I am the EC


Ahh, ok... I thought you were a GC like your profile said.


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## Tiger (Jan 3, 2008)

What is the distance between the service and the unit?


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## Podagrower (Mar 16, 2008)

Pulling the 80 amps from the main panel instead of a subpanel might help, if it is currently fed from a subpanel. Progress Energy has a notice on their website about these water heaters causing issues, and that it is not their problem, and upgrading equipment to fix it will be done at the customer's expense.

If you lost 5 volts after the POCO repairs using their 5KW load simulator, what do you think it is with a 20KW load?


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## Semi-Ret Electrician (Nov 10, 2011)

Tankless water heaters are a great idea but most of the "older homes" can't handle the demand on their electrical systems.


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## Podagrower (Mar 16, 2008)

Also, what size transformer is the POCO using, add that to the #1 aluminum triplex they probably have run 200' to get to the weatherhead


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## mbednarik (Oct 10, 2011)

I was told that some of those tankless water heaters pulse the elements to create an even output temp. I bet if you put an analog meter on the line you could see the voltage drop.


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## backstay (Feb 3, 2011)

You say this is 19kW, and is fed with 2-40 amp circuits. I calculate that as 39.58 amps per circuit. Do you see a problem there?


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## scorogers (Jul 24, 2012)

Wirenuting said:


> Ahh, ok... I thought you were a GC like your profile said.


Welcome to California where the GC can be the EC. Anything else?


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## scorogers (Jul 24, 2012)

Tiger said:


> What is the distance between the service and the unit?


The distance from the main panel to the unit is exactly 50'. I am running 8AWG through 3/4"Liq Tite in a crawl space. The ground is 10awg. So 5 total wires in 3/4" lig tite.


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## scorogers (Jul 24, 2012)

Podagrower said:


> Pulling the 80 amps from the main panel instead of a subpanel might help, if it is currently fed from a subpanel. Progress Energy has a notice on their website about these water heaters causing issues, and that it is not their problem, and upgrading equipment to fix it will be done at the customer's expense.
> 
> If you lost 5 volts after the POCO repairs using their 5KW load simulator, what do you think it is with a 20KW load?


I am currently pulling 80amps-240v ( 2 double pole 40amp breakers) through the main panel located approximately halfway down the bus bar.

When PGE (WHAT DOES POCO MEAN?) ran their simulator, it was my understanding that it was to read what the voltage drop was a result of running their 5K simulator. I didn't even think of checking their simulator if I turned on the POU water heater continuously with their 5kw simulator and then simultaneoulsy checking voltage. They did offer to hook up a voltimeter that conduct 15 second pings over 15 days to check voltage.
PGE (as far as I am aware) does not require any upgrades on the customer's behalf. Prior to doing a 200amp upgrade, they did a site visit to ensure everything was OK.


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## scorogers (Jul 24, 2012)

backstay said:


> You say this is 19kW, and is fed with 2-40 amp circuits. I calculate that as 39.58 amps per circuit. Do you see a problem there?


I am currently running 8AWG THHN through 50' of liq tite in an enclosed crawl space (so it isn't in the wall, just strapped to the bottom of floor joists). 

I am assuming a 75degree rating since it is encased versus 60 degree rating for 8awg romex. 8awg THHN rated 75degrees should carry 45amps. So allowing 39.58 amps shouldnt be an issue?


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## scorogers (Jul 24, 2012)

mbednarik said:


> I was told that some of those tankless water heaters pulse the elements to create an even output temp. I bet if you put an analog meter on the line you could see the voltage drop.


An analog meter? Actually, the pulsing of the machine coincides with the pulsing of the lights. Maybe I can try that. Thanks.


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## scorogers (Jul 24, 2012)

Podagrower said:


> Also, what size transformer is the POCO using, add that to the #1 aluminum triplex they probably have run 200' to get to the weatherhead


The transformer is right across the street and they are using #4 strand triplex over an approximate 100' run to the weather head. This wire configuration is very common in Santa Cruz as it never really gets above 80 degrees.


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## scorogers (Jul 24, 2012)

Semi-Ret Electrician said:


> Tankless water heaters are a great idea but most of the "older homes" can't handle the demand on their electrical systems.


Some of the lights are definitely on the older wiring. However, a lot has been upgraded and even the lights on the newer wiring has a distinctive pulsating.


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## Podagrower (Mar 16, 2008)

scorogers said:


> When PGE (WHAT DOES POCO MEAN?)


Power Company. 

If they have #4 triplex 100' in free air, fed from a 25?KVA transformer, it doesn't matter what you do at the house. You don't have enough power to run that heater.


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## backstay (Feb 3, 2011)

scorogers said:


> I am currently running 8AWG THHN through 50' of liq tite in an enclosed crawl space (so it isn't in the wall, just strapped to the bottom of floor joists).
> 
> I am assuming a 75degree rating since it is encased versus 60 degree rating for 8awg romex. 8awg THHN rated 75degrees should carry 45amps. So allowing 39.58 amps shouldnt be an issue?


I didn't know you were using thhn in LFMC. Your calculation are correct.


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## scorogers (Jul 24, 2012)

Podagrower said:


> Power Company.
> 
> If they have #4 triplex 100' in free air, fed from a 25?KVA transformer, it doesn't matter what you do at the house. You don't have enough power to run that heater.


Well it appears thare is enough power to run the heater because the heater works fine. The elements heat up and we get 140 degree hot water in about 20seconds. The light "pulsating" is the issue. By saying not enough power do you mean voltage? Would asking the local POCO to attach a voltimeter with 15 second pings help get a better understanding? The manufacturer did mention that this machine operates at 20Kva.


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## Semi-Ret Electrician (Nov 10, 2011)

scorogers said:


> Well it appears thare is enough power to run the heater because the heater works fine. The elements heat up and we get 140 degree hot water in about 20seconds. The light "pulsating" is the issue. By saying not enough power do you mean voltage? Would asking the local POCO to attach a voltimeter with 15 second pings help get a better understanding? The manufacturer did mention that this machine operates at 20Kva.


Yes the heater will work just fine because it's a resistive load and unless the electronics don't cut off because of low voltage (unlikely) you will still heat water at the 212V terminal voltage (calculated), if that is the only load running. It just won't be at the rated BTU/hr.

But, the real problem here, as Podagrower pointed out, is the #4 feed to a 200A service. The POCO's still don't see any problem attaching a #4 wire to a 4/0. I've had them try to do that w/ my 350 KCmil CU and had to shame them into going larger.

The bottom line w/ your installation now is: you will have high voltage with a light load and low voltage w/ even an 80A load; motors will run real slow and burn out quicker; lights will dim when running water and they will think of you every time they wash their hands.


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## CraigV (May 12, 2011)

scorogers said:


> I am currently running 8AWG THHN through 50' of liq tite in an enclosed crawl space (so it isn't in the wall, just strapped to the bottom of floor joists).
> 
> I am assuming a 75degree rating since it is encased versus 60 degree rating for 8awg romex. 8awg THHN rated 75degrees should carry 45amps. So allowing 39.58 amps shouldnt be an issue?


No to derail, but wouldn't the calculation be 55a for Cu 8AWG THHN @90C, less a 20% derating for 4 conductors in conduit, or 44 amps?


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## Semi-Ret Electrician (Nov 10, 2011)

CraigV said:


> No to derail, but wouldn't the calculation be 55a for Cu 8AWG THHN @90C, less a 20% derating for 4 conductors in conduit, or 44 amps?


Since water heaters are continuous don't we have to go 80% of the 44 to 35.2A ?


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## scorogers (Jul 24, 2012)

Semi-Ret Electrician said:


> Yes the heater will work just fine because it's a resistive load and unless the electronics don't cut off because of low voltage (unlikely) you will still heat water at the 212V terminal voltage (calculated), if that is the only load running. It just won't be at the rated BTU/hr.
> 
> But, the real problem here, as Podagrower pointed out, is the #4 feed to a 200A service. The POCO's still don't see any problem attaching a #4 wire to a 4/0. I've had them try to do that w/ my 350 KCmil CU and had to shame them into going larger.
> 
> The bottom line w/ your installation now is: you will have high voltage with a light load and low voltage w/ even an 80A load; motors will run real slow and burn out quicker; lights will dim when running water and they will think of you every time they wash their hands.


You are so correct. Customers have a tendency to think of you when something goes wrong. Not when you do what you were paid to do. I am going to have PGE (POCO) hook up a voltimeter that gets sandwiched between the meter and socket so we can get a telltale story of the voltage. The thing is, they approved a 200amp upgrade via a field visit. If their wires are undersized even though they wrote off the approval, then they need to fix it. My back up plan is to go with a smaller sized heater (about $350) that will draw less load. But I do wish to pursue POCO into fixing their drop. Will keep you posted. You are also correct on the BYU/HR output. The efficiency definitely drops as a result of voltage dropping. Guess it is no surprise they put that chart in the owners manual.

I ran they 30A electric dryer today to get a feel for a lighter load comparitively to the POU water heater. Lights still pulsated albeit at a much more less noticeable rate.


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## scorogers (Jul 24, 2012)

Semi-Ret Electrician said:


> Since water heaters are continuous don't we have to go 80% of the 44 to 35.2A ?


Good question....


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## A Little Short (Nov 11, 2010)

Tankless heaters are not a continuous load. Tanked heaters are.
If you ran one of those (tankless) for 3 hours straight, you would need a 2nd or 3rd job to pay the electric bill.:laughing:


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## Semi-Ret Electrician (Nov 10, 2011)

Little-Lectric said:


> Tankless heaters are not a continuous load. Tanked heaters are.
> If you ran one of those (tankless) for 3 hours straight, you would need a 2nd or 3rd job to pay the electric bill.:laughing:


I agree but does the Code ?


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## A Little Short (Nov 11, 2010)

Semi-Ret Electrician said:


> I agree but does the Code ?


I believe it does. 422.13 for Storage-Type Water Heaters.

I don't see anywhere in the code that says instantaneous (tankless) is to be considered a continuous load. 
Barring that, a continuous load is one that the max current is expected to continue for 3 hours or more.

Again, if a tankless runs 3 hours or more continuous, you're in trouble!


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## MDShunk (Jan 7, 2007)

The lights pulsating (as opposed to just dimming) is more classical for a transformer on its way out more than things just being undersized. These point of use water heaters have contactors (or thermostats), and not SCR's, so there's nothing inherent in them that would ever make lights flicker. The transformer is overtaxed or on its way out. It will be a long ass time before the power company does anything about it, unless you can prove it with your own recording volt meters.


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## bobelectric (Feb 24, 2007)

My thoughts on instant water heaters are:

The power companys are phasing in smart meters.

They will phase in peak demand next.


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## scorogers (Jul 24, 2012)

Which is why I want to take up POCO's offer to hook up a volt meter which gets sandwiched between the meter and meter socket. The field technician said it monitors usage over 15 days with 15 second pings to get an overall understanding of what is happening between the meter and the transformer. The field technician (who has worked for the company for 30 years) was really determined to help investigate my situation and make it right, but was getting frustrated over the bureaucracy involved to remedy the situation. Which is why I think he was told to flip on the (capacitor bank?) to bump me up a few volts and get me within their threshold of acceptibility. 

Another way to remedy the situation, is to decrease the size of the POU heater to less of a draw (maybe 2 double pole 30s instead of 40s) will making a small sacrifice of water flow. The POU is hooked up inline with the tankless watter heater so the will eventually get the hot water at the flow rate they desire. 

I do think a lot of it is on POCO's end, I just want to cover my ass and make sure everything is safe for my client.


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## scorogers (Jul 24, 2012)

*Fixed!!!!!!*

After dealing with POCO and not really getting anywhere with them, we decided to recalculate what POU water heater to use and went with a Stiebel Eltron 12Kw model instead of the 19Kw Eemax currently installed. The 12Kw model eliminated all pulsating, delivered the right GPM for his kitchen sink, and eliminated a lot of headaches. The Stiebel eltron is even much quieter and delivers hot water 5 seconds faster.

It even allowed us to put in a charging station for his Model S Tesla (the cost of putting in a charging stations qualify for a 30% tax credit with a cap of $1000). 

Thank you all for your input.....


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## Semi-Ret Electrician (Nov 10, 2011)

scorogers said:


> Which is why I want to take up POCO's offer to hook up a volt meter which gets sandwiched between the meter and meter socket. The field technician said it monitors usage over 15 days with 15 second pings to get an overall understanding of what is happening between the meter and the transformer. The field technician (who has worked for the company for 30 years) was really determined to help investigate my situation and make it right, but was getting frustrated over the bureaucracy involved to remedy the situation. Which is why I think he was told to flip on the (capacitor bank?) to bump me up a few volts and get me within their threshold of acceptibility.
> 
> Another way to remedy the situation, is to decrease the size of the POU heater to less of a draw (maybe 2 double pole 30s instead of 40s) will making a small sacrifice of water flow. The POU is hooked up inline with the tankless watter heater so the will eventually get the hot water at the flow rate they desire.
> 
> I do think a lot of it is on POCO's end, I just want to cover my ass and make sure everything is safe for my client.


The 15 sec digital samples aren't nearly as good at picking up spikes as an ole fashioned analog recorder. And yes, two SCR driven heaters which come in gradually would be a whole lot better than one across the line contactor, which simulates striking a welding arc.

I've always gotten POCO attention before by telling then I've launched an engineering study of the problem. Problem always clears up by itself...go figure :thumbsup:


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## bds (Jan 8, 2016)

*were you able to resolve this?*

In Los Angeles and I have the same issue with a unit i own. Can you help me fix mine?


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## 480sparky (Sep 20, 2007)

bds said:


> In Los Angeles and I have the same issue with a unit i own. Can you help me fix mine?


You're best bet is to contact a local electrician.


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## dmxtothemax (Jun 15, 2010)

scorogers said:


> the voltage on one leg down to 112v and the other leg jumped to 121v.
> Is there anything else I should be looking at?


Yes! 
If one goes down whilst the other goes up? 
Usually Indicates a neutral problem.


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## 480sparky (Sep 20, 2007)

In case you haven't noticed, this is a 2½-year-old thread.


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## dmxtothemax (Jun 15, 2010)

So why are they resurrecting old threads again?


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## 480sparky (Sep 20, 2007)

dmxtothemax said:


> So why are they resurrecting old threads again?


A DIYer looking for help.


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## Bad Electrician (May 20, 2014)

dmxtothemax said:


> So why are they resurrecting old threads again?


I think they google or search some way and this comes they do not see the date and respond. No harm in that, is there?:no:


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## NC Plc (Mar 24, 2014)

Before this is locked, what is the benefit of using a tankless water heater? I honestly don't see the appeal.


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## macmikeman (Jan 23, 2007)

Before this thread is locked, they work good in Europe cause its 240 volts or close to that supplied each phase, and over 400 between phases (calling legs phases for simplicity, don't have a cow about it.) Works better. The things don't work as good as propane tankless in the North American Continent cause the infrastructure isn't designed for it in most residential areas. Maybe in the cities, but not so much in the miles and miles of suburbs.. I think they should go away.


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## 480sparky (Sep 20, 2007)

NC Plc said:


> Before this is locked, what is the benefit of using a tankless water heater? I honestly don't see the appeal.


You only heat water when you draw water through the heater. No heating a tank of water, then continually heating it to _keep_ it hot, just in case you want hot water now.

Kinda like turning your oven on, baking the pizza, then turning your oven off. You don't keep your oven running 24/7.


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## pete87 (Oct 22, 2012)

Had a Gas Tank less Water Heater in the 70.s in N.O.

Loved It ... I would not want a electric one ...



Pete


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