# Tankless heater= Flickering lights



## chicken steve

Sems the focus should be on the element in question Tim, does the unit have a 800 tech support # _(y no hablan ingles?)_:whistling2: ~CS~


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## 8V71

Flicker as in fast flicker or dim/bright following the element on or off.


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## drm

Already called tech support at rheem. It's a rheem rte-27.They were useless. It is a fast flicker. I'm talkin strobe light. Only when 1 element is running. 2nd element kicks on problem disappears.


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## 8V71

Are there electronics that pulse the elements on or is it strictly mechanical contacts.


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## chicken steve

drm said:


> Already called tech support at rheem. It's a rheem rte-27.They were useless. It is a fast flicker. I'm talkin strobe light. Only when 1 element is running. 2nd element kicks on problem disappears.


Ok, is it possible to swap connections between element #1 &#2 ?

Process of elimination and all....

~CS~


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## chicken steve

8V71 said:


> Are there electronics that pulse the element on or is it strictly mechanical contacts.


good one....~CS~


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## 8V71

chicken steve said:


> good one....~CS~


That's about all I have ~CS~ Don't know where to go after this. 

Edit: Swaping conductors is a very good idea also.


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## Big John

Can you confirm whether there is pulsating voltage or current at the WH and to what extent? Can you confirm that it stops on the bad element when the second element is energized?

Is it a regular pulse that might suggest a control problem causing rapid switching of the element? Is it a variable pulse that might suggest a poor connection somewhere causing an intermittent?


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## 8V71

I found some more info. The elements are SCR controlled.


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## 8V71

From the troubleshooting guide.​ 
Remember, this is a *“modulating”* appliance. It
will only provide the voltage necessary to heat
the water (based on dial setting) that is being demanded.​


So is there something wrong with the unit or it's working ok and you have voltage drop problems. These do draw a lot of current.


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## Big John

Aha. That's absolutely the first place I'd look. Dollars to donuts the SCRs are firing improperly.


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## 8V71

http://www.rheem.com/docs/FetchDocument.aspx?ID=87d15e35-5adf-4e9f-8860-ef2528b9a64d


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## 8V71

When you increase the water flow the heaters are probably on continous to keep up with the flow which may be why the flickering stops.


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## Jlarson

Did poco check drop connections yet?


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## chicken steve

My $$$'s on 8V71.....:thumbsup: ~CS~


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## Rollie73

Im with the Chicken dude and 8V71 on this one. The SCR's have an issue or maybe just the one SCR. 

Swap your conductors around and make element #1 into #2 and vice versa. That will at least let you know if the issue is exclusive to one or the other SCR.


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## brian john

Check both elements,

Arrange so that one and then the other cycle on if the lights flicker than it is a product of VD

VD of as little as 4 VAC is sufficent for noticeable voltage drop.

Check the size of the utility XMFR, distance to the XMFR


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## sbrn33

You have a bad neutral.


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## 8V71

8V71 said:


> So is there something wrong with the unit or it's working ok and you have voltage drop problems. These do draw a lot of current.


Actually I made no statement at all and left it open for more troubleshooting. The OP should check with Rheem and see if it's normal for the unit to cycle as fast as he is seeing the lights flicker. Remember these heaters have almost no tank so it may be normal. Then he should look into voltage drop issues. Then it could be that there is a difficult or no fix because of PoCo limitations.


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## CFL

I think this issue has come up before on this forum. I believe the SCR's are firing normal based on the other thread. I agree with an earlier post that the SCR's are more constant with increase in demand. That's the usual way controllers are programmed.


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## bkmichael65

May need to look at the size of the POCO transformer


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## rrolleston

bkmichael65 said:


> May need to look at the size of the POCO transformer


We upgraded our service with the intention of installing one they were told. We can make the voltage on the service drop go down 10+ volts and flicker the neighbors lights.


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## frenchelectrican

We have simair situatuion with the flicking lights with tankless waterheaters and they are more noticeable on single phase verison than triphase verison.

Even thru if POCO did put a larger transfomer it will not really elemated the flickering lights 100% but it will reduce somehow unless they do upsizing the transfomer and put a larger service drop ( or lateral if they will do that ) that should pretty much reduce it much as possible.

Merci,
Marc


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## LATTC

http://www.electriciantalk.com/f2/flickering-lights-point-use-heater-41278/index2/

same problem last year. solution on page 2


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## LATTC

drm said:


> We were called in on a service call today. Every time the customer turned on the hot water the lights would flicker real bad. We determined it was the tankless water heater (which was installed a few weeks back by a plumber and another electrical contractor who the customer no longer wants to deal with for various reasons).. The water heater has 2 60 amp 240 v lines going to it. There are 2 heating elements in the unit. Each drawing around 50 amps. The lights only flicker when 1 element is on. If we turn on more than 1 faucet or a bathtub and the second element kicks on, this problem goes away. We checked for bad neutrals and grounds at the service. There is a 200amp service on the house and minor voltage drop (less than 4 amps)when this unit is running (It draws 110 amps).
> Any suggestions?


I've been thinking maybe there is a balance issue since the light flicks only when one element is active.


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## frenchelectrican

LATTC said:


> I've been thinking maybe there is a balance issue since the light flicks only when one element is active.


Maybe and maybe not but as the heating element is straight 240 volts ., Oui, 

But as far for the load cycling with SCR and with very low water useage the SCR will " fire " very rapid to keep the voltage level low so it will not overheat the water as soon more volume of water goes the SCR cycle do slow down to the point it not cycling anymore and when the second heating element kick in that flicking dissapair. 

The key issue is the SCR is pretty much bypassed once you get very high water flowage that why the lights are not blinking at all. 

Just think of souped up dimmer to control the monster indentscent lamp to warm up the water basically the same function.

I have ran simair situation over here in France the single phase units are more noticeable than triphase verison ( the triphase verison will flicker < not super noticeable> but super rare in most case unless you blow the heating element then it will show up )

Merci,
Marc


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## LATTC

frenchelectrican said:


> Maybe and maybe not but as the heating element is straight 240 volts ., Oui,
> 
> 
> Marc


What was I thinking LOL


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## Spunk#7

Has any tried throwing a scope on the unit while the lights are flickering ?


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## guest

drm said:


> We were called in on a service call today. Every time the customer turned on the hot water the lights would flicker real bad. We determined it was the tankless water heater (which was installed a few weeks back by a plumber and another electrical contractor who the customer no longer wants to deal with for various reasons).. The water heater has 2 60 amp 240 v lines going to it. *There are 2 heating elements *in the unit. Each drawing around 50 amps. The lights only flicker when 1 element is on. If we turn on more than 1 faucet or a bathtub and _*the second element kicks on, this problem goes away.*_ We checked for bad neutrals and grounds at the service. There is a 200amp service on the house and minor voltage drop (less than 4 amps)when this unit is running (It draws 110 amps).
> Any suggestions?





drm said:


> Already called tech support at rheem. It's a rheem rte-27.They were useless. It is a fast flicker. I'm talkin strobe light. *Only when 1 element is running. 2nd element kicks on problem disappears.*


The clue is in the fact that the second element kicking in stops the flicker. :thumbsup:



sbrn33 said:


> You have a bad neutral.


:no::no::no::no: (A bad neutral would show the classic one leg high, one leg low, which is not happening in this case.) 

Check your main breaker for bad bus or lug connections (Or bad contacts, do a FOP test) and both line and load of the meter socket for a loose hot connection. (Or could be at the POA or the POCO transformer.) 

You problem lies there. 

This has the same effect as the case where a missing leg can "recover" when elements of an electric stove are turned on...the more elements are on the better the "dead" leg works. 

In this case, the lighting is on the BAD leg, and adding the second element to the load of the IWH brings the voltage up and the flicker goes away. 

If you are lucky, you can hear the bad connection crackling when one element is on.


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## drm

Thanks for the advice guys. The panel is brand new and the connections are tight. I will try some of these suggestions and see if I net any results.


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## drsparky

Just for fun I would compare the current on the neutrals.


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## Southeast Power

I think it might just simply be something demonstrating a bit of resistance at Something is loose.
You gotta find out where.


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## 8V71

drm said:


> Thanks for the advice guys. The panel is brand new and the connections are tight. I will try some of these suggestions and see if I net any results.


I'm going to put my money on the utility transformer/feeder not being up to the task or a loose connection outside. I noticed your customer has the largest model when I was looking up info on these. The solution to a similar thread that was linked here was to use smaller less wattage model.


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