Tankless Electric

[FullySprinklered]

I have a customer who wants an electric tankless water heater. On the wall outside his front door, (fourth floor condo) he has a disconnect. The main on this disconnect is two conjoined breakers each labeled 100. The age of this panel predates my foray into the world of wiring, so I'm not sure what I'm looking at. Does he just have 100amps of juice available?

 

[Terry]

I'm not into electrical, except to know that any tankless electric will require a panel upgrade.
A standard tank water heater heats with a 4500 watt element. Tankless needs much, much more than that.

I installed a tankless electric for a winery, but they also brought in more power, just for the tankless.

In Washington State I'm looking at a temperature rise of 70 degrees. It takes a heck of a unit to do much more than wash your hands in luke warm water.

 

[Sponsor]

 

[FullySprinklered]

I'm not into electrical, except to know that any tankless electric will require a panel upgrade.
A standard tank water heater heats with a 4500 watt element. Tankless needs much, much more than that.

I installed a tankless electric for a winery, but they also brought in more power, just for the tankless.

I'm not into electrical, except to know that any tankless electric will require a panel upgrade.
A standard tank water heater heats with a 4500 watt element. Tankless needs much, much more than that.

I installed a tankless electric for a winery, but they also brought in more power, just for the tankless.

Thanks, Terry. Didn't mean to jerk you around, but I put the tankless in five years ago for this guy (dude from Ireland), and it works fine for him. He has a 1 BR unit and has minimal demand on the water heater. I installed another one for him in a rental unit, same 1BR set-up, in the same complex. I asked him about the original install, expecting the worst. He said that if he runs three fixtures at the same time for a couple of minutes it kicks the main. He said he was happy with it. I give them the facts and let them decide.
I did one for a friend of his in a regular house. I got someone it to upgrade the panel before I installed the tankless.

 

[Terry]

" He said that if he runs three fixtures at the same time for a couple of minutes it kicks the main. "

It kicks the main.....................

Also, you're in Georgia, where you can get by with a 35 degree rise.
In Seattle, I need 70 degrees.

 

[FullySprinklered]

" He said that if he runs three fixtures at the same time for a couple of minutes it kicks the main. "

It kicks the main.....................

Also, you're in Georgia, where you can get by with a 35 degree rise.
In Seattle, I need 70 degrees.

70 degree rise. Unreal.

 

[Terry]

70 degree rise. Unreal.

Well, I see 35 degrees and think unreal. It's so disapointing to read the advertised ratings for tankless and realize I need to double the numbers for the frozen North. I almost sprang for two 199,000 tankless to run a multi head system. I have one tankless still in the box in case I change my mind.

This is also why I like to know where posters are living. It makes a difference for so many things. Even Washington State. The West and the East side of the state have different weather climates.

 

[FullySprinklered]

How true. I had a helper one time who grew up in Key West. He said the tap water on the cold side comes out warm.

 

[hj]

Many electric tankless heaters are "staged" so they do not pull their full amperage until the flow approaches their maximum, which is probably why it did not trip the main breaker until it was running for a while. With 100 amp mains, I would be surprised if he could dedicate much more than 40 or 50 amps to the water heater which would mean a very "wimpy" capacity.

 

[DonL]

How true. I had a helper one time who grew up in Key West. He said the tap water on the cold side comes out warm.

We have Hot water here on the cold tap for awhile. Until the well water cools the pipes down.

The pipes in the attic get a bit warm.

When it gets really cold, It is like the water heater is broke.


Putting a tank-less on a 100A main panel is asking for trouble, and will most likely not pass inspection.

 

[Jadnashua]

A 200K BTU gas tankless verses an electric running on 240vac is about equivalent to a 244A load. Now, the electric is running close to 100%, and the tankless isn't, so maybe closer to 220A equivalent. Unless you go industrial, you probably won't find an electric tankless comparable to one of the more typical gas tankless units...power is power, whether you measure it in BTU or watts. As a result, you either get a much smaller delta T (temperature rise) out of it, or reduced flow. Think hand through the flame of a candle verses a blowtorch - you can achieve the same temp, but you'll have to run it through the candle flame a lot slower than if it were a blowtorch! A typical electric tankless is closer to a candle than a blowtorch! You either need really warm incoming water or a very low flow to make sense of an electric tankless system.

 

[hj]

IT would ONLY "not pass inspection" if it overloaded the panel, which would depend on WHICH tankless electric heater he used.

 

[DonL]

If you are running a cloths washer and dryer and a electric Tankless That Really Works on a 100 amp service , You will most likely be resetting the breaker.

A Good inspector will test that theory.

 

[FullySprinklered]

Seriously, I tried the talk the guy out of it. Repeatedly. I felt like a squirrel doing that little zig-zag dance in the road. I finally relented and put the thing in. Main panel, 100 amps; subpanel, 120 amps.
After all's said and done, it works for him. Single guy, one bedroom unit. Never a problem. Good hot water on one fixture, very warm on two, barely warm on three. Kicks breaker if everything is turned on he says.

 

[DonL]

Seriously, I tried the talk the guy out of it. Repeatedly. I felt like a squirrel doing that little zig-zag dance in the road. I finally relented and put the thing in. Main panel, 100 amps; subpanel, 120 amps.
After all's said and done, it works for him. Single guy, one bedroom unit. Never a problem. Good hot water on one fixture, very warm on two, barely warm on three. Kicks breaker if everything is turned on he says.

Main is 100 and sub is 120 amp ?

You and him should not be playing with electricity.


Me Thinks.

 

[Jadnashua]

Is it to code to have a subpanel with a larger main CB than the panel that is feeding it? I guess if the wiring between them was suitable for 120A, you could trip the main panel's main breaker before messing with the sub's main, but that just seems so wrong to me. Maybe done in anticipation of reworking the main at some time for more power in?

Will a main panel with a 100A service even allow a 120A breaker to be installed in one of its load slots?

 

[FullySprinklered]

Main is 100 and sub is 120 amp ?

You and him should not be playing with electricity.


Me Thinks.

You are right. I ought to be shot for that stunt, but the guy was persuasive and I kind of wanted to do one. Next one was for a family of four in a regular house and we bumped the service up to 200a from 150.

 

[FullySprinklered]

Is it to code to have a subpanel with a larger main CB than the panel that is feeding it? I guess if the wiring between them was suitable for 120A, you could trip the main panel's main breaker before messing with the sub's main, but that just seems so wrong to me. Maybe done in anticipation of reworking the main at some time for more power in?

Will a main panel with a 100A service even allow a 120A breaker to be installed in one of its load slots?

I had to pull one existing 15amp circuit into the subpanel to get the two slots for the big breaker. It's been years now, but I might have put a 100a in the main for the sub panel. Not sure anymore. Using a 125 would be even more pointless than the 100a. Specs called for three 40a breakers for the water heater.

 

[McClary's Electrical]

Since you will not find a100 amp single pole breaker, the two conjoined breakers are actually a200 amp ge panel. Ive never ever heard, or repeated, that a tankless heater automatically requires a panel upgrade.....very comical. .....very

 

[FullySprinklered]

Since you will not find a100 amp single pole breaker, the two conjoined breakers are actually a200 amp ge panel. Ive never ever heard, or repeated, that a tankless heater automatically requires a panel upgrade.....very comical. .....very

Well, that was my original question, Mac. I went into the job not knowing how much juice I had to work with. Assuming the worst, I told the customer that I wasn't sure his panel would push a tankless. He indicated that he would take the hit if it didn't pan out, so I went for it. He's happy with it.

 

[hj]

quote; the two conjoined breakers are actually a200 amp ge panel.

NO! They are actually a 100 amp breaker on a 240 v feed. EACH leg is only 100 amps.